/*

 * Copyright (c) 1996, David Mazieres <dm@uun.org>

 * Copyright (c) 2008, Damien Miller <djm@openbsd.org>

 * Copyright (c) 2013, Markus Friedl <markus@openbsd.org>

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

#include "includes.h"

#ifndef SSH_RANDOM_DEV

# define SSH_RANDOM_DEV "/dev/urandom"

#endif /* SSH_RANDOM_DEV */

#include <sys/types.h>

#ifdef HAVE_SYS_RANDOM_H

# include <sys/random.h>

#endif

#include <fcntl.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#ifdef WITH_OPENSSL

#include <openssl/rand.h>

#include <openssl/err.h>

#endif

#include "log.h"

int

_ssh_compat_getentropy(void *s, size_t len)

{

#if defined(WITH_OPENSSL) && defined(OPENSSL_PRNG_ONLY)

  if (RAND_bytes(s, len) <= 0)

    fatal("Couldn't obtain random bytes (error 0x%lx)",

        (unsigned long)ERR_get_error());

#else

  int fd, save_errno;

  ssize_t r;

  size_t o = 0;

#ifdef WITH_OPENSSL

  if (RAND_bytes(s, len) == 1)

    return 0;

#endif

#ifdef HAVE_GETENTROPY

  if ((r = getentropy(s, len)) == 0)

    return 0;

#endif /* HAVE_GETENTROPY */

#ifdef HAVE_GETRANDOM

  if ((r = getrandom(s, len, 0)) > 0 && (size_t)r == len)

    return 0;

#endif /* HAVE_GETRANDOM */

  if ((fd = open(SSH_RANDOM_DEV, O_RDONLY)) == -1) {

    save_errno = errno;

    /* Try egd/prngd before giving up. */

    if (seed_from_prngd(s, len) == 0)

      return 0;

    fatal("Couldn't open %s: %s", SSH_RANDOM_DEV,

        strerror(save_errno));

  }

  while (o < len) {

    r = read(fd, (u_char *)s + o, len - o);

    if (r < 0) {

      if (errno == EAGAIN || errno == EINTR ||

          errno == EWOULDBLOCK)

        continue;

      fatal("read %s: %s", SSH_RANDOM_DEV, strerror(errno));

    }

    o += r;

  }

  close(fd);

#endif /* WITH_OPENSSL */

  return 0;

}