crypto/random-platform.c

   1 /*
   2  * QEMU Crypto random number provider
   3  *
   4  * Copyright (c) 2015-2016 Red Hat, Inc.
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  *
  19  */
  20
  21 #include "qemu/osdep.h"
  22
  23 #include "crypto/random.h"
  24 #include "qapi/error.h"
  25
  26 #ifdef _WIN32
  27 #include <wincrypt.h>
  28 static HCRYPTPROV hCryptProv;
  29 #else
  30 # ifdef CONFIG_GETRANDOM
  31 #  include <sys/random.h>
  32 # endif
  33 /* This is -1 for getrandom(), or a file handle for /dev/{u,}random.  */
  34 static int fd;
  35 #endif
  36
  37 int qcrypto_random_init(Error **errp)
  38 {
  39 #ifdef _WIN32
  40     if (!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
  41                              CRYPT_SILENT | CRYPT_VERIFYCONTEXT)) {
  42         error_setg_win32(errp, GetLastError(),
  43                          "Unable to create cryptographic provider");
  44         return -1;
  45     }
  46 #else
  47 # ifdef CONFIG_GETRANDOM
  48     if (getrandom(NULL, 0, 0) == 0) {
  49         /* Use getrandom() */
  50         fd = -1;
  51         return 0;
  52     }
  53     /* Fall through to /dev/urandom case.  */
  54 # endif
  55     fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
  56     if (fd == -1 && errno == ENOENT) {
  57         fd = open("/dev/random", O_RDONLY | O_CLOEXEC);
  58     }
  59     if (fd < 0) {
  60         error_setg_errno(errp, errno, "No /dev/urandom or /dev/random");
  61         return -1;
  62     }
  63 #endif
  64     return 0;
  65 }
  66
  67 int qcrypto_random_bytes(void *buf,
  68                          size_t buflen,
  69                          Error **errp)
  70 {
  71 #ifdef _WIN32
  72     if (!CryptGenRandom(hCryptProv, buflen, buf)) {
  73         error_setg_win32(errp, GetLastError(),
  74                          "Unable to read random bytes");
  75         return -1;
  76     }
  77 #else
  78 # ifdef CONFIG_GETRANDOM
  79     if (likely(fd < 0)) {
  80         while (1) {
  81             ssize_t got = getrandom(buf, buflen, 0);
  82             if (likely(got == buflen)) {
  83                 return 0;
  84             }
  85             if (got >= 0) {
  86                 buflen -= got;
  87                 buf += got;
  88             } else if (errno != EINTR) {
  89                 error_setg_errno(errp, errno, "getrandom");
  90                 return -1;
  91             }
  92         }
  93     }
  94     /* Fall through to /dev/urandom case.  */
  95 # endif
  96     while (1) {
  97         ssize_t got = read(fd, buf, buflen);
  98         if (likely(got == buflen)) {
  99             return 0;
 100         }
 101         if (got > 0) {
 102             buflen -= got;
 103             buf += got;
 104         } else if (got == 0) {
 105             error_setg(errp, "Unexpected EOF reading random bytes");
 106             return -1;
 107         } else if (errno != EINTR) {
 108             error_setg_errno(errp, errno, "Unable to read random bytes");
 109             return -1;
 110         }
 111     }
 112 #endif
 113     return 0;
 114 }