lib/entropy.c

   1 /* Copyright (c) 2008, 2009, 2010, 2011, 2013 Nicira, Inc.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at:
   6  *
   7  *     http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  */
  15
  16 #include <config.h>
  17
  18 #include "entropy.h"
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <unistd.h>
  23 #ifdef _WIN32
  24 #include <Wincrypt.h>
  25 #endif
  26 #include "util.h"
  27 #include "socket-util.h"
  28 #include "openvswitch/vlog.h"
  29
  30 VLOG_DEFINE_THIS_MODULE(entropy);
  31
  32 static const char urandom[] = "/dev/urandom";
  33
  34 /* Initializes 'buffer' with 'n' bytes of high-quality random numbers.  Returns
  35  * 0 if successful, otherwise a positive errno value or EOF on error. */
  36 int
  37 get_entropy(void *buffer, size_t n)
  38 {
  39 #ifndef _WIN32
  40     size_t bytes_read;
  41     int error;
  42     int fd;
  43
  44     fd = open(urandom, O_RDONLY);
  45     if (fd < 0) {
  46         VLOG_ERR("%s: open failed (%s)", urandom, ovs_strerror(errno));
  47         return errno ? errno : EINVAL;
  48     }
  49
  50     error = read_fully(fd, buffer, n, &bytes_read);
  51     close(fd);
  52
  53     if (error) {
  54         VLOG_ERR("%s: read error (%s)", urandom, ovs_retval_to_string(error));
  55     }
  56 #else
  57     int error = 0;
  58     HCRYPTPROV   crypt_prov = 0;
  59
  60     CryptAcquireContext(&crypt_prov, NULL, NULL,
  61                         PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
  62     if (!CryptGenRandom(crypt_prov, n, buffer)) {
  63         VLOG_ERR("CryptGenRandom: read error (%s)", ovs_lasterror_to_string());
  64         error = EINVAL;
  65     }
  66
  67     CryptReleaseContext(crypt_prov, 0);
  68 #endif
  69     return error;
  70 }
  71
  72 /* Initializes 'buffer' with 'n' bytes of high-quality random numbers.  Exits
  73  * if an error occurs. */
  74 void
  75 get_entropy_or_die(void *buffer, size_t n)
  76 {
  77     int error = get_entropy(buffer, n);
  78     if (error) {
  79         VLOG_FATAL("%s: read error (%s)",
  80                    urandom, ovs_retval_to_string(error));
  81     }
  82 }