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src/decrypt.c
652 строки
17 KB
Werner Koch
New decryption flag GPGME_DECRYPT_SESSION_HASH.
23 апр 2026, 15:29
Не верифицирован
23 апр 2026, 15:29
63f1829
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/* decrypt.c - Decrypt function. * Copyright (C) 2000 Werner Koch (dd9jn) * Copyright (C) 2001, 2002, 2003, 2004, 2017 g10 Code GmbH * * This file is part of GPGME. * * GPGME is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * GPGME is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this program; if not, see <https://gnu.org/licenses/>. * SPDX-License-Identifier: LGPL-2.1-or-later */ #if HAVE_CONFIG_H #include <config.h> #endif #include <stdlib.h> #include <string.h> #include <errno.h> #include <assert.h> #include "debug.h" #include "gpgme.h" #include "util.h" #include "context.h" #include "ops.h" #include "data.h" typedef struct { struct _gpgme_op_decrypt_result result; /* The error code from a FAILURE status line or 0. */ gpg_error_t failure_code; int okay; /* Indicates that list only mode is active. */ int list_only; /* A flag telling that the decryption failed and two optional error * codes to further specify the failure for public key decryption and * symmetric decryption. */ int failed; gpg_error_t pkdecrypt_failed; gpg_error_t symdecrypt_failed; /* At least one secret key is not available. gpg issues NO_SECKEY * status lines for each key the message has been encrypted to but * that secret key is not available. This can't be done for hidden * recipients, though. We track it here to allow for a better error * message than the general DECRYPTION_FAILED. */ int any_no_seckey; /* If the engine emits a DECRYPTION_INFO status and that does not * indicate that an integrity protection mode is active, this flag * is set. */ int not_integrity_protected; /* The error code from the first ERROR line. This is in some cases * used to return a better matching error code to the caller. */ gpg_error_t first_status_error; /* A pointer to the next pointer of the last recipient in the list. This makes appending new invalid signers painless while preserving the order. */ gpgme_recipient_t *last_recipient_p; /* The data object serial number of the plaintext. */ uint64_t plaintext_dserial; } *op_data_t; static void release_op_data (void *hook) { op_data_t opd = (op_data_t) hook; gpgme_recipient_t recipient = opd->result.recipients; free (opd->result.unsupported_algorithm); free (opd->result.file_name); free (opd->result.session_key); free (opd->result.session_hash); free (opd->result.symkey_algo); while (recipient) { gpgme_recipient_t next = recipient->next; free (recipient); recipient = next; } } gpgme_decrypt_result_t gpgme_op_decrypt_result (gpgme_ctx_t ctx) { void *hook; op_data_t opd; gpgme_error_t err; TRACE_BEG (DEBUG_CTX, "gpgme_op_decrypt_result", ctx, ""); ctx->ignore_mdc_error = 0; /* Always reset this flag. */ err = _gpgme_op_data_lookup (ctx, OPDATA_DECRYPT, &hook, -1, NULL); opd = hook; if (err || !opd) { TRACE_SUC ("result=(null)"); return NULL; } /* Make sure that SYMKEY_ALGO has a value. */ if (!opd->result.symkey_algo) { opd->result.symkey_algo = strdup ("?.?"); if (!opd->result.symkey_algo) { TRACE_SUC ("result=(null)"); return NULL; } } if (_gpgme_debug_trace ()) { gpgme_recipient_t rcp; if (opd->result.unsupported_algorithm) { TRACE_LOG ("result: unsupported_algorithm: %s", opd->result.unsupported_algorithm); } if (opd->result.wrong_key_usage) { TRACE_LOG ("result: wrong key usage"); } rcp = opd->result.recipients; while (rcp) { TRACE_LOG ("result: recipient: keyid=%s, pubkey_algo=%i, " "status=%s", rcp->keyid, rcp->pubkey_algo, gpg_strerror (rcp->status)); rcp = rcp->next; } if (opd->result.file_name) { TRACE_LOG ("result: original file name: %s", opd->result.file_name); } } TRACE_SUC ("result=%p", &opd->result); return &opd->result; } /* Parse the ARGS of an error status line and record some error * conditions at OPD. Returns 0 on success. */ static gpgme_error_t parse_status_error (char *args, op_data_t opd) { gpgme_error_t err; char *field[3]; int nfields; char *args2; if (!args) return trace_gpg_error (GPG_ERR_INV_ENGINE); args2 = strdup (args); /* Split modifies the input string. */ nfields = _gpgme_split_fields (args2, field, DIM (field)); if (nfields < 1) { free (args2); return trace_gpg_error (GPG_ERR_INV_ENGINE); /* Required arg missing. */ } err = nfields < 2 ? 0 : atoi (field[1]); if (!strcmp (field[0], "decrypt.algorithm")) { if (gpg_err_code (err) == GPG_ERR_UNSUPPORTED_ALGORITHM && nfields > 2 && strcmp (field[2], "?")) { opd->result.unsupported_algorithm = strdup (field[2]); if (!opd->result.unsupported_algorithm) { free (args2); return gpg_error_from_syserror (); } } } else if (!strcmp (field[0], "decrypt.keyusage")) { if (gpg_err_code (err) == GPG_ERR_WRONG_KEY_USAGE) opd->result.wrong_key_usage = 1; } else if (!strcmp (field[0], "pkdecrypt_failed")) { switch (gpg_err_code (err)) { case GPG_ERR_CANCELED: case GPG_ERR_FULLY_CANCELED: /* It is better to return with a cancel error code than the * general decryption failed error code. */ opd->pkdecrypt_failed = gpg_err_make (gpg_err_source (err), GPG_ERR_CANCELED); break; case GPG_ERR_BAD_PASSPHRASE: /* A bad passphrase is severe enough that we return this * error code. */ opd->pkdecrypt_failed = err; break; default: /* For now all other error codes are ignored and the * standard DECRYPT_FAILED is returned. */ break; } } else if (!strcmp (field[0], "nomdc_with_legacy_cipher")) { opd->result.legacy_cipher_nomdc = 1; opd->not_integrity_protected = 1; } else if (!strcmp (field[0], "symkey_decrypt.maybe_error")) { switch (gpg_err_code (err)) { case GPG_ERR_BAD_PASSPHRASE: /* A bad passphrase is severe enough that we return this * error code. */ opd->symdecrypt_failed = err; break; default: /* For now all other error codes are ignored and the * standard DECRYPT_FAILED is returned. */ break; } } /* Record the first error code. */ if (err && !opd->first_status_error) opd->first_status_error = err; free (args2); return 0; } static gpgme_error_t parse_enc_to (char *args, gpgme_recipient_t *recp, gpgme_protocol_t protocol) { gpgme_recipient_t rec; char *tail; int i; rec = malloc (sizeof (*rec)); if (!rec) return gpg_error_from_syserror (); rec->next = NULL; rec->keyid = rec->_keyid; rec->status = 0; for (i = 0; i < sizeof (rec->_keyid) - 1; i++) { if (args[i] == '\0' || args[i] == ' ') break; rec->_keyid[i] = args[i]; } rec->_keyid[i] = '\0'; args = &args[i]; if (*args != '\0' && *args != ' ') { free (rec); return trace_gpg_error (GPG_ERR_INV_ENGINE); } while (*args == ' ') args++; if (*args) { gpg_err_set_errno (0); rec->pubkey_algo = _gpgme_map_pk_algo (strtol (args, &tail, 0), protocol); if (errno || args == tail || *tail != ' ') { /* The crypto backend does not behave. */ free (rec); return trace_gpg_error (GPG_ERR_INV_ENGINE); } } /* FIXME: The key length is always 0 right now, so no need to parse it. */ *recp = rec; return 0; } /* Parse the ARGS of a * DECRYPTION_INFO <mdc_method> <sym_algo> [<aead_algo>] * status. Returns 0 on success and updates the OPD. */ static gpgme_error_t parse_decryption_info (char *args, op_data_t opd, gpgme_protocol_t protocol) { char *field[3]; int nfields; char *args2; int mdc, aead_algo; const char *algostr, *modestr; if (!args) return trace_gpg_error (GPG_ERR_INV_ENGINE); args2 = strdup (args); /* Split modifies the input string. */ nfields = _gpgme_split_fields (args2, field, DIM (field)); if (nfields < 2) { free (args2); return trace_gpg_error (GPG_ERR_INV_ENGINE); /* Required arg missing. */ } mdc = atoi (field[0]); algostr = _gpgme_cipher_algo_name (atoi (field[1]), protocol); aead_algo = nfields < 3? 0 : atoi (field[2]); modestr = _gpgme_cipher_mode_name (aead_algo, protocol); free (args2); free (opd->result.symkey_algo); if (!aead_algo && mdc != 2) opd->result.symkey_algo = _gpgme_strconcat (algostr, ".PGPCFB", NULL); else opd->result.symkey_algo = _gpgme_strconcat (algostr, ".", modestr, NULL); if (!opd->result.symkey_algo) return gpg_error_from_syserror (); if (!mdc && !aead_algo) opd->not_integrity_protected = 1; return 0; } gpgme_error_t _gpgme_decrypt_status_handler (void *priv, gpgme_status_code_t code, char *args) { gpgme_ctx_t ctx = (gpgme_ctx_t) priv; gpgme_error_t err; void *hook; op_data_t opd; err = _gpgme_passphrase_status_handler (priv, code, args); if (err) return err; err = _gpgme_op_data_lookup (ctx, OPDATA_DECRYPT, &hook, -1, NULL); opd = hook; if (err) return err; switch (code) { case GPGME_STATUS_FAILURE: if (!opd->failure_code || gpg_err_code (opd->failure_code) == GPG_ERR_GENERAL) opd->failure_code = _gpgme_parse_failure (args); break; case GPGME_STATUS_EOF: /* We force an encryption failure if we know that integrity * protection is missing. For modern version of gpg using * modern cipher algorithms this is not required because gpg * will issue a failure anyway. However older gpg versions emit * only a warning. * Fixme: These error values should probably be attributed to * the underlying crypto engine (as error source). */ if (opd->failed) { /* This comes from a specialized ERROR status line. */ if (opd->pkdecrypt_failed) return opd->pkdecrypt_failed; if (opd->symdecrypt_failed) return opd->symdecrypt_failed; /* For an integrity failure return just DECRYPTION_FAILED; * the actual cause can be taken from an already set * decryption result flag. */ if ((opd->not_integrity_protected && !ctx->ignore_mdc_error)) return gpg_error (GPG_ERR_DECRYPT_FAILED); /* If we have any other ERROR code we prefer that over * NO_SECKEY because it is probably the better matching * code. For example a garbled message with multiple * plaintext will return BAD_DATA here but may also have * indicated a NO_SECKEY. */ if (opd->first_status_error) return opd->first_status_error; /* No secret key is pretty common reason. */ if (opd->any_no_seckey) return gpg_error (GPG_ERR_NO_SECKEY); /* Generic decryption failed error code. */ return gpg_error (GPG_ERR_DECRYPT_FAILED); } else if (!opd->okay && !opd->list_only) { /* No data was found. */ return gpg_error (GPG_ERR_NO_DATA); } else if (opd->failure_code) { /* The engine returned failure code at program exit. */ return opd->failure_code; } break; case GPGME_STATUS_DECRYPTION_INFO: err = parse_decryption_info (args, opd, ctx->protocol); if (err) return err; break; case GPGME_STATUS_DECRYPTION_OKAY: opd->okay = 1; break; case GPGME_STATUS_DECRYPTION_FAILED: opd->failed = 1; /* Tell the data object that it shall not return any data. We * use the serial number because the data object may be owned by * another thread. We also don't check for an error because it * is possible that the data object has already been destroyed * and we are then not interested in returning an error. */ if (!ctx->ignore_mdc_error) _gpgme_data_set_prop (NULL, opd->plaintext_dserial, DATA_PROP_BLANKOUT, 1); break; case GPGME_STATUS_ERROR: /* Note that this is an informational status code which should * not lead to an error return unless it is something not * related to the backend. However, it is used to return a * better matching final error code. */ err = parse_status_error (args, opd); if (err) return err; break; case GPGME_STATUS_ENC_TO: err = parse_enc_to (args, opd->last_recipient_p, ctx->protocol); if (err) return err; opd->last_recipient_p = &(*opd->last_recipient_p)->next; break; case GPGME_STATUS_SESSION_KEY: if (opd->result.session_key) free (opd->result.session_key); opd->result.session_key = strdup(args); break; case GPGME_STATUS_SESSION_HASH: if (opd->result.session_hash) free (opd->result.session_hash); opd->result.session_hash = strdup (args); break; case GPGME_STATUS_NO_SECKEY: { gpgme_recipient_t rec = opd->result.recipients; while (rec) { if (!strcmp (rec->keyid, args)) { rec->status = gpg_error (GPG_ERR_NO_SECKEY); break; } rec = rec->next; } /* FIXME: Is this ok? */ if (!rec) return trace_gpg_error (GPG_ERR_INV_ENGINE); opd->any_no_seckey = 1; } break; case GPGME_STATUS_PLAINTEXT: { int mime = 0; err = _gpgme_parse_plaintext (args, &opd->result.file_name, &mime); if (err) return err; opd->result.is_mime = !!mime; } break; case GPGME_STATUS_INQUIRE_MAXLEN: if (ctx->status_cb && !ctx->full_status) { err = ctx->status_cb (ctx->status_cb_value, "INQUIRE_MAXLEN", args); if (err) return err; } break; case GPGME_STATUS_DECRYPTION_COMPLIANCE_MODE: PARSE_COMPLIANCE_FLAGS (args, &opd->result); break; default: break; } return 0; } static gpgme_error_t decrypt_status_handler (void *priv, gpgme_status_code_t code, char *args) { gpgme_error_t err; err = _gpgme_progress_status_handler (priv, code, args); if (!err) err = _gpgme_decrypt_status_handler (priv, code, args); return err; } gpgme_error_t _gpgme_op_decrypt_init_result (gpgme_ctx_t ctx, gpgme_data_t plaintext, gpgme_decrypt_flags_t flags) { gpgme_error_t err; void *hook; op_data_t opd; err = _gpgme_op_data_lookup (ctx, OPDATA_DECRYPT, &hook, sizeof (*opd), release_op_data); opd = hook; if (err) return err; opd->list_only = !!(flags & GPGME_DECRYPT_LISTONLY); opd->last_recipient_p = &opd->result.recipients; opd->plaintext_dserial = _gpgme_data_get_dserial (plaintext); return 0; } gpgme_error_t _gpgme_decrypt_start (gpgme_ctx_t ctx, int synchronous, gpgme_decrypt_flags_t flags, gpgme_data_t cipher, gpgme_data_t plain) { gpgme_error_t err; assert (!(flags & GPGME_DECRYPT_VERIFY)); err = _gpgme_op_reset (ctx, synchronous); if (err) return err; err = _gpgme_op_decrypt_init_result (ctx, plain, flags); if (err) return err; if (!cipher) return gpg_error (GPG_ERR_NO_DATA); if (!plain) return gpg_error (GPG_ERR_INV_VALUE); if (err) return err; if (ctx->passphrase_cb) { err = _gpgme_engine_set_command_handler (ctx->engine, _gpgme_passphrase_command_handler, ctx); if (err) return err; } _gpgme_engine_set_status_handler (ctx->engine, decrypt_status_handler, ctx); return _gpgme_engine_op_decrypt (ctx->engine, flags, cipher, plain, ctx->export_session_keys, ctx->override_session_key, ctx->auto_key_retrieve); } gpgme_error_t gpgme_op_decrypt_start (gpgme_ctx_t ctx, gpgme_data_t cipher, gpgme_data_t plain) { gpgme_error_t err; TRACE_BEG (DEBUG_CTX, "gpgme_op_decrypt_start", ctx, "cipher=%p, plain=%p", cipher, plain); if (!ctx) return TRACE_ERR (gpg_error (GPG_ERR_INV_VALUE)); err = _gpgme_decrypt_start (ctx, 0, 0, cipher, plain); return TRACE_ERR (err); } /* Decrypt ciphertext CIPHER within CTX and store the resulting plaintext in PLAIN. */ gpgme_error_t gpgme_op_decrypt (gpgme_ctx_t ctx, gpgme_data_t cipher, gpgme_data_t plain) { gpgme_error_t err; TRACE_BEG (DEBUG_CTX, "gpgme_op_decrypt", ctx, "cipher=%p, plain=%p", cipher, plain); if (!ctx) return TRACE_ERR (gpg_error (GPG_ERR_INV_VALUE)); err = _gpgme_decrypt_start (ctx, 1, 0, cipher, plain); if (!err) err = _gpgme_wait_one (ctx); ctx->ignore_mdc_error = 0; /* Always reset. */ return TRACE_ERR (err); }