githubmirror/cpython

Modules/_ssl.c
7 467 строк217 KB
Victor Stinner
gh-148292: Update _ssl._SSLSocket for OpenSSL 4 (#149102)
04 май 2026, 14:52
04 май 2026, 14:527b7fa3f
/* SSL socket module

   SSL support based on patches by Brian E Gallew and Laszlo Kovacs.
   Re-worked a bit by Bill Janssen to add server-side support and
   certificate decoding.  Chris Stawarz contributed some non-blocking
   patches.

   This module is imported by ssl.py. It should *not* be used
   directly.

   XXX should partial writes be enabled, SSL_MODE_ENABLE_PARTIAL_WRITE?

   XXX integrate several "shutdown modes" as suggested in
       http://bugs.python.org/issue8108#msg102867 ?
*/

#ifndef Py_BUILD_CORE_BUILTIN
#  define Py_BUILD_CORE_MODULE 1
#endif

/* Don't warn about deprecated functions, */
#ifndef OPENSSL_API_COMPAT
  // 0x10101000L == 1.1.1, 30000 == 3.0.0
  #define OPENSSL_API_COMPAT 0x10101000L
#endif
#define OPENSSL_NO_DEPRECATED 1

#include "Python.h"
#include "pycore_fileutils.h"     // _PyIsSelectable_fd()
#include "pycore_long.h"          // _PyLong_UnsignedLongLong_Converter()
#include "pycore_pyerrors.h"      // _PyErr_ChainExceptions1()
#include "pycore_time.h"          // _PyDeadline_Init()
#include "pycore_tuple.h"         // _PyTuple_FromPair

/* Include symbols from _socket module */
#include "socketmodule.h"

#ifdef MS_WINDOWS
#  include <wincrypt.h>
#endif

#include "_ssl.h"

/* Redefined below for Windows debug builds after important #includes */
#define _PySSL_FIX_ERRNO

#define PySSL_BEGIN_ALLOW_THREADS_S(save) \
    do { (save) = PyEval_SaveThread(); } while(0)
#define PySSL_END_ALLOW_THREADS_S(save) \
    do { PyEval_RestoreThread(save); _PySSL_FIX_ERRNO; } while(0)
#define PySSL_BEGIN_ALLOW_THREADS(self) { \
            PyThreadState *_save = NULL;  \
            PySSL_BEGIN_ALLOW_THREADS_S(_save); \
            PyMutex_Lock(&(self)->tstate_mutex);
#define PySSL_END_ALLOW_THREADS(self) \
            PyMutex_Unlock(&(self)->tstate_mutex); \
            PySSL_END_ALLOW_THREADS_S(_save); }

#if defined(HAVE_POLL_H)
#include <poll.h>
#elif defined(HAVE_SYS_POLL_H)
#include <sys/poll.h>
#endif

/* Include OpenSSL header files */
#include "openssl/rsa.h"
#include "openssl/crypto.h"
#include "openssl/x509.h"
#include "openssl/x509v3.h"
#include "openssl/pem.h"
#include "openssl/ssl.h"
#include "openssl/err.h"
#include "openssl/rand.h"
#include "openssl/bio.h"
#include "openssl/dh.h"

#ifndef OPENSSL_THREADS
#  error "OPENSSL_THREADS is not defined, Python requires thread-safe OpenSSL"
#endif


#ifdef BIO_get_ktls_send
#  ifdef MS_WINDOWS
typedef long long Py_off_t;
#  else
typedef off_t Py_off_t;
#  endif

static int
Py_off_t_converter(PyObject *arg, void *addr)
{
#ifdef HAVE_LARGEFILE_SUPPORT
    *((Py_off_t *)addr) = PyLong_AsLongLong(arg);
#else
    *((Py_off_t *)addr) = PyLong_AsLong(arg);
#endif
    return PyErr_Occurred() ? 0 : 1;
}

/*[python input]

class Py_off_t_converter(CConverter):
    type = 'Py_off_t'
    converter = 'Py_off_t_converter'

[python start generated code]*/
/*[python end generated code: output=da39a3ee5e6b4b0d input=3fd9ca8ca6f0cbb8]*/
#endif /* BIO_get_ktls_send */

struct py_ssl_error_code {
    const char *mnemonic;
    int library, reason;
};

struct py_ssl_library_code {
    const char *library;
    int code;
};

#if defined(MS_WINDOWS) && defined(Py_DEBUG)
/* Debug builds on Windows rely on getting errno directly from OpenSSL.
 * However, because it uses a different CRT, we need to transfer the
 * value of errno from OpenSSL into our debug CRT.
 *
 * Don't be fooled - this is horribly ugly code. The only reasonable
 * alternative is to do both debug and release builds of OpenSSL, which
 * requires much uglier code to transform their automatically generated
 * makefile. This is the lesser of all the evils.
 */

static void _PySSLFixErrno(void) {
    HMODULE ucrtbase = GetModuleHandleW(L"ucrtbase.dll");
    if (!ucrtbase) {
        /* If ucrtbase.dll is not loaded but the SSL DLLs are, we likely
         * have a catastrophic failure, but this function is not the
         * place to raise it. */
        return;
    }

    typedef int *(__stdcall *errno_func)(void);
    errno_func ssl_errno = (errno_func)GetProcAddress(ucrtbase, "_errno");
    if (ssl_errno) {
        errno = *ssl_errno();
        *ssl_errno() = 0;
    } else {
        errno = ENOTRECOVERABLE;
    }
}

#undef _PySSL_FIX_ERRNO
#define _PySSL_FIX_ERRNO _PySSLFixErrno()
#endif

/* Include generated data (error codes) */
/* See Tools/ssl/make_ssl_data.py for notes on adding a new version. */
#if (OPENSSL_VERSION_NUMBER >= 0x40000000L)
#  include "_ssl_data_40.h"
#elif (OPENSSL_VERSION_NUMBER >= 0x30401000L)
#  include "_ssl_data_36.h"
#elif (OPENSSL_VERSION_NUMBER >= 0x30100000L)
#  include "_ssl_data_340.h"
#elif (OPENSSL_VERSION_NUMBER >= 0x30000000L)
#  include "_ssl_data_300.h"
#elif (OPENSSL_VERSION_NUMBER >= 0x10101000L)
#  include "_ssl_data_111.h"
#else
#  error Unsupported OpenSSL version
#endif

#if (OPENSSL_VERSION_NUMBER >= 0x40000000L)
#  define OPENSSL_NO_SSL3
#  define OPENSSL_NO_TLS1
#  define OPENSSL_NO_TLS1_1
#  define OPENSSL_NO_TLS1_2
#  define OPENSSL_NO_SSL3_METHOD
#  define OPENSSL_NO_TLS1_METHOD
#  define OPENSSL_NO_TLS1_1_METHOD
#  define OPENSSL_NO_TLS1_2_METHOD
#endif

/* OpenSSL API 1.1.0+ does not include version methods */
#ifndef OPENSSL_NO_SSL3_METHOD
extern const SSL_METHOD *SSLv3_method(void);
#endif
#ifndef OPENSSL_NO_TLS1_METHOD
extern const SSL_METHOD *TLSv1_method(void);
#endif
#ifndef OPENSSL_NO_TLS1_1_METHOD
extern const SSL_METHOD *TLSv1_1_method(void);
#endif
#ifndef OPENSSL_NO_TLS1_2_METHOD
extern const SSL_METHOD *TLSv1_2_method(void);
#endif

#ifndef INVALID_SOCKET /* MS defines this */
#define INVALID_SOCKET (-1)
#endif

/* Default cipher suites */
#ifndef PY_SSL_DEFAULT_CIPHERS
#define PY_SSL_DEFAULT_CIPHERS 1
#endif

#if PY_SSL_DEFAULT_CIPHERS == 0
  #ifndef PY_SSL_DEFAULT_CIPHER_STRING
     #error "Py_SSL_DEFAULT_CIPHERS 0 needs Py_SSL_DEFAULT_CIPHER_STRING"
  #endif
  #ifndef PY_SSL_MIN_PROTOCOL
    #define PY_SSL_MIN_PROTOCOL TLS1_2_VERSION
  #endif
#elif PY_SSL_DEFAULT_CIPHERS == 1
/* Python custom selection of sensible cipher suites
 * @SECLEVEL=2: security level 2 with 112 bits minimum security (e.g. 2048 bits RSA key)
 * ECDH+*: enable ephemeral elliptic curve Diffie-Hellman
 * DHE+*: fallback to ephemeral finite field Diffie-Hellman
 * encryption order: AES AEAD (GCM), ChaCha AEAD, AES CBC
 * !aNULL:!eNULL: really no NULL ciphers
 * !aDSS: no authentication with discrete logarithm DSA algorithm
 * !SHA1: no weak SHA1 MAC
 * !AESCCM: no CCM mode, it's uncommon and slow
 *
 * Based on Hynek's excellent blog post (update 2021-02-11)
 * https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/
 */
  #define PY_SSL_DEFAULT_CIPHER_STRING "@SECLEVEL=2:ECDH+AESGCM:ECDH+CHACHA20:ECDH+AES:DHE+AES:!aNULL:!eNULL:!aDSS:!SHA1:!AESCCM"
  #ifndef PY_SSL_MIN_PROTOCOL
    #define PY_SSL_MIN_PROTOCOL TLS1_2_VERSION
  #endif
#elif PY_SSL_DEFAULT_CIPHERS == 2
/* Ignored in SSLContext constructor, only used to as _ssl.DEFAULT_CIPHER_STRING */
  #define PY_SSL_DEFAULT_CIPHER_STRING SSL_DEFAULT_CIPHER_LIST
#else
  #error "Unsupported PY_SSL_DEFAULT_CIPHERS"
#endif


#if defined(SSL_VERIFY_POST_HANDSHAKE) && defined(TLS1_3_VERSION) && !defined(OPENSSL_NO_TLS1_3)
  #define PySSL_HAVE_POST_HS_AUTH
#endif


enum py_ssl_error {
    /* these mirror ssl.h */
    PY_SSL_ERROR_NONE,
    PY_SSL_ERROR_SSL,
    PY_SSL_ERROR_WANT_READ,
    PY_SSL_ERROR_WANT_WRITE,
    PY_SSL_ERROR_WANT_X509_LOOKUP,
    PY_SSL_ERROR_SYSCALL,     /* look at error stack/return value/errno */
    PY_SSL_ERROR_ZERO_RETURN,
    PY_SSL_ERROR_WANT_CONNECT,
    /* start of non ssl.h errorcodes */
    PY_SSL_ERROR_EOF,         /* special case of SSL_ERROR_SYSCALL */
    PY_SSL_ERROR_NO_SOCKET,   /* socket has been GC'd */
    PY_SSL_ERROR_INVALID_ERROR_CODE
};

enum py_ssl_server_or_client {
    PY_SSL_CLIENT,
    PY_SSL_SERVER
};

enum py_ssl_cert_requirements {
    PY_SSL_CERT_NONE,
    PY_SSL_CERT_OPTIONAL,
    PY_SSL_CERT_REQUIRED
};

enum py_ssl_version {
    PY_SSL_VERSION_SSL2,
    PY_SSL_VERSION_SSL3=1,
    PY_SSL_VERSION_TLS, /* SSLv23 */
    PY_SSL_VERSION_TLS1,
    PY_SSL_VERSION_TLS1_1,
    PY_SSL_VERSION_TLS1_2,
    PY_SSL_VERSION_TLS_CLIENT=0x10,
    PY_SSL_VERSION_TLS_SERVER,
};

enum py_proto_version {
    PY_PROTO_MINIMUM_SUPPORTED = -2,
    PY_PROTO_SSLv3 = SSL3_VERSION,
    PY_PROTO_TLSv1 = TLS1_VERSION,
    PY_PROTO_TLSv1_1 = TLS1_1_VERSION,
    PY_PROTO_TLSv1_2 = TLS1_2_VERSION,
#if defined(TLS1_3_VERSION)
    PY_PROTO_TLSv1_3 = TLS1_3_VERSION,
#else
    PY_PROTO_TLSv1_3 = 0x304,
#endif
    PY_PROTO_MAXIMUM_SUPPORTED = -1,

/* OpenSSL has no dedicated API to set the minimum version to the maximum
 * available version, and the other way around. We have to figure out the
 * minimum and maximum available version on our own and hope for the best.
 */
#if defined(SSL3_VERSION) && !defined(OPENSSL_NO_SSL3)
    PY_PROTO_MINIMUM_AVAILABLE = PY_PROTO_SSLv3,
#elif defined(TLS1_VERSION) && !defined(OPENSSL_NO_TLS1)
    PY_PROTO_MINIMUM_AVAILABLE = PY_PROTO_TLSv1,
#elif defined(TLS1_1_VERSION) && !defined(OPENSSL_NO_TLS1_1)
    PY_PROTO_MINIMUM_AVAILABLE = PY_PROTO_TLSv1_1,
#elif defined(TLS1_2_VERSION) && !defined(OPENSSL_NO_TLS1_2)
    PY_PROTO_MINIMUM_AVAILABLE = PY_PROTO_TLSv1_2,
#elif defined(TLS1_3_VERSION) && !defined(OPENSSL_NO_TLS1_3)
    PY_PROTO_MINIMUM_AVAILABLE = PY_PROTO_TLSv1_3,
#else
    #error "PY_PROTO_MINIMUM_AVAILABLE not found"
#endif

#if defined(TLS1_3_VERSION) && !defined(OPENSSL_NO_TLS1_3)
    PY_PROTO_MAXIMUM_AVAILABLE = PY_PROTO_TLSv1_3,
#elif defined(TLS1_2_VERSION) && !defined(OPENSSL_NO_TLS1_2)
    PY_PROTO_MAXIMUM_AVAILABLE = PY_PROTO_TLSv1_2,
#elif defined(TLS1_1_VERSION) && !defined(OPENSSL_NO_TLS1_1)
    PY_PROTO_MAXIMUM_AVAILABLE = PY_PROTO_TLSv1_1,
#elif defined(TLS1_VERSION) && !defined(OPENSSL_NO_TLS1)
    PY_PROTO_MAXIMUM_AVAILABLE = PY_PROTO_TLSv1,
#elif defined(SSL3_VERSION) && !defined(OPENSSL_NO_SSL3)
    PY_PROTO_MAXIMUM_AVAILABLE = PY_PROTO_SSLv3,
#else
    #error "PY_PROTO_MAXIMUM_AVAILABLE not found"
#endif
};

/* SSL socket object */

#define X509_NAME_MAXLEN 256


/* In case of 'tls-unique' it will be 12 bytes for TLS, 36 bytes for
 * older SSL, but let's be safe */
#define PySSL_CB_MAXLEN 128


typedef struct {
    PyObject_HEAD
    SSL_CTX *ctx;
    unsigned char *alpn_protocols;
    unsigned int alpn_protocols_len;
    PyObject *set_sni_cb;
    int check_hostname;
    int protocol;
#if defined(PySSL_HAVE_POST_HS_AUTH)
    int post_handshake_auth;
#endif
    PyObject *msg_cb;
    PyObject *keylog_filename;  // can be anything accepted by Py_fopen()
    BIO *keylog_bio;
    /* Cached module state, also used in SSLSocket and SSLSession code. */
    _sslmodulestate *state;
#ifndef OPENSSL_NO_PSK
    PyObject *psk_client_callback;
    PyObject *psk_server_callback;
#endif
    /* Lock to synchronize calls when the thread state is detached.
       See also gh-134698. */
    PyMutex tstate_mutex;
} PySSLContext;

#define PySSLContext_CAST(op)   ((PySSLContext *)(op))

typedef struct {
    int ssl; /* last seen error from SSL */
    int c; /* last seen error from libc */
#ifdef MS_WINDOWS
    int ws; /* last seen error from winsock */
#endif
} _PySSLError;

typedef struct {
    PyObject_HEAD
    PyObject *Socket; /* weakref to socket on which we're layered */
    SSL *ssl;
    PySSLContext *ctx; /* weakref to SSL context */
    char shutdown_seen_zero;
    enum py_ssl_server_or_client socket_type;
    PyObject *owner; /* weakref to Python level "owner" passed to servername callback */
    PyObject *server_hostname;
    // gh-148292: If non-zero, read(), sendfile(), write() and do_handshake()
    // methods raise SSLEOFError without calling the underlying OpenSSL
    // function. Set to 1 on PY_SSL_ERROR_EOF error.
    //
    // On OpenSSL 4, if SSL_read_ex() fails with
    // SSL_R_UNEXPECTED_EOF_WHILE_READING, the following SSL_read_ex() call
    // fails with a generic protocol error (ERR_peek_last_error() returns 0).
    // Use got_eof_error to have the same behavior on OpenSSL 4 and newer and
    // on OpenSSL 3 and older.
    int got_eof_error;
} PySSLSocket;

#define PySSLSocket_CAST(op)    ((PySSLSocket *)(op))

typedef struct {
    PyObject_HEAD
    BIO *bio;
    int eof_written;
} PySSLMemoryBIO;

#define PySSLMemoryBIO_CAST(op) ((PySSLMemoryBIO *)(op))

typedef struct {
    PyObject_HEAD
    SSL_SESSION *session;
    PySSLContext *ctx;
} PySSLSession;

#define PySSLSession_CAST(op)   ((PySSLSession *)(op))

static inline _PySSLError _PySSL_errno(int failed, const SSL *ssl, int retcode)
{
    _PySSLError err = { 0 };
    if (failed) {
#ifdef MS_WINDOWS
        err.ws = WSAGetLastError();
        _PySSL_FIX_ERRNO;
#endif
        err.c = errno;
        err.ssl = SSL_get_error(ssl, retcode);
    }
    return err;
}

/*[clinic input]
module _ssl
class _ssl._SSLContext "PySSLContext *" "get_state_type(type)->PySSLContext_Type"
class _ssl._SSLSocket "PySSLSocket *" "get_state_type(type)->PySSLSocket_Type"
class _ssl.MemoryBIO "PySSLMemoryBIO *" "get_state_type(type)->PySSLMemoryBIO_Type"
class _ssl.SSLSession "PySSLSession *" "get_state_type(type)->PySSLSession_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=d293bed8bae240fd]*/

#include "clinic/_ssl.c.h"

static int PySSL_select(PySocketSockObject *s, int writing, PyTime_t timeout);

typedef enum {
    SOCKET_IS_NONBLOCKING,
    SOCKET_IS_BLOCKING,
    SOCKET_HAS_TIMED_OUT,
    SOCKET_HAS_BEEN_CLOSED,
    SOCKET_TOO_LARGE_FOR_SELECT,
    SOCKET_OPERATION_OK
} timeout_state;

/* Wrap error strings with filename and line # */
#define ERRSTR1(x,y,z) (x ":" y ": " z)
#define ERRSTR(x) ERRSTR1("_ssl.c", Py_STRINGIFY(__LINE__), x)

/* If sock is NULL, use a timeout of 0 second */
#define GET_SOCKET_TIMEOUT(sock) \
    ((sock != NULL) ? (sock)->sock_timeout : 0)

#include "_ssl/debughelpers.c"

/*
 * SSL errors.
 */

PyDoc_STRVAR(SSLError_doc,
"An error occurred in the SSL implementation.");

PyDoc_STRVAR(SSLCertVerificationError_doc,
"A certificate could not be verified.");

PyDoc_STRVAR(SSLZeroReturnError_doc,
"SSL/TLS session closed cleanly.");

PyDoc_STRVAR(SSLWantReadError_doc,
"Non-blocking SSL socket needs to read more data\n"
"before the requested operation can be completed.");

PyDoc_STRVAR(SSLWantWriteError_doc,
"Non-blocking SSL socket needs to write more data\n"
"before the requested operation can be completed.");

PyDoc_STRVAR(SSLSyscallError_doc,
"System error when attempting SSL operation.");

PyDoc_STRVAR(SSLEOFError_doc,
"SSL/TLS connection terminated abruptly.");

static PyObject *
SSLError_str(PyObject *op)
{
    PyOSErrorObject *self = (PyOSErrorObject*)op;
    if (self->strerror != NULL && PyUnicode_Check(self->strerror)) {
        return Py_NewRef(self->strerror);
    }
    else
        return PyObject_Str(self->args);
}

static PyType_Slot sslerror_type_slots[] = {
    {Py_tp_doc, (void*)SSLError_doc},
    {Py_tp_str, SSLError_str},
    {0, 0},
};

static PyType_Spec sslerror_type_spec = {
    .name = "ssl.SSLError",
    .basicsize = sizeof(PyOSErrorObject),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_IMMUTABLETYPE),
    .slots = sslerror_type_slots
};

static void
fill_and_set_sslerror(_sslmodulestate *state,
                      PySSLSocket *sslsock, PyObject *type, int ssl_errno,
                      const char *errstr, int lineno, unsigned long errcode)
{
    PyObject *err_value = NULL, *reason_obj = NULL, *lib_obj = NULL;
    PyObject *verify_obj = NULL, *verify_code_obj = NULL;
    PyObject *init_value, *msg, *key;
    PyUnicodeWriter *writer = NULL;

    if (ssl_errno == PY_SSL_ERROR_EOF && sslsock != NULL) {
        sslsock->got_eof_error = 1;
    }

    if (errcode != 0) {
        int lib, reason;

        lib = ERR_GET_LIB(errcode);
        reason = ERR_GET_REASON(errcode);
        key = Py_BuildValue("ii", lib, reason);
        if (key == NULL)
            goto fail;
        reason_obj = PyDict_GetItemWithError(state->err_codes_to_names, key);
        Py_DECREF(key);
        if (reason_obj == NULL && PyErr_Occurred()) {
            goto fail;
        }
        key = PyLong_FromLong(lib);
        if (key == NULL)
            goto fail;
        lib_obj = PyDict_GetItemWithError(state->lib_codes_to_names, key);
        Py_DECREF(key);
        if (lib_obj == NULL && PyErr_Occurred()) {
            goto fail;
        }
        if (errstr == NULL) {
            errstr = ERR_reason_error_string(errcode);
        }
    }

    /* verify code for cert validation error */
    if ((sslsock != NULL) && (type == state->PySSLCertVerificationErrorObject)) {
        const char *verify_str = NULL;
        long verify_code;

        verify_code = SSL_get_verify_result(sslsock->ssl);
        verify_code_obj = PyLong_FromLong(verify_code);
        if (verify_code_obj == NULL) {
            goto fail;
        }

        switch (verify_code) {
        case X509_V_ERR_HOSTNAME_MISMATCH:
            verify_obj = PyUnicode_FromFormat(
                "Hostname mismatch, certificate is not valid for '%S'.",
                sslsock->server_hostname
            );
            break;
        case X509_V_ERR_IP_ADDRESS_MISMATCH:
            verify_obj = PyUnicode_FromFormat(
                "IP address mismatch, certificate is not valid for '%S'.",
                sslsock->server_hostname
            );
            break;
        default:
            verify_str = X509_verify_cert_error_string(verify_code);
            if (verify_str != NULL) {
                verify_obj = PyUnicode_FromString(verify_str);
            } else {
                verify_obj = Py_NewRef(Py_None);
            }
            break;
        }
        if (verify_obj == NULL) {
            goto fail;
        }
    }

    // Format message roughly as:
    // [lib_obj: reason_obj] errstr: verify_obj (_ssl.c:lineno)
    // with parts missing/replaced if unavailable
    writer = PyUnicodeWriter_Create(64);
    if (!writer) {
        goto fail;
    }
    if (lib_obj) {
        if (PyUnicodeWriter_Format(writer, "[%S", lib_obj) < 0) {
            goto fail;
        }
        if (reason_obj) {
            if (PyUnicodeWriter_Format(writer, ": %S", reason_obj) < 0) {
                goto fail;
            }
        }
        if (PyUnicodeWriter_WriteASCII(writer, "] ", 2) < 0) {
            goto fail;
        }
    }
    if (errstr) {
        if (PyUnicodeWriter_Format(writer, "%s", errstr) < 0) {
            goto fail;
        }
    }
    else {
        if (PyUnicodeWriter_Format(
                writer, "unknown error (0x%lx)", errcode) < 0) {
            goto fail;
        }
    }
    if (verify_obj) {
        if (PyUnicodeWriter_Format(writer, ": %S", verify_obj) < 0) {
            goto fail;
        }
    }
    if (PyUnicodeWriter_Format(writer, " (_ssl.c:%d)", lineno) < 0) {
        goto fail;
    }
    msg = PyUnicodeWriter_Finish(writer);
    writer = NULL;
    if (!msg) {
        goto fail;
    }

    init_value = Py_BuildValue("iN", ERR_GET_REASON(ssl_errno), msg);
    if (init_value == NULL)
        goto fail;

    err_value = PyObject_CallObject(type, init_value);
    Py_DECREF(init_value);
    if (err_value == NULL)
        goto fail;

    if (reason_obj == NULL)
        reason_obj = Py_None;
    if (PyObject_SetAttr(err_value, state->str_reason, reason_obj))
        goto fail;

    if (lib_obj == NULL)
        lib_obj = Py_None;
    if (PyObject_SetAttr(err_value, state->str_library, lib_obj))
        goto fail;

    if ((sslsock != NULL) && (type == state->PySSLCertVerificationErrorObject)) {
        /* Only set verify code / message for SSLCertVerificationError */
        if (PyObject_SetAttr(err_value, state->str_verify_code,
                                verify_code_obj))
            goto fail;
        if (PyObject_SetAttr(err_value, state->str_verify_message, verify_obj))
            goto fail;
    }

    PyErr_SetObject(type, err_value);
fail:
    Py_XDECREF(err_value);
    Py_XDECREF(verify_code_obj);
    Py_XDECREF(verify_obj);
    PyUnicodeWriter_Discard(writer);
}


static void
set_eof_error(PySSLSocket *sslsock)
{
    _sslmodulestate *state = get_state_sock(sslsock);
    fill_and_set_sslerror(state, sslsock, state->PySSLEOFErrorObject,
                          PY_SSL_ERROR_EOF,
                          "EOF occurred in violation of protocol",
                          __LINE__, 0);
}


// Set the appropriate SSL error exception.
// err - error information from SSL and libc
// exc - if not NULL, an exception from _debughelpers.c callback to be chained
static PyObject *
PySSL_SetError(PySSLSocket *sslsock, _PySSLError err, PyObject *exc,
               const char *filename, int lineno)
{
    PyObject *type;
    char *errstr = NULL;
    enum py_ssl_error p = PY_SSL_ERROR_NONE;
    unsigned long e = 0;

    assert(sslsock != NULL);

    _sslmodulestate *state = get_state_sock(sslsock);
    type = state->PySSLErrorObject;

    // ERR functions are thread local, no need to lock them.
    e = ERR_peek_last_error();

    if (sslsock->ssl != NULL) {
        switch (err.ssl) {
        case SSL_ERROR_ZERO_RETURN:
            errstr = "TLS/SSL connection has been closed (EOF)";
            type = state->PySSLZeroReturnErrorObject;
            p = PY_SSL_ERROR_ZERO_RETURN;
            break;
        case SSL_ERROR_WANT_READ:
            errstr = "The operation did not complete (read)";
            type = state->PySSLWantReadErrorObject;
            p = PY_SSL_ERROR_WANT_READ;
            break;
        case SSL_ERROR_WANT_WRITE:
            p = PY_SSL_ERROR_WANT_WRITE;
            type = state->PySSLWantWriteErrorObject;
            errstr = "The operation did not complete (write)";
            break;
        case SSL_ERROR_WANT_X509_LOOKUP:
            p = PY_SSL_ERROR_WANT_X509_LOOKUP;
            errstr = "The operation did not complete (X509 lookup)";
            break;
        case SSL_ERROR_WANT_CONNECT:
            p = PY_SSL_ERROR_WANT_CONNECT;
            errstr = "The operation did not complete (connect)";
            break;
        case SSL_ERROR_SYSCALL:
        {
            if (e == 0) {
                /* underlying BIO reported an I/O error */
                ERR_clear_error();
#ifdef MS_WINDOWS
                if (err.ws) {
                    return PyErr_SetFromWindowsErr(err.ws);
                }
#endif
                if (err.c) {
                    errno = err.c;
                    return PyErr_SetFromErrno(PyExc_OSError);
                }
                else {
                    p = PY_SSL_ERROR_EOF;
                    type = state->PySSLEOFErrorObject;
                    errstr = "EOF occurred in violation of protocol";
                }
            } else {
                if (ERR_GET_LIB(e) == ERR_LIB_SSL &&
                        ERR_GET_REASON(e) == SSL_R_CERTIFICATE_VERIFY_FAILED) {
                    type = state->PySSLCertVerificationErrorObject;
                }
                if (ERR_GET_LIB(e) == ERR_LIB_SYS) {
                    // A system error is being reported; reason is set to errno
                    errno = ERR_GET_REASON(e);
                    return PyErr_SetFromErrno(PyExc_OSError);
                }
                p = PY_SSL_ERROR_SYSCALL;
            }
            break;
        }
        case SSL_ERROR_SSL:
        {
            p = PY_SSL_ERROR_SSL;
            if (e == 0) {
                /* possible? */
                errstr = "A failure in the SSL library occurred";
            }
            if (ERR_GET_LIB(e) == ERR_LIB_SSL &&
                    ERR_GET_REASON(e) == SSL_R_CERTIFICATE_VERIFY_FAILED) {
                type = state->PySSLCertVerificationErrorObject;
            }
#if defined(SSL_R_UNEXPECTED_EOF_WHILE_READING)
            /* OpenSSL 3.0 changed transport EOF from SSL_ERROR_SYSCALL with
             * zero return value to SSL_ERROR_SSL with a special error code. */
            if (ERR_GET_LIB(e) == ERR_LIB_SSL &&
                    ERR_GET_REASON(e) == SSL_R_UNEXPECTED_EOF_WHILE_READING) {
                p = PY_SSL_ERROR_EOF;
                type = state->PySSLEOFErrorObject;
                errstr = "EOF occurred in violation of protocol";
            }
#endif
            if (ERR_GET_LIB(e) == ERR_LIB_SYS) {
                // A system error is being reported; reason is set to errno
                errno = ERR_GET_REASON(e);
                return PyErr_SetFromErrno(PyExc_OSError);
            }
            break;
        }
        default:
            p = PY_SSL_ERROR_INVALID_ERROR_CODE;
            errstr = "Invalid error code";
        }
    }
    fill_and_set_sslerror(state, sslsock, type, p, errstr, lineno, e);
    ERR_clear_error();
    _PyErr_ChainExceptions1(exc);  // chain any exceptions from callbacks
    return NULL;
}

static PyObject *
_setSSLError (_sslmodulestate *state, const char *errstr, int errcode, const char *filename, int lineno)
{
    if (errstr == NULL)
        errcode = ERR_peek_last_error();
    else
        errcode = 0;
    fill_and_set_sslerror(state, NULL, state->PySSLErrorObject, errcode, errstr, lineno, errcode);
    ERR_clear_error();
    return NULL;
}

static int
_ssl_deprecated(const char* msg, int stacklevel) {
    return PyErr_WarnEx(
        PyExc_DeprecationWarning, msg, stacklevel
    );
}

#define PY_SSL_DEPRECATED(name, stacklevel, ret) \
    if (_ssl_deprecated((name), (stacklevel)) == -1) return (ret)

// Get the socket from a PySSLSocket, if it has one.
// Stores a strong reference in out_sock.
static int
get_socket(PySSLSocket *obj, PySocketSockObject **out_sock,
           const char *filename, int lineno)
{
    if (!obj->Socket) {
        *out_sock = NULL;
        return 0;
    }
    PySocketSockObject *sock;
    int res = PyWeakref_GetRef(obj->Socket, (PyObject **)&sock);
    if (res == 0 || sock->sock_fd == INVALID_SOCKET) {
        _setSSLError(get_state_sock(obj),
                     "Underlying socket connection gone",
                     PY_SSL_ERROR_NO_SOCKET, filename, lineno);
        *out_sock = NULL;
        return -1;
    }
    if (sock != NULL) {
        /* just in case the blocking state of the socket has been changed */
        int nonblocking = (sock->sock_timeout >= 0);
        BIO_set_nbio(SSL_get_rbio(obj->ssl), nonblocking);
        BIO_set_nbio(SSL_get_wbio(obj->ssl), nonblocking);
    }
    *out_sock = sock;
    return res;
}

/*
 * SSL objects
 */

static int
_ssl_configure_hostname(PySSLSocket *self, const char* server_hostname)
{
    int retval = -1;
    ASN1_OCTET_STRING *ip;
    PyObject *hostname;
    size_t len;

    assert(server_hostname);

    /* Disable OpenSSL's special mode with leading dot in hostname:
     * When name starts with a dot (e.g ".example.com"), it will be
     * matched by a certificate valid for any sub-domain of name.
     */
    len = strlen(server_hostname);
    if (len == 0 || *server_hostname == '.') {
        PyErr_SetString(
            PyExc_ValueError,
            "server_hostname cannot be an empty string or start with a "
            "leading dot.");
        return retval;
    }

    /* inet_pton is not available on all platforms. */
    ip = a2i_IPADDRESS(server_hostname);
    if (ip == NULL) {
        ERR_clear_error();
    }

    hostname = PyUnicode_Decode(server_hostname, len, "ascii", "strict");
    if (hostname == NULL) {
        goto error;
    }
    self->server_hostname = hostname;

    /* Only send SNI extension for non-IP hostnames */
    if (ip == NULL) {
        if (!SSL_set_tlsext_host_name(self->ssl, server_hostname)) {
            _setSSLError(get_state_sock(self), NULL, 0, __FILE__, __LINE__);
            goto error;
        }
    }
    if (self->ctx->check_hostname) {
        X509_VERIFY_PARAM *ssl_verification_params = SSL_get0_param(self->ssl);
        if (ip == NULL) {
            if (!X509_VERIFY_PARAM_set1_host(ssl_verification_params, server_hostname,
                                             strlen(server_hostname))) {
                _setSSLError(get_state_sock(self), NULL, 0, __FILE__, __LINE__);
                goto error;
            }
        } else {
            if (!X509_VERIFY_PARAM_set1_ip(ssl_verification_params, ASN1_STRING_get0_data(ip),
                                           ASN1_STRING_length(ip))) {
                _setSSLError(get_state_sock(self), NULL, 0, __FILE__, __LINE__);
                goto error;
            }
        }
    }
    retval = 0;
  error:
    if (ip != NULL) {
        ASN1_OCTET_STRING_free(ip);
    }
    return retval;
}

static PySSLSocket *
newPySSLSocket(PySSLContext *sslctx, PySocketSockObject *sock,
               enum py_ssl_server_or_client socket_type,
               char *server_hostname,
               PyObject *owner, PyObject *session,
               PySSLMemoryBIO *inbio, PySSLMemoryBIO *outbio)
{
    PySSLSocket *self;
    SSL_CTX *ctx = sslctx->ctx;

    if ((socket_type == PY_SSL_SERVER) &&
        (sslctx->protocol == PY_SSL_VERSION_TLS_CLIENT)) {
        _setSSLError(get_state_ctx(sslctx),
                     "Cannot create a server socket with a "
                     "PROTOCOL_TLS_CLIENT context", 0, __FILE__, __LINE__);
        return NULL;
    }
    if ((socket_type == PY_SSL_CLIENT) &&
        (sslctx->protocol == PY_SSL_VERSION_TLS_SERVER)) {
        _setSSLError(get_state_ctx(sslctx),
                     "Cannot create a client socket with a "
                     "PROTOCOL_TLS_SERVER context", 0, __FILE__, __LINE__);
        return NULL;
    }

    self = PyObject_GC_New(PySSLSocket,
                           get_state_ctx(sslctx)->PySSLSocket_Type);
    if (self == NULL)
        return NULL;

    self->ssl = NULL;
    self->Socket = NULL;
    self->ctx = (PySSLContext*)Py_NewRef(sslctx);
    self->shutdown_seen_zero = 0;
    self->owner = NULL;
    self->server_hostname = NULL;
    self->got_eof_error = 0;

    /* Make sure the SSL error state is initialized */
    ERR_clear_error();

    PySSL_BEGIN_ALLOW_THREADS(sslctx)
    self->ssl = SSL_new(ctx);
    PySSL_END_ALLOW_THREADS(sslctx)
    if (self->ssl == NULL) {
        _setSSLError(get_state_ctx(sslctx), NULL, 0, __FILE__, __LINE__);
        Py_DECREF(self);
        return NULL;
    }

    if (socket_type == PY_SSL_SERVER) {
#define SID_CTX "Python"
        /* Set the session id context (server-side only) */
        SSL_set_session_id_context(self->ssl, (const unsigned char *) SID_CTX,
                                   sizeof(SID_CTX));
#undef SID_CTX
    }

    /* bpo43522 and OpenSSL < 1.1.1l: copy hostflags manually */
#if OPENSSL_VERSION_NUMBER < 0x101010cf
    X509_VERIFY_PARAM *ssl_verification_params = SSL_get0_param(self->ssl);
    X509_VERIFY_PARAM *ssl_ctx_verification_params = SSL_CTX_get0_param(ctx);

    unsigned int ssl_ctx_host_flags = X509_VERIFY_PARAM_get_hostflags(ssl_ctx_verification_params);
    X509_VERIFY_PARAM_set_hostflags(ssl_verification_params, ssl_ctx_host_flags);
#endif
    SSL_set_app_data(self->ssl, self);
    if (sock) {
        SSL_set_fd(self->ssl, Py_SAFE_DOWNCAST(sock->sock_fd, SOCKET_T, int));
    } else {
        /* BIOs are reference counted and SSL_set_bio borrows our reference.
         * To prevent a double free in memory_bio_dealloc() we need to take an
         * extra reference here. */
        BIO_up_ref(inbio->bio);
        BIO_up_ref(outbio->bio);
        SSL_set_bio(self->ssl, inbio->bio, outbio->bio);
    }
    SSL_set_mode(self->ssl,
                 SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER | SSL_MODE_AUTO_RETRY);

#if defined(PySSL_HAVE_POST_HS_AUTH)
    if (sslctx->post_handshake_auth == 1) {
        if (socket_type == PY_SSL_SERVER) {
            /* bpo-37428: OpenSSL does not ignore SSL_VERIFY_POST_HANDSHAKE.
             * Set SSL_VERIFY_POST_HANDSHAKE flag only for server sockets and
             * only in combination with SSL_VERIFY_PEER flag. */
            int mode = SSL_get_verify_mode(self->ssl);
            if (mode & SSL_VERIFY_PEER) {
                mode |= SSL_VERIFY_POST_HANDSHAKE;
                SSL_set_verify(self->ssl, mode, NULL);
            }
        } else {
            /* client socket */
            SSL_set_post_handshake_auth(self->ssl, 1);
        }
    }
#endif

    if (server_hostname != NULL) {
        if (_ssl_configure_hostname(self, server_hostname) < 0) {
            Py_DECREF(self);
            return NULL;
        }
    }
    /* If the socket is in non-blocking mode or timeout mode, set the BIO
     * to non-blocking mode (blocking is the default)
     */
    if (sock && sock->sock_timeout >= 0) {
        BIO_set_nbio(SSL_get_rbio(self->ssl), 1);
        BIO_set_nbio(SSL_get_wbio(self->ssl), 1);
    }

    Py_BEGIN_ALLOW_THREADS;
    if (socket_type == PY_SSL_CLIENT)
        SSL_set_connect_state(self->ssl);
    else
        SSL_set_accept_state(self->ssl);
    Py_END_ALLOW_THREADS;

    self->socket_type = socket_type;
    if (sock != NULL) {
        self->Socket = PyWeakref_NewRef((PyObject *) sock, NULL);
        if (self->Socket == NULL) {
            Py_DECREF(self);
            return NULL;
        }
    }
    if (owner && owner != Py_None) {
        if (_ssl__SSLSocket_owner_set((PyObject *)self, owner, NULL) < 0) {
            Py_DECREF(self);
            return NULL;
        }
    }
    if (session && session != Py_None) {
        if (_ssl__SSLSocket_session_set((PyObject *)self, session, NULL) < 0) {
            Py_DECREF(self);
            return NULL;
        }
    }

    PyObject_GC_Track(self);
    return self;
}

/* SSL object methods */

/*[clinic input]
@critical_section
_ssl._SSLSocket.do_handshake
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_do_handshake_impl(PySSLSocket *self)
/*[clinic end generated code: output=6c0898a8936548f6 input=65619a7a4bea3176]*/
{
    int ret;
    _PySSLError err;
    PyObject *exc = NULL;
    int sockstate;
    PyTime_t timeout, deadline = 0;
    int has_timeout;

    PySocketSockObject *sock = NULL;
    if (get_socket(self, &sock, __FILE__, __LINE__) < 0) {
        return NULL;
    }

    if (self->got_eof_error) {
        set_eof_error(self);
        goto error;
    }

    timeout = GET_SOCKET_TIMEOUT(sock);
    has_timeout = (timeout > 0);
    if (has_timeout) {
        deadline = _PyDeadline_Init(timeout);
    }

    /* Actually negotiate SSL connection */
    /* XXX If SSL_do_handshake() returns 0, it's also a failure. */
    do {
        Py_BEGIN_ALLOW_THREADS
        ret = SSL_do_handshake(self->ssl);
        err = _PySSL_errno(ret < 1, self->ssl, ret);
        Py_END_ALLOW_THREADS;
        _PySSL_FIX_ERRNO;

        // Get any exception that occurred in a debughelpers.c callback
        exc = PyErr_GetRaisedException();
        if (exc != NULL) {
            break;
        }

        if (PyErr_CheckSignals())
            goto error;

        if (has_timeout)
            timeout = _PyDeadline_Get(deadline);

        if (err.ssl == SSL_ERROR_WANT_READ) {
            sockstate = PySSL_select(sock, 0, timeout);
        } else if (err.ssl == SSL_ERROR_WANT_WRITE) {
            sockstate = PySSL_select(sock, 1, timeout);
        } else {
            sockstate = SOCKET_OPERATION_OK;
        }

        if (sockstate == SOCKET_HAS_TIMED_OUT) {
            PyErr_SetString(PyExc_TimeoutError,
                            ERRSTR("The handshake operation timed out"));
            goto error;
        } else if (sockstate == SOCKET_HAS_BEEN_CLOSED) {
            PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                            ERRSTR("Underlying socket has been closed."));
            goto error;
        } else if (sockstate == SOCKET_TOO_LARGE_FOR_SELECT) {
            PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                            ERRSTR("Underlying socket too large for select()."));
            goto error;
        } else if (sockstate == SOCKET_IS_NONBLOCKING) {
            break;
        }
    } while (err.ssl == SSL_ERROR_WANT_READ ||
             err.ssl == SSL_ERROR_WANT_WRITE);
    Py_XDECREF(sock);

    if (ret < 1)
        return PySSL_SetError(self, err, exc, __FILE__, __LINE__);
    if (exc != NULL) {
        PyErr_SetRaisedException(exc);
        return NULL;
    }
    Py_RETURN_NONE;
error:
    assert(exc == NULL);
    Py_XDECREF(sock);
    return NULL;
}

static PyObject *
_asn1obj2py(_sslmodulestate *state, const ASN1_OBJECT *name, int no_name)
{
    char buf[X509_NAME_MAXLEN];
    char *namebuf = buf;
    int buflen;
    PyObject *name_obj = NULL;

    buflen = OBJ_obj2txt(namebuf, X509_NAME_MAXLEN, name, no_name);
    if (buflen < 0) {
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        return NULL;
    }
    /* initial buffer is too small for oid + terminating null byte */
    if (buflen > X509_NAME_MAXLEN - 1) {
        /* make OBJ_obj2txt() calculate the required buflen */
        buflen = OBJ_obj2txt(NULL, 0, name, no_name);
        /* allocate len + 1 for terminating NULL byte */
        namebuf = PyMem_Malloc(buflen + 1);
        if (namebuf == NULL) {
            PyErr_NoMemory();
            return NULL;
        }
        buflen = OBJ_obj2txt(namebuf, buflen + 1, name, no_name);
        if (buflen < 0) {
            _setSSLError(state, NULL, 0, __FILE__, __LINE__);
            goto done;
        }
    }
    if (!buflen && no_name) {
        name_obj = Py_NewRef(Py_None);
    }
    else {
        name_obj = PyUnicode_FromStringAndSize(namebuf, buflen);
    }

  done:
    if (buf != namebuf) {
        PyMem_Free(namebuf);
    }
    return name_obj;
}

static PyObject *
_create_tuple_for_attribute(_sslmodulestate *state,
                            const ASN1_OBJECT *name, const ASN1_STRING *value)
{
    Py_ssize_t buflen;
    PyObject *pyattr;
    PyObject *pyname = _asn1obj2py(state, name, 0);

    if (pyname == NULL) {
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        return NULL;
    }

    if (ASN1_STRING_type(value) == V_ASN1_BIT_STRING) {
        buflen = ASN1_STRING_length(value);
        pyattr = Py_BuildValue("Ny#", pyname, ASN1_STRING_get0_data(value), buflen);
    } else {
        unsigned char *valuebuf = NULL;
        buflen = ASN1_STRING_to_UTF8(&valuebuf, value);
        if (buflen < 0) {
            _setSSLError(state, NULL, 0, __FILE__, __LINE__);
            Py_DECREF(pyname);
            return NULL;
        }
        pyattr = Py_BuildValue("Ns#", pyname, valuebuf, buflen);
        OPENSSL_free(valuebuf);
    }
    return pyattr;
}

static PyObject *
_create_tuple_for_X509_NAME(_sslmodulestate *state, const X509_NAME *xname)
{
    PyObject *dn = NULL;    /* tuple which represents the "distinguished name" */
    PyObject *rdn = NULL;   /* tuple to hold a "relative distinguished name" */
    PyObject *rdnt;
    PyObject *attr = NULL;   /* tuple to hold an attribute */
    int entry_count = X509_NAME_entry_count(xname);
    const X509_NAME_ENTRY *entry;
    const ASN1_OBJECT *name;
    const ASN1_STRING *value;
    int index_counter;
    int rdn_level = -1;
    int retcode;

    dn = PyList_New(0);
    if (dn == NULL)
        return NULL;
    /* now create another tuple to hold the top-level RDN */
    rdn = PyList_New(0);
    if (rdn == NULL)
        goto fail0;

    for (index_counter = 0;
         index_counter < entry_count;
         index_counter++)
    {
        entry = X509_NAME_get_entry(xname, index_counter);

        /* check to see if we've gotten to a new RDN */
        if (rdn_level >= 0) {
            if (rdn_level != X509_NAME_ENTRY_set(entry)) {
                /* yes, new RDN */
                /* add old RDN to DN */
                rdnt = PyList_AsTuple(rdn);
                Py_DECREF(rdn);
                if (rdnt == NULL)
                    goto fail0;
                retcode = PyList_Append(dn, rdnt);
                Py_DECREF(rdnt);
                if (retcode < 0)
                    goto fail0;
                /* create new RDN */
                rdn = PyList_New(0);
                if (rdn == NULL)
                    goto fail0;
            }
        }
        rdn_level = X509_NAME_ENTRY_set(entry);

        /* now add this attribute to the current RDN */
        name = X509_NAME_ENTRY_get_object(entry);
        value = X509_NAME_ENTRY_get_data(entry);
        attr = _create_tuple_for_attribute(state, name, value);
        /*
        fprintf(stderr, "RDN level %d, attribute %s: %s\n",
            entry->set,
            PyBytes_AS_STRING(PyTuple_GET_ITEM(attr, 0)),
            PyBytes_AS_STRING(PyTuple_GET_ITEM(attr, 1)));
        */
        if (attr == NULL)
            goto fail1;
        retcode = PyList_Append(rdn, attr);
        Py_DECREF(attr);
        if (retcode < 0)
            goto fail1;
    }
    /* now, there's typically a dangling RDN */
    if (rdn != NULL) {
        if (PyList_GET_SIZE(rdn) > 0) {
            rdnt = PyList_AsTuple(rdn);
            Py_DECREF(rdn);
            if (rdnt == NULL)
                goto fail0;
            retcode = PyList_Append(dn, rdnt);
            Py_DECREF(rdnt);
            if (retcode < 0)
                goto fail0;
        }
        else {
            Py_DECREF(rdn);
        }
    }

    /* convert list to tuple */
    rdnt = PyList_AsTuple(dn);
    Py_DECREF(dn);
    if (rdnt == NULL)
        return NULL;
    return rdnt;

  fail1:
    Py_XDECREF(rdn);

  fail0:
    Py_XDECREF(dn);
    return NULL;
}

static PyObject *
_get_peer_alt_names (_sslmodulestate *state, X509 *certificate) {

    /* this code follows the procedure outlined in
       OpenSSL's crypto/x509v3/v3_prn.c:X509v3_EXT_print()
       function to extract the STACK_OF(GENERAL_NAME),
       then iterates through the stack to add the
       names. */

    int j;
    PyObject *peer_alt_names = Py_None;
    PyObject *v = NULL, *t;
    GENERAL_NAMES *names = NULL;
    GENERAL_NAME *name;
    BIO *biobuf = NULL;
    char buf[2048];
    char *vptr;
    int len;

    if (certificate == NULL)
        return peer_alt_names;

    /* get a memory buffer */
    biobuf = BIO_new(BIO_s_mem());
    if (biobuf == NULL) {
        PyErr_SetString(state->PySSLErrorObject, "failed to allocate BIO");
        return NULL;
    }

    names = (GENERAL_NAMES *)X509_get_ext_d2i(
        certificate, NID_subject_alt_name, NULL, NULL);
    if (names != NULL) {
        if (peer_alt_names == Py_None) {
            peer_alt_names = PyList_New(0);
            if (peer_alt_names == NULL)
                goto fail;
        }

        for(j = 0; j < sk_GENERAL_NAME_num(names); j++) {
            /* get a rendering of each name in the set of names */
            int gntype;
            ASN1_STRING *as = NULL;

            name = sk_GENERAL_NAME_value(names, j);
            gntype = name->type;
            switch (gntype) {
            case GEN_DIRNAME:
                /* we special-case DirName as a tuple of
                   tuples of attributes */

                t = PyTuple_New(2);
                if (t == NULL) {
                    goto fail;
                }

                v = PyUnicode_FromString("DirName");
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 0, v);

                v = _create_tuple_for_X509_NAME(state, name->d.dirn);
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 1, v);
                break;

            case GEN_EMAIL:
            case GEN_DNS:
            case GEN_URI:
                /* GENERAL_NAME_print() doesn't handle NULL bytes in ASN1_string
                   correctly, CVE-2013-4238 */
                t = PyTuple_New(2);
                if (t == NULL)
                    goto fail;
                switch (gntype) {
                case GEN_EMAIL:
                    v = PyUnicode_FromString("email");
                    as = name->d.rfc822Name;
                    break;
                case GEN_DNS:
                    v = PyUnicode_FromString("DNS");
                    as = name->d.dNSName;
                    break;
                case GEN_URI:
                    v = PyUnicode_FromString("URI");
                    as = name->d.uniformResourceIdentifier;
                    break;
                }
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 0, v);
                v = PyUnicode_FromStringAndSize((char *)ASN1_STRING_get0_data(as),
                                                ASN1_STRING_length(as));
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 1, v);
                break;

            case GEN_RID:
                t = PyTuple_New(2);
                if (t == NULL)
                    goto fail;

                v = PyUnicode_FromString("Registered ID");
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 0, v);

                len = i2t_ASN1_OBJECT(buf, sizeof(buf)-1, name->d.rid);
                if (len < 0) {
                    Py_DECREF(t);
                    _setSSLError(state, NULL, 0, __FILE__, __LINE__);
                    goto fail;
                } else if (len >= (int)sizeof(buf)) {
                    v = PyUnicode_FromString("<INVALID>");
                } else {
                    v = PyUnicode_FromStringAndSize(buf, len);
                }
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 1, v);
                break;

            case GEN_IPADD:
                /* OpenSSL < 3.0.0 adds a trailing \n to IPv6. 3.0.0 removed
                 * the trailing newline. Remove it in all versions
                 */
                t = PyTuple_New(2);
                if (t == NULL)
                    goto fail;

                v = PyUnicode_FromString("IP Address");
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 0, v);

                if (ASN1_STRING_length(name->d.ip) == 4) {
                    const unsigned char *p = ASN1_STRING_get0_data(name->d.ip);
                    v = PyUnicode_FromFormat(
                        "%d.%d.%d.%d",
                        p[0], p[1], p[2], p[3]
                    );
                } else if (ASN1_STRING_length(name->d.ip) == 16) {
                    const unsigned char *p = ASN1_STRING_get0_data(name->d.ip);
                    v = PyUnicode_FromFormat(
                        "%X:%X:%X:%X:%X:%X:%X:%X",
                        p[0] << 8 | p[1],
                        p[2] << 8 | p[3],
                        p[4] << 8 | p[5],
                        p[6] << 8 | p[7],
                        p[8] << 8 | p[9],
                        p[10] << 8 | p[11],
                        p[12] << 8 | p[13],
                        p[14] << 8 | p[15]
                    );
                } else {
                    v = PyUnicode_FromString("<invalid>");
                }

                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 1, v);
                break;

            default:
                /* for everything else, we use the OpenSSL print form */
                switch (gntype) {
                    /* check for new general name type */
                    case GEN_OTHERNAME:
                    case GEN_X400:
                    case GEN_EDIPARTY:
                    case GEN_RID:
                        break;
                    default:
                        if (PyErr_WarnFormat(PyExc_RuntimeWarning, 1,
                                             "Unknown general name type %d",
                                             gntype) == -1) {
                            goto fail;
                        }
                        break;
                }
                (void) BIO_reset(biobuf);
                GENERAL_NAME_print(biobuf, name);
                len = BIO_gets(biobuf, buf, sizeof(buf)-1);
                if (len < 0) {
                    _setSSLError(state, NULL, 0, __FILE__, __LINE__);
                    goto fail;
                }
                vptr = strchr(buf, ':');
                if (vptr == NULL) {
                    PyErr_Format(PyExc_ValueError,
                                 "Invalid value %.200s",
                                 buf);
                    goto fail;
                }
                t = PyTuple_New(2);
                if (t == NULL)
                    goto fail;
                v = PyUnicode_FromStringAndSize(buf, (vptr - buf));
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 0, v);
                v = PyUnicode_FromStringAndSize((vptr + 1),
                                                (len - (vptr - buf + 1)));
                if (v == NULL) {
                    Py_DECREF(t);
                    goto fail;
                }
                PyTuple_SET_ITEM(t, 1, v);
                break;
            }

            /* and add that rendering to the list */

            if (PyList_Append(peer_alt_names, t) < 0) {
                Py_DECREF(t);
                goto fail;
            }
            Py_DECREF(t);
        }
        sk_GENERAL_NAME_pop_free(names, GENERAL_NAME_free);
    }
    BIO_free(biobuf);
    if (peer_alt_names != Py_None) {
        v = PyList_AsTuple(peer_alt_names);
        Py_DECREF(peer_alt_names);
        return v;
    } else {
        return peer_alt_names;
    }


  fail:
    if (biobuf != NULL)
        BIO_free(biobuf);

    if (peer_alt_names != Py_None) {
        Py_XDECREF(peer_alt_names);
    }

    return NULL;
}

static PyObject *
_get_aia_uri(X509 *certificate, int nid) {
    PyObject *lst = NULL, *ostr = NULL;
    int i, result;
    AUTHORITY_INFO_ACCESS *info;

    info = X509_get_ext_d2i(certificate, NID_info_access, NULL, NULL);
    if (info == NULL)
        return Py_None;
    if (sk_ACCESS_DESCRIPTION_num(info) == 0) {
        AUTHORITY_INFO_ACCESS_free(info);
        return Py_None;
    }

    if ((lst = PyList_New(0)) == NULL) {
        goto fail;
    }

    for (i = 0; i < sk_ACCESS_DESCRIPTION_num(info); i++) {
        ACCESS_DESCRIPTION *ad = sk_ACCESS_DESCRIPTION_value(info, i);
        ASN1_IA5STRING *uri;

        if ((OBJ_obj2nid(ad->method) != nid) ||
                (ad->location->type != GEN_URI)) {
            continue;
        }
        uri = ad->location->d.uniformResourceIdentifier;
        ostr = PyUnicode_FromStringAndSize(
                   (const char *)ASN1_STRING_get0_data(uri),
                   ASN1_STRING_length(uri));
        if (ostr == NULL) {
            goto fail;
        }
        result = PyList_Append(lst, ostr);
        Py_DECREF(ostr);
        if (result < 0) {
            goto fail;
        }
    }
    AUTHORITY_INFO_ACCESS_free(info);

    /* convert to tuple or None */
    if (PyList_Size(lst) == 0) {
        Py_DECREF(lst);
        return Py_None;
    } else {
        PyObject *tup;
        tup = PyList_AsTuple(lst);
        Py_DECREF(lst);
        return tup;
    }

  fail:
    AUTHORITY_INFO_ACCESS_free(info);
    Py_XDECREF(lst);
    return NULL;
}

static PyObject *
_get_crl_dp(X509 *certificate) {
    STACK_OF(DIST_POINT) *dps;
    int i, j;
    PyObject *lst, *res = NULL;

    dps = X509_get_ext_d2i(certificate, NID_crl_distribution_points, NULL, NULL);

    if (dps == NULL)
        return Py_None;

    lst = PyList_New(0);
    if (lst == NULL)
        goto done;

    for (i=0; i < sk_DIST_POINT_num(dps); i++) {
        DIST_POINT *dp;
        STACK_OF(GENERAL_NAME) *gns;

        dp = sk_DIST_POINT_value(dps, i);
        if (dp->distpoint == NULL) {
            /* Ignore empty DP value, CVE-2019-5010 */
            continue;
        }
        gns = dp->distpoint->name.fullname;

        for (j=0; j < sk_GENERAL_NAME_num(gns); j++) {
            GENERAL_NAME *gn;
            ASN1_IA5STRING *uri;
            PyObject *ouri;
            int err;

            gn = sk_GENERAL_NAME_value(gns, j);
            if (gn->type != GEN_URI) {
                continue;
            }
            uri = gn->d.uniformResourceIdentifier;
            ouri = PyUnicode_FromStringAndSize(
                       (const char *)ASN1_STRING_get0_data(uri),
                       ASN1_STRING_length(uri));
            if (ouri == NULL)
                goto done;

            err = PyList_Append(lst, ouri);
            Py_DECREF(ouri);
            if (err < 0)
                goto done;
        }
    }

    /* Convert to tuple. */
    res = (PyList_GET_SIZE(lst) > 0) ? PyList_AsTuple(lst) : Py_None;

  done:
    Py_XDECREF(lst);
    CRL_DIST_POINTS_free(dps);
    return res;
}

static PyObject *
_decode_certificate(_sslmodulestate *state, X509 *certificate) {

    PyObject *retval = NULL;
    BIO *biobuf = NULL;
    PyObject *peer;
    PyObject *peer_alt_names = NULL;
    PyObject *issuer;
    PyObject *version;
    PyObject *sn_obj;
    PyObject *obj;
    ASN1_INTEGER *serialNumber;
    char buf[2048];
    int len, result;
    const ASN1_TIME *notBefore, *notAfter;
    PyObject *pnotBefore, *pnotAfter;

    retval = PyDict_New();
    if (retval == NULL)
        return NULL;

    peer = _create_tuple_for_X509_NAME(
        state,
        X509_get_subject_name(certificate));
    if (peer == NULL)
        goto fail0;
    if (PyDict_SetItemString(retval, (const char *) "subject", peer) < 0) {
        Py_DECREF(peer);
        goto fail0;
    }
    Py_DECREF(peer);

    issuer = _create_tuple_for_X509_NAME(
        state,
        X509_get_issuer_name(certificate));
    if (issuer == NULL)
        goto fail0;
    if (PyDict_SetItemString(retval, (const char *)"issuer", issuer) < 0) {
        Py_DECREF(issuer);
        goto fail0;
    }
    Py_DECREF(issuer);

    version = PyLong_FromLong(X509_get_version(certificate) + 1);
    if (version == NULL)
        goto fail0;
    if (PyDict_SetItemString(retval, "version", version) < 0) {
        Py_DECREF(version);
        goto fail0;
    }
    Py_DECREF(version);

    /* get a memory buffer */
    biobuf = BIO_new(BIO_s_mem());
    if (biobuf == NULL) {
        PyErr_SetString(state->PySSLErrorObject, "failed to allocate BIO");
        goto fail0;
    }

    (void) BIO_reset(biobuf);
    serialNumber = X509_get_serialNumber(certificate);
    /* should not exceed 20 octets, 160 bits, so buf is big enough */
    i2a_ASN1_INTEGER(biobuf, serialNumber);
    len = BIO_gets(biobuf, buf, sizeof(buf)-1);
    if (len < 0) {
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        goto fail1;
    }
    sn_obj = PyUnicode_FromStringAndSize(buf, len);
    if (sn_obj == NULL)
        goto fail1;
    if (PyDict_SetItemString(retval, "serialNumber", sn_obj) < 0) {
        Py_DECREF(sn_obj);
        goto fail1;
    }
    Py_DECREF(sn_obj);

    (void) BIO_reset(biobuf);
    notBefore = X509_get0_notBefore(certificate);
    ASN1_TIME_print(biobuf, notBefore);
    len = BIO_gets(biobuf, buf, sizeof(buf)-1);
    if (len < 0) {
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        goto fail1;
    }
    pnotBefore = PyUnicode_FromStringAndSize(buf, len);
    if (pnotBefore == NULL)
        goto fail1;
    if (PyDict_SetItemString(retval, "notBefore", pnotBefore) < 0) {
        Py_DECREF(pnotBefore);
        goto fail1;
    }
    Py_DECREF(pnotBefore);

    (void) BIO_reset(biobuf);
    notAfter = X509_get0_notAfter(certificate);
    ASN1_TIME_print(biobuf, notAfter);
    len = BIO_gets(biobuf, buf, sizeof(buf)-1);
    if (len < 0) {
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        goto fail1;
    }
    pnotAfter = PyUnicode_FromStringAndSize(buf, len);
    if (pnotAfter == NULL)
        goto fail1;
    if (PyDict_SetItemString(retval, "notAfter", pnotAfter) < 0) {
        Py_DECREF(pnotAfter);
        goto fail1;
    }
    Py_DECREF(pnotAfter);

    /* Now look for subjectAltName */

    peer_alt_names = _get_peer_alt_names(state, certificate);
    if (peer_alt_names == NULL)
        goto fail1;
    else if (peer_alt_names != Py_None) {
        if (PyDict_SetItemString(retval, "subjectAltName",
                                 peer_alt_names) < 0) {
            Py_DECREF(peer_alt_names);
            goto fail1;
        }
        Py_DECREF(peer_alt_names);
    }

    /* Authority Information Access: OCSP URIs */
    obj = _get_aia_uri(certificate, NID_ad_OCSP);
    if (obj == NULL) {
        goto fail1;
    } else if (obj != Py_None) {
        result = PyDict_SetItemString(retval, "OCSP", obj);
        Py_DECREF(obj);
        if (result < 0) {
            goto fail1;
        }
    }

    obj = _get_aia_uri(certificate, NID_ad_ca_issuers);
    if (obj == NULL) {
        goto fail1;
    } else if (obj != Py_None) {
        result = PyDict_SetItemString(retval, "caIssuers", obj);
        Py_DECREF(obj);
        if (result < 0) {
            goto fail1;
        }
    }

    /* CDP (CRL distribution points) */
    obj = _get_crl_dp(certificate);
    if (obj == NULL) {
        goto fail1;
    } else if (obj != Py_None) {
        result = PyDict_SetItemString(retval, "crlDistributionPoints", obj);
        Py_DECREF(obj);
        if (result < 0) {
            goto fail1;
        }
    }

    BIO_free(biobuf);
    return retval;

  fail1:
    if (biobuf != NULL)
        BIO_free(biobuf);
  fail0:
    Py_XDECREF(retval);
    return NULL;
}

static PyObject *
_certificate_to_der(_sslmodulestate *state, X509 *certificate)
{
    unsigned char *bytes_buf = NULL;
    int len;
    PyObject *retval;

    bytes_buf = NULL;
    len = i2d_X509(certificate, &bytes_buf);
    if (len < 0) {
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        return NULL;
    }
    /* this is actually an immutable bytes sequence */
    retval = PyBytes_FromStringAndSize((const char *) bytes_buf, len);
    OPENSSL_free(bytes_buf);
    return retval;
}

#include "_ssl/misc.c"
#include "_ssl/cert.c"

/*[clinic input]
_ssl._test_decode_cert
    path: unicode_fs_encoded
    /

[clinic start generated code]*/

static PyObject *
_ssl__test_decode_cert_impl(PyObject *module, PyObject *path)
/*[clinic end generated code: output=96becb9abb23c091 input=cb4988d5e651a4f8]*/
{
    PyObject *retval = NULL;
    X509 *x=NULL;
    BIO *cert;
    _sslmodulestate *state = get_ssl_state(module);

    if ((cert=BIO_new(BIO_s_file())) == NULL) {
        PyErr_SetString(state->PySSLErrorObject,
                        "Can't malloc memory to read file");
        goto fail0;
    }

    if (BIO_read_filename(cert, PyBytes_AsString(path)) <= 0) {
        PyErr_SetString(state->PySSLErrorObject,
                        "Can't open file");
        goto fail0;
    }

    x = PEM_read_bio_X509(cert, NULL, NULL, NULL);
    if (x == NULL) {
        PyErr_SetString(state->PySSLErrorObject,
                        "Error decoding PEM-encoded file");
        goto fail0;
    }

    retval = _decode_certificate(state, x);
    X509_free(x);

  fail0:
    if (cert != NULL) BIO_free(cert);
    return retval;
}


/*[clinic input]
@critical_section
_ssl._SSLSocket.getpeercert
    der as binary_mode: bool = False
    /

Returns the certificate for the peer.

If no certificate was provided, returns None.  If a certificate was
provided, but not validated, returns an empty dictionary.  Otherwise
returns a dict containing information about the peer certificate.

If the optional argument is True, returns a DER-encoded copy of the
peer certificate, or None if no certificate was provided.  This will
return the certificate even if it wasn't validated.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_getpeercert_impl(PySSLSocket *self, int binary_mode)
/*[clinic end generated code: output=1f0ab66dfb693c88 input=e35af55fa5f9bab8]*/
{
    int verification;
    X509 *peer_cert;
    PyObject *result;

    if (!SSL_is_init_finished(self->ssl)) {
        PyErr_SetString(PyExc_ValueError,
                        "handshake not done yet");
        return NULL;
    }
    peer_cert = SSL_get_peer_certificate(self->ssl);
    if (peer_cert == NULL)
        Py_RETURN_NONE;

    if (binary_mode) {
        /* return cert in DER-encoded format */
        result = _certificate_to_der(get_state_sock(self), peer_cert);
    } else {
        verification = SSL_CTX_get_verify_mode(SSL_get_SSL_CTX(self->ssl));
        if ((verification & SSL_VERIFY_PEER) == 0)
            result = PyDict_New();
        else
            result = _decode_certificate(get_state_sock(self), peer_cert);
    }
    X509_free(peer_cert);
    return result;
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.get_verified_chain

[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_get_verified_chain_impl(PySSLSocket *self)
/*[clinic end generated code: output=802421163cdc3110 input=83035fe238ec057b]*/
{
    /* borrowed reference */
    STACK_OF(X509) *chain = SSL_get0_verified_chain(self->ssl);
    if (chain == NULL) {
        Py_RETURN_NONE;
    }
    return _PySSL_CertificateFromX509Stack(self->ctx->state, chain, 1);
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.get_unverified_chain

[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_get_unverified_chain_impl(PySSLSocket *self)
/*[clinic end generated code: output=5acdae414e13f913 input=079f8ff5c205cb3b]*/
{
    PyObject *retval;
    /* borrowed reference */
    /* TODO: include SSL_get_peer_certificate() for server-side sockets */
    STACK_OF(X509) *chain = SSL_get_peer_cert_chain(self->ssl);
    if (chain == NULL) {
        Py_RETURN_NONE;
    }
    retval = _PySSL_CertificateFromX509Stack(self->ctx->state, chain, 1);
    if (retval == NULL) {
        return NULL;
    }
    /* OpenSSL does not include peer cert for server side connections */
    if (self->socket_type == PY_SSL_SERVER) {
        PyObject *peerobj = NULL;
        X509 *peer = SSL_get_peer_certificate(self->ssl);

        if (peer == NULL) {
            peerobj = Py_NewRef(Py_None);
        } else {
            /* consume X509 reference on success */
            peerobj = _PySSL_CertificateFromX509(self->ctx->state, peer, 0);
            if (peerobj == NULL) {
                X509_free(peer);
                Py_DECREF(retval);
                return NULL;
            }
        }
        int res = PyList_Insert(retval, 0, peerobj);
        Py_DECREF(peerobj);
        if (res < 0) {
            Py_DECREF(retval);
            return NULL;
        }
    }
    return retval;
}

static PyObject *
cipher_to_tuple(const SSL_CIPHER *cipher)
{
    const char *cipher_name, *cipher_protocol;
    PyObject *v, *retval = PyTuple_New(3);
    if (retval == NULL)
        return NULL;

    cipher_name = SSL_CIPHER_get_name(cipher);
    if (cipher_name == NULL) {
        PyTuple_SET_ITEM(retval, 0, Py_NewRef(Py_None));
    } else {
        v = PyUnicode_FromString(cipher_name);
        if (v == NULL)
            goto fail;
        PyTuple_SET_ITEM(retval, 0, v);
    }

    cipher_protocol = SSL_CIPHER_get_version(cipher);
    if (cipher_protocol == NULL) {
        PyTuple_SET_ITEM(retval, 1, Py_NewRef(Py_None));
    } else {
        v = PyUnicode_FromString(cipher_protocol);
        if (v == NULL)
            goto fail;
        PyTuple_SET_ITEM(retval, 1, v);
    }

    v = PyLong_FromLong(SSL_CIPHER_get_bits(cipher, NULL));
    if (v == NULL)
        goto fail;
    PyTuple_SET_ITEM(retval, 2, v);

    return retval;

  fail:
    Py_DECREF(retval);
    return NULL;
}

static PyObject *
cipher_to_dict(const SSL_CIPHER *cipher)
{
    const char *cipher_name, *cipher_protocol;

    unsigned long cipher_id;
    int alg_bits, strength_bits, len;
    char buf[512] = {0};
    int aead, nid;
    const char *skcipher = NULL, *digest = NULL, *kx = NULL, *auth = NULL;

    /* can be NULL */
    cipher_name = SSL_CIPHER_get_name(cipher);
    cipher_protocol = SSL_CIPHER_get_version(cipher);
    cipher_id = SSL_CIPHER_get_id(cipher);
    SSL_CIPHER_description(cipher, buf, sizeof(buf) - 1);
    /* Downcast to avoid a warning. Safe since buf is always 512 bytes */
    len = (int)strlen(buf);
    if (len > 1 && buf[len-1] == '\n')
        buf[len-1] = '\0';
    strength_bits = SSL_CIPHER_get_bits(cipher, &alg_bits);

    aead = SSL_CIPHER_is_aead(cipher);
    nid = SSL_CIPHER_get_cipher_nid(cipher);
    skcipher = nid != NID_undef ? OBJ_nid2ln(nid) : NULL;
    nid = SSL_CIPHER_get_digest_nid(cipher);
    digest = nid != NID_undef ? OBJ_nid2ln(nid) : NULL;
    nid = SSL_CIPHER_get_kx_nid(cipher);
    kx = nid != NID_undef ? OBJ_nid2ln(nid) : NULL;
    nid = SSL_CIPHER_get_auth_nid(cipher);
    auth = nid != NID_undef ? OBJ_nid2ln(nid) : NULL;

    return Py_BuildValue(
        "{sksssssssisi"
        "sOssssssss"
        "}",
        "id", cipher_id,
        "name", cipher_name,
        "protocol", cipher_protocol,
        "description", buf,
        "strength_bits", strength_bits,
        "alg_bits", alg_bits
        ,"aead", aead ? Py_True : Py_False,
        "symmetric", skcipher,
        "digest", digest,
        "kea", kx,
        "auth", auth
       );
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.shared_ciphers
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_shared_ciphers_impl(PySSLSocket *self)
/*[clinic end generated code: output=3d174ead2e42c4fd input=869645271e3bc6d0]*/
{
    STACK_OF(SSL_CIPHER) *server_ciphers;
    STACK_OF(SSL_CIPHER) *client_ciphers;
    int i, len;
    PyObject *res;
    const SSL_CIPHER* cipher;

    /* Rather than use SSL_get_shared_ciphers, we use an equivalent algorithm because:

       1) It returns a colon separated list of strings, in an undefined
          order, that we would have to post process back into tuples.
       2) It will return a truncated string with no indication that it has
          done so, if the buffer is too small.
     */

    server_ciphers = SSL_get_ciphers(self->ssl);
    if (!server_ciphers)
        Py_RETURN_NONE;
    client_ciphers = SSL_get_client_ciphers(self->ssl);
    if (!client_ciphers)
        Py_RETURN_NONE;

    res = PyList_New(sk_SSL_CIPHER_num(server_ciphers));
    if (!res)
        return NULL;
    len = 0;
    for (i = 0; i < sk_SSL_CIPHER_num(server_ciphers); i++) {
        cipher = sk_SSL_CIPHER_value(server_ciphers, i);
        if (sk_SSL_CIPHER_find(client_ciphers, cipher) < 0)
            continue;

        PyObject *tup = cipher_to_tuple(cipher);
        if (!tup) {
            Py_DECREF(res);
            return NULL;
        }
        PyList_SET_ITEM(res, len++, tup);
    }
    Py_SET_SIZE(res, len);
    return res;
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.cipher
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_cipher_impl(PySSLSocket *self)
/*[clinic end generated code: output=376417c16d0e5815 input=39e180269a36f486]*/
{
    const SSL_CIPHER *current;

    if (self->ssl == NULL)
        Py_RETURN_NONE;
    current = SSL_get_current_cipher(self->ssl);
    if (current == NULL)
        Py_RETURN_NONE;
    return cipher_to_tuple(current);
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.group
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_group_impl(PySSLSocket *self)
/*[clinic end generated code: output=9c168ee877017b95 input=5f187d8bf0d433b7]*/
{
#if OPENSSL_VERSION_NUMBER >= 0x30200000L
    const char *group_name;

    if (self->ssl == NULL) {
        Py_RETURN_NONE;
    }
    group_name = SSL_get0_group_name(self->ssl);
    if (group_name == NULL) {
        Py_RETURN_NONE;
    }
    return PyUnicode_DecodeFSDefault(group_name);
#else
    PyErr_SetString(PyExc_NotImplementedError,
                    "Getting selected group requires OpenSSL 3.2 or later.");
    return NULL;
#endif
}

static PyObject *
ssl_socket_signame_impl(PySSLSocket *socket,
                        enum py_ssl_server_or_client self_socket_type)
{
#if OPENSSL_VERSION_NUMBER >= 0x30500000L
    int ret;
    const char *sigalg;

    if (socket->ssl == NULL) {
        Py_RETURN_NONE;
    }
    ret = (socket->socket_type == self_socket_type)
        ? SSL_get0_signature_name(socket->ssl, &sigalg)
        : SSL_get0_peer_signature_name(socket->ssl, &sigalg);
    if (ret == 0) {
        Py_RETURN_NONE;
    }
    assert(sigalg != NULL);
    return PyUnicode_DecodeFSDefault(sigalg);
#else
    PyErr_SetString(PyExc_NotImplementedError,
                    "Getting sig algorithms requires OpenSSL 3.5 or later.");
    return NULL;
#endif
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.client_sigalg
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_client_sigalg_impl(PySSLSocket *self)
/*[clinic end generated code: output=499dd7fbf021a47b input=a0d9696b5414c627]*/
{
    return ssl_socket_signame_impl(self, PY_SSL_CLIENT);
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.server_sigalg
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_server_sigalg_impl(PySSLSocket *self)
/*[clinic end generated code: output=c508a766a8e275dc input=9063e562a1e6b946]*/
{
    return ssl_socket_signame_impl(self, PY_SSL_SERVER);
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.version
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_version_impl(PySSLSocket *self)
/*[clinic end generated code: output=178aed33193b2cdb input=2732bc3f7f597d09]*/
{
    const char *version;

    if (self->ssl == NULL)
        Py_RETURN_NONE;
    if (!SSL_is_init_finished(self->ssl)) {
        /* handshake not finished */
        Py_RETURN_NONE;
    }
    version = SSL_get_version(self->ssl);
    if (!strcmp(version, "unknown"))
        Py_RETURN_NONE;
    return PyUnicode_FromString(version);
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.selected_alpn_protocol
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_selected_alpn_protocol_impl(PySSLSocket *self)
/*[clinic end generated code: output=ec33688b303d250f input=f0b53506c9acdf8c]*/
{
    const unsigned char *out;
    unsigned int outlen;

    SSL_get0_alpn_selected(self->ssl, &out, &outlen);

    if (out == NULL)
        Py_RETURN_NONE;
    return PyUnicode_FromStringAndSize((char *)out, outlen);
}

/*[clinic input]
_ssl._SSLSocket.compression
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_compression_impl(PySSLSocket *self)
/*[clinic end generated code: output=bd16cb1bb4646ae7 input=5d059d0a2bbc32c8]*/
{
#ifdef OPENSSL_NO_COMP
    Py_RETURN_NONE;
#else
    const COMP_METHOD *comp_method;
    const char *short_name;

    if (self->ssl == NULL)
        Py_RETURN_NONE;
    comp_method = SSL_get_current_compression(self->ssl);
    if (comp_method == NULL || COMP_get_type(comp_method) == NID_undef)
        Py_RETURN_NONE;
    short_name = OBJ_nid2sn(COMP_get_type(comp_method));
    if (short_name == NULL)
        Py_RETURN_NONE;
    return PyUnicode_DecodeFSDefault(short_name);
#endif
}

/*[clinic input]
@permit_long_docstring_body
@critical_section
@getter
_ssl._SSLSocket.context

This changes the context associated with the SSLSocket.

This is typically used from within a callback function set by the sni_callback
on the SSLContext to change the certificate information associated with the
SSLSocket before the cryptographic exchange handshake messages.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_context_get_impl(PySSLSocket *self)
/*[clinic end generated code: output=d23e82f72f32e3d7 input=0cc8e773a079295e]*/
{
    return Py_NewRef(self->ctx);
}

/*[clinic input]
@permit_long_docstring_body
@critical_section
@setter
_ssl._SSLSocket.context
[clinic start generated code]*/

static int
_ssl__SSLSocket_context_set_impl(PySSLSocket *self, PyObject *value)
/*[clinic end generated code: output=6b0a6cc5cf33d9fe input=f7fc1674b660df96]*/
{
    if (PyObject_TypeCheck(value, self->ctx->state->PySSLContext_Type)) {
        Py_SETREF(self->ctx, (PySSLContext *)Py_NewRef(value));
        SSL_set_SSL_CTX(self->ssl, self->ctx->ctx);
        /* Set SSL* internal msg_callback to state of new context's state */
        SSL_set_msg_callback(
            self->ssl,
            self->ctx->msg_cb ? _PySSL_msg_callback : NULL
        );
    } else {
        PyErr_SetString(PyExc_TypeError, "The value must be a SSLContext");
        return -1;
    }

    return 0;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLSocket.server_side

Whether this is a server-side socket.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_server_side_get_impl(PySSLSocket *self)
/*[clinic end generated code: output=ae51e372489148e3 input=b09b320510bc7cae]*/
{
    return PyBool_FromLong(self->socket_type == PY_SSL_SERVER);
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLSocket.server_hostname

The currently set server hostname (for SNI).
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_server_hostname_get_impl(PySSLSocket *self)
/*[clinic end generated code: output=1f40ea5a076de8e7 input=55d12a1dc6634b08]*/
{
    if (self->server_hostname == NULL)
        Py_RETURN_NONE;
    return Py_NewRef(self->server_hostname);
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLSocket.owner

The Python-level owner of this object.

Passed as "self" in servername callback.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_owner_get_impl(PySSLSocket *self)
/*[clinic end generated code: output=1f278cb930382927 input=978a8382d9c25c92]*/
{
    if (self->owner == NULL) {
        Py_RETURN_NONE;
    }
    PyObject *owner;
    if (!PyWeakref_GetRef(self->owner, &owner)) {
        Py_RETURN_NONE;
    }
    return owner;
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLSocket.owner
[clinic start generated code]*/

static int
_ssl__SSLSocket_owner_set_impl(PySSLSocket *self, PyObject *value)
/*[clinic end generated code: output=2e3924498f2b6cde input=875666fd32367a73]*/
{
    Py_XSETREF(self->owner, PyWeakref_NewRef(value, NULL));
    if (self->owner == NULL)
        return -1;
    return 0;
}

static int
PySSL_traverse(PyObject *op, visitproc visit, void *arg)
{
    Py_VISIT(Py_TYPE(op));
    return 0;
}

static int
PySSL_clear(PyObject *op)
{
    PySSLSocket *self = PySSLSocket_CAST(op);
    Py_CLEAR(self->Socket);
    Py_CLEAR(self->ctx);
    Py_CLEAR(self->owner);
    Py_CLEAR(self->server_hostname);
    return 0;
}

static void
PySSL_dealloc(PyObject *op)
{
    PySSLSocket *self = PySSLSocket_CAST(op);
    PyTypeObject *tp = Py_TYPE(self);
    PyObject_GC_UnTrack(self);
    if (self->ssl) {
        // If we free the SSL socket object without having called SSL_shutdown,
        // OpenSSL will invalidate the linked SSL session object. While this
        // behavior is strictly RFC-compliant, it makes session reuse less
        // likely and it would also break compatibility with older stdlib
        // versions (which used an ugly workaround of duplicating the
        // SSL_SESSION object).
        // Therefore, we ensure the socket is marked as shutdown in any case.
        //
        // See elaborate explanation at
        // https://github.com/python/cpython/pull/123249#discussion_r1766164530
        SSL_set_shutdown(self->ssl, SSL_SENT_SHUTDOWN | SSL_get_shutdown(self->ssl));
        SSL_free(self->ssl);
    }
    (void)PySSL_clear(op);
    PyObject_GC_Del(self);
    Py_DECREF(tp);
}

/* If the socket has a timeout, do a select()/poll() on the socket.
   The argument writing indicates the direction.
   Returns one of the possibilities in the timeout_state enum (above).
 */

static int
PySSL_select(PySocketSockObject *s, int writing, PyTime_t timeout)
{
    int rc;
#ifdef HAVE_POLL
    struct pollfd pollfd;
    PyTime_t ms;
#else
    int nfds;
    fd_set fds;
    struct timeval tv;
#endif

    /* Nothing to do unless we're in timeout mode (not non-blocking) */
    if ((s == NULL) || (timeout == 0))
        return SOCKET_IS_NONBLOCKING;
    else if (timeout < 0) {
        if (s->sock_timeout > 0)
            return SOCKET_HAS_TIMED_OUT;
        else
            return SOCKET_IS_BLOCKING;
    }

    /* Guard against closed socket */
    if (s->sock_fd == INVALID_SOCKET)
        return SOCKET_HAS_BEEN_CLOSED;

    /* Prefer poll, if available, since you can poll() any fd
     * which can't be done with select(). */
#ifdef HAVE_POLL
    pollfd.fd = s->sock_fd;
    pollfd.events = writing ? POLLOUT : POLLIN;

    /* timeout is in seconds, poll() uses milliseconds */
    ms = (int)_PyTime_AsMilliseconds(timeout, _PyTime_ROUND_CEILING);
    assert(ms <= INT_MAX);

    Py_BEGIN_ALLOW_THREADS
    rc = poll(&pollfd, 1, (int)ms);
    Py_END_ALLOW_THREADS
    _PySSL_FIX_ERRNO;
#else
    /* Guard against socket too large for select*/
    if (!_PyIsSelectable_fd(s->sock_fd))
        return SOCKET_TOO_LARGE_FOR_SELECT;

    _PyTime_AsTimeval_clamp(timeout, &tv, _PyTime_ROUND_CEILING);

    FD_ZERO(&fds);
    FD_SET(s->sock_fd, &fds);

    /* Wait until the socket becomes ready */
    Py_BEGIN_ALLOW_THREADS
    nfds = Py_SAFE_DOWNCAST(s->sock_fd+1, SOCKET_T, int);
    if (writing)
        rc = select(nfds, NULL, &fds, NULL, &tv);
    else
        rc = select(nfds, &fds, NULL, NULL, &tv);
    Py_END_ALLOW_THREADS
    _PySSL_FIX_ERRNO;
#endif

    /* Return SOCKET_TIMED_OUT on timeout, SOCKET_OPERATION_OK otherwise
       (when we are able to write or when there's something to read) */
    return rc == 0 ? SOCKET_HAS_TIMED_OUT : SOCKET_OPERATION_OK;
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.uses_ktls_for_send

Check if the Kernel TLS data-path is used for sending.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_uses_ktls_for_send_impl(PySSLSocket *self)
/*[clinic end generated code: output=f9d95fbefceb5068 input=8d1ce4a131190e6b]*/
{
#ifdef BIO_get_ktls_send
    int uses = BIO_get_ktls_send(SSL_get_wbio(self->ssl));
    // BIO_get_ktls_send() returns 1 if kTLS is used and 0 if not.
    // Also, it returns -1 for failure before OpenSSL 3.0.4.
    return Py_NewRef(uses == 1 ? Py_True : Py_False);
#else
    Py_RETURN_FALSE;
#endif
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.uses_ktls_for_recv

Check if the Kernel TLS data-path is used for receiving.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_uses_ktls_for_recv_impl(PySSLSocket *self)
/*[clinic end generated code: output=ce38b00317a1f681 input=a13778a924fc7d44]*/
{
#ifdef BIO_get_ktls_recv
    int uses = BIO_get_ktls_recv(SSL_get_rbio(self->ssl));
    // BIO_get_ktls_recv() returns 1 if kTLS is used and 0 if not.
    // Also, it returns -1 for failure before OpenSSL 3.0.4.
    return Py_NewRef(uses == 1 ? Py_True : Py_False);
#else
    Py_RETURN_FALSE;
#endif
}

#ifdef BIO_get_ktls_send
/*[clinic input]
@permit_long_summary
@permit_long_docstring_body
@critical_section
_ssl._SSLSocket.sendfile
    fd: int
    offset: Py_off_t
    size: size_t
    flags: int = 0
    /

Write size bytes from offset in the file descriptor fd to the SSL connection.

This method uses the zero-copy technique and returns the number of bytes
written. It should be called only when Kernel TLS is used for sending data in
the connection.

The meaning of flags is platform dependent.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_sendfile_impl(PySSLSocket *self, int fd, Py_off_t offset,
                              size_t size, int flags)
/*[clinic end generated code: output=0c6815b0719ca8d5 input=1f193e681bbae664]*/
{
    Py_ssize_t retval;
    int sockstate;
    _PySSLError err;
    PyObject *exc = NULL;
    PyTime_t timeout, deadline = 0;
    int has_timeout;

    PySocketSockObject *sock = NULL;
    if (get_socket(self, &sock, __FILE__, __LINE__) < 0) {
        return NULL;
    }

    if (self->got_eof_error) {
        set_eof_error(self);
        goto error;
    }

    timeout = GET_SOCKET_TIMEOUT(sock);
    has_timeout = (timeout > 0);
    if (has_timeout) {
        deadline = _PyDeadline_Init(timeout);
    }

    sockstate = PySSL_select(sock, 1, timeout);
    switch (sockstate) {
        case SOCKET_HAS_TIMED_OUT:
            PyErr_SetString(PyExc_TimeoutError,
                            "The write operation timed out");
            goto error;
        case SOCKET_HAS_BEEN_CLOSED:
            PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                            "Underlying socket has been closed.");
            goto error;
        case SOCKET_TOO_LARGE_FOR_SELECT:
            PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                            "Underlying socket too large for select().");
            goto error;
    }

    do {
        Py_BEGIN_ALLOW_THREADS
        retval = SSL_sendfile(self->ssl, fd, (off_t)offset, size, flags);
        err = _PySSL_errno(retval < 0, self->ssl, (int)retval);
        Py_END_ALLOW_THREADS;
        _PySSL_FIX_ERRNO;

        exc = PyErr_GetRaisedException();
        if (exc != NULL) {
            break;
        }

        if (PyErr_CheckSignals()) {
            goto error;
        }

        if (has_timeout) {
            timeout = _PyDeadline_Get(deadline);
        }

        switch (err.ssl) {
            case SSL_ERROR_WANT_READ:
                sockstate = PySSL_select(sock, 0, timeout);
                break;
            case SSL_ERROR_WANT_WRITE:
                sockstate = PySSL_select(sock, 1, timeout);
                break;
            default:
                sockstate = SOCKET_OPERATION_OK;
                break;
        }

        if (sockstate == SOCKET_HAS_TIMED_OUT) {
            PyErr_SetString(PyExc_TimeoutError,
                            "The sendfile operation timed out");
            goto error;
        }
        else if (sockstate == SOCKET_HAS_BEEN_CLOSED) {
            PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                            "Underlying socket has been closed.");
            goto error;
        }
        else if (sockstate == SOCKET_IS_NONBLOCKING) {
            break;
        }
    } while (err.ssl == SSL_ERROR_WANT_READ
             || err.ssl == SSL_ERROR_WANT_WRITE);

    if (err.ssl == SSL_ERROR_SSL
        && ERR_GET_REASON(ERR_peek_error()) == SSL_R_UNINITIALIZED)
    {
        /* OpenSSL fails to return SSL_ERROR_SYSCALL if an error
         * happens in sendfile(), and returns SSL_ERROR_SSL with
         * SSL_R_UNINITIALIZED reason instead. */
        _setSSLError(get_state_sock(self),
                     "Some I/O error occurred in sendfile()",
                     PY_SSL_ERROR_SYSCALL, __FILE__, __LINE__);
        goto error;
    }
    Py_XDECREF(sock);
    if (retval < 0) {
        return PySSL_SetError(self, err, exc, __FILE__, __LINE__);
    }
    if (exc != NULL) {
        PyErr_SetRaisedException(exc);
        return NULL;
    }
    return PyLong_FromSize_t(retval);
error:
    Py_XDECREF(sock);
    if (exc != NULL) {
        _PyErr_ChainExceptions1(exc);
    }
    return NULL;
}
#endif /* BIO_get_ktls_send */

/*[clinic input]
@critical_section
_ssl._SSLSocket.write
    b: Py_buffer
    /

Writes the bytes-like object b into the SSL object.

Returns the number of bytes written.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_write_impl(PySSLSocket *self, Py_buffer *b)
/*[clinic end generated code: output=aa7a6be5527358d8 input=967b5feeae641a26]*/
{
    size_t count = 0;
    int retval;
    int sockstate;
    _PySSLError err;
    PyObject *exc = NULL;
    PyTime_t timeout, deadline = 0;
    int has_timeout;

    PySocketSockObject *sock = NULL;
    if (get_socket(self, &sock, __FILE__, __LINE__) < 0) {
        return NULL;
    }

    if (self->got_eof_error) {
        set_eof_error(self);
        goto error;
    }

    timeout = GET_SOCKET_TIMEOUT(sock);
    has_timeout = (timeout > 0);
    if (has_timeout) {
        deadline = _PyDeadline_Init(timeout);
    }

    sockstate = PySSL_select(sock, 1, timeout);
    if (sockstate == SOCKET_HAS_TIMED_OUT) {
        PyErr_SetString(PyExc_TimeoutError,
                        "The write operation timed out");
        goto error;
    } else if (sockstate == SOCKET_HAS_BEEN_CLOSED) {
        PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                        "Underlying socket has been closed.");
        goto error;
    } else if (sockstate == SOCKET_TOO_LARGE_FOR_SELECT) {
        PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                        "Underlying socket too large for select().");
        goto error;
    }

    do {
        Py_BEGIN_ALLOW_THREADS;
        retval = SSL_write_ex(self->ssl, b->buf, (size_t)b->len, &count);
        err = _PySSL_errno(retval == 0, self->ssl, retval);
        Py_END_ALLOW_THREADS;
        _PySSL_FIX_ERRNO;

        exc = PyErr_GetRaisedException();
        if (exc != NULL) {
            break;
        }

        if (PyErr_CheckSignals())
            goto error;

        if (has_timeout) {
            timeout = _PyDeadline_Get(deadline);
        }

        if (err.ssl == SSL_ERROR_WANT_READ) {
            sockstate = PySSL_select(sock, 0, timeout);
        } else if (err.ssl == SSL_ERROR_WANT_WRITE) {
            sockstate = PySSL_select(sock, 1, timeout);
        } else {
            sockstate = SOCKET_OPERATION_OK;
        }

        if (sockstate == SOCKET_HAS_TIMED_OUT) {
            PyErr_SetString(PyExc_TimeoutError,
                            "The write operation timed out");
            goto error;
        } else if (sockstate == SOCKET_HAS_BEEN_CLOSED) {
            PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                            "Underlying socket has been closed.");
            goto error;
        } else if (sockstate == SOCKET_IS_NONBLOCKING) {
            break;
        }
    } while (err.ssl == SSL_ERROR_WANT_READ ||
             err.ssl == SSL_ERROR_WANT_WRITE);

    Py_XDECREF(sock);
    if (retval == 0)
        return PySSL_SetError(self, err, exc, __FILE__, __LINE__);
    if (exc != NULL) {
        PyErr_SetRaisedException(exc);
        return NULL;
    }
    return PyLong_FromSize_t(count);
error:
    assert(exc == NULL);
    Py_XDECREF(sock);
    return NULL;
}

/*[clinic input]
@permit_long_summary
@critical_section
_ssl._SSLSocket.pending

Returns the number of already decrypted bytes available for read, pending on the connection.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_pending_impl(PySSLSocket *self)
/*[clinic end generated code: output=983d9fecdc308a83 input=042dcc48bdf3e312]*/
{
    int count = 0;
    _PySSLError err;

    Py_BEGIN_ALLOW_THREADS;
    count = SSL_pending(self->ssl);
    err = _PySSL_errno(count < 0, self->ssl, count);
    Py_END_ALLOW_THREADS;
    _PySSL_FIX_ERRNO;

    if (count < 0)
        return PySSL_SetError(self, err, NULL, __FILE__, __LINE__);
    else
        return PyLong_FromLong(count);
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.read
    size as len: Py_ssize_t
    [
    buffer: Py_buffer(accept={rwbuffer})
    ]
    /

Read up to size bytes from the SSL socket.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_read_impl(PySSLSocket *self, Py_ssize_t len,
                          int group_right_1, Py_buffer *buffer)
/*[clinic end generated code: output=49b16e6406023734 input=80ed30436df01a71]*/
{
    PyBytesWriter *writer = NULL;
    char *mem;
    size_t count = 0;
    int retval;
    int sockstate;
    _PySSLError err;
    PyObject *exc = NULL;
    PyTime_t timeout, deadline = 0;
    int has_timeout;

    if (!group_right_1 && len < 0) {
        PyErr_SetString(PyExc_ValueError, "size should not be negative");
        return NULL;
    }

    PySocketSockObject *sock = NULL;
    if (get_socket(self, &sock, __FILE__, __LINE__) < 0) {
        return NULL;
    }

    if (self->got_eof_error) {
        set_eof_error(self);
        goto error;
    }

    if (!group_right_1) {
        if (len == 0) {
            Py_XDECREF(sock);
            return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
        }

        writer = PyBytesWriter_Create(len);
        if (writer == NULL) {
            goto error;
        }
        mem = PyBytesWriter_GetData(writer);
    }
    else {
        mem = buffer->buf;
        if (len <= 0 || len > buffer->len) {
            len = (int) buffer->len;
            if (buffer->len != len) {
                PyErr_SetString(PyExc_OverflowError,
                                "maximum length can't fit in a C 'int'");
                goto error;
            }
            if (len == 0) {
                count = 0;
                goto done;
            }
        }
    }

    timeout = GET_SOCKET_TIMEOUT(sock);
    has_timeout = (timeout > 0);
    if (has_timeout)
        deadline = _PyDeadline_Init(timeout);

    do {
        Py_BEGIN_ALLOW_THREADS;
        retval = SSL_read_ex(self->ssl, mem, (size_t)len, &count);
        err = _PySSL_errno(retval == 0, self->ssl, retval);
        Py_END_ALLOW_THREADS;
        _PySSL_FIX_ERRNO;

        exc = PyErr_GetRaisedException();
        if (exc != NULL) {
            break;
        }

        if (PyErr_CheckSignals())
            goto error;

        if (has_timeout) {
            timeout = _PyDeadline_Get(deadline);
        }

        if (err.ssl == SSL_ERROR_WANT_READ) {
            sockstate = PySSL_select(sock, 0, timeout);
        } else if (err.ssl == SSL_ERROR_WANT_WRITE) {
            sockstate = PySSL_select(sock, 1, timeout);
        } else if (err.ssl == SSL_ERROR_ZERO_RETURN &&
                   SSL_get_shutdown(self->ssl) == SSL_RECEIVED_SHUTDOWN)
        {
            count = 0;
            goto done;
        }
        else
            sockstate = SOCKET_OPERATION_OK;

        if (sockstate == SOCKET_HAS_TIMED_OUT) {
            PyErr_SetString(PyExc_TimeoutError,
                            "The read operation timed out");
            goto error;
        } else if (sockstate == SOCKET_IS_NONBLOCKING) {
            break;
        }
    } while (err.ssl == SSL_ERROR_WANT_READ ||
             err.ssl == SSL_ERROR_WANT_WRITE);

    if (retval == 0) {
        PySSL_SetError(self, err, exc, __FILE__, __LINE__);
        exc = NULL;
        goto error;
    }
    else if (exc != NULL) {
        PyErr_SetRaisedException(exc);
        exc = NULL;
        goto error;
    }

done:
    assert(exc == NULL);
    Py_XDECREF(sock);
    if (!group_right_1) {
        return PyBytesWriter_FinishWithSize(writer, count);
    }
    else {
        return PyLong_FromSize_t(count);
    }

error:
    assert(exc == NULL);
    Py_XDECREF(sock);
    if (!group_right_1) {
        PyBytesWriter_Discard(writer);
    }
    return NULL;
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.shutdown

Does the SSL shutdown handshake with the remote end.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_shutdown_impl(PySSLSocket *self)
/*[clinic end generated code: output=ca1aa7ed9d25ca42 input=98d9635cd4e16514]*/
{
    _PySSLError err;
    PyObject *exc = NULL;
    int sockstate, ret;
    int zeros = 0;
    PyTime_t timeout, deadline = 0;
    int has_timeout;

    PySocketSockObject *sock = NULL;
    if (get_socket(self, &sock, __FILE__, __LINE__) < 0) {
        return NULL;
    }

    timeout = GET_SOCKET_TIMEOUT(sock);
    has_timeout = (timeout > 0);
    if (has_timeout) {
        deadline = _PyDeadline_Init(timeout);
    }

    while (1) {
        Py_BEGIN_ALLOW_THREADS;
        /* Disable read-ahead so that unwrap can work correctly.
         * Otherwise OpenSSL might read in too much data,
         * eating clear text data that happens to be
         * transmitted after the SSL shutdown.
         * Should be safe to call repeatedly every time this
         * function is used and the shutdown_seen_zero != 0
         * condition is met.
         */
        if (self->shutdown_seen_zero)
            SSL_set_read_ahead(self->ssl, 0);
        ret = SSL_shutdown(self->ssl);
        err = _PySSL_errno(ret < 0, self->ssl, ret);
        Py_END_ALLOW_THREADS;
        _PySSL_FIX_ERRNO;

        exc = PyErr_GetRaisedException();
        if (exc != NULL) {
            break;
        }

        /* If err == 1, a secure shutdown with SSL_shutdown() is complete */
        if (ret > 0)
            break;
        if (ret == 0) {
            /* Don't loop endlessly; instead preserve legacy
               behaviour of trying SSL_shutdown() only twice.
               This looks necessary for OpenSSL < 0.9.8m */
            if (++zeros > 1)
                break;
            /* Shutdown was sent, now try receiving */
            self->shutdown_seen_zero = 1;
            continue;
        }

        if (has_timeout) {
            timeout = _PyDeadline_Get(deadline);
        }

        /* Possibly retry shutdown until timeout or failure */
        if (err.ssl == SSL_ERROR_WANT_READ)
            sockstate = PySSL_select(sock, 0, timeout);
        else if (err.ssl == SSL_ERROR_WANT_WRITE)
            sockstate = PySSL_select(sock, 1, timeout);
        else
            break;

        if (sockstate == SOCKET_HAS_TIMED_OUT) {
            if (err.ssl == SSL_ERROR_WANT_READ)
                PyErr_SetString(PyExc_TimeoutError,
                                "The read operation timed out");
            else
                PyErr_SetString(PyExc_TimeoutError,
                                "The write operation timed out");
            goto error;
        }
        else if (sockstate == SOCKET_TOO_LARGE_FOR_SELECT) {
            PyErr_SetString(get_state_sock(self)->PySSLErrorObject,
                            "Underlying socket too large for select().");
            goto error;
        }
        else if (sockstate != SOCKET_OPERATION_OK)
            /* Retain the SSL error code */
            break;
    }
    if (ret < 0) {
        Py_XDECREF(sock);
        PySSL_SetError(self, err, exc, __FILE__, __LINE__);
        return NULL;
    }
    else if (exc != NULL) {
        Py_XDECREF(sock);
        PyErr_SetRaisedException(exc);
        return NULL;
    }
    if (sock)
        /* It's already INCREF'ed */
        return (PyObject *) sock;
    else
        Py_RETURN_NONE;

error:
    assert(exc == NULL);
    Py_XDECREF(sock);
    return NULL;
}

/*[clinic input]
@permit_long_docstring_body
@critical_section
_ssl._SSLSocket.get_channel_binding
   cb_type: str = "tls-unique"

Get channel binding data for current connection.

Raise ValueError if the requested `cb_type` is not supported.  Return bytes
of the data or None if the data is not available (e.g. before the handshake).
Only 'tls-unique' channel binding data from RFC 5929 is supported.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_get_channel_binding_impl(PySSLSocket *self,
                                         const char *cb_type)
/*[clinic end generated code: output=34bac9acb6a61d31 input=26fad522435ecca1]*/
{
    char buf[PySSL_CB_MAXLEN];
    size_t len;

    if (strcmp(cb_type, "tls-unique") == 0) {
        if (SSL_session_reused(self->ssl) ^ !self->socket_type) {
            /* if session is resumed XOR we are the client */
            len = SSL_get_finished(self->ssl, buf, PySSL_CB_MAXLEN);
        }
        else {
            /* if a new session XOR we are the server */
            len = SSL_get_peer_finished(self->ssl, buf, PySSL_CB_MAXLEN);
        }
    }
    else {
        PyErr_Format(
            PyExc_ValueError,
            "'%s' channel binding type not implemented",
            cb_type
        );
        return NULL;
    }

    /* It cannot be negative in current OpenSSL version as of July 2011 */
    if (len == 0)
        Py_RETURN_NONE;

    return PyBytes_FromStringAndSize(buf, len);
}

/*[clinic input]
@critical_section
_ssl._SSLSocket.verify_client_post_handshake

Initiate TLS 1.3 post-handshake authentication
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_verify_client_post_handshake_impl(PySSLSocket *self)
/*[clinic end generated code: output=532147f3b1341425 input=42b5bb1f0981eda1]*/
{
#if defined(PySSL_HAVE_POST_HS_AUTH)
    int err = SSL_verify_client_post_handshake(self->ssl);
    if (err == 0)
        return _setSSLError(get_state_sock(self), NULL, 0, __FILE__, __LINE__);
    else
        Py_RETURN_NONE;
#else
    PyErr_SetString(PyExc_NotImplementedError,
                    "Post-handshake auth is not supported by your "
                    "OpenSSL version.");
    return NULL;
#endif
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLSocket.session

The underlying SSLSession object.
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_session_get_impl(PySSLSocket *self)
/*[clinic end generated code: output=a5cd5755b35da670 input=d427318604244bf8]*/
{
    /* get_session can return sessions from a server-side connection,
     * it does not check for handshake done or client socket. */
    PySSLSession *pysess;
    SSL_SESSION *session;

    session = SSL_get1_session(self->ssl);
    if (session == NULL) {
        Py_RETURN_NONE;
    }
    pysess = PyObject_GC_New(PySSLSession, self->ctx->state->PySSLSession_Type);
    if (pysess == NULL) {
        // It's not possible for another thread to access this, so
        // we don't need to lock it.
        SSL_SESSION_free(session);
        return NULL;
    }

    assert(self->ctx);
    pysess->ctx = (PySSLContext*)Py_NewRef(self->ctx);
    pysess->session = session;
    PyObject_GC_Track(pysess);
    return (PyObject *)pysess;
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLSocket.session
[clinic start generated code]*/

static int
_ssl__SSLSocket_session_set_impl(PySSLSocket *self, PyObject *value)
/*[clinic end generated code: output=a3fa2ddd7c2d54a2 input=5fa5f921640db98b]*/
{
    PySSLSession *pysess;

    if (!Py_IS_TYPE(value, get_state_sock(self)->PySSLSession_Type)) {
        PyErr_SetString(PyExc_TypeError, "Value is not a SSLSession.");
        return -1;
    }
    pysess = (PySSLSession *)value;

    if (self->ctx->ctx != pysess->ctx->ctx) {
        PyErr_SetString(PyExc_ValueError,
                        "Session refers to a different SSLContext.");
        return -1;
    }
    if (self->socket_type != PY_SSL_CLIENT) {
        PyErr_SetString(PyExc_ValueError,
                        "Cannot set session for server-side SSLSocket.");
        return -1;
    }
    if (SSL_is_init_finished(self->ssl)) {
        PyErr_SetString(PyExc_ValueError,
                        "Cannot set session after handshake.");
        return -1;
    }

    if (SSL_set_session(self->ssl, pysess->session) == 0) {
        _setSSLError(get_state_sock(self), NULL, 0, __FILE__, __LINE__);
        return -1;
    }
    return 0;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLSocket.session_reused

Was the client session reused during handshake?
[clinic start generated code]*/

static PyObject *
_ssl__SSLSocket_session_reused_get_impl(PySSLSocket *self)
/*[clinic end generated code: output=c8916909bcb80893 input=cec8bfec73a4461e]*/
{
    int res = SSL_session_reused(self->ssl);
    return res ? Py_True : Py_False;
}

static PyGetSetDef ssl_getsetlist[] = {
    _SSL__SSLSOCKET_CONTEXT_GETSETDEF
    _SSL__SSLSOCKET_SERVER_SIDE_GETSETDEF
    _SSL__SSLSOCKET_SERVER_HOSTNAME_GETSETDEF
    _SSL__SSLSOCKET_OWNER_GETSETDEF
    _SSL__SSLSOCKET_SESSION_GETSETDEF
    _SSL__SSLSOCKET_SESSION_REUSED_GETSETDEF
    {NULL},            /* sentinel */
};

static PyMethodDef PySSLMethods[] = {
    _SSL__SSLSOCKET_DO_HANDSHAKE_METHODDEF
    _SSL__SSLSOCKET_USES_KTLS_FOR_SEND_METHODDEF
    _SSL__SSLSOCKET_USES_KTLS_FOR_RECV_METHODDEF
    _SSL__SSLSOCKET_SENDFILE_METHODDEF
    _SSL__SSLSOCKET_WRITE_METHODDEF
    _SSL__SSLSOCKET_READ_METHODDEF
    _SSL__SSLSOCKET_PENDING_METHODDEF
    _SSL__SSLSOCKET_GETPEERCERT_METHODDEF
    _SSL__SSLSOCKET_GET_CHANNEL_BINDING_METHODDEF
    _SSL__SSLSOCKET_CIPHER_METHODDEF
    _SSL__SSLSOCKET_GROUP_METHODDEF
    _SSL__SSLSOCKET_CLIENT_SIGALG_METHODDEF
    _SSL__SSLSOCKET_SERVER_SIGALG_METHODDEF
    _SSL__SSLSOCKET_SHARED_CIPHERS_METHODDEF
    _SSL__SSLSOCKET_VERSION_METHODDEF
    _SSL__SSLSOCKET_SELECTED_ALPN_PROTOCOL_METHODDEF
    _SSL__SSLSOCKET_COMPRESSION_METHODDEF
    _SSL__SSLSOCKET_SHUTDOWN_METHODDEF
    _SSL__SSLSOCKET_VERIFY_CLIENT_POST_HANDSHAKE_METHODDEF
    _SSL__SSLSOCKET_GET_UNVERIFIED_CHAIN_METHODDEF
    _SSL__SSLSOCKET_GET_VERIFIED_CHAIN_METHODDEF
    {NULL, NULL}
};

static PyType_Slot PySSLSocket_slots[] = {
    {Py_tp_methods, PySSLMethods},
    {Py_tp_getset, ssl_getsetlist},
    {Py_tp_dealloc, PySSL_dealloc},
    {Py_tp_traverse, PySSL_traverse},
    {0, 0},
};

static PyType_Spec PySSLSocket_spec = {
    .name = "_ssl._SSLSocket",
    .basicsize = sizeof(PySSLSocket),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE |
              Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_DISALLOW_INSTANTIATION),
    .slots = PySSLSocket_slots,
};

/*
 * _SSLContext objects
 */

static int
_set_verify_mode(PySSLContext *self, enum py_ssl_cert_requirements n)
{
    int mode;

    switch(n) {
    case PY_SSL_CERT_NONE:
        mode = SSL_VERIFY_NONE;
        break;
    case PY_SSL_CERT_OPTIONAL:
        mode = SSL_VERIFY_PEER;
        break;
    case PY_SSL_CERT_REQUIRED:
        mode = SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
        break;
    default:
         PyErr_SetString(PyExc_ValueError,
                        "invalid value for verify_mode");
        return -1;
    }

    /* bpo-37428: newPySSLSocket() sets SSL_VERIFY_POST_HANDSHAKE flag for
     * server sockets and SSL_set_post_handshake_auth() for client. */

    SSL_CTX_set_verify(self->ctx, mode, NULL);
    return 0;
}

/*[clinic input]
@critical_section
@classmethod
_ssl._SSLContext.__new__
    protocol as proto_version: int
    /
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_impl(PyTypeObject *type, int proto_version)
/*[clinic end generated code: output=2cf0d7a0741b6bd1 input=6fc79e62ae9d143c]*/
{
    PySSLContext *self;
    uint64_t options;
    const SSL_METHOD *method = NULL;
    SSL_CTX *ctx = NULL;
    X509_VERIFY_PARAM *ssl_verification_params;
    int result;

   /* slower approach, walk MRO and get borrowed reference to module.
    * PyType_GetModuleByDef is required for SSLContext subclasses */
    PyObject *module = PyType_GetModuleByDef(type, &_sslmodule_def);
    if (module == NULL) {
        PyErr_SetString(PyExc_RuntimeError,
                        "Cannot find internal module state");
        return NULL;
    }

    switch(proto_version) {
#if defined(SSL3_VERSION) && !defined(OPENSSL_NO_SSL3)
    case PY_SSL_VERSION_SSL3:
        PY_SSL_DEPRECATED("ssl.PROTOCOL_SSLv3 is deprecated", 2, NULL);
        method = SSLv3_method();
        break;
#endif
#if (defined(TLS1_VERSION) && \
        !defined(OPENSSL_NO_TLS1) && \
        !defined(OPENSSL_NO_TLS1_METHOD))
    case PY_SSL_VERSION_TLS1:
        PY_SSL_DEPRECATED("ssl.PROTOCOL_TLSv1 is deprecated", 2, NULL);
        method = TLSv1_method();
        break;
#endif
#if (defined(TLS1_1_VERSION) && \
        !defined(OPENSSL_NO_TLS1_1) && \
        !defined(OPENSSL_NO_TLS1_1_METHOD))
    case PY_SSL_VERSION_TLS1_1:
        PY_SSL_DEPRECATED("ssl.PROTOCOL_TLSv1_1 is deprecated", 2, NULL);
        method = TLSv1_1_method();
        break;
#endif
#if (defined(TLS1_2_VERSION) && \
        !defined(OPENSSL_NO_TLS1_2) && \
        !defined(OPENSSL_NO_TLS1_2_METHOD))
    case PY_SSL_VERSION_TLS1_2:
        PY_SSL_DEPRECATED("ssl.PROTOCOL_TLSv1_2 is deprecated", 2, NULL);
        method = TLSv1_2_method();
        break;
#endif
    case PY_SSL_VERSION_TLS:
        PY_SSL_DEPRECATED("ssl.PROTOCOL_TLS is deprecated", 2, NULL);
        method = TLS_method();
        break;
    case PY_SSL_VERSION_TLS_CLIENT:
        method = TLS_client_method();
        break;
    case PY_SSL_VERSION_TLS_SERVER:
        method = TLS_server_method();
        break;
    default:
        method = NULL;
    }

    if (method == NULL) {
        PyErr_Format(PyExc_ValueError,
                     "invalid or unsupported protocol version %i",
                     proto_version);
        return NULL;
    }

    // This is the constructor, no need to lock it, because
    // no other thread can be touching this object yet.
    // (Technically, we can't even lock if we wanted to, as the
    // lock hasn't been initialized yet.)
    Py_BEGIN_ALLOW_THREADS
    ctx = SSL_CTX_new(method);
    Py_END_ALLOW_THREADS
    _PySSL_FIX_ERRNO;

    if (ctx == NULL) {
        _setSSLError(get_ssl_state(module), NULL, 0, __FILE__, __LINE__);
        return NULL;
    }

    assert(type != NULL && type->tp_alloc != NULL);
    self = (PySSLContext *) type->tp_alloc(type, 0);
    if (self == NULL) {
        SSL_CTX_free(ctx);
        return NULL;
    }
    self->ctx = ctx;
    self->protocol = proto_version;
    self->msg_cb = NULL;
    self->keylog_filename = NULL;
    self->keylog_bio = NULL;
    self->alpn_protocols = NULL;
    self->set_sni_cb = NULL;
    self->state = get_ssl_state(module);
#ifndef OPENSSL_NO_PSK
    self->psk_client_callback = NULL;
    self->psk_server_callback = NULL;
#endif
    self->tstate_mutex = (PyMutex){0};

    /* Don't check host name by default */
    if (proto_version == PY_SSL_VERSION_TLS_CLIENT) {
        self->check_hostname = 1;
        if (_set_verify_mode(self, PY_SSL_CERT_REQUIRED) == -1) {
            Py_DECREF(self);
            return NULL;
        }
    } else {
        self->check_hostname = 0;
        if (_set_verify_mode(self, PY_SSL_CERT_NONE) == -1) {
            Py_DECREF(self);
            return NULL;
        }
    }
    /* Defaults */
    options = SSL_OP_ALL & ~SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
    if (proto_version != PY_SSL_VERSION_SSL2)
        options |= SSL_OP_NO_SSLv2;
    if (proto_version != PY_SSL_VERSION_SSL3)
        options |= SSL_OP_NO_SSLv3;
    /* Minimal security flags for server and client side context.
     * Client sockets ignore server-side parameters. */
#ifdef SSL_OP_NO_COMPRESSION
    options |= SSL_OP_NO_COMPRESSION;
#endif
#ifdef SSL_OP_CIPHER_SERVER_PREFERENCE
    options |= SSL_OP_CIPHER_SERVER_PREFERENCE;
#endif
#ifdef SSL_OP_SINGLE_DH_USE
    options |= SSL_OP_SINGLE_DH_USE;
#endif
#ifdef SSL_OP_SINGLE_ECDH_USE
    options |= SSL_OP_SINGLE_ECDH_USE;
#endif
    SSL_CTX_set_options(self->ctx, options);

    /* A bare minimum cipher list without completely broken cipher suites.
     * It's far from perfect but gives users a better head start. */
    if (proto_version != PY_SSL_VERSION_SSL2) {
#if PY_SSL_DEFAULT_CIPHERS == 2
        /* stick to OpenSSL's default settings */
        result = 1;
#else
        result = SSL_CTX_set_cipher_list(ctx, PY_SSL_DEFAULT_CIPHER_STRING);
#endif
    } else {
        /* SSLv2 needs MD5 */
        result = SSL_CTX_set_cipher_list(ctx, "HIGH:!aNULL:!eNULL");
    }
    if (result == 0) {
        ERR_clear_error();
        PyErr_SetString(get_state_ctx(self)->PySSLErrorObject,
                        "No cipher can be selected.");
        goto error;
    }
#ifdef PY_SSL_MIN_PROTOCOL
    switch(proto_version) {
    case PY_SSL_VERSION_TLS:
    case PY_SSL_VERSION_TLS_CLIENT:
    case PY_SSL_VERSION_TLS_SERVER:
        result = SSL_CTX_set_min_proto_version(ctx, PY_SSL_MIN_PROTOCOL);
        if (result == 0) {
            PyErr_Format(PyExc_ValueError,
                         "Failed to set minimum protocol 0x%x",
                          PY_SSL_MIN_PROTOCOL);
            goto error;
        }
        break;
    default:
        break;
    }
#endif

    /* Set SSL_MODE_RELEASE_BUFFERS. This potentially greatly reduces memory
       usage for no cost at all. */
    SSL_CTX_set_mode(self->ctx, SSL_MODE_RELEASE_BUFFERS);

    ssl_verification_params = SSL_CTX_get0_param(self->ctx);
    /* Improve trust chain building when cross-signed intermediate
       certificates are present. See https://bugs.python.org/issue23476. */
    X509_VERIFY_PARAM_set_flags(ssl_verification_params, X509_V_FLAG_TRUSTED_FIRST);
    X509_VERIFY_PARAM_set_hostflags(ssl_verification_params, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS);

#if defined(PySSL_HAVE_POST_HS_AUTH)
    self->post_handshake_auth = 0;
    SSL_CTX_set_post_handshake_auth(self->ctx, self->post_handshake_auth);
#endif

    return (PyObject *)self;
  error:
    Py_XDECREF(self);
    ERR_clear_error();
    return NULL;
}

static int
context_traverse(PyObject *op, visitproc visit, void *arg)
{
    PySSLContext *self = PySSLContext_CAST(op);
    Py_VISIT(self->set_sni_cb);
    Py_VISIT(self->msg_cb);
    Py_VISIT(self->keylog_filename);
#ifndef OPENSSL_NO_PSK
    Py_VISIT(self->psk_client_callback);
    Py_VISIT(self->psk_server_callback);
#endif
    Py_VISIT(Py_TYPE(self));
    return 0;
}

static int
context_clear(PyObject *op)
{
    PySSLContext *self = PySSLContext_CAST(op);
    Py_CLEAR(self->set_sni_cb);
    Py_CLEAR(self->msg_cb);
    Py_CLEAR(self->keylog_filename);
#ifndef OPENSSL_NO_PSK
    Py_CLEAR(self->psk_client_callback);
    Py_CLEAR(self->psk_server_callback);
#endif
    if (self->keylog_bio != NULL) {
        Py_BEGIN_ALLOW_THREADS
        BIO_free_all(self->keylog_bio);
        Py_END_ALLOW_THREADS
        _PySSL_FIX_ERRNO;
        self->keylog_bio = NULL;
    }
    return 0;
}

static void
context_dealloc(PyObject *op)
{
    PySSLContext *self = PySSLContext_CAST(op);
    PyTypeObject *tp = Py_TYPE(self);
    /* bpo-31095: UnTrack is needed before calling any callbacks */
    PyObject_GC_UnTrack(self);
    (void)context_clear(op);
    SSL_CTX_free(self->ctx);
    PyMem_FREE(self->alpn_protocols);
    tp->tp_free(self);
    Py_DECREF(tp);
}

/*[clinic input]
@critical_section
_ssl._SSLContext.set_ciphers
    cipherlist: str
    /
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_ciphers_impl(PySSLContext *self, const char *cipherlist)
/*[clinic end generated code: output=3a3162f3557c0f3f input=40b583cded5c6ff9]*/
{
    int ret = SSL_CTX_set_cipher_list(self->ctx, cipherlist);
    if (ret == 0) {
        /* Clearing the error queue is necessary on some OpenSSL versions,
           otherwise the error will be reported again when another SSL call
           is done. */
        ERR_clear_error();
        PyErr_SetString(get_state_ctx(self)->PySSLErrorObject,
                        "No cipher can be selected.");
        return NULL;
    }
    Py_RETURN_NONE;
}

/*[clinic input]
@critical_section
_ssl._SSLContext.set_ciphersuites
    ciphersuites: str
    /
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_ciphersuites_impl(PySSLContext *self,
                                       const char *ciphersuites)
/*[clinic end generated code: output=9915bec58e54d76d input=2afcc3693392be41]*/
{
    if (!SSL_CTX_set_ciphersuites(self->ctx, ciphersuites)) {
        _setSSLError(get_state_ctx(self), "No cipher suite can be selected.", 0, __FILE__, __LINE__);
        return NULL;
    }
    Py_RETURN_NONE;
}

/*[clinic input]
@critical_section
_ssl._SSLContext.get_ciphers
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_get_ciphers_impl(PySSLContext *self)
/*[clinic end generated code: output=a56e4d68a406dfc4 input=d7fff51631a260ae]*/
{
    SSL *ssl = NULL;
    STACK_OF(SSL_CIPHER) *sk = NULL;
    const SSL_CIPHER *cipher;
    int i=0;
    PyObject *result = NULL, *dct;

    ssl = SSL_new(self->ctx);
    if (ssl == NULL) {
        _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        goto exit;
    }
    sk = SSL_get_ciphers(ssl);

    result = PyList_New(sk_SSL_CIPHER_num(sk));
    if (result == NULL) {
        goto exit;
    }

    for (i = 0; i < sk_SSL_CIPHER_num(sk); i++) {
        cipher = sk_SSL_CIPHER_value(sk, i);
        dct = cipher_to_dict(cipher);
        if (dct == NULL) {
            Py_CLEAR(result);
            goto exit;
        }
        PyList_SET_ITEM(result, i, dct);
    }

  exit:
    if (ssl != NULL)
        SSL_free(ssl);
    return result;

}

/*[clinic input]
@critical_section
_ssl._SSLContext.set_groups
    grouplist: str
    /
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_groups_impl(PySSLContext *self, const char *grouplist)
/*[clinic end generated code: output=0b5d05dfd371ffd0 input=2cc64cef21930741]*/
{
    if (!SSL_CTX_set1_groups_list(self->ctx, grouplist)) {
        _setSSLError(get_state_ctx(self), "unrecognized group", 0, __FILE__, __LINE__);
        return NULL;
    }
    Py_RETURN_NONE;
}

/*[clinic input]
@critical_section
_ssl._SSLContext.get_groups
    *
    include_aliases: bool = False
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_get_groups_impl(PySSLContext *self, int include_aliases)
/*[clinic end generated code: output=6d6209dd1051529b input=3e8ee5deb277dcc5]*/
{
#if OPENSSL_VERSION_NUMBER >= 0x30500000L
    STACK_OF(OPENSSL_CSTRING) *groups = NULL;
    const char *group;
    int i, num;
    PyObject *item, *result = NULL;

    // This "groups" object is dynamically allocated, but the strings inside
    // it are internal constants which shouldn't ever be modified or freed.
    if ((groups = sk_OPENSSL_CSTRING_new_null()) == NULL) {
        _setSSLError(get_state_ctx(self), "Can't allocate stack", 0, __FILE__, __LINE__);
        goto error;
    }

    if (!SSL_CTX_get0_implemented_groups(self->ctx, include_aliases, groups)) {
        _setSSLError(get_state_ctx(self), "Can't get groups", 0, __FILE__, __LINE__);
        goto error;
    }

    num = sk_OPENSSL_CSTRING_num(groups);
    result = PyList_New(num);
    if (result == NULL) {
        goto error;
    }

    for (i = 0; i < num; ++i) {
        // There's no allocation here, so group won't ever be NULL.
        group = sk_OPENSSL_CSTRING_value(groups, i);
        assert(group != NULL);

        // Group names are plain ASCII, so there's no chance of a decoding
        // error here. However, an allocation failure could occur when
        // constructing the Unicode version of the names.
        if ((item = PyUnicode_DecodeFSDefault(group)) == NULL) {
            goto error;
        }

        PyList_SET_ITEM(result, i, item);
    }

    sk_OPENSSL_CSTRING_free(groups);
    return result;
error:
    Py_XDECREF(result);
    sk_OPENSSL_CSTRING_free(groups);
    return NULL;
#else
    PyErr_SetString(PyExc_NotImplementedError,
                    "Getting implemented groups requires OpenSSL 3.5 or later.");
    return NULL;
#endif
}

/*[clinic input]
@critical_section
_ssl._SSLContext.set_client_sigalgs
    sigalgslist: str
    /
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_client_sigalgs_impl(PySSLContext *self,
                                         const char *sigalgslist)
/*[clinic end generated code: output=f4f5be160a29c7d6 input=500d853ce9fd94ff]*/
{
#ifdef OPENSSL_IS_AWSLC
    _setSSLError(get_state_ctx(self), "can't set client sigalgs on AWS-LC", 0, __FILE__, __LINE__);
    return NULL;
#else
    if (!SSL_CTX_set1_client_sigalgs_list(self->ctx, sigalgslist)) {
        _setSSLError(get_state_ctx(self), "unrecognized signature algorithm", 0, __FILE__, __LINE__);
        return NULL;
    }
    Py_RETURN_NONE;
#endif
}

/*[clinic input]
@critical_section
_ssl._SSLContext.set_server_sigalgs
    sigalgslist: str
    /
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_server_sigalgs_impl(PySSLContext *self,
                                         const char *sigalgslist)
/*[clinic end generated code: output=31ecb1d310285644 input=653b752e4f8d801b]*/
{
    if (!SSL_CTX_set1_sigalgs_list(self->ctx, sigalgslist)) {
        _setSSLError(get_state_ctx(self), "unrecognized signature algorithm", 0, __FILE__, __LINE__);
        return NULL;
    }
    Py_RETURN_NONE;
}

static int
do_protocol_selection(int alpn, unsigned char **out, unsigned char *outlen,
                      const unsigned char *server_protocols, unsigned int server_protocols_len,
                      const unsigned char *client_protocols, unsigned int client_protocols_len)
{
    int ret;
    if (client_protocols == NULL) {
        client_protocols = (unsigned char *)"";
        client_protocols_len = 0;
    }
    if (server_protocols == NULL) {
        server_protocols = (unsigned char *)"";
        server_protocols_len = 0;
    }

    ret = SSL_select_next_proto(out, outlen,
                                server_protocols, server_protocols_len,
                                client_protocols, client_protocols_len);
    if (alpn && ret != OPENSSL_NPN_NEGOTIATED)
        return SSL_TLSEXT_ERR_NOACK;

    return SSL_TLSEXT_ERR_OK;
}

static int
_selectALPN_cb(SSL *s,
              const unsigned char **out, unsigned char *outlen,
              const unsigned char *client_protocols, unsigned int client_protocols_len,
              void *args)
{
    PySSLContext *ctx = (PySSLContext *)args;
    return do_protocol_selection(1, (unsigned char **)out, outlen,
                                 ctx->alpn_protocols, ctx->alpn_protocols_len,
                                 client_protocols, client_protocols_len);
}

/*[clinic input]
@critical_section
_ssl._SSLContext._set_alpn_protocols
    protos: Py_buffer
    /
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext__set_alpn_protocols_impl(PySSLContext *self,
                                          Py_buffer *protos)
/*[clinic end generated code: output=87599a7f76651a9b input=b5096b186e49287d]*/
{
    if ((size_t)protos->len > UINT_MAX) {
        PyErr_Format(PyExc_OverflowError,
            "protocols longer than %u bytes", UINT_MAX);
        return NULL;
    }

    PyMem_Free(self->alpn_protocols);
    self->alpn_protocols = PyMem_Malloc(protos->len);
    if (!self->alpn_protocols) {
        return PyErr_NoMemory();
    }
    memcpy(self->alpn_protocols, protos->buf, protos->len);
    self->alpn_protocols_len = (unsigned int)protos->len;
    if (SSL_CTX_set_alpn_protos(self->ctx, self->alpn_protocols, self->alpn_protocols_len)) {
        return PyErr_NoMemory();
    }
    SSL_CTX_set_alpn_select_cb(self->ctx, _selectALPN_cb, self);

    Py_RETURN_NONE;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.verify_mode
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_verify_mode_get_impl(PySSLContext *self)
/*[clinic end generated code: output=3e788736cc7229bc input=7e3c7f4454121d0a]*/
{
    /* ignore SSL_VERIFY_CLIENT_ONCE and SSL_VERIFY_POST_HANDSHAKE */
    int mask = (SSL_VERIFY_NONE | SSL_VERIFY_PEER |
                SSL_VERIFY_FAIL_IF_NO_PEER_CERT);
    int verify_mode = SSL_CTX_get_verify_mode(self->ctx);
    switch (verify_mode & mask) {
    case SSL_VERIFY_NONE:
        return PyLong_FromLong(PY_SSL_CERT_NONE);
    case SSL_VERIFY_PEER:
        return PyLong_FromLong(PY_SSL_CERT_OPTIONAL);
    case SSL_VERIFY_PEER | SSL_VERIFY_FAIL_IF_NO_PEER_CERT:
        return PyLong_FromLong(PY_SSL_CERT_REQUIRED);
    }
    PyErr_SetString(get_state_ctx(self)->PySSLErrorObject,
                    "invalid return value from SSL_CTX_get_verify_mode");
    return NULL;
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext.verify_mode
[clinic start generated code]*/

static int
_ssl__SSLContext_verify_mode_set_impl(PySSLContext *self, PyObject *value)
/*[clinic end generated code: output=d698e16c58db3118 input=3ee60057c3a22378]*/
{
    int n;
    if (!PyArg_Parse(value, "i", &n))
        return -1;
    if (n == PY_SSL_CERT_NONE && self->check_hostname) {
        PyErr_SetString(PyExc_ValueError,
                        "Cannot set verify_mode to CERT_NONE when "
                        "check_hostname is enabled.");
        return -1;
    }
    return _set_verify_mode(self, n);
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.verify_flags
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_verify_flags_get_impl(PySSLContext *self)
/*[clinic end generated code: output=fbbf8ba28ad6e56e input=c1ec36d610b3f391]*/
{
    X509_VERIFY_PARAM *ssl_verification_params;
    unsigned long flags;

    ssl_verification_params = SSL_CTX_get0_param(self->ctx);
    flags = X509_VERIFY_PARAM_get_flags(ssl_verification_params);
    return PyLong_FromUnsignedLong(flags);
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext.verify_flags
[clinic start generated code]*/

static int
_ssl__SSLContext_verify_flags_set_impl(PySSLContext *self, PyObject *value)
/*[clinic end generated code: output=a3e3b2a0ce6c2e99 input=b2a0c42583d4f34e]*/
{
    X509_VERIFY_PARAM *ssl_verification_params;
    unsigned long new_flags, flags, set, clear;

    if (!PyArg_Parse(value, "k", &new_flags))
        return -1;
    ssl_verification_params = SSL_CTX_get0_param(self->ctx);
    flags = X509_VERIFY_PARAM_get_flags(ssl_verification_params);
    clear = flags & ~new_flags;
    set = ~flags & new_flags;
    if (clear) {
        if (!X509_VERIFY_PARAM_clear_flags(ssl_verification_params, clear)) {
            _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
            return -1;
        }
    }
    if (set) {
        if (!X509_VERIFY_PARAM_set_flags(ssl_verification_params, set)) {
            _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
            return -1;
        }
    }
    return 0;
}

/* Getter and setter for protocol version */
static int
set_min_max_proto_version(PySSLContext *self, PyObject *arg, int what)
{
    int v;
    int result;

    if (!PyArg_Parse(arg, "i", &v))
        return -1;

    switch(self->protocol) {
    case PY_SSL_VERSION_TLS_CLIENT: _Py_FALLTHROUGH;
    case PY_SSL_VERSION_TLS_SERVER: _Py_FALLTHROUGH;
    case PY_SSL_VERSION_TLS:
        break;
    default:
        PyErr_SetString(
            PyExc_ValueError,
            "The context's protocol doesn't support modification of "
            "highest and lowest version."
        );
        return -1;
    }

    /* check for deprecations and supported values */
    switch(v) {
        case PY_PROTO_SSLv3:
            PY_SSL_DEPRECATED("ssl.TLSVersion.SSLv3 is deprecated", 2, -1);
            break;
        case PY_PROTO_TLSv1:
            PY_SSL_DEPRECATED("ssl.TLSVersion.TLSv1 is deprecated", 2, -1);
            break;
        case PY_PROTO_TLSv1_1:
            PY_SSL_DEPRECATED("ssl.TLSVersion.TLSv1_1 is deprecated", 2, -1);
            break;
        case PY_PROTO_MINIMUM_SUPPORTED:
        case PY_PROTO_MAXIMUM_SUPPORTED:
        case PY_PROTO_TLSv1_2:
        case PY_PROTO_TLSv1_3:
            /* ok */
            break;
        default:
            PyErr_Format(PyExc_ValueError,
                     "Unsupported TLS/SSL version 0x%x", (unsigned)v);
            return -1;
    }

    if (what == 0) {
        switch(v) {
        case PY_PROTO_MINIMUM_SUPPORTED:
            v = 0;
            break;
        case PY_PROTO_MAXIMUM_SUPPORTED:
            /* Emulate max for set_min_proto_version */
            v = PY_PROTO_MAXIMUM_AVAILABLE;
            break;
        default:
            break;
        }
        result = SSL_CTX_set_min_proto_version(self->ctx, v);
    }
    else {
        switch(v) {
        case PY_PROTO_MAXIMUM_SUPPORTED:
            v = 0;
            break;
        case PY_PROTO_MINIMUM_SUPPORTED:
            /* Emulate max for set_min_proto_version */
            v = PY_PROTO_MINIMUM_AVAILABLE;
            break;
        default:
            break;
        }
        result = SSL_CTX_set_max_proto_version(self->ctx, v);
    }
    if (result == 0) {
        PyErr_Format(PyExc_ValueError,
                     "Unsupported protocol version 0x%x", (unsigned)v);
        return -1;
    }
    return 0;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.minimum_version
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_minimum_version_get_impl(PySSLContext *self)
/*[clinic end generated code: output=27fa8382276635ed input=6832821e7e974d40]*/
{
    int v = SSL_CTX_get_min_proto_version(self->ctx);
    if (v == 0) {
        v = PY_PROTO_MINIMUM_SUPPORTED;
    }
    return PyLong_FromLong(v);
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext.minimum_version
[clinic start generated code]*/

static int
_ssl__SSLContext_minimum_version_set_impl(PySSLContext *self,
                                          PyObject *value)
/*[clinic end generated code: output=482e82f7372afb78 input=2c64724901a514b3]*/
{
    return set_min_max_proto_version(self, value, 0);
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.maximum_version
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_maximum_version_get_impl(PySSLContext *self)
/*[clinic end generated code: output=889249475112826a input=2b9e4c2d45f16b14]*/
{
    int v = SSL_CTX_get_max_proto_version(self->ctx);
    if (v == 0) {
        v = PY_PROTO_MAXIMUM_SUPPORTED;
    }
    return PyLong_FromLong(v);
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext.maximum_version
[clinic start generated code]*/

static int
_ssl__SSLContext_maximum_version_set_impl(PySSLContext *self,
                                          PyObject *value)
/*[clinic end generated code: output=4c0eed3042ca20d5 input=fe27e9fbbeb73c89]*/
{
    return set_min_max_proto_version(self, value, 1);
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.num_tickets

Control the number of TLSv1.3 session tickets.
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_num_tickets_get_impl(PySSLContext *self)
/*[clinic end generated code: output=3d06d016318846c9 input=1e2599a2e22564ff]*/
{
    // Clinic seems to be misbehaving when the comment is wrapped with in directive
#if defined(TLS1_3_VERSION) && !defined(OPENSSL_NO_TLS1_3)
    PyObject *res = PyLong_FromSize_t(SSL_CTX_get_num_tickets(self->ctx));
    return res;
#else
    return 0;
#endif
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext.num_tickets
[clinic start generated code]*/

static int
_ssl__SSLContext_num_tickets_set_impl(PySSLContext *self, PyObject *value)
/*[clinic end generated code: output=ced81b46f3beab09 input=6ef8067ac55607e7]*/
{
    long num;
    if (!PyArg_Parse(value, "l", &num))
        return -1;
    if (num < 0) {
        PyErr_SetString(PyExc_ValueError, "value must be non-negative");
        return -1;
    }
    if (self->protocol != PY_SSL_VERSION_TLS_SERVER) {
        PyErr_SetString(PyExc_ValueError,
                        "SSLContext is not a server context.");
        return -1;
    }
    if (SSL_CTX_set_num_tickets(self->ctx, num) != 1) {
        PyErr_SetString(PyExc_ValueError, "failed to set num tickets.");
        return -1;
    }
    return 0;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.security_level

The current security level.
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_security_level_get_impl(PySSLContext *self)
/*[clinic end generated code: output=56ece09e6a9572d0 input=2bdeecb57bb86e3f]*/
{
    PyObject *res = PyLong_FromLong(SSL_CTX_get_security_level(self->ctx));
    return res;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.options
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_options_get_impl(PySSLContext *self)
/*[clinic end generated code: output=3dfa6a74837f525b input=f5a2805c7cda6f25]*/
{
    uint64_t options = SSL_CTX_get_options(self->ctx);
    Py_BUILD_ASSERT(sizeof(unsigned long long) >= sizeof(options));
    return PyLong_FromUnsignedLongLong(options);
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext.options
[clinic start generated code]*/

static int
_ssl__SSLContext_options_set_impl(PySSLContext *self, PyObject *value)
/*[clinic end generated code: output=92ca34731ece5dbb input=2b94bf789e9ae5dd]*/
{
    unsigned long long new_opts_arg;
    uint64_t new_opts, opts, clear, set;
    uint64_t opt_no = (
        SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3 | SSL_OP_NO_TLSv1 |
        SSL_OP_NO_TLSv1_1 | SSL_OP_NO_TLSv1_2 | SSL_OP_NO_TLSv1_3
    );

    if (!PyArg_Parse(value, "O&", _PyLong_UnsignedLongLong_Converter, &new_opts_arg)) {
        return -1;
    }
    Py_BUILD_ASSERT(sizeof(new_opts) >= sizeof(new_opts_arg));
    new_opts = (uint64_t)new_opts_arg;

    opts = SSL_CTX_get_options(self->ctx);
    clear = opts & ~new_opts;
    set = ~opts & new_opts;

    if ((set & opt_no) != 0) {
        if (_ssl_deprecated("ssl.OP_NO_SSL*/ssl.OP_NO_TLS* options are "
                            "deprecated", 2) < 0) {
            return -1;
        }
    }
    if (clear) {
        SSL_CTX_clear_options(self->ctx, clear);
    }
    if (set) {
        SSL_CTX_set_options(self->ctx, set);
    }
    return 0;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext._host_flags
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext__host_flags_get_impl(PySSLContext *self)
/*[clinic end generated code: output=0f9db6654ce32582 input=8e3c49499eefd0e5]*/
{
    X509_VERIFY_PARAM *ssl_verification_params;
    unsigned int host_flags;

    ssl_verification_params = SSL_CTX_get0_param(self->ctx);
    host_flags = X509_VERIFY_PARAM_get_hostflags(ssl_verification_params);
    return PyLong_FromUnsignedLong(host_flags);
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext._host_flags
[clinic start generated code]*/

static int
_ssl__SSLContext__host_flags_set_impl(PySSLContext *self, PyObject *value)
/*[clinic end generated code: output=1ed6f4027aaf2e3e input=28caf1fb9c32f6cb]*/
{
    X509_VERIFY_PARAM *ssl_verification_params;
    unsigned int new_flags = 0;

    if (!PyArg_Parse(value, "I", &new_flags))
        return -1;

    ssl_verification_params = SSL_CTX_get0_param(self->ctx);
    X509_VERIFY_PARAM_set_hostflags(ssl_verification_params, new_flags);
    return 0;
}

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.check_hostname
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_check_hostname_get_impl(PySSLContext *self)
/*[clinic end generated code: output=e046d6eeefc76063 input=1b8341e705f9ecf5]*/
{
    return PyBool_FromLong(self->check_hostname);
}

/*[clinic input]
@critical_section
@setter
_ssl._SSLContext.check_hostname
[clinic start generated code]*/

static int
_ssl__SSLContext_check_hostname_set_impl(PySSLContext *self, PyObject *value)
/*[clinic end generated code: output=0e767b4784e7dc3f input=e6a771cb5919f74d]*/
{
    int check_hostname;
    if (!PyArg_Parse(value, "p", &check_hostname))
        return -1;
    int verify_mode = check_hostname ? SSL_CTX_get_verify_mode(self->ctx) : 0;
    if (check_hostname &&
            verify_mode == SSL_VERIFY_NONE) {
        /* check_hostname = True sets verify_mode = CERT_REQUIRED */
        if (_set_verify_mode(self, PY_SSL_CERT_REQUIRED) == -1) {
            return -1;
        }
    }
    self->check_hostname = check_hostname;
    return 0;
}

static PyObject *
get_post_handshake_auth(PyObject *op, void *Py_UNUSED(closure))
{
    PySSLContext *self = PySSLContext_CAST(op);
#if defined(PySSL_HAVE_POST_HS_AUTH)
    return PyBool_FromLong(self->post_handshake_auth);
#else
    Py_RETURN_NONE;
#endif
}

#if defined(PySSL_HAVE_POST_HS_AUTH)
static int
set_post_handshake_auth(PyObject *op, PyObject *arg, void *Py_UNUSED(closure))
{
    PySSLContext *self = PySSLContext_CAST(op);
    if (arg == NULL) {
        PyErr_SetString(PyExc_AttributeError, "cannot delete attribute");
        return -1;
    }
    int pha = PyObject_IsTrue(arg);

    if (pha == -1) {
        return -1;
    }
    self->post_handshake_auth = pha;

    /* bpo-37428: newPySSLSocket() sets SSL_VERIFY_POST_HANDSHAKE flag for
     * server sockets and SSL_set_post_handshake_auth() for client. */

    return 0;
}
#endif

/*[clinic input]
@critical_section
@getter
_ssl._SSLContext.protocol
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_protocol_get_impl(PySSLContext *self)
/*[clinic end generated code: output=a9a48febc16cee22 input=c9f5fa1a2bd4b8a8]*/
{
    return PyLong_FromLong(self->protocol);
}

typedef struct {
    PyThreadState *thread_state;
    PyObject *callable;
    char *password;
    int size;
    int error;
} _PySSLPasswordInfo;

static int
_pwinfo_set(_PySSLPasswordInfo *pw_info, PyObject* password,
            const char *bad_type_error)
{
    /* Set the password and size fields of a _PySSLPasswordInfo struct
       from a unicode, bytes, or byte array object.
       The password field will be dynamically allocated and must be freed
       by the caller */
    PyObject *password_bytes = NULL;
    const char *data = NULL;
    Py_ssize_t size;

    if (PyUnicode_Check(password)) {
        password_bytes = PyUnicode_AsUTF8String(password);
        if (!password_bytes) {
            goto error;
        }
        data = PyBytes_AS_STRING(password_bytes);
        size = PyBytes_GET_SIZE(password_bytes);
    } else if (PyBytes_Check(password)) {
        data = PyBytes_AS_STRING(password);
        size = PyBytes_GET_SIZE(password);
    } else if (PyByteArray_Check(password)) {
        data = PyByteArray_AS_STRING(password);
        size = PyByteArray_GET_SIZE(password);
    } else {
        PyErr_SetString(PyExc_TypeError, bad_type_error);
        goto error;
    }

    if (size > (Py_ssize_t)INT_MAX) {
        PyErr_Format(PyExc_ValueError,
                     "password cannot be longer than %d bytes", INT_MAX);
        goto error;
    }

    PyMem_Free(pw_info->password);
    pw_info->password = PyMem_Malloc(size);
    if (!pw_info->password) {
        PyErr_SetString(PyExc_MemoryError,
                        "unable to allocate password buffer");
        goto error;
    }
    memcpy(pw_info->password, data, size);
    pw_info->size = (int)size;

    Py_XDECREF(password_bytes);
    return 1;

error:
    Py_XDECREF(password_bytes);
    return 0;
}

static int
_password_callback(char *buf, int size, int rwflag, void *userdata)
{
    _PySSLPasswordInfo *pw_info = (_PySSLPasswordInfo*) userdata;
    PyObject *fn_ret = NULL;

    pw_info->thread_state = PyThreadState_Swap(pw_info->thread_state);
    _PySSL_FIX_ERRNO;

    if (pw_info->error) {
        /* already failed previously. OpenSSL 3.0.0-alpha14 invokes the
         * callback multiple times which can lead to fatal Python error in
         * exception check. */
        goto error;
    }

    if (pw_info->callable) {
        fn_ret = PyObject_CallNoArgs(pw_info->callable);
        if (!fn_ret) {
            /* TODO: It would be nice to move _ctypes_add_traceback() into the
               core python API, so we could use it to add a frame here */
            goto error;
        }

        if (!_pwinfo_set(pw_info, fn_ret,
                         "password callback must return a string")) {
            goto error;
        }
        Py_CLEAR(fn_ret);
    }

    if (pw_info->size > size) {
        PyErr_Format(PyExc_ValueError,
                     "password cannot be longer than %d bytes", size);
        goto error;
    }

    pw_info->thread_state = PyThreadState_Swap(pw_info->thread_state);
    memcpy(buf, pw_info->password, pw_info->size);
    return pw_info->size;

error:
    Py_XDECREF(fn_ret);
    pw_info->thread_state = PyThreadState_Swap(pw_info->thread_state);
    pw_info->error = 1;
    return -1;
}

static PyObject *
load_cert_chain_lock_held(PySSLContext *self, _PySSLPasswordInfo *pw_info,
                          PyObject *certfile_bytes, PyObject *keyfile_bytes)
{
    int r;
    PyObject *ret = NULL;

    pem_password_cb *orig_passwd_cb = SSL_CTX_get_default_passwd_cb(self->ctx);
    void *orig_passwd_userdata = SSL_CTX_get_default_passwd_cb_userdata(self->ctx);

    SSL_CTX_set_default_passwd_cb(self->ctx, _password_callback);
    SSL_CTX_set_default_passwd_cb_userdata(self->ctx, pw_info);

    PySSL_BEGIN_ALLOW_THREADS_S(pw_info->thread_state);
    r = SSL_CTX_use_certificate_chain_file(self->ctx,
        PyBytes_AS_STRING(certfile_bytes));
    PySSL_END_ALLOW_THREADS_S(pw_info->thread_state);
    if (r != 1) {
        if (pw_info->error) {
            ERR_clear_error();
            /* the password callback has already set the error information */
        }
        else if (errno != 0) {
            PyErr_SetFromErrnoWithFilename(PyExc_OSError,
                PyBytes_AS_STRING(certfile_bytes));
            ERR_clear_error();
        }
        else {
            _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        }
        goto error;
    }

    PySSL_BEGIN_ALLOW_THREADS_S(pw_info->thread_state);
    r = SSL_CTX_use_PrivateKey_file(self->ctx,
        PyBytes_AS_STRING(keyfile_bytes ? keyfile_bytes : certfile_bytes),
        SSL_FILETYPE_PEM);
    PySSL_END_ALLOW_THREADS_S(pw_info->thread_state);
    if (r != 1) {
        if (pw_info->error) {
            ERR_clear_error();
            /* the password callback has already set the error information */
        }
        else if (errno != 0) {
            PyErr_SetFromErrnoWithFilename(PyExc_OSError,
                PyBytes_AS_STRING(keyfile_bytes ? keyfile_bytes : certfile_bytes));
            ERR_clear_error();
        }
        else {
            _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        }
        goto error;
    }

    PySSL_BEGIN_ALLOW_THREADS_S(pw_info->thread_state);
    r = SSL_CTX_check_private_key(self->ctx);
    PySSL_END_ALLOW_THREADS_S(pw_info->thread_state);
    if (r != 1) {
        _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        goto error;
    }
    ret = Py_None;
error:
    SSL_CTX_set_default_passwd_cb(self->ctx, orig_passwd_cb);
    SSL_CTX_set_default_passwd_cb_userdata(self->ctx, orig_passwd_userdata);
    return ret;
}

/*[clinic input]
_ssl._SSLContext.load_cert_chain
    certfile: object
    keyfile: object = None
    password: object = None

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_load_cert_chain_impl(PySSLContext *self, PyObject *certfile,
                                      PyObject *keyfile, PyObject *password)
/*[clinic end generated code: output=9480bc1c380e2095 input=30bc7e967ea01a58]*/
{
    PyObject *certfile_bytes = NULL, *keyfile_bytes = NULL;
    _PySSLPasswordInfo pw_info = { NULL, NULL, NULL, 0, 0 };
    PyObject *ret = NULL;

    errno = 0;
    ERR_clear_error();
    if (keyfile == Py_None)
        keyfile = NULL;
    if (!PyUnicode_FSConverter(certfile, &certfile_bytes)) {
        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
            PyErr_SetString(PyExc_TypeError,
                            "certfile should be a valid filesystem path");
        }
        return NULL;
    }
    if (keyfile && !PyUnicode_FSConverter(keyfile, &keyfile_bytes)) {
        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
            PyErr_SetString(PyExc_TypeError,
                            "keyfile should be a valid filesystem path");
        }
        goto done;
    }
    if (password != Py_None) {
        if (PyCallable_Check(password)) {
            pw_info.callable = password;
        } else if (!_pwinfo_set(&pw_info, password,
                                "password should be a string or callable")) {
            goto done;
        }
    }

    PyMutex_Lock(&self->tstate_mutex);
    ret = load_cert_chain_lock_held(self, &pw_info, certfile_bytes, keyfile_bytes);
    PyMutex_Unlock(&self->tstate_mutex);

done:
    PyMem_Free(pw_info.password);
    Py_XDECREF(keyfile_bytes);
    Py_XDECREF(certfile_bytes);
    return ret;
}

/* internal helper function, returns -1 on error
 */
static int
_add_ca_certs(PySSLContext *self, const void *data, Py_ssize_t len,
              int filetype)
{
    BIO *biobuf = NULL;
    X509_STORE *store;
    int retval = -1, err, loaded = 0, was_bio_eof = 0;

    assert(filetype == SSL_FILETYPE_ASN1 || filetype == SSL_FILETYPE_PEM);

    if (len <= 0) {
        PyErr_SetString(PyExc_ValueError,
                        "Empty certificate data");
        return -1;
    } else if (len > INT_MAX) {
        PyErr_SetString(PyExc_OverflowError,
                        "Certificate data is too long.");
        return -1;
    }

    biobuf = BIO_new_mem_buf(data, (int)len);
    if (biobuf == NULL) {
        _setSSLError(get_state_ctx(self), "Can't allocate buffer", 0, __FILE__, __LINE__);
        return -1;
    }

    store = SSL_CTX_get_cert_store(self->ctx);
    assert(store != NULL);

    while (1) {
        X509 *cert = NULL;
        int r;

        if (filetype == SSL_FILETYPE_ASN1) {
            if (BIO_eof(biobuf)) {
                was_bio_eof = 1;
                break;
            }
            cert = d2i_X509_bio(biobuf, NULL);
        } else {
            cert = PEM_read_bio_X509(biobuf, NULL,
                                     SSL_CTX_get_default_passwd_cb(self->ctx),
                                     SSL_CTX_get_default_passwd_cb_userdata(self->ctx)
                                    );
        }
        if (cert == NULL) {
            break;
        }
        r = X509_STORE_add_cert(store, cert);
        X509_free(cert);
        if (!r) {
            err = ERR_peek_last_error();
            if ((ERR_GET_LIB(err) == ERR_LIB_X509) &&
                (ERR_GET_REASON(err) == X509_R_CERT_ALREADY_IN_HASH_TABLE)) {
                /* cert already in hash table, not an error */
                ERR_clear_error();
            } else {
                break;
            }
        }
        loaded++;
    }

    err = ERR_peek_last_error();
    if (loaded == 0) {
        const char *msg = NULL;
        if (filetype == SSL_FILETYPE_PEM) {
            msg = "no start line: cadata does not contain a certificate";
        } else {
            msg = "not enough data: cadata does not contain a certificate";
        }
        _setSSLError(get_state_ctx(self), msg, 0, __FILE__, __LINE__);
        retval = -1;
    } else if ((filetype == SSL_FILETYPE_ASN1) && was_bio_eof) {
        /* EOF ASN1 file, not an error */
        ERR_clear_error();
        retval = 0;
    } else if ((filetype == SSL_FILETYPE_PEM) &&
                   (ERR_GET_LIB(err) == ERR_LIB_PEM) &&
                   (ERR_GET_REASON(err) == PEM_R_NO_START_LINE)) {
        /* EOF PEM file, not an error */
        ERR_clear_error();
        retval = 0;
    } else if (err != 0) {
        _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        retval = -1;
    } else {
        retval = 0;
    }

    BIO_free(biobuf);
    return retval;
}


/*[clinic input]
@critical_section
_ssl._SSLContext.load_verify_locations
    cafile: object = None
    capath: object = None
    cadata: object = None

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_load_verify_locations_impl(PySSLContext *self,
                                            PyObject *cafile,
                                            PyObject *capath,
                                            PyObject *cadata)
/*[clinic end generated code: output=454c7e41230ca551 input=b178852b41618414]*/
{
    PyObject *cafile_bytes = NULL, *capath_bytes = NULL;
    const char *cafile_buf = NULL, *capath_buf = NULL;
    int r = 0, ok = 1;

    errno = 0;
    if (cafile == Py_None)
        cafile = NULL;
    if (capath == Py_None)
        capath = NULL;
    if (cadata == Py_None)
        cadata = NULL;

    if (cafile == NULL && capath == NULL && cadata == NULL) {
        PyErr_SetString(PyExc_TypeError,
                        "cafile, capath and cadata cannot be all omitted");
        goto error;
    }
    if (cafile && !PyUnicode_FSConverter(cafile, &cafile_bytes)) {
        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
            PyErr_SetString(PyExc_TypeError,
                            "cafile should be a valid filesystem path");
        }
        goto error;
    }
    if (capath && !PyUnicode_FSConverter(capath, &capath_bytes)) {
        if (PyErr_ExceptionMatches(PyExc_TypeError)) {
            PyErr_SetString(PyExc_TypeError,
                            "capath should be a valid filesystem path");
        }
        goto error;
    }

    /* validate cadata type and load cadata */
    if (cadata) {
        if (PyUnicode_Check(cadata)) {
            PyObject *cadata_ascii = PyUnicode_AsASCIIString(cadata);
            if (cadata_ascii == NULL) {
                if (PyErr_ExceptionMatches(PyExc_UnicodeEncodeError)) {
                    goto invalid_cadata;
                }
                goto error;
            }
            r = _add_ca_certs(self,
                              PyBytes_AS_STRING(cadata_ascii),
                              PyBytes_GET_SIZE(cadata_ascii),
                              SSL_FILETYPE_PEM);
            Py_DECREF(cadata_ascii);
            if (r == -1) {
                goto error;
            }
        }
        else if (PyObject_CheckBuffer(cadata)) {
            Py_buffer buf;
            if (PyObject_GetBuffer(cadata, &buf, PyBUF_SIMPLE)) {
                goto error;
            }
            assert(PyBuffer_IsContiguous(&buf, 'C'));
            if (buf.ndim > 1) {
                PyBuffer_Release(&buf);
                PyErr_SetString(PyExc_TypeError,
                                "cadata should be a contiguous buffer with "
                                "a single dimension");
                goto error;
            }
            r = _add_ca_certs(self, buf.buf, buf.len, SSL_FILETYPE_ASN1);
            PyBuffer_Release(&buf);
            if (r == -1) {
                goto error;
            }
        }
        else {
  invalid_cadata:
            PyErr_SetString(PyExc_TypeError,
                            "cadata should be an ASCII string or a "
                            "bytes-like object");
            goto error;
        }
    }

    /* load cafile or capath */
    if (cafile || capath) {
        if (cafile)
            cafile_buf = PyBytes_AS_STRING(cafile_bytes);
        if (capath)
            capath_buf = PyBytes_AS_STRING(capath_bytes);
        PySSL_BEGIN_ALLOW_THREADS(self)
        r = SSL_CTX_load_verify_locations(self->ctx, cafile_buf, capath_buf);
        PySSL_END_ALLOW_THREADS(self)
        if (r != 1) {
            if (errno != 0) {
                PyErr_SetFromErrno(PyExc_OSError);
                ERR_clear_error();
            }
            else {
                _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
            }
            goto error;
        }
    }
    goto end;

  error:
    ok = 0;
  end:
    Py_XDECREF(cafile_bytes);
    Py_XDECREF(capath_bytes);
    if (ok) {
        Py_RETURN_NONE;
    } else {
        return NULL;
    }
}

/*[clinic input]
@critical_section
_ssl._SSLContext.load_dh_params
    path as filepath: object
    /

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_load_dh_params_impl(PySSLContext *self, PyObject *filepath)
/*[clinic end generated code: output=dd74b3c524dd2723 input=832769a0734b8c4d]*/
{
    FILE *f;
    DH *dh;

#if defined(MS_WINDOWS) && defined(Py_DEBUG)
    PyErr_SetString(PyExc_NotImplementedError,
                    "load_dh_params: unavailable on Windows debug build");
    return NULL;
#endif

    f = Py_fopen(filepath, "rb");
    if (f == NULL)
        return NULL;

    errno = 0;
    Py_BEGIN_ALLOW_THREADS
    dh = PEM_read_DHparams(f, NULL, NULL, NULL);
    fclose(f);
    Py_END_ALLOW_THREADS
    _PySSL_FIX_ERRNO;
    if (dh == NULL) {
        if (errno != 0) {
            PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, filepath);
            ERR_clear_error();
        }
        else {
            _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        }
        return NULL;
    }
    if (!SSL_CTX_set_tmp_dh(self->ctx, dh)) {
        DH_free(dh);
        return _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
    }
    DH_free(dh);
    Py_RETURN_NONE;
}

/*[clinic input]
@critical_section
_ssl._SSLContext._wrap_socket
    sock: object(subclass_of="get_state_ctx(self)->Sock_Type")
    server_side: bool
    server_hostname as hostname_obj: object = None
    *
    owner: object = None
    session: object = None

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext__wrap_socket_impl(PySSLContext *self, PyObject *sock,
                                   int server_side, PyObject *hostname_obj,
                                   PyObject *owner, PyObject *session)
/*[clinic end generated code: output=f103f238633940b4 input=eceadcee4434a06f]*/
{
    char *hostname = NULL;
    PyObject *res;

    /* server_hostname is either None (or absent), or to be encoded
       as IDN A-label (ASCII str) without NULL bytes. */
    if (hostname_obj != Py_None) {
        if (!PyArg_Parse(hostname_obj, "es", "ascii", &hostname))
            return NULL;
    }

    res = (PyObject *) newPySSLSocket(self, (PySocketSockObject *)sock,
                                      server_side, hostname,
                                      owner, session,
                                      NULL, NULL);
    if (hostname != NULL)
        PyMem_Free(hostname);
    return res;
}

/*[clinic input]
@critical_section
_ssl._SSLContext._wrap_bio
    incoming: object(subclass_of="get_state_ctx(self)->PySSLMemoryBIO_Type", type="PySSLMemoryBIO *")
    outgoing: object(subclass_of="get_state_ctx(self)->PySSLMemoryBIO_Type", type="PySSLMemoryBIO *")
    server_side: bool
    server_hostname as hostname_obj: object = None
    *
    owner: object = None
    session: object = None

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext__wrap_bio_impl(PySSLContext *self, PySSLMemoryBIO *incoming,
                                PySSLMemoryBIO *outgoing, int server_side,
                                PyObject *hostname_obj, PyObject *owner,
                                PyObject *session)
/*[clinic end generated code: output=5c5d6d9b41f99332 input=58277fc962a60182]*/
{
    char *hostname = NULL;
    PyObject *res;

    /* server_hostname is either None (or absent), or to be encoded
       as IDN A-label (ASCII str) without NULL bytes. */
    if (hostname_obj != Py_None) {
        if (!PyArg_Parse(hostname_obj, "es", "ascii", &hostname))
            return NULL;
    }

    res = (PyObject *) newPySSLSocket(self, NULL, server_side, hostname,
                                      owner, session,
                                      incoming, outgoing);

    PyMem_Free(hostname);
    return res;
}

/*[clinic input]
@critical_section
_ssl._SSLContext.session_stats
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_session_stats_impl(PySSLContext *self)
/*[clinic end generated code: output=0d96411c42893bfb input=db62af53004127a4]*/
{
    int r;
    PyObject *value, *stats = PyDict_New();
    if (!stats)
        return NULL;

#define ADD_STATS(SSL_NAME, KEY_NAME) \
    value = PyLong_FromLong(SSL_CTX_sess_ ## SSL_NAME (self->ctx)); \
    if (value == NULL) \
        goto error; \
    r = PyDict_SetItemString(stats, KEY_NAME, value); \
    Py_DECREF(value); \
    if (r < 0) \
        goto error;

    ADD_STATS(number, "number");
    ADD_STATS(connect, "connect");
    ADD_STATS(connect_good, "connect_good");
    ADD_STATS(connect_renegotiate, "connect_renegotiate");
    ADD_STATS(accept, "accept");
    ADD_STATS(accept_good, "accept_good");
    ADD_STATS(accept_renegotiate, "accept_renegotiate");
    ADD_STATS(accept, "accept");
    ADD_STATS(hits, "hits");
    ADD_STATS(misses, "misses");
    ADD_STATS(timeouts, "timeouts");
    ADD_STATS(cache_full, "cache_full");

#undef ADD_STATS

    return stats;

error:
    Py_DECREF(stats);
    return NULL;
}

/*[clinic input]
@critical_section
_ssl._SSLContext.set_default_verify_paths
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_default_verify_paths_impl(PySSLContext *self)
/*[clinic end generated code: output=0bee74e6e09deaaa input=939a88e78f634119]*/
{
    int rc;
    Py_BEGIN_ALLOW_THREADS
    rc = SSL_CTX_set_default_verify_paths(self->ctx);
    Py_END_ALLOW_THREADS
    _PySSL_FIX_ERRNO;
    if (!rc) {
        _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        return NULL;
    }
    Py_RETURN_NONE;
}

/*[clinic input]
@critical_section
_ssl._SSLContext.set_ecdh_curve
    name: object
    /

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_ecdh_curve_impl(PySSLContext *self, PyObject *name)
/*[clinic end generated code: output=01081151ce0ecc45 input=039df032e666870e]*/
{
    PyObject *name_bytes;
    int nid;
    if (!PyUnicode_FSConverter(name, &name_bytes))
        return NULL;
    assert(PyBytes_Check(name_bytes));
    nid = OBJ_sn2nid(PyBytes_AS_STRING(name_bytes));
    Py_DECREF(name_bytes);
    if (nid == 0) {
        PyErr_Format(PyExc_ValueError,
                     "unknown elliptic curve name %R", name);
        return NULL;
    }
#if OPENSSL_VERSION_MAJOR < 3
    EC_KEY *key = EC_KEY_new_by_curve_name(nid);
    if (key == NULL) {
        _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        return NULL;
    }
    SSL_CTX_set_tmp_ecdh(self->ctx, key);
    EC_KEY_free(key);
#else
    if (!SSL_CTX_set1_groups(self->ctx, &nid, 1)) {
        _setSSLError(get_state_ctx(self), NULL, 0, __FILE__, __LINE__);
        return NULL;
    }
#endif
    Py_RETURN_NONE;
}

static int
_servername_callback(SSL *s, int *al, void *args)
{
    int ret;
    PySSLContext *sslctx = (PySSLContext *) args;
    PySSLSocket *ssl;
    PyObject *result;
    /* The high-level ssl.SSLSocket object */
    PyObject *ssl_socket;
    const char *servername = SSL_get_servername(s, TLSEXT_NAMETYPE_host_name);
    PyGILState_STATE gstate = PyGILState_Ensure();

    if (sslctx->set_sni_cb == NULL) {
        /* remove race condition in this the call back while if removing the
         * callback is in progress */
        PyGILState_Release(gstate);
        return SSL_TLSEXT_ERR_OK;
    }

    ssl = SSL_get_app_data(s);
    assert(Py_IS_TYPE(ssl, get_state_ctx(sslctx)->PySSLSocket_Type));

    /* The servername callback expects an argument that represents the current
     * SSL connection and that has a .context attribute that can be changed to
     * identify the requested hostname. Since the official API is the Python
     * level API we want to pass the callback a Python level object rather than
     * a _ssl.SSLSocket instance. If there's an "owner" (typically an
     * SSLObject) that will be passed. Otherwise if there's a socket then that
     * will be passed. If both do not exist only then the C-level object is
     * passed. */
    if (ssl->owner)
        PyWeakref_GetRef(ssl->owner, &ssl_socket);
    else if (ssl->Socket)
        PyWeakref_GetRef(ssl->Socket, &ssl_socket);
    else
        ssl_socket = Py_NewRef(ssl);

    if (ssl_socket == NULL)
        goto error;

    if (servername == NULL) {
        result = PyObject_CallFunctionObjArgs(sslctx->set_sni_cb, ssl_socket,
                                              Py_None, sslctx, NULL);
    }
    else {
        PyObject *servername_bytes;
        PyObject *servername_str;

        servername_bytes = PyBytes_FromString(servername);
        if (servername_bytes == NULL) {
            PyErr_FormatUnraisable("Exception ignored "
                                   "in ssl servername callback");
            goto error;
        }
        /* server_hostname was encoded to an A-label by our caller; put it
         * back into a str object, but still as an A-label (bpo-28414)
         */
        servername_str = PyUnicode_FromEncodedObject(servername_bytes, "ascii", NULL);
        if (servername_str == NULL) {
            PyErr_FormatUnraisable("Exception ignored "
                                   "in ssl servername callback "
                                   "while decoding name %R",
                                   servername_bytes);
            Py_DECREF(servername_bytes);
            goto error;
        }
        Py_DECREF(servername_bytes);
        result = PyObject_CallFunctionObjArgs(
            sslctx->set_sni_cb, ssl_socket, servername_str,
            sslctx, NULL);
        Py_DECREF(servername_str);
    }
    Py_DECREF(ssl_socket);

    if (result == NULL) {
        PyErr_FormatUnraisable("Exception ignored "
                               "in ssl servername callback "
                               "while calling set SNI callback %R",
                               sslctx->set_sni_cb);
        *al = SSL_AD_HANDSHAKE_FAILURE;
        ret = SSL_TLSEXT_ERR_ALERT_FATAL;
    }
    else {
        /* Result may be None, a SSLContext or an integer
         * None and SSLContext are OK, integer or other values are an error.
         */
        if (result == Py_None) {
            ret = SSL_TLSEXT_ERR_OK;
        } else {
            *al = (int) PyLong_AsLong(result);
            if (PyErr_Occurred()) {
                PyErr_FormatUnraisable("Exception ignored "
                                       "in ssl servername callback "
                                       "while calling set SNI callback "
                                       "(result=%R)",
                                       result);
                *al = SSL_AD_INTERNAL_ERROR;
            }
            ret = SSL_TLSEXT_ERR_ALERT_FATAL;
        }
        Py_DECREF(result);
    }

    PyGILState_Release(gstate);
    return ret;

error:
    Py_XDECREF(ssl_socket);
    *al = SSL_AD_INTERNAL_ERROR;
    ret = SSL_TLSEXT_ERR_ALERT_FATAL;
    PyGILState_Release(gstate);
    return ret;
}

/*[clinic input]
@permit_long_summary
@permit_long_docstring_body
@critical_section
@getter
_ssl._SSLContext.sni_callback

Set a callback that will be called when a server name is provided by the SSL/TLS client in the SNI extension.

If the argument is None then the callback is disabled. The method is called
with the SSLSocket, the server name as a string, and the SSLContext object.

See RFC 6066 for details of the SNI extension.
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_sni_callback_get_impl(PySSLContext *self)
/*[clinic end generated code: output=961e6575cdfaf036 input=3aee06696b0874d9]*/
{
    PyObject *cb = self->set_sni_cb;
    if (cb == NULL) {
        Py_RETURN_NONE;
    }
    return Py_NewRef(cb);
}

/*[clinic input]
@permit_long_summary
@permit_long_docstring_body
@critical_section
@setter
_ssl._SSLContext.sni_callback
[clinic start generated code]*/

static int
_ssl__SSLContext_sni_callback_set_impl(PySSLContext *self, PyObject *value)
/*[clinic end generated code: output=b32736c6b891f61a input=332def1d8c81d549]*/
{
    if (self->protocol == PY_SSL_VERSION_TLS_CLIENT) {
        PyErr_SetString(PyExc_ValueError,
                        "sni_callback cannot be set on TLS_CLIENT context");
        return -1;
    }
    Py_CLEAR(self->set_sni_cb);
    if (value == Py_None) {
        SSL_CTX_set_tlsext_servername_callback(self->ctx, NULL);
    }
    else {
        if (!PyCallable_Check(value)) {
            SSL_CTX_set_tlsext_servername_callback(self->ctx, NULL);
            PyErr_SetString(PyExc_TypeError,
                            "not a callable object");
            return -1;
        }
        self->set_sni_cb = Py_NewRef(value);
        SSL_CTX_set_tlsext_servername_callback(self->ctx, _servername_callback);
        SSL_CTX_set_tlsext_servername_arg(self->ctx, self);
    }
    return 0;
}

#if OPENSSL_VERSION_NUMBER < 0x30300000L && !defined(LIBRESSL_VERSION_NUMBER)
static X509_OBJECT *x509_object_dup(const X509_OBJECT *obj)
{
    int ok;
    X509_OBJECT *ret = X509_OBJECT_new();
    if (ret == NULL) {
        return NULL;
    }
    switch (X509_OBJECT_get_type(obj)) {
        case X509_LU_X509:
            ok = X509_OBJECT_set1_X509(ret, X509_OBJECT_get0_X509(obj));
            break;
        case X509_LU_CRL:
            /* X509_OBJECT_get0_X509_CRL was not const-correct prior to 3.0.*/
            ok = X509_OBJECT_set1_X509_CRL(
                ret, X509_OBJECT_get0_X509_CRL((X509_OBJECT *)obj));
            break;
        default:
            /* We cannot duplicate unrecognized types in a polyfill, but it is
             * safe to leave an empty object. The caller will ignore it. */
            ok = 1;
            break;
    }
    if (!ok) {
        X509_OBJECT_free(ret);
        return NULL;
    }
    return ret;
}

static STACK_OF(X509_OBJECT) *
X509_STORE_get1_objects(X509_STORE *store)
{
    STACK_OF(X509_OBJECT) *ret;
    if (!X509_STORE_lock(store)) {
        return NULL;
    }
    ret = sk_X509_OBJECT_deep_copy(X509_STORE_get0_objects(store),
                                   x509_object_dup, X509_OBJECT_free);
    X509_STORE_unlock(store);
    return ret;
}
#endif

/*[clinic input]
@critical_section
_ssl._SSLContext.cert_store_stats

Returns quantities of loaded X.509 certificates.

X.509 certificates with a CA extension and certificate revocation lists
inside the context's cert store.

NOTE: Certificates in a capath directory aren't loaded unless they have
been used at least once.
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_cert_store_stats_impl(PySSLContext *self)
/*[clinic end generated code: output=5f356f4d9cca874d input=d13c6e3f2b48539b]*/
{
    X509_STORE *store;
    STACK_OF(X509_OBJECT) *objs;
    X509_OBJECT *obj;
    int x509 = 0, crl = 0, ca = 0, i;

    store = SSL_CTX_get_cert_store(self->ctx);
    objs = X509_STORE_get1_objects(store);
    if (objs == NULL) {
        PyErr_SetString(PyExc_MemoryError, "failed to query cert store");
        return NULL;
    }

    for (i = 0; i < sk_X509_OBJECT_num(objs); i++) {
        obj = sk_X509_OBJECT_value(objs, i);
        switch (X509_OBJECT_get_type(obj)) {
            case X509_LU_X509:
                x509++;
                if (X509_check_ca(X509_OBJECT_get0_X509(obj))) {
                    ca++;
                }
                break;
            case X509_LU_CRL:
                crl++;
                break;
            default:
                /* Ignore unrecognized types. */
                break;
        }
    }
    sk_X509_OBJECT_pop_free(objs, X509_OBJECT_free);
    return Py_BuildValue("{sisisi}", "x509", x509, "crl", crl,
        "x509_ca", ca);
}

/*[clinic input]
@critical_section
_ssl._SSLContext.get_ca_certs
    binary_form: bool = False

Returns a list of dicts with information of loaded CA certs.

If the optional argument is True, returns a DER-encoded copy of the CA
certificate.

NOTE: Certificates in a capath directory aren't loaded unless they have
been used at least once.
[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_get_ca_certs_impl(PySSLContext *self, int binary_form)
/*[clinic end generated code: output=0d58f148f37e2938 input=eb0592909c9ad6e7]*/
{
    X509_STORE *store;
    STACK_OF(X509_OBJECT) *objs;
    PyObject *ci = NULL, *rlist = NULL;
    int i;

    if ((rlist = PyList_New(0)) == NULL) {
        return NULL;
    }

    store = SSL_CTX_get_cert_store(self->ctx);
    objs = X509_STORE_get1_objects(store);
    if (objs == NULL) {
        PyErr_SetString(PyExc_MemoryError, "failed to query cert store");
        goto error;
    }

    for (i = 0; i < sk_X509_OBJECT_num(objs); i++) {
        X509_OBJECT *obj;
        X509 *cert;

        obj = sk_X509_OBJECT_value(objs, i);
        if (X509_OBJECT_get_type(obj) != X509_LU_X509) {
            /* not a x509 cert */
            continue;
        }
        /* CA for any purpose */
        cert = X509_OBJECT_get0_X509(obj);
        if (!X509_check_ca(cert)) {
            continue;
        }
        if (binary_form) {
            ci = _certificate_to_der(get_state_ctx(self), cert);
        } else {
            ci = _decode_certificate(get_state_ctx(self), cert);
        }
        if (ci == NULL) {
            goto error;
        }
        if (PyList_Append(rlist, ci) == -1) {
            goto error;
        }
        Py_CLEAR(ci);
    }
    sk_X509_OBJECT_pop_free(objs, X509_OBJECT_free);
    return rlist;

  error:
    sk_X509_OBJECT_pop_free(objs, X509_OBJECT_free);
    Py_XDECREF(ci);
    Py_XDECREF(rlist);
    return NULL;
}

#ifndef OPENSSL_NO_PSK
static unsigned int psk_client_callback(SSL *s,
                                        const char *hint,
                                        char *identity,
                                        unsigned int max_identity_len,
                                        unsigned char *psk,
                                        unsigned int max_psk_len)
{
    PyGILState_STATE gstate = PyGILState_Ensure();
    PyObject *callback = NULL;

    PySSLSocket *ssl = SSL_get_app_data(s);
    if (ssl == NULL || ssl->ctx == NULL) {
        goto error;
    }
    callback = ssl->ctx->psk_client_callback;
    if (callback == NULL) {
        goto error;
    }

    PyObject *hint_str = (hint != NULL && hint[0] != '\0') ?
            PyUnicode_DecodeUTF8(hint, strlen(hint), "strict") :
            Py_NewRef(Py_None);
    if (hint_str == NULL) {
        /* The remote side has sent an invalid UTF-8 string
         * (breaking the standard), drop the connection without
         * raising a decode exception. */
        PyErr_Clear();
        goto error;
    }
    PyObject *result = PyObject_CallFunctionObjArgs(callback, hint_str, NULL);
    Py_DECREF(hint_str);

    if (result == NULL) {
        goto error;
    }

    const char *psk_;
    const char *identity_;
    Py_ssize_t psk_len_;
    Py_ssize_t identity_len_ = 0;
    if (!PyArg_ParseTuple(result, "z#y#", &identity_, &identity_len_, &psk_, &psk_len_)) {
        Py_DECREF(result);
        goto error;
    }

    if ((size_t)identity_len_ + 1 > max_identity_len
        || (size_t)psk_len_ > max_psk_len)
    {
        Py_DECREF(result);
        goto error;
    }
    memcpy(psk, psk_, psk_len_);
    if (identity_ != NULL) {
        memcpy(identity, identity_, identity_len_);
    }
    identity[identity_len_] = 0;

    Py_DECREF(result);

    PyGILState_Release(gstate);
    return (unsigned int)psk_len_;

error:
    if (PyErr_Occurred()) {
        PyErr_FormatUnraisable("Exception ignored in ssl PSK client callback "
                               "while calling callback %R", callback);
    }
    PyGILState_Release(gstate);
    return 0;
}
#endif

/*[clinic input]
@critical_section
_ssl._SSLContext.set_psk_client_callback
    callback: object

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_psk_client_callback_impl(PySSLContext *self,
                                              PyObject *callback)
/*[clinic end generated code: output=0aba86f6ed75119e input=1e436eea625cfc35]*/
{
#ifndef OPENSSL_NO_PSK
    if (self->protocol == PY_SSL_VERSION_TLS_SERVER) {
        _setSSLError(get_state_ctx(self),
                     "Cannot add PSK client callback to a "
                     "PROTOCOL_TLS_SERVER context", 0, __FILE__, __LINE__);
        return NULL;
    }

    SSL_psk_client_cb_func ssl_callback;
    if (callback == Py_None) {
        callback = NULL;
        // Delete the existing callback
        ssl_callback = NULL;
    } else {
        if (!PyCallable_Check(callback)) {
            PyErr_SetString(PyExc_TypeError, "callback must be callable");
            return NULL;
        }
        ssl_callback = psk_client_callback;
    }

    Py_XDECREF(self->psk_client_callback);
    Py_XINCREF(callback);

    self->psk_client_callback = callback;
    SSL_CTX_set_psk_client_callback(self->ctx, ssl_callback);

    Py_RETURN_NONE;
#else
    PyErr_SetString(PyExc_NotImplementedError,
                    "TLS-PSK is not supported by your OpenSSL version.");
    return NULL;
#endif
}

#ifndef OPENSSL_NO_PSK
static unsigned int psk_server_callback(SSL *s,
                                        const char *identity,
                                        unsigned char *psk,
                                        unsigned int max_psk_len)
{
    PyGILState_STATE gstate = PyGILState_Ensure();
    PyObject *callback = NULL;

    PySSLSocket *ssl = SSL_get_app_data(s);
    if (ssl == NULL || ssl->ctx == NULL) {
        goto error;
    }
    callback = ssl->ctx->psk_server_callback;
    if (callback == NULL) {
        goto error;
    }

    PyObject *identity_str = (identity != NULL && identity[0] != '\0') ?
            PyUnicode_DecodeUTF8(identity, strlen(identity), "strict") :
            Py_NewRef(Py_None);
    if (identity_str == NULL) {
        /* The remote side has sent an invalid UTF-8 string
         * (breaking the standard), drop the connection without
         * raising a decode exception. */
        PyErr_Clear();
        goto error;
    }
    PyObject *result = PyObject_CallFunctionObjArgs(callback, identity_str, NULL);
    Py_DECREF(identity_str);

    if (result == NULL) {
        goto error;
    }

    char *psk_;
    Py_ssize_t psk_len_;
    if (PyBytes_AsStringAndSize(result, &psk_, &psk_len_) < 0) {
        Py_DECREF(result);
        goto error;
    }

    if ((size_t)psk_len_ > max_psk_len) {
        Py_DECREF(result);
        goto error;
    }
    memcpy(psk, psk_, psk_len_);

    Py_DECREF(result);

    PyGILState_Release(gstate);
    return (unsigned int)psk_len_;

error:
    if (PyErr_Occurred()) {
        PyErr_FormatUnraisable("Exception ignored in ssl PSK server callback "
                               "while calling callback %R", callback);
    }
    PyGILState_Release(gstate);
    return 0;
}
#endif

/*[clinic input]
@critical_section
_ssl._SSLContext.set_psk_server_callback
    callback: object
    identity_hint: str(accept={str, NoneType}) = None

[clinic start generated code]*/

static PyObject *
_ssl__SSLContext_set_psk_server_callback_impl(PySSLContext *self,
                                              PyObject *callback,
                                              const char *identity_hint)
/*[clinic end generated code: output=1f4d6a4e09a92b03 input=5f79d932458284a7]*/
{
#ifndef OPENSSL_NO_PSK
    if (self->protocol == PY_SSL_VERSION_TLS_CLIENT) {
        _setSSLError(get_state_ctx(self),
                     "Cannot add PSK server callback to a "
                     "PROTOCOL_TLS_CLIENT context", 0, __FILE__, __LINE__);
        return NULL;
    }

    SSL_psk_server_cb_func ssl_callback;
    if (callback == Py_None) {
        callback = NULL;
        // Delete the existing callback and hint
        ssl_callback = NULL;
        identity_hint = NULL;
    } else {
        if (!PyCallable_Check(callback)) {
            PyErr_SetString(PyExc_TypeError, "callback must be callable");
            return NULL;
        }
        ssl_callback = psk_server_callback;
    }

    if (SSL_CTX_use_psk_identity_hint(self->ctx, identity_hint) != 1) {
        PyErr_SetString(PyExc_ValueError, "failed to set identity hint");
        return NULL;
    }

    Py_XDECREF(self->psk_server_callback);
    Py_XINCREF(callback);

    self->psk_server_callback = callback;
    SSL_CTX_set_psk_server_callback(self->ctx, ssl_callback);

    Py_RETURN_NONE;
#else
    PyErr_SetString(PyExc_NotImplementedError,
                    "TLS-PSK is not supported by your OpenSSL version.");
    return NULL;
#endif
}


static PyGetSetDef context_getsetlist[] = {
    _SSL__SSLCONTEXT_CHECK_HOSTNAME_GETSETDEF
    _SSL__SSLCONTEXT__HOST_FLAGS_GETSETDEF
    _SSL__SSLCONTEXT_MINIMUM_VERSION_GETSETDEF
    _SSL__SSLCONTEXT_MAXIMUM_VERSION_GETSETDEF
    {"keylog_filename", _PySSLContext_get_keylog_filename,
                        _PySSLContext_set_keylog_filename, NULL},
    {"_msg_callback", _PySSLContext_get_msg_callback,
                      _PySSLContext_set_msg_callback, NULL},
    _SSL__SSLCONTEXT_SNI_CALLBACK_GETSETDEF
#if defined(TLS1_3_VERSION) && !defined(OPENSSL_NO_TLS1_3)
    _SSL__SSLCONTEXT_NUM_TICKETS_GETSETDEF
#endif
    _SSL__SSLCONTEXT_OPTIONS_GETSETDEF
    {"post_handshake_auth", get_post_handshake_auth,
#if defined(PySSL_HAVE_POST_HS_AUTH)
                            set_post_handshake_auth,
#else
                            NULL,
#endif
                            NULL},
    _SSL__SSLCONTEXT_PROTOCOL_GETSETDEF
    _SSL__SSLCONTEXT_VERIFY_FLAGS_GETSETDEF
    _SSL__SSLCONTEXT_VERIFY_MODE_GETSETDEF
    _SSL__SSLCONTEXT_SECURITY_LEVEL_GETSETDEF
    {NULL},            /* sentinel */
};

static struct PyMethodDef context_methods[] = {
    _SSL__SSLCONTEXT__WRAP_SOCKET_METHODDEF
    _SSL__SSLCONTEXT__WRAP_BIO_METHODDEF
    _SSL__SSLCONTEXT_SET_CIPHERS_METHODDEF
    _SSL__SSLCONTEXT_SET_CIPHERSUITES_METHODDEF
    _SSL__SSLCONTEXT_SET_GROUPS_METHODDEF
    _SSL__SSLCONTEXT_SET_CLIENT_SIGALGS_METHODDEF
    _SSL__SSLCONTEXT_SET_SERVER_SIGALGS_METHODDEF
    _SSL__SSLCONTEXT__SET_ALPN_PROTOCOLS_METHODDEF
    _SSL__SSLCONTEXT_LOAD_CERT_CHAIN_METHODDEF
    _SSL__SSLCONTEXT_LOAD_DH_PARAMS_METHODDEF
    _SSL__SSLCONTEXT_LOAD_VERIFY_LOCATIONS_METHODDEF
    _SSL__SSLCONTEXT_SESSION_STATS_METHODDEF
    _SSL__SSLCONTEXT_SET_DEFAULT_VERIFY_PATHS_METHODDEF
    _SSL__SSLCONTEXT_SET_ECDH_CURVE_METHODDEF
    _SSL__SSLCONTEXT_CERT_STORE_STATS_METHODDEF
    _SSL__SSLCONTEXT_GET_CA_CERTS_METHODDEF
    _SSL__SSLCONTEXT_GET_CIPHERS_METHODDEF
    _SSL__SSLCONTEXT_GET_GROUPS_METHODDEF
    _SSL__SSLCONTEXT_SET_PSK_CLIENT_CALLBACK_METHODDEF
    _SSL__SSLCONTEXT_SET_PSK_SERVER_CALLBACK_METHODDEF
    {NULL, NULL}        /* sentinel */
};

static PyType_Slot PySSLContext_slots[] = {
    {Py_tp_methods, context_methods},
    {Py_tp_getset, context_getsetlist},
    {Py_tp_new, _ssl__SSLContext},
    {Py_tp_dealloc, context_dealloc},
    {Py_tp_traverse, context_traverse},
    {Py_tp_clear, context_clear},
    {0, 0},
};

static PyType_Spec PySSLContext_spec = {
    .name = "_ssl._SSLContext",
    .basicsize = sizeof(PySSLContext),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
              Py_TPFLAGS_IMMUTABLETYPE),
    .slots = PySSLContext_slots,
};


/*
 * MemoryBIO objects
 */

/*[clinic input]
@critical_section
@classmethod
_ssl.MemoryBIO.__new__

[clinic start generated code]*/

static PyObject *
_ssl_MemoryBIO_impl(PyTypeObject *type)
/*[clinic end generated code: output=8820a58db78330ac input=87f146cf30af454e]*/
{
    BIO *bio;
    PySSLMemoryBIO *self;

    bio = BIO_new(BIO_s_mem());
    if (bio == NULL) {
        PyErr_SetString(PyExc_MemoryError, "failed to allocate BIO");
        return NULL;
    }
    /* Since our BIO is non-blocking an empty read() does not indicate EOF,
     * just that no data is currently available. The SSL routines should retry
     * the read, which we can achieve by calling BIO_set_retry_read(). */
    BIO_set_retry_read(bio);
    BIO_set_mem_eof_return(bio, -1);

    assert(type != NULL && type->tp_alloc != NULL);
    self = (PySSLMemoryBIO *) type->tp_alloc(type, 0);
    if (self == NULL) {
        BIO_free(bio);
        return NULL;
    }
    self->bio = bio;
    self->eof_written = 0;

    return (PyObject *) self;
}

static void
memory_bio_dealloc(PyObject *op)
{
    PySSLMemoryBIO *self = PySSLMemoryBIO_CAST(op);
    PyTypeObject *tp = Py_TYPE(self);
    (void)BIO_free(self->bio);
    tp->tp_free(self);
    Py_DECREF(tp);
}

/*[clinic input]
@critical_section
@getter
_ssl.MemoryBIO.pending

The number of bytes pending in the memory BIO.
[clinic start generated code]*/

static PyObject *
_ssl_MemoryBIO_pending_get_impl(PySSLMemoryBIO *self)
/*[clinic end generated code: output=19236a32a51ac8ff input=02d9063d8ac31732]*/
{
    size_t res = BIO_ctrl_pending(self->bio);
    return PyLong_FromSize_t(res);
}

/*[clinic input]
@critical_section
@getter
_ssl.MemoryBIO.eof

Whether the memory BIO is at EOF.
[clinic start generated code]*/

static PyObject *
_ssl_MemoryBIO_eof_get_impl(PySSLMemoryBIO *self)
/*[clinic end generated code: output=c255a9ea16e31b92 input=c6ecc12c4509de1f]*/
{
    size_t pending = BIO_ctrl_pending(self->bio);
    return PyBool_FromLong((pending == 0) && self->eof_written);
}

/*[clinic input]
@critical_section
_ssl.MemoryBIO.read
    size as len: int = -1
    /

Read up to size bytes from the memory BIO.

If size is not specified, read the entire buffer.
If the return value is an empty bytes instance, this means either
EOF or that no data is available. Use the "eof" property to
distinguish between the two.
[clinic start generated code]*/

static PyObject *
_ssl_MemoryBIO_read_impl(PySSLMemoryBIO *self, int len)
/*[clinic end generated code: output=a657aa1e79cd01b3 input=21046f2d7dac3a90]*/
{
    int avail, nbytes;

    avail = (int)Py_MIN(BIO_ctrl_pending(self->bio), INT_MAX);
    if ((len < 0) || (len > avail))
        len = avail;

    if (len == 0) {
        return Py_GetConstant(Py_CONSTANT_EMPTY_BYTES);
    }

    PyBytesWriter *writer = PyBytesWriter_Create(len);
    if (writer == NULL) {
        return NULL;
    }

    nbytes = BIO_read(self->bio, PyBytesWriter_GetData(writer), len);
    if (nbytes < 0) {
        _sslmodulestate *state = get_state_mbio(self);
        PyBytesWriter_Discard(writer);
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        return NULL;
    }

    return PyBytesWriter_FinishWithSize(writer, nbytes);
}

/*[clinic input]
@critical_section
_ssl.MemoryBIO.write
    b: Py_buffer
    /

Writes the bytes b into the memory BIO.

Returns the number of bytes written.
[clinic start generated code]*/

static PyObject *
_ssl_MemoryBIO_write_impl(PySSLMemoryBIO *self, Py_buffer *b)
/*[clinic end generated code: output=156ec59110d75935 input=107da3f5fba26b37]*/
{
    int nbytes;

    if (b->len > INT_MAX) {
        PyErr_Format(PyExc_OverflowError,
                     "string longer than %d bytes", INT_MAX);
        return NULL;
    }

    if (self->eof_written) {
        PyObject *module = PyType_GetModule(Py_TYPE(self));
        if (module == NULL)
            return NULL;
        PyErr_SetString(get_ssl_state(module)->PySSLErrorObject,
                        "cannot write() after write_eof()");
        return NULL;
    }

    nbytes = BIO_write(self->bio, b->buf, (int)b->len);
    if (nbytes < 0) {
        _sslmodulestate *state = get_state_mbio(self);
        _setSSLError(state, NULL, 0, __FILE__, __LINE__);
        return NULL;
    }

    return PyLong_FromLong(nbytes);
}

/*[clinic input]
@critical_section
_ssl.MemoryBIO.write_eof

Write an EOF marker to the memory BIO.

When all data has been read, the "eof" property will be True.
[clinic start generated code]*/

static PyObject *
_ssl_MemoryBIO_write_eof_impl(PySSLMemoryBIO *self)
/*[clinic end generated code: output=d4106276ccd1ed34 input=1e914231b1c5900a]*/
{
    self->eof_written = 1;
    /* After an EOF is written, a zero return from read() should be a real EOF
     * i.e. it should not be retried. Clear the SHOULD_RETRY flag. */
    BIO_clear_retry_flags(self->bio);
    BIO_set_mem_eof_return(self->bio, 0);

    Py_RETURN_NONE;
}

static PyGetSetDef memory_bio_getsetlist[] = {
    _SSL_MEMORYBIO_PENDING_GETSETDEF
    _SSL_MEMORYBIO_EOF_GETSETDEF
    {NULL},            /* sentinel */
};

static struct PyMethodDef memory_bio_methods[] = {
    _SSL_MEMORYBIO_READ_METHODDEF
    _SSL_MEMORYBIO_WRITE_METHODDEF
    _SSL_MEMORYBIO_WRITE_EOF_METHODDEF
    {NULL, NULL}        /* sentinel */
};

static PyType_Slot PySSLMemoryBIO_slots[] = {
    {Py_tp_methods, memory_bio_methods},
    {Py_tp_getset, memory_bio_getsetlist},
    {Py_tp_new, _ssl_MemoryBIO},
    {Py_tp_dealloc, memory_bio_dealloc},
    {0, 0},
};

static PyType_Spec PySSLMemoryBIO_spec = {
    .name = "_ssl.MemoryBIO",
    .basicsize = sizeof(PySSLMemoryBIO),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE),
    .slots = PySSLMemoryBIO_slots,
};

/*
 * SSL Session object
 */

static void
PySSLSession_dealloc(PyObject *op)
{
    PySSLSession *self = PySSLSession_CAST(op);
    PyTypeObject *tp = Py_TYPE(self);
    /* bpo-31095: UnTrack is needed before calling any callbacks */
    PyObject_GC_UnTrack(self);
    Py_XDECREF(self->ctx);
    if (self->session != NULL) {
        SSL_SESSION_free(self->session);
    }
    PyObject_GC_Del(self);
    Py_DECREF(tp);
}

static PyObject *
PySSLSession_richcompare(PyObject *left, PyObject *right, int op)
{
    if (left == NULL || right == NULL) {
        PyErr_BadInternalCall();
        return NULL;
    }

    int result;
    PyTypeObject *sesstype = PySSLSession_CAST(left)->ctx->state->PySSLSession_Type;

    if (!Py_IS_TYPE(left, sesstype) || !Py_IS_TYPE(right, sesstype)) {
        Py_RETURN_NOTIMPLEMENTED;
    }

    if (left == right) {
        result = 0;
    } else {
        const unsigned char *left_id, *right_id;
        unsigned int left_len, right_len;
        left_id = SSL_SESSION_get_id(PySSLSession_CAST(left)->session,
                                     &left_len);
        right_id = SSL_SESSION_get_id(PySSLSession_CAST(right)->session,
                                      &right_len);
        if (left_len == right_len) {
            result = memcmp(left_id, right_id, left_len);
        } else {
            result = 1;
        }
    }

    switch (op) {
      case Py_EQ:
        if (result == 0) {
            Py_RETURN_TRUE;
        } else {
            Py_RETURN_FALSE;
        }
        break;
      case Py_NE:
        if (result != 0) {
            Py_RETURN_TRUE;
        } else {
            Py_RETURN_FALSE;
        }
        break;
      case Py_LT:
      case Py_LE:
      case Py_GT:
      case Py_GE:
        Py_RETURN_NOTIMPLEMENTED;
        break;
      default:
        PyErr_BadArgument();
        return NULL;
    }
}

static int
PySSLSession_traverse(PyObject *op, visitproc visit, void *arg)
{
    PySSLSession *self = PySSLSession_CAST(op);
    Py_VISIT(self->ctx);
    Py_VISIT(Py_TYPE(self));
    return 0;
}

static int
PySSLSession_clear(PyObject *op)
{
    PySSLSession *self = PySSLSession_CAST(op);
    Py_CLEAR(self->ctx);
    return 0;
}


/*[clinic input]
@critical_section
@getter
_ssl.SSLSession.time

Session creation time (seconds since epoch).
[clinic start generated code]*/

static PyObject *
_ssl_SSLSession_time_get_impl(PySSLSession *self)
/*[clinic end generated code: output=4b887b9299de9be4 input=67f2325284450ae2]*/
{
#if OPENSSL_VERSION_NUMBER >= 0x30300000L
    return _PyLong_FromTime_t(SSL_SESSION_get_time_ex(self->session));
#else
    return PyLong_FromLong(SSL_SESSION_get_time(self->session));
#endif
}

/*[clinic input]
@critical_section
@getter
_ssl.SSLSession.timeout

Session timeout (delta in seconds).
[clinic start generated code]*/

static PyObject *
_ssl_SSLSession_timeout_get_impl(PySSLSession *self)
/*[clinic end generated code: output=82339c148ab2f7d1 input=cd17c2b087c442f2]*/
{
    long timeout = SSL_SESSION_get_timeout(self->session);
    PyObject *res = PyLong_FromLong(timeout);
    return res;
}

/*[clinic input]
@critical_section
@getter
_ssl.SSLSession.ticket_lifetime_hint

Ticket life time hint.
[clinic start generated code]*/

static PyObject *
_ssl_SSLSession_ticket_lifetime_hint_get_impl(PySSLSession *self)
/*[clinic end generated code: output=c8b6db498136c275 input=f0e2df50961a7806]*/
{
    unsigned long hint = SSL_SESSION_get_ticket_lifetime_hint(self->session);
    return PyLong_FromUnsignedLong(hint);
}

/*[clinic input]
@critical_section
@getter
_ssl.SSLSession.id

Session ID.
[clinic start generated code]*/

static PyObject *
_ssl_SSLSession_id_get_impl(PySSLSession *self)
/*[clinic end generated code: output=c532fb96b10c5adf input=0a379e64312b776d]*/

{
    const unsigned char *id;
    unsigned int len;
    id = SSL_SESSION_get_id(self->session, &len);
    return PyBytes_FromStringAndSize((const char *)id, len);
}

/*[clinic input]
@critical_section
@getter
_ssl.SSLSession.has_ticket

Does the session contain a ticket?
[clinic start generated code]*/

static PyObject *
_ssl_SSLSession_has_ticket_get_impl(PySSLSession *self)
/*[clinic end generated code: output=aa3ccfc40b10b96d input=fa475555f53a5086]*/
{
    int res = SSL_SESSION_has_ticket(self->session);
    return res ? Py_True : Py_False;
}

static PyGetSetDef PySSLSession_getsetlist[] = {
    _SSL_SSLSESSION_HAS_TICKET_GETSETDEF
    _SSL_SSLSESSION_ID_GETSETDEF
    _SSL_SSLSESSION_TICKET_LIFETIME_HINT_GETSETDEF
    _SSL_SSLSESSION_TIME_GETSETDEF
    _SSL_SSLSESSION_TIMEOUT_GETSETDEF
    {NULL},            /* sentinel */
};

static PyType_Slot PySSLSession_slots[] = {
    {Py_tp_getset,PySSLSession_getsetlist},
    {Py_tp_richcompare, PySSLSession_richcompare},
    {Py_tp_dealloc, PySSLSession_dealloc},
    {Py_tp_traverse, PySSLSession_traverse},
    {Py_tp_clear, PySSLSession_clear},
    {0, 0},
};

static PyType_Spec PySSLSession_spec = {
    .name = "_ssl.SSLSession",
    .basicsize = sizeof(PySSLSession),
    .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
              Py_TPFLAGS_IMMUTABLETYPE |
              Py_TPFLAGS_DISALLOW_INSTANTIATION),
    .slots = PySSLSession_slots,
};


/* helper routines for seeding the SSL PRNG */
/*[clinic input]
@critical_section
_ssl.RAND_add
    string as view: Py_buffer(accept={str, buffer})
    entropy: double
    /

Mix string into the OpenSSL PRNG state.

entropy (a float) is a lower bound on the entropy contained in
string.  See RFC 4086.
[clinic start generated code]*/

static PyObject *
_ssl_RAND_add_impl(PyObject *module, Py_buffer *view, double entropy)
/*[clinic end generated code: output=e6dd48df9c9024e9 input=313cb73b34db31d5]*/
{
    const char *buf;
    Py_ssize_t len, written;

    buf = (const char *)view->buf;
    len = view->len;
    do {
        written = Py_MIN(len, INT_MAX);
        RAND_add(buf, (int)written, entropy);
        buf += written;
        len -= written;
    } while (len);
    Py_RETURN_NONE;
}

static PyObject *
PySSL_RAND(PyObject *module, int len, int pseudo)
{
    int ok;
    PyObject *bytes;
    unsigned long err;
    const char *errstr;
    PyObject *v;

    if (len < 0) {
        PyErr_SetString(PyExc_ValueError, "num must be positive");
        return NULL;
    }

    bytes = PyBytes_FromStringAndSize(NULL, len);
    if (bytes == NULL)
        return NULL;
    if (pseudo) {
        ok = RAND_bytes((unsigned char*)PyBytes_AS_STRING(bytes), len);
        if (ok == 0 || ok == 1)
            return Py_BuildValue("NO", bytes, ok == 1 ? Py_True : Py_False);
    }
    else {
        ok = RAND_bytes((unsigned char*)PyBytes_AS_STRING(bytes), len);
        if (ok == 1)
            return bytes;
    }
    Py_DECREF(bytes);

    err = ERR_get_error();
    errstr = ERR_reason_error_string(err);
    v = Py_BuildValue("(ks)", err, errstr);
    if (v != NULL) {
        PyErr_SetObject(get_ssl_state(module)->PySSLErrorObject, v);
        Py_DECREF(v);
    }
    return NULL;
}

/*[clinic input]
@critical_section
_ssl.RAND_bytes
    n: int
    /

Generate n cryptographically strong pseudo-random bytes.
[clinic start generated code]*/

static PyObject *
_ssl_RAND_bytes_impl(PyObject *module, int n)
/*[clinic end generated code: output=977da635e4838bc7 input=2e78ce1e86336776]*/
{
    return PySSL_RAND(module, n, 0);
}


/*[clinic input]
@permit_long_summary
@critical_section
_ssl.RAND_status

Returns True if the OpenSSL PRNG has been seeded with enough data and False if not.

It is necessary to seed the PRNG with RAND_add() on some platforms before
using the ssl() function.
[clinic start generated code]*/

static PyObject *
_ssl_RAND_status_impl(PyObject *module)
/*[clinic end generated code: output=7e0aaa2d39fdc1ad input=aba24a3f3af3b184]*/
{
    return PyBool_FromLong(RAND_status());
}

/*[clinic input]
@permit_long_summary
@critical_section
_ssl.get_default_verify_paths

Return search paths and environment vars that are used by SSLContext's set_default_verify_paths() to load default CAs.

The values are 'cert_file_env', 'cert_file', 'cert_dir_env', 'cert_dir'.
[clinic start generated code]*/

static PyObject *
_ssl_get_default_verify_paths_impl(PyObject *module)
/*[clinic end generated code: output=e5b62a466271928b input=255507e1be890095]*/
{
    PyObject *ofile_env = NULL;
    PyObject *ofile = NULL;
    PyObject *odir_env = NULL;
    PyObject *odir = NULL;

#define CONVERT(info, target) { \
        const char *tmp = (info); \
        target = NULL; \
        if (!tmp) { target = Py_NewRef(Py_None); } \
        else if ((target = PyUnicode_DecodeFSDefault(tmp)) == NULL) { \
            target = PyBytes_FromString(tmp); } \
        if (!target) goto error; \
    }

    CONVERT(X509_get_default_cert_file_env(), ofile_env);
    CONVERT(X509_get_default_cert_file(), ofile);
    CONVERT(X509_get_default_cert_dir_env(), odir_env);
    CONVERT(X509_get_default_cert_dir(), odir);
#undef CONVERT

    return Py_BuildValue("NNNN", ofile_env, ofile, odir_env, odir);

  error:
    Py_XDECREF(ofile_env);
    Py_XDECREF(ofile);
    Py_XDECREF(odir_env);
    Py_XDECREF(odir);
    return NULL;
}

/*[clinic input]
_ssl.get_sigalgs
[clinic start generated code]*/

static PyObject *
_ssl_get_sigalgs_impl(PyObject *module)
/*[clinic end generated code: output=ab0791b63856854b input=d96dd6cefec3f86b]*/
{
#if OPENSSL_VERSION_NUMBER >= 0x30400000L
    const char *sigalgs;
    PyObject *sigalgs_str, *sigalgs_list;

    if ((sigalgs = SSL_get1_builtin_sigalgs(NULL)) == NULL) {
        PyErr_NoMemory();
        return NULL;
    }

    if ((sigalgs_str = PyUnicode_DecodeFSDefault(sigalgs)) == NULL) {
        OPENSSL_free((void *)sigalgs);
        return NULL;
    }

    OPENSSL_free((void *)sigalgs);
    sigalgs_list = PyUnicode_Split(sigalgs_str, _Py_LATIN1_CHR(':'), -1);
    Py_DECREF(sigalgs_str);
    return sigalgs_list;
#else
    PyErr_SetString(PyExc_NotImplementedError,
                    "Getting signature algorithms requires OpenSSL 3.4 or later.");
    return NULL;
#endif
}

static PyObject*
asn1obj2py(_sslmodulestate *state, ASN1_OBJECT *obj)
{
    int nid;
    const char *ln, *sn;

    nid = OBJ_obj2nid(obj);
    if (nid == NID_undef) {
        PyErr_Format(PyExc_ValueError, "Unknown object");
        return NULL;
    }
    sn = OBJ_nid2sn(nid);
    ln = OBJ_nid2ln(nid);
    return Py_BuildValue("issN", nid, sn, ln, _asn1obj2py(state, obj, 1));
}

/*[clinic input]
@critical_section
_ssl.txt2obj
    txt: str
    name: bool = False

Lookup NID, short name, long name and OID of an ASN1_OBJECT.

By default objects are looked up by OID. With name=True short and
long name are also matched.
[clinic start generated code]*/

static PyObject *
_ssl_txt2obj_impl(PyObject *module, const char *txt, int name)
/*[clinic end generated code: output=c38e3991347079c1 input=c99b134d70173c5e]*/
{
    PyObject *result = NULL;
    ASN1_OBJECT *obj;

    obj = OBJ_txt2obj(txt, name ? 0 : 1);
    if (obj == NULL) {
        PyErr_Format(PyExc_ValueError, "unknown object '%.100s'", txt);
        return NULL;
    }
    result = asn1obj2py(get_ssl_state(module), obj);
    ASN1_OBJECT_free(obj);
    return result;
}

/*[clinic input]
@critical_section
_ssl.nid2obj
    nid: int
    /

Lookup NID, short name, long name and OID of an ASN1_OBJECT by NID.
[clinic start generated code]*/

static PyObject *
_ssl_nid2obj_impl(PyObject *module, int nid)
/*[clinic end generated code: output=4a98ab691cd4f84a input=1b1170506fa83a53]*/
{
    PyObject *result = NULL;
    ASN1_OBJECT *obj;

    if (nid < NID_undef) {
        PyErr_SetString(PyExc_ValueError, "NID must be positive.");
        return NULL;
    }
    obj = OBJ_nid2obj(nid);
    if (obj == NULL) {
        PyErr_Format(PyExc_ValueError, "unknown NID %i", nid);
        return NULL;
    }
    result = asn1obj2py(get_ssl_state(module), obj);
    ASN1_OBJECT_free(obj);
    return result;
}

#ifdef _MSC_VER

static PyObject*
certEncodingType(DWORD encodingType)
{
    static PyObject *x509_asn = NULL;
    static PyObject *pkcs_7_asn = NULL;

    if (x509_asn == NULL) {
        x509_asn = PyUnicode_InternFromString("x509_asn");
        if (x509_asn == NULL)
            return NULL;
    }
    if (pkcs_7_asn == NULL) {
        pkcs_7_asn = PyUnicode_InternFromString("pkcs_7_asn");
        if (pkcs_7_asn == NULL)
            return NULL;
    }
    switch(encodingType) {
    case X509_ASN_ENCODING:
        return Py_NewRef(x509_asn);
    case PKCS_7_ASN_ENCODING:
        return Py_NewRef(pkcs_7_asn);
    default:
        return PyLong_FromLong(encodingType);
    }
}

static PyObject*
parseKeyUsage(PCCERT_CONTEXT pCertCtx, DWORD flags)
{
    CERT_ENHKEY_USAGE *usage;
    DWORD size, error, i;
    PyObject *retval;

    if (!CertGetEnhancedKeyUsage(pCertCtx, flags, NULL, &size)) {
        error = GetLastError();
        if (error == CRYPT_E_NOT_FOUND) {
            Py_RETURN_TRUE;
        }
        return PyErr_SetFromWindowsErr(error);
    }

    usage = (CERT_ENHKEY_USAGE*)PyMem_Malloc(size);
    if (usage == NULL) {
        return PyErr_NoMemory();
    }

    /* Now get the actual enhanced usage property */
    if (!CertGetEnhancedKeyUsage(pCertCtx, flags, usage, &size)) {
        PyMem_Free(usage);
        error = GetLastError();
        if (error == CRYPT_E_NOT_FOUND) {
            Py_RETURN_TRUE;
        }
        return PyErr_SetFromWindowsErr(error);
    }
    retval = PyFrozenSet_New(NULL);
    if (retval == NULL) {
        goto error;
    }
    for (i = 0; i < usage->cUsageIdentifier; ++i) {
        if (usage->rgpszUsageIdentifier[i]) {
            PyObject *oid;
            int err;
            oid = PyUnicode_FromString(usage->rgpszUsageIdentifier[i]);
            if (oid == NULL) {
                Py_CLEAR(retval);
                goto error;
            }
            err = PySet_Add(retval, oid);
            Py_DECREF(oid);
            if (err == -1) {
                Py_CLEAR(retval);
                goto error;
            }
        }
    }
  error:
    PyMem_Free(usage);
    return retval;
}

static HCERTSTORE
ssl_collect_certificates(const char *store_name)
{
/* this function collects the system certificate stores listed in
 * system_stores into a collection certificate store for being
 * enumerated. The store must be readable to be added to the
 * store collection.
 */

    HCERTSTORE hCollectionStore = NULL, hSystemStore = NULL;
    static DWORD system_stores[] = {
        CERT_SYSTEM_STORE_LOCAL_MACHINE,
        CERT_SYSTEM_STORE_LOCAL_MACHINE_ENTERPRISE,
        CERT_SYSTEM_STORE_LOCAL_MACHINE_GROUP_POLICY,
        CERT_SYSTEM_STORE_CURRENT_USER,
        CERT_SYSTEM_STORE_CURRENT_USER_GROUP_POLICY,
        CERT_SYSTEM_STORE_SERVICES,
        CERT_SYSTEM_STORE_USERS};
    size_t i, storesAdded;
    BOOL result;

    hCollectionStore = CertOpenStore(CERT_STORE_PROV_COLLECTION, 0,
                                     (HCRYPTPROV)NULL, 0, NULL);
    if (!hCollectionStore) {
        return NULL;
    }
    storesAdded = 0;
    for (i = 0; i < sizeof(system_stores) / sizeof(DWORD); i++) {
        hSystemStore = CertOpenStore(CERT_STORE_PROV_SYSTEM_A, 0,
                                     (HCRYPTPROV)NULL,
                                     CERT_STORE_READONLY_FLAG |
                                     system_stores[i], store_name);
        if (hSystemStore) {
            result = CertAddStoreToCollection(hCollectionStore, hSystemStore,
                                     CERT_PHYSICAL_STORE_ADD_ENABLE_FLAG, 0);
            if (result) {
                ++storesAdded;
            }
            CertCloseStore(hSystemStore, 0);  /* flag must be 0 */
        }
    }
    if (storesAdded == 0) {
        CertCloseStore(hCollectionStore, CERT_CLOSE_STORE_FORCE_FLAG);
        return NULL;
    }

    return hCollectionStore;
}

/*[clinic input]
@critical_section
_ssl.enum_certificates
    store_name: str

Retrieve certificates from Windows' cert store.

store_name may be one of 'CA', 'ROOT' or 'MY'.  The system may provide
more cert storages, too.  The function returns a list of (bytes,
encoding_type, trust) tuples.  The encoding_type flag can be interpreted
with X509_ASN_ENCODING or PKCS_7_ASN_ENCODING. The trust setting is either
a set of OIDs or the boolean True.
[clinic start generated code]*/

static PyObject *
_ssl_enum_certificates_impl(PyObject *module, const char *store_name)
/*[clinic end generated code: output=5134dc8bb3a3c893 input=263c22e6c6988cf3]*/
{
    HCERTSTORE hCollectionStore = NULL;
    PCCERT_CONTEXT pCertCtx = NULL;
    PyObject *keyusage = NULL, *cert = NULL, *enc = NULL, *tup = NULL;
    PyObject *result = NULL;

    result = PySet_New(NULL);
    if (result == NULL) {
        return NULL;
    }
    hCollectionStore = ssl_collect_certificates(store_name);
    if (hCollectionStore == NULL) {
        Py_DECREF(result);
        return PyErr_SetFromWindowsErr(GetLastError());
    }

    while ((pCertCtx = CertEnumCertificatesInStore(hCollectionStore, pCertCtx))) {
        cert = PyBytes_FromStringAndSize((const char*)pCertCtx->pbCertEncoded,
                                            pCertCtx->cbCertEncoded);
        if (!cert) {
            Py_CLEAR(result);
            break;
        }
        if ((enc = certEncodingType(pCertCtx->dwCertEncodingType)) == NULL) {
            Py_CLEAR(result);
            break;
        }
        keyusage = parseKeyUsage(pCertCtx, CERT_FIND_PROP_ONLY_ENHKEY_USAGE_FLAG);
        if (keyusage == Py_True) {
            Py_DECREF(keyusage);
            keyusage = parseKeyUsage(pCertCtx, CERT_FIND_EXT_ONLY_ENHKEY_USAGE_FLAG);
        }
        if (keyusage == NULL) {
            Py_CLEAR(result);
            break;
        }
        if ((tup = PyTuple_New(3)) == NULL) {
            Py_CLEAR(result);
            break;
        }
        PyTuple_SET_ITEM(tup, 0, cert);
        cert = NULL;
        PyTuple_SET_ITEM(tup, 1, enc);
        enc = NULL;
        PyTuple_SET_ITEM(tup, 2, keyusage);
        keyusage = NULL;
        if (PySet_Add(result, tup) == -1) {
            Py_CLEAR(result);
            Py_CLEAR(tup);
            break;
        }
        Py_CLEAR(tup);
    }
    if (pCertCtx) {
        /* loop ended with an error, need to clean up context manually */
        CertFreeCertificateContext(pCertCtx);
    }

    /* In error cases cert, enc and tup may not be NULL */
    Py_XDECREF(cert);
    Py_XDECREF(enc);
    Py_XDECREF(keyusage);
    Py_XDECREF(tup);

    /* CERT_CLOSE_STORE_FORCE_FLAG forces freeing of memory for all contexts
       associated with the store, in this case our collection store and the
       associated system stores. */
    if (!CertCloseStore(hCollectionStore, CERT_CLOSE_STORE_FORCE_FLAG)) {
        /* This error case might shadow another exception.*/
        Py_XDECREF(result);
        return PyErr_SetFromWindowsErr(GetLastError());
    }

    /* convert set to list */
    if (result == NULL) {
        return NULL;
    } else {
        PyObject *lst = PySequence_List(result);
        Py_DECREF(result);
        return lst;
    }
}

/*[clinic input]
@critical_section
_ssl.enum_crls
    store_name: str

Retrieve CRLs from Windows' cert store.

store_name may be one of 'CA', 'ROOT' or 'MY'.  The system may provide
more cert storages, too.  The function returns a list of (bytes,
encoding_type) tuples.  The encoding_type flag can be interpreted with
X509_ASN_ENCODING or PKCS_7_ASN_ENCODING.
[clinic start generated code]*/

static PyObject *
_ssl_enum_crls_impl(PyObject *module, const char *store_name)
/*[clinic end generated code: output=bce467f60ccd03b6 input=51a1b1059e55ce43]*/
{
    HCERTSTORE hCollectionStore = NULL;
    PCCRL_CONTEXT pCrlCtx = NULL;
    PyObject *crl = NULL, *enc = NULL, *tup = NULL;
    PyObject *result = NULL;

    result = PySet_New(NULL);
    if (result == NULL) {
        return NULL;
    }
    hCollectionStore = ssl_collect_certificates(store_name);
    if (hCollectionStore == NULL) {
        Py_DECREF(result);
        return PyErr_SetFromWindowsErr(GetLastError());
    }

    while ((pCrlCtx = CertEnumCRLsInStore(hCollectionStore, pCrlCtx))) {
        crl = PyBytes_FromStringAndSize((const char*)pCrlCtx->pbCrlEncoded,
                                            pCrlCtx->cbCrlEncoded);
        if (!crl) {
            Py_CLEAR(result);
            break;
        }
        if ((enc = certEncodingType(pCrlCtx->dwCertEncodingType)) == NULL) {
            Py_CLEAR(result);
            break;
        }
        if ((tup = PyTuple_New(2)) == NULL) {
            Py_CLEAR(result);
            break;
        }
        PyTuple_SET_ITEM(tup, 0, crl);
        crl = NULL;
        PyTuple_SET_ITEM(tup, 1, enc);
        enc = NULL;

        if (PySet_Add(result, tup) == -1) {
            Py_CLEAR(result);
            Py_CLEAR(tup);
            break;
        }
        Py_CLEAR(tup);
    }
    if (pCrlCtx) {
        /* loop ended with an error, need to clean up context manually */
        CertFreeCRLContext(pCrlCtx);
    }

    /* In error cases cert, enc and tup may not be NULL */
    Py_XDECREF(crl);
    Py_XDECREF(enc);
    Py_XDECREF(tup);

    /* CERT_CLOSE_STORE_FORCE_FLAG forces freeing of memory for all contexts
       associated with the store, in this case our collection store and the
       associated system stores. */
    if (!CertCloseStore(hCollectionStore, CERT_CLOSE_STORE_FORCE_FLAG)) {
        /* This error case might shadow another exception.*/
        Py_XDECREF(result);
        return PyErr_SetFromWindowsErr(GetLastError());
    }
    /* convert set to list */
    if (result == NULL) {
        return NULL;
    } else {
        PyObject *lst = PySequence_List(result);
        Py_DECREF(result);
        return lst;
    }
}

#endif /* _MSC_VER */

/* List of functions exported by this module. */
static PyMethodDef PySSL_methods[] = {
    _SSL__TEST_DECODE_CERT_METHODDEF
    _SSL_RAND_ADD_METHODDEF
    _SSL_RAND_BYTES_METHODDEF
    _SSL_RAND_STATUS_METHODDEF
    _SSL_GET_DEFAULT_VERIFY_PATHS_METHODDEF
    _SSL_GET_SIGALGS_METHODDEF
    _SSL_ENUM_CERTIFICATES_METHODDEF
    _SSL_ENUM_CRLS_METHODDEF
    _SSL_TXT2OBJ_METHODDEF
    _SSL_NID2OBJ_METHODDEF
    {NULL,                  NULL}            /* Sentinel */
};


PyDoc_STRVAR(module_doc,
"Implementation module for SSL socket operations.  See the socket module\n\
for documentation.");

static int
sslmodule_init_exceptions(PyObject *module)
{
    _sslmodulestate *state = get_ssl_state(module);
    PyObject *bases = NULL;

#define add_exception(exc, name, doc, base)                                 \
do {                                                                        \
    (exc) = PyErr_NewExceptionWithDoc("ssl." name, (doc), (base), NULL);    \
    if ((state) == NULL) goto error;                                        \
    if (PyModule_AddObjectRef(module, name, exc) < 0) goto error;           \
} while(0)

    state->PySSLErrorObject = PyType_FromSpecWithBases(
        &sslerror_type_spec, PyExc_OSError);
    if (state->PySSLErrorObject == NULL) {
        goto error;
    }
    if (PyModule_AddObjectRef(module, "SSLError", state->PySSLErrorObject) < 0) {
        goto error;
    }

    /* ssl.CertificateError used to be a subclass of ValueError */
    bases = _PyTuple_FromPair(state->PySSLErrorObject, PyExc_ValueError);
    if (bases == NULL) {
        goto error;
    }
    add_exception(
        state->PySSLCertVerificationErrorObject,
        "SSLCertVerificationError",
        SSLCertVerificationError_doc,
        bases
    );
    Py_CLEAR(bases);

    add_exception(
        state->PySSLZeroReturnErrorObject,
        "SSLZeroReturnError",
        SSLZeroReturnError_doc,
        state->PySSLErrorObject
    );

    add_exception(
        state->PySSLWantWriteErrorObject,
        "SSLWantWriteError",
        SSLWantWriteError_doc,
        state->PySSLErrorObject
    );

    add_exception(
        state->PySSLWantReadErrorObject,
        "SSLWantReadError",
        SSLWantReadError_doc,
        state->PySSLErrorObject
    );

    add_exception(
        state->PySSLSyscallErrorObject,
        "SSLSyscallError",
        SSLSyscallError_doc,
        state->PySSLErrorObject
    );

    add_exception(
        state->PySSLEOFErrorObject,
        "SSLEOFError",
        SSLEOFError_doc,
        state->PySSLErrorObject
    );
#undef add_exception

    return 0;
  error:
    Py_XDECREF(bases);
    return -1;
}

static int
sslmodule_init_socketapi(PyObject *module)
{
    _sslmodulestate *state = get_ssl_state(module);
    PySocketModule_APIObject *sockmod = PySocketModule_ImportModuleAndAPI();

    if ((sockmod == NULL) || (sockmod->Sock_Type == NULL)) {
        return -1;
    }
    state->Sock_Type = (PyTypeObject*)Py_NewRef(sockmod->Sock_Type);
    return 0;
}


static int
sslmodule_add_option(PyObject *m, const char *name, uint64_t value)
{
    Py_BUILD_ASSERT(sizeof(unsigned long long) >= sizeof(value));
    return PyModule_Add(m, name, PyLong_FromUnsignedLongLong(value));
}


static int
sslmodule_init_constants(PyObject *m)
{
    if (PyModule_AddStringConstant(m, "_DEFAULT_CIPHERS",
                                   PY_SSL_DEFAULT_CIPHER_STRING) < 0)
    {
        return -1;
    }

#define ADD_INT_CONST(NAME, VALUE) do {                 \
    if (PyModule_AddIntConstant(m, NAME, VALUE) < 0) {  \
        return -1;                                      \
    }                                                   \
} while (0)

    ADD_INT_CONST("SSL_ERROR_ZERO_RETURN", PY_SSL_ERROR_ZERO_RETURN);
    ADD_INT_CONST("SSL_ERROR_WANT_READ", PY_SSL_ERROR_WANT_READ);
    ADD_INT_CONST("SSL_ERROR_WANT_WRITE", PY_SSL_ERROR_WANT_WRITE);
    ADD_INT_CONST("SSL_ERROR_WANT_X509_LOOKUP", PY_SSL_ERROR_WANT_X509_LOOKUP);
    ADD_INT_CONST("SSL_ERROR_SYSCALL", PY_SSL_ERROR_SYSCALL);
    ADD_INT_CONST("SSL_ERROR_SSL", PY_SSL_ERROR_SSL);
    ADD_INT_CONST("SSL_ERROR_WANT_CONNECT", PY_SSL_ERROR_WANT_CONNECT);
    /* non ssl.h errorcodes */
    ADD_INT_CONST("SSL_ERROR_EOF", PY_SSL_ERROR_EOF);
    ADD_INT_CONST("SSL_ERROR_INVALID_ERROR_CODE",
                  PY_SSL_ERROR_INVALID_ERROR_CODE);
    /* cert requirements */
    ADD_INT_CONST("CERT_NONE", PY_SSL_CERT_NONE);
    ADD_INT_CONST("CERT_OPTIONAL", PY_SSL_CERT_OPTIONAL);
    ADD_INT_CONST("CERT_REQUIRED", PY_SSL_CERT_REQUIRED);
    /* CRL verification for verification_flags */
    ADD_INT_CONST("VERIFY_DEFAULT", 0);
    ADD_INT_CONST("VERIFY_CRL_CHECK_LEAF", X509_V_FLAG_CRL_CHECK);
    ADD_INT_CONST("VERIFY_CRL_CHECK_CHAIN",
                  X509_V_FLAG_CRL_CHECK|X509_V_FLAG_CRL_CHECK_ALL);
    ADD_INT_CONST("VERIFY_X509_STRICT", X509_V_FLAG_X509_STRICT);
    ADD_INT_CONST("VERIFY_ALLOW_PROXY_CERTS", X509_V_FLAG_ALLOW_PROXY_CERTS);
    ADD_INT_CONST("VERIFY_X509_TRUSTED_FIRST", X509_V_FLAG_TRUSTED_FIRST);

#ifdef X509_V_FLAG_PARTIAL_CHAIN
    ADD_INT_CONST("VERIFY_X509_PARTIAL_CHAIN", X509_V_FLAG_PARTIAL_CHAIN);
#endif

    /* Alert Descriptions from ssl.h */
    /* note RESERVED constants no longer intended for use have been removed */
    /* http://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-6 */

#define ADD_AD_CONSTANT(s) \
    ADD_INT_CONST("ALERT_DESCRIPTION_"#s, \
                            SSL_AD_##s)

    ADD_AD_CONSTANT(CLOSE_NOTIFY);
    ADD_AD_CONSTANT(UNEXPECTED_MESSAGE);
    ADD_AD_CONSTANT(BAD_RECORD_MAC);
    ADD_AD_CONSTANT(RECORD_OVERFLOW);
    ADD_AD_CONSTANT(DECOMPRESSION_FAILURE);
    ADD_AD_CONSTANT(HANDSHAKE_FAILURE);
    ADD_AD_CONSTANT(BAD_CERTIFICATE);
    ADD_AD_CONSTANT(UNSUPPORTED_CERTIFICATE);
    ADD_AD_CONSTANT(CERTIFICATE_REVOKED);
    ADD_AD_CONSTANT(CERTIFICATE_EXPIRED);
    ADD_AD_CONSTANT(CERTIFICATE_UNKNOWN);
    ADD_AD_CONSTANT(ILLEGAL_PARAMETER);
    ADD_AD_CONSTANT(UNKNOWN_CA);
    ADD_AD_CONSTANT(ACCESS_DENIED);
    ADD_AD_CONSTANT(DECODE_ERROR);
    ADD_AD_CONSTANT(DECRYPT_ERROR);
    ADD_AD_CONSTANT(PROTOCOL_VERSION);
    ADD_AD_CONSTANT(INSUFFICIENT_SECURITY);
    ADD_AD_CONSTANT(INTERNAL_ERROR);
    ADD_AD_CONSTANT(USER_CANCELLED);
    ADD_AD_CONSTANT(NO_RENEGOTIATION);
    /* Not all constants are in old OpenSSL versions */
#ifdef SSL_AD_UNSUPPORTED_EXTENSION
    ADD_AD_CONSTANT(UNSUPPORTED_EXTENSION);
#endif
#ifdef SSL_AD_CERTIFICATE_UNOBTAINABLE
    ADD_AD_CONSTANT(CERTIFICATE_UNOBTAINABLE);
#endif
#ifdef SSL_AD_UNRECOGNIZED_NAME
    ADD_AD_CONSTANT(UNRECOGNIZED_NAME);
#endif
#ifdef SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE
    ADD_AD_CONSTANT(BAD_CERTIFICATE_STATUS_RESPONSE);
#endif
#ifdef SSL_AD_BAD_CERTIFICATE_HASH_VALUE
    ADD_AD_CONSTANT(BAD_CERTIFICATE_HASH_VALUE);
#endif
#ifdef SSL_AD_UNKNOWN_PSK_IDENTITY
    ADD_AD_CONSTANT(UNKNOWN_PSK_IDENTITY);
#endif

#undef ADD_AD_CONSTANT

    /* protocol versions */
#ifndef OPENSSL_NO_SSL3
    ADD_INT_CONST("PROTOCOL_SSLv3", PY_SSL_VERSION_SSL3);
#endif
    ADD_INT_CONST("PROTOCOL_SSLv23", PY_SSL_VERSION_TLS);
    ADD_INT_CONST("PROTOCOL_TLS", PY_SSL_VERSION_TLS);
    ADD_INT_CONST("PROTOCOL_TLS_CLIENT", PY_SSL_VERSION_TLS_CLIENT);
    ADD_INT_CONST("PROTOCOL_TLS_SERVER", PY_SSL_VERSION_TLS_SERVER);
#ifndef OPENSSL_NO_TLS1
    ADD_INT_CONST("PROTOCOL_TLSv1", PY_SSL_VERSION_TLS1);
#endif
#ifndef OPENSSL_NO_TLS1_1
    ADD_INT_CONST("PROTOCOL_TLSv1_1", PY_SSL_VERSION_TLS1_1);
#endif
#ifndef OPENSSL_NO_TLS1_2
    ADD_INT_CONST("PROTOCOL_TLSv1_2", PY_SSL_VERSION_TLS1_2);
#endif

#define ADD_OPTION(NAME, VALUE) if (sslmodule_add_option(m, NAME, (VALUE)) < 0) return -1

    /* protocol options */
    ADD_OPTION("OP_ALL", SSL_OP_ALL & ~SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS);
    ADD_OPTION("OP_NO_SSLv2", SSL_OP_NO_SSLv2);
    ADD_OPTION("OP_NO_SSLv3", SSL_OP_NO_SSLv3);
    ADD_OPTION("OP_NO_TLSv1", SSL_OP_NO_TLSv1);
    ADD_OPTION("OP_NO_TLSv1_1", SSL_OP_NO_TLSv1_1);
    ADD_OPTION("OP_NO_TLSv1_2", SSL_OP_NO_TLSv1_2);
#ifdef SSL_OP_NO_TLSv1_3
    ADD_OPTION("OP_NO_TLSv1_3", SSL_OP_NO_TLSv1_3);
#else
    ADD_OPTION("OP_NO_TLSv1_3", 0);
#endif
    ADD_OPTION("OP_CIPHER_SERVER_PREFERENCE",
                            SSL_OP_CIPHER_SERVER_PREFERENCE);
    ADD_OPTION("OP_SINGLE_DH_USE", SSL_OP_SINGLE_DH_USE);
    ADD_OPTION("OP_NO_TICKET", SSL_OP_NO_TICKET);
    ADD_OPTION("OP_LEGACY_SERVER_CONNECT",
                            SSL_OP_LEGACY_SERVER_CONNECT);
#ifdef SSL_OP_SINGLE_ECDH_USE
    ADD_OPTION("OP_SINGLE_ECDH_USE", SSL_OP_SINGLE_ECDH_USE);
#endif
#ifdef SSL_OP_NO_COMPRESSION
    ADD_OPTION("OP_NO_COMPRESSION",
                            SSL_OP_NO_COMPRESSION);
#endif
#ifdef SSL_OP_ENABLE_MIDDLEBOX_COMPAT
    ADD_OPTION("OP_ENABLE_MIDDLEBOX_COMPAT",
                            SSL_OP_ENABLE_MIDDLEBOX_COMPAT);
#endif
#ifdef SSL_OP_NO_RENEGOTIATION
    ADD_OPTION("OP_NO_RENEGOTIATION",
                            SSL_OP_NO_RENEGOTIATION);
#endif
#ifdef SSL_OP_IGNORE_UNEXPECTED_EOF
    ADD_OPTION("OP_IGNORE_UNEXPECTED_EOF",
                            SSL_OP_IGNORE_UNEXPECTED_EOF);
#endif
#ifdef SSL_OP_ENABLE_KTLS
    ADD_OPTION("OP_ENABLE_KTLS", SSL_OP_ENABLE_KTLS);
#endif

#undef ADD_OPTION

#ifdef X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT
    ADD_INT_CONST("HOSTFLAG_ALWAYS_CHECK_SUBJECT",
                  X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT);
#endif
#ifdef X509_CHECK_FLAG_NEVER_CHECK_SUBJECT
    ADD_INT_CONST("HOSTFLAG_NEVER_CHECK_SUBJECT",
                  X509_CHECK_FLAG_NEVER_CHECK_SUBJECT);
#endif
#ifdef X509_CHECK_FLAG_NO_WILDCARDS
    ADD_INT_CONST("HOSTFLAG_NO_WILDCARDS",
                  X509_CHECK_FLAG_NO_WILDCARDS);
#endif
#ifdef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
    ADD_INT_CONST("HOSTFLAG_NO_PARTIAL_WILDCARDS",
                  X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS);
#endif
#ifdef X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS
    ADD_INT_CONST("HOSTFLAG_MULTI_LABEL_WILDCARDS",
                  X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS);
#endif
#ifdef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
    ADD_INT_CONST("HOSTFLAG_SINGLE_LABEL_SUBDOMAINS",
                  X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS);
#endif

    /* file types */
    ADD_INT_CONST("ENCODING_PEM", PY_SSL_ENCODING_PEM);
    ADD_INT_CONST("ENCODING_DER", PY_SSL_ENCODING_DER);

    /* protocol versions */
    ADD_INT_CONST("PROTO_MINIMUM_SUPPORTED", PY_PROTO_MINIMUM_SUPPORTED);
    ADD_INT_CONST("PROTO_MAXIMUM_SUPPORTED", PY_PROTO_MAXIMUM_SUPPORTED);
    ADD_INT_CONST("PROTO_SSLv3", PY_PROTO_SSLv3);
    ADD_INT_CONST("PROTO_TLSv1", PY_PROTO_TLSv1);
    ADD_INT_CONST("PROTO_TLSv1_1", PY_PROTO_TLSv1_1);
    ADD_INT_CONST("PROTO_TLSv1_2", PY_PROTO_TLSv1_2);
    ADD_INT_CONST("PROTO_TLSv1_3", PY_PROTO_TLSv1_3);

#define addbool(m, key, value) \
    do { \
        PyObject *bool_obj = (value) ? Py_True : Py_False; \
        if (PyModule_AddObjectRef((m), (key), bool_obj) < 0) { \
            return -1; \
        } \
    } while (0)

    addbool(m, "HAS_SNI", 1);
    addbool(m, "HAS_TLS_UNIQUE", 1);
    addbool(m, "HAS_ECDH", 1);
    addbool(m, "HAS_NPN", 0);
    addbool(m, "HAS_ALPN", 1);

    addbool(m, "HAS_SSLv2", 0);

#if defined(SSL3_VERSION) && !defined(OPENSSL_NO_SSL3)
    addbool(m, "HAS_SSLv3", 1);
#else
    addbool(m, "HAS_SSLv3", 0);
#endif

#if defined(TLS1_VERSION) && !defined(OPENSSL_NO_TLS1)
    addbool(m, "HAS_TLSv1", 1);
#else
    addbool(m, "HAS_TLSv1", 0);
#endif

#if defined(TLS1_1_VERSION) && !defined(OPENSSL_NO_TLS1_1)
    addbool(m, "HAS_TLSv1_1", 1);
#else
    addbool(m, "HAS_TLSv1_1", 0);
#endif

#if defined(TLS1_2_VERSION) && !defined(OPENSSL_NO_TLS1_2)
    addbool(m, "HAS_TLSv1_2", 1);
#else
    addbool(m, "HAS_TLSv1_2", 0);
#endif

#if defined(TLS1_3_VERSION) && !defined(OPENSSL_NO_TLS1_3)
    addbool(m, "HAS_TLSv1_3", 1);
#else
    addbool(m, "HAS_TLSv1_3", 0);
#endif

#ifdef OPENSSL_NO_PSK
    addbool(m, "HAS_PSK", 0);
#else
    addbool(m, "HAS_PSK", 1);
#endif

#ifdef OPENSSL_NO_EXTERNAL_PSK_TLS13
    addbool(m, "HAS_PSK_TLS13", 0);
#else
    addbool(m, "HAS_PSK_TLS13", 1);
#endif

#ifdef SSL_VERIFY_POST_HANDSHAKE
    addbool(m, "HAS_PHA", 1);
#else
    addbool(m, "HAS_PHA", 0);
#endif

#undef addbool
#undef ADD_INT_CONST

    return 0;
}

static int
sslmodule_init_errorcodes(PyObject *module)
{
    _sslmodulestate *state = get_ssl_state(module);

    struct py_ssl_error_code *errcode;
    struct py_ssl_library_code *libcode;

    /* Mappings for error codes */
    state->err_codes_to_names = PyDict_New();
    if (state->err_codes_to_names == NULL)
        return -1;
    state->lib_codes_to_names = PyDict_New();
    if (state->lib_codes_to_names == NULL)
        return -1;

    errcode = error_codes;
    while (errcode->mnemonic != NULL) {
        PyObject *mnemo = PyUnicode_FromString(errcode->mnemonic);
        if (mnemo == NULL) {
            return -1;
        }
        PyObject *key = Py_BuildValue("ii", errcode->library, errcode->reason);
        if (key == NULL) {
            Py_DECREF(mnemo);
            return -1;
        }
        int rc = PyDict_SetItem(state->err_codes_to_names, key, mnemo);
        Py_DECREF(key);
        Py_DECREF(mnemo);
        if (rc < 0) {
            return -1;
        }
        errcode++;
    }

    libcode = library_codes;
    while (libcode->library != NULL) {
        PyObject *mnemo, *key;
        key = PyLong_FromLong(libcode->code);
        mnemo = PyUnicode_FromString(libcode->library);
        if (key == NULL || mnemo == NULL)
            return -1;
        if (PyDict_SetItem(state->lib_codes_to_names, key, mnemo))
            return -1;
        Py_DECREF(key);
        Py_DECREF(mnemo);
        libcode++;
    }

    return 0;
}

static void
parse_openssl_version(unsigned long libver,
                      unsigned int *major, unsigned int *minor,
                      unsigned int *fix, unsigned int *patch,
                      unsigned int *status)
{
    *status = libver & 0xF;
    libver >>= 4;
    *patch = libver & 0xFF;
    libver >>= 8;
    *fix = libver & 0xFF;
    libver >>= 8;
    *minor = libver & 0xFF;
    libver >>= 8;
    *major = libver & 0xFF;
}

static int
sslmodule_init_versioninfo(PyObject *m)
{
    PyObject *r;
    unsigned long libver;
    unsigned int major, minor, fix, patch, status;

    /* OpenSSL version */
    /* SSLeay() gives us the version of the library linked against,
       which could be different from the headers version.
    */
    libver = OpenSSL_version_num();
    r = PyLong_FromUnsignedLong(libver);
    if (PyModule_Add(m, "OPENSSL_VERSION_NUMBER", r) < 0)
        return -1;

    parse_openssl_version(libver, &major, &minor, &fix, &patch, &status);
    r = Py_BuildValue("IIIII", major, minor, fix, patch, status);
    if (PyModule_Add(m, "OPENSSL_VERSION_INFO", r) < 0)
        return -1;

    r = PyUnicode_FromString(OpenSSL_version(OPENSSL_VERSION));
    if (PyModule_Add(m, "OPENSSL_VERSION", r) < 0)
        return -1;

    libver = OPENSSL_VERSION_NUMBER;
    parse_openssl_version(libver, &major, &minor, &fix, &patch, &status);
    r = Py_BuildValue("IIIII", major, minor, fix, patch, status);
    if (PyModule_Add(m, "_OPENSSL_API_VERSION", r) < 0)
        return -1;

    return 0;
}

static int
sslmodule_init_types(PyObject *module)
{
    _sslmodulestate *state = get_ssl_state(module);

    state->PySSLContext_Type = (PyTypeObject *)PyType_FromModuleAndSpec(
        module, &PySSLContext_spec, NULL
    );
    if (state->PySSLContext_Type == NULL)
        return -1;

    state->PySSLSocket_Type = (PyTypeObject *)PyType_FromModuleAndSpec(
        module, &PySSLSocket_spec, NULL
    );
    if (state->PySSLSocket_Type == NULL)
        return -1;

    state->PySSLMemoryBIO_Type = (PyTypeObject *)PyType_FromModuleAndSpec(
        module, &PySSLMemoryBIO_spec, NULL
    );
    if (state->PySSLMemoryBIO_Type == NULL)
        return -1;

    state->PySSLSession_Type = (PyTypeObject *)PyType_FromModuleAndSpec(
        module, &PySSLSession_spec, NULL
    );
    if (state->PySSLSession_Type == NULL)
        return -1;

    state->PySSLCertificate_Type = (PyTypeObject *)PyType_FromModuleAndSpec(
        module, &PySSLCertificate_spec, NULL
    );
    if (state->PySSLCertificate_Type == NULL)
        return -1;

    if (PyModule_AddType(module, state->PySSLContext_Type))
        return -1;
    if (PyModule_AddType(module, state->PySSLSocket_Type))
        return -1;
    if (PyModule_AddType(module, state->PySSLMemoryBIO_Type))
        return -1;
    if (PyModule_AddType(module, state->PySSLSession_Type))
        return -1;
    if (PyModule_AddType(module, state->PySSLCertificate_Type))
        return -1;
    return 0;
}

static int
sslmodule_init_strings(PyObject *module)
{
    _sslmodulestate *state = get_ssl_state(module);
    state->str_library = PyUnicode_InternFromString("library");
    if (state->str_library == NULL) {
        return -1;
    }
    state->str_reason = PyUnicode_InternFromString("reason");
    if (state->str_reason == NULL) {
        return -1;
    }
    state->str_verify_message = PyUnicode_InternFromString("verify_message");
    if (state->str_verify_message == NULL) {
        return -1;
    }
    state->str_verify_code = PyUnicode_InternFromString("verify_code");
    if (state->str_verify_code == NULL) {
        return -1;
    }
    return 0;
}

static int
sslmodule_init_lock(PyObject *module)
{
    _sslmodulestate *state = get_ssl_state(module);
    state->keylog_lock = PyThread_allocate_lock();
    if (state->keylog_lock == NULL) {
        PyErr_NoMemory();
        return -1;
    }
    return 0;
}

static PyModuleDef_Slot sslmodule_slots[] = {
    _Py_ABI_SLOT,
    {Py_mod_exec, sslmodule_init_types},
    {Py_mod_exec, sslmodule_init_exceptions},
    {Py_mod_exec, sslmodule_init_socketapi},
    {Py_mod_exec, sslmodule_init_errorcodes},
    {Py_mod_exec, sslmodule_init_constants},
    {Py_mod_exec, sslmodule_init_versioninfo},
    {Py_mod_exec, sslmodule_init_strings},
    {Py_mod_exec, sslmodule_init_lock},
    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
    {0, NULL}
};

static int
sslmodule_traverse(PyObject *m, visitproc visit, void *arg)
{
    _sslmodulestate *state = get_ssl_state(m);

    Py_VISIT(state->PySSLContext_Type);
    Py_VISIT(state->PySSLSocket_Type);
    Py_VISIT(state->PySSLMemoryBIO_Type);
    Py_VISIT(state->PySSLSession_Type);
    Py_VISIT(state->PySSLCertificate_Type);
    Py_VISIT(state->PySSLErrorObject);
    Py_VISIT(state->PySSLCertVerificationErrorObject);
    Py_VISIT(state->PySSLZeroReturnErrorObject);
    Py_VISIT(state->PySSLWantReadErrorObject);
    Py_VISIT(state->PySSLWantWriteErrorObject);
    Py_VISIT(state->PySSLSyscallErrorObject);
    Py_VISIT(state->PySSLEOFErrorObject);
    Py_VISIT(state->err_codes_to_names);
    Py_VISIT(state->lib_codes_to_names);
    Py_VISIT(state->Sock_Type);

    return 0;
}

static int
sslmodule_clear(PyObject *m)
{
    _sslmodulestate *state = get_ssl_state(m);

    Py_CLEAR(state->PySSLContext_Type);
    Py_CLEAR(state->PySSLSocket_Type);
    Py_CLEAR(state->PySSLMemoryBIO_Type);
    Py_CLEAR(state->PySSLSession_Type);
    Py_CLEAR(state->PySSLCertificate_Type);
    Py_CLEAR(state->PySSLErrorObject);
    Py_CLEAR(state->PySSLCertVerificationErrorObject);
    Py_CLEAR(state->PySSLZeroReturnErrorObject);
    Py_CLEAR(state->PySSLWantReadErrorObject);
    Py_CLEAR(state->PySSLWantWriteErrorObject);
    Py_CLEAR(state->PySSLSyscallErrorObject);
    Py_CLEAR(state->PySSLEOFErrorObject);
    Py_CLEAR(state->err_codes_to_names);
    Py_CLEAR(state->lib_codes_to_names);
    Py_CLEAR(state->Sock_Type);
    Py_CLEAR(state->str_library);
    Py_CLEAR(state->str_reason);
    Py_CLEAR(state->str_verify_code);
    Py_CLEAR(state->str_verify_message);
    return 0;
}

static void
sslmodule_free(void *m)
{
    sslmodule_clear((PyObject *)m);
    _sslmodulestate *state = get_ssl_state(m);
    PyThread_free_lock(state->keylog_lock);
}

static struct PyModuleDef _sslmodule_def = {
    PyModuleDef_HEAD_INIT,
    .m_name = "_ssl",
    .m_doc = module_doc,
    .m_size = sizeof(_sslmodulestate),
    .m_methods = PySSL_methods,
    .m_slots = sslmodule_slots,
    .m_traverse = sslmodule_traverse,
    .m_clear = sslmodule_clear,
    .m_free = sslmodule_free
};

PyMODINIT_FUNC
PyInit__ssl(void)
{
    return PyModuleDef_Init(&_sslmodule_def);
}