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 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
  25 #ifdef _WIN32
  26 #include <wincrypt.h>
  27 static HCRYPTPROV hCryptProv;
  28 #else
  29 static int fd; /* a file handle to either /dev/urandom or /dev/random */
  30 #endif
  31
  32 int qcrypto_random_init(Error **errp)
  33 {
  34 #ifndef _WIN32
  35     /* TBD perhaps also add support for BSD getentropy / Linux
  36      * getrandom syscalls directly */
  37     fd = open("/dev/urandom", O_RDONLY);
  38     if (fd == -1 && errno == ENOENT) {
  39         fd = open("/dev/random", O_RDONLY);
  40     }
  41
  42     if (fd < 0) {
  43         error_setg(errp, "No /dev/urandom or /dev/random found");
  44         return -1;
  45     }
  46 #else
  47     if (!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
  48                              CRYPT_SILENT | CRYPT_VERIFYCONTEXT)) {
  49         error_setg_win32(errp, GetLastError(),
  50                          "Unable to create cryptographic provider");
  51         return -1;
  52     }
  53 #endif
  54
  55     return 0;
  56 }
  57
  58 int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
  59                          size_t buflen G_GNUC_UNUSED,
  60                          Error **errp)
  61 {
  62 #ifndef _WIN32
  63     int ret = -1;
  64     int got;
  65
  66     while (buflen > 0) {
  67         got = read(fd, buf, buflen);
  68         if (got < 0) {
  69             error_setg_errno(errp, errno,
  70                              "Unable to read random bytes");
  71             goto cleanup;
  72         } else if (!got) {
  73             error_setg(errp,
  74                        "Unexpected EOF reading random bytes");
  75             goto cleanup;
  76         }
  77         buflen -= got;
  78         buf += got;
  79     }
  80
  81     ret = 0;
  82  cleanup:
  83     return ret;
  84 #else
  85     if (!CryptGenRandom(hCryptProv, buflen, buf)) {
  86         error_setg_win32(errp, GetLastError(),
  87                          "Unable to read random bytes");
  88         return -1;
  89     }
  90
  91     return 0;
  92 #endif
  93 }