rnd.c

   1 #include <sys/types.h>
   2 #include <sys/stat.h>
   3 #include <fcntl.h>
   4 #include <unistd.h>
   5
   6 #include "rnd.h"
   7
   8 static int fd_rnd = -1;
   9
  10 static void randombytes(unsigned char *x, unsigned long long xlen)
  11 {
  12         int ret;
  13
  14         if (fd_rnd == -1) {
  15                 for (;;) {
  16                         fd_rnd = open("/dev/urandom", O_RDONLY);
  17                         if (fd_rnd != -1)
  18                                 break;
  19                         sleep(1);
  20                 }
  21         }
  22
  23         while (xlen > 0) {
  24                 if (xlen < 1048576)
  25                         ret = xlen;
  26                 else
  27                         ret = 1048576;
  28
  29                 ret = read(fd_rnd, x, ret);
  30                 if (ret < 1) {
  31                         sleep(1);
  32                         continue;
  33                 }
  34
  35                 x += ret;
  36                 xlen -= ret;
  37         }
  38 }
  39
  40 /* Note: it's not really secure, but the name only suggests it's better to use
  41  * than rand(3) when transferring bytes over the network in non-security
  42  * critical structure members. secrand() is only used to fill up salts actually.
  43  */
  44 int secrand(void)
  45 {
  46         int ret;
  47         randombytes((void *) &ret, sizeof(ret));
  48         return ret;
  49 }