qemu

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/*
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 * QEMU Crypto random number provider
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 *
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 * Copyright (c) 2015-2016 Red Hat, Inc.
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 *
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 * This library is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * This library is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
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 *
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 */
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#include "qemu/osdep.h"
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#include "crypto/random.h"
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#include "qapi/error.h"
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#ifdef _WIN32
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#include <wincrypt.h>
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static HCRYPTPROV hCryptProv;
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#else
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# ifdef CONFIG_GETRANDOM
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#  include <sys/random.h>
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# endif
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/* This is -1 for getrandom(), or a file handle for /dev/{u,}random.  */
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static int fd;
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#endif
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int qcrypto_random_init(Error **errp)
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{
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#ifdef _WIN32
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    if (!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
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                             CRYPT_SILENT | CRYPT_VERIFYCONTEXT)) {
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        error_setg_win32(errp, GetLastError(),
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                         "Unable to create cryptographic provider");
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        return -1;
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    }
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#else
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# ifdef CONFIG_GETRANDOM
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    if (getrandom(NULL, 0, 0) == 0) {
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        /* Use getrandom() */
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        fd = -1;
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        return 0;
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    }
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    /* Fall through to /dev/urandom case.  */
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# endif
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    fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
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    if (fd == -1 && errno == ENOENT) {
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        fd = open("/dev/random", O_RDONLY | O_CLOEXEC);
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    }
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    if (fd < 0) {
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        error_setg_errno(errp, errno, "No /dev/urandom or /dev/random");
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        return -1;
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    }
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#endif
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    return 0;
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}
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int qcrypto_random_bytes(void *buf,
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                         size_t buflen,
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                         Error **errp)
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{
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#ifdef _WIN32
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    if (!CryptGenRandom(hCryptProv, buflen, buf)) {
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        error_setg_win32(errp, GetLastError(),
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                         "Unable to read random bytes");
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        return -1;
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    }
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#else
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# ifdef CONFIG_GETRANDOM
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    if (likely(fd < 0)) {
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        while (1) {
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            ssize_t got = getrandom(buf, buflen, 0);
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            if (likely(got == buflen)) {
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                return 0;
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            }
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            if (got >= 0) {
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                buflen -= got;
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                buf += got;
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            } else if (errno != EINTR) {
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                error_setg_errno(errp, errno, "getrandom");
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                return -1;
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            }
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        }
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    }
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    /* Fall through to /dev/urandom case.  */
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# endif
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    while (1) {
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        ssize_t got = read(fd, buf, buflen);
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        if (likely(got == buflen)) {
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            return 0;
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        }
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        if (got > 0) {
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            buflen -= got;
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            buf += got;
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        } else if (got == 0) {
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            error_setg(errp, "Unexpected EOF reading random bytes");
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            return -1;
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        } else if (errno != EINTR) {
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            error_setg_errno(errp, errno, "Unable to read random bytes");
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            return -1;
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        }
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    }
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#endif
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    return 0;
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}
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