random.c

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#include "config.h"
#include <stddef.h>
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "random.h"
#include "exit.h"
#include "logging.h"
#include "message.h"
#ifdef HAVE_SYS_RANDOM_H
#include <sys/random.h>
#endif
 
static FILE *fp_random = NULL;
 
static const unsigned char base32[] = "abcdefghijklmnopqrstuvwxyz234567";
 
static int mutt_randbuf(void *buf, size_t buflen)
{
  if (buflen > 1048576)
  {
    mutt_error(_("mutt_randbuf buflen=%zu"), buflen);
    return -1;
  }
 
#ifdef HAVE_GETRANDOM
  ssize_t rc;
  ssize_t count = 0;
  do
  {
    // getrandom() can return less than requested if there's insufficient
    // entropy or it's interrupted by a signal.
    rc = getrandom((char *) buf + count, buflen - count, 0);
    if (rc > 0)
      count += rc;
  } while (((rc >= 0) && (count < buflen)) || ((rc == -1) && (errno == EINTR)));
  if (count == buflen)
    return 0;
#endif
  /* let's try urandom in case we're on an old kernel, or the user has
   * configured selinux, seccomp or something to not allow getrandom */
  if (!fp_random)
  {
    fp_random = fopen("/dev/urandom", "rb");
    if (!fp_random)
    {
      mutt_error(_("open /dev/urandom: %s"), strerror(errno));
      return -1;
    }
    setbuf(fp_random, NULL);
  }
  if (fread(buf, 1, buflen, fp_random) != buflen)
  {
    mutt_error(_("read /dev/urandom: %s"), strerror(errno));
    return -1;
  }
 
  return 0;
}
 
void mutt_rand_base32(char *buf, size_t buflen)
{
  uint8_t *p = (uint8_t *) buf;
 
  if (mutt_randbuf(p, buflen) < 0)
    mutt_exit(1);
  for (size_t pos = 0; pos < buflen; pos++)
    p[pos] = base32[p[pos] % 32];
}
 
uint32_t mutt_rand32(void)
{
  uint32_t num = 0;
 
  if (mutt_randbuf(&num, sizeof(num)) < 0)
    mutt_exit(1);
  return num;
}
 
uint64_t mutt_rand64(void)
{
  uint64_t num = 0;
 
  if (mutt_randbuf(&num, sizeof(num)) < 0)
    mutt_exit(1);
  return num;
}