lib/entropy.c

   1 /* Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks
   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
  24 #include "socket-util.h"
  25 #include "vlog.h"
  26
  27 VLOG_DEFINE_THIS_MODULE(entropy);
  28
  29 static const char urandom[] = "/dev/urandom";
  30
  31 /* Initializes 'buffer' with 'n' bytes of high-quality random numbers.  Returns
  32  * 0 if successful, otherwise a positive errno value or EOF on error. */
  33 int
  34 get_entropy(void *buffer, size_t n)
  35 {
  36     size_t bytes_read;
  37     int error;
  38     int fd;
  39
  40     fd = open(urandom, O_RDONLY);
  41     if (fd < 0) {
  42         VLOG_ERR("%s: open failed (%s)", urandom, strerror(errno));
  43         return errno ? errno : EINVAL;
  44     }
  45
  46     error = read_fully(fd, buffer, n, &bytes_read);
  47     close(fd);
  48
  49     if (error) {
  50         VLOG_ERR("%s: read error (%s)", urandom, ovs_retval_to_string(error));
  51     }
  52     return error;
  53 }
  54
  55 /* Initializes 'buffer' with 'n' bytes of high-quality random numbers.  Exits
  56  * if an error occurs. */
  57 void
  58 get_entropy_or_die(void *buffer, size_t n)
  59 {
  60     int error = get_entropy(buffer, n);
  61     if (error) {
  62         VLOG_FATAL("%s: read error (%s)",
  63                    urandom, ovs_retval_to_string(error));
  64     }
  65 }