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 int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
  26                          size_t buflen G_GNUC_UNUSED,
  27                          Error **errp)
  28 {
  29     int fd;
  30     int ret = -1;
  31     int got;
  32
  33     /* TBD perhaps also add support for BSD getentropy / Linux
  34      * getrandom syscalls directly */
  35     fd = open("/dev/urandom", O_RDONLY);
  36     if (fd == -1 && errno == ENOENT) {
  37         fd = open("/dev/random", O_RDONLY);
  38     }
  39
  40     if (fd < 0) {
  41         error_setg(errp, "No /dev/urandom or /dev/random found");
  42         return -1;
  43     }
  44
  45     while (buflen > 0) {
  46         got = read(fd, buf, buflen);
  47         if (got < 0) {
  48             error_setg_errno(errp, errno,
  49                              "Unable to read random bytes");
  50             goto cleanup;
  51         } else if (!got) {
  52             error_setg(errp,
  53                        "Unexpected EOF reading random bytes");
  54             goto cleanup;
  55         }
  56         buflen -= got;
  57         buf += got;
  58     }
  59
  60     ret = 0;
  61  cleanup:
  62     close(fd);
  63     return ret;
  64 }