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/* rndgetentropy.c - raw random number for OSes by getentropy function.
* Copyright (C) 1998, 2001, 2002, 2003, 2007,
* 2009 Free Software Foundation, Inc.
*
* This file is part of Libgcrypt.
*
* Libgcrypt is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* Libgcrypt is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <string.h>
#include <unistd.h>
#ifdef HAVE_SYS_RANDOM_H
#include <sys/random.h>
#endif
#include "types.h"
#include "g10lib.h"
#include "rand-internal.h"
/* The function returns 0 on success or true on failure (in which case
* the caller will signal a fatal error). */
int
_gcry_rndgetentropy_gather_random (void (*add)(const void*, size_t,
enum random_origins),
enum random_origins origin,
size_t length, int level)
{
byte buffer[256];
if (!add)
{
/* Special mode to release resouces. */
_gcry_rndjent_fini ();
return 0;
}
/* When using a blocking random generator try to get some entropy
* from the jitter based RNG. In this case we take up to 50% of the
* remaining requested bytes. */
if (level >= GCRY_VERY_STRONG_RANDOM)
{
size_t n;
n = _gcry_rndjent_poll (add, origin, length/2);
if (n > length/2)
n = length/2;
if (length > 1)
length -= n;
}
/* Enter the loop. */
while (length)
{
int ret;
size_t nbytes;
/* For a modern operating system, we use the new getentropy
* function. That call guarantees that the kernel's RNG has
* been properly seeded before returning any data. This is
* different from /dev/urandom which may, due to its
* non-blocking semantics, return data even if the kernel has
* not been properly seeded. And it differs from /dev/random by
* never blocking once the kernel is seeded. */
do
{
_gcry_pre_syscall ();
#ifdef GRND_RANDOM
if (fips_mode ())
{
/* DRBG chaining defined in SP 800-90A (rev 1) specify
* the upstream (kernel) DRBG needs to be reseeded for
* initialization of downstream (libgcrypt) DRBG. For this
* in RHEL, we repurposed the GRND_RANDOM flag of getrandom API.
* The libgcrypt DRBG is initialized with 48B of entropy, but
* the kernel can provide only 32B at a time after reseeding
* so we need to limit our requests to 32B here.
* This is clarified in IG 7.19 / IG D.K. for FIPS 140-2 / 3
* and might not be applicable on other FIPS modules not running
* RHEL kernel.
*/
nbytes = length < 32 ? length : 32;
ret = getrandom (buffer, nbytes, GRND_RANDOM);
}
else
#endif
{
nbytes = length < sizeof (buffer) ? length : sizeof (buffer);
ret = getentropy (buffer, nbytes);
}
_gcry_post_syscall ();
}
while (ret == -1 && errno == EINTR);
if (ret == -1 && errno == ENOSYS)
log_fatal ("getentropy is not supported: %s\n", strerror (errno));
else
{ /* getentropy is supported. Some sanity checks. */
if (ret == -1)
log_fatal ("unexpected error from getentropy: %s\n",
strerror (errno));
(*add) (buffer, nbytes, origin);
length -= nbytes;
}
}
wipememory (buffer, sizeof buffer);
return 0; /* success */
}
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