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 #include "qapi/error.h"
  25
  26 #ifdef _WIN32
  27 #include <wincrypt.h>
  28 static HCRYPTPROV hCryptProv;
  29 #else
  30 static int fd; /* a file handle to either /dev/urandom or /dev/random */
  31 #endif
  32
  33 int qcrypto_random_init(Error **errp)
  34 {
  35 #ifndef _WIN32
  36     /* TBD perhaps also add support for BSD getentropy / Linux
  37      * getrandom syscalls directly */
  38     fd = open("/dev/urandom", O_RDONLY);
  39     if (fd == -1 && errno == ENOENT) {
  40         fd = open("/dev/random", O_RDONLY);
  41     }
  42
  43     if (fd < 0) {
  44         error_setg(errp, "No /dev/urandom or /dev/random found");
  45         return -1;
  46     }
  47 #else
  48     if (!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
  49                              CRYPT_SILENT | CRYPT_VERIFYCONTEXT)) {
  50         error_setg_win32(errp, GetLastError(),
  51                          "Unable to create cryptographic provider");
  52         return -1;
  53     }
  54 #endif
  55
  56     return 0;
  57 }
  58
  59 int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
  60                          size_t buflen G_GNUC_UNUSED,
  61                          Error **errp)
  62 {
  63 #ifndef _WIN32
  64     int ret = -1;
  65     int got;
  66
  67     while (buflen > 0) {
  68         got = read(fd, buf, buflen);
  69         if (got < 0) {
  70             error_setg_errno(errp, errno,
  71                              "Unable to read random bytes");
  72             goto cleanup;
  73         } else if (!got) {
  74             error_setg(errp,
  75                        "Unexpected EOF reading random bytes");
  76             goto cleanup;
  77         }
  78         buflen -= got;
  79         buf += got;
  80     }
  81
  82     ret = 0;
  83  cleanup:
  84     return ret;
  85 #else
  86     if (!CryptGenRandom(hCryptProv, buflen, buf)) {
  87         error_setg_win32(errp, GetLastError(),
  88                          "Unable to read random bytes");
  89         return -1;
  90     }
  91
  92     return 0;
  93 #endif
  94 }