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/*
* Copyright (C) 2013-2017 Red Hat
*
* This file is part of GnuTLS.
*
* 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 <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <drbg-aes.h>
#include <fips.h>
#include "gnutls_int.h"
#include "errors.h"
#include <nettle/aes.h>
#include <nettle/memxor.h>
#include <locks.h>
#include <atfork.h>
#include <rnd-common.h>
/* This provides a random generator for gnutls. It uses
* two instances of the DRBG-AES-CTR generator, one for
* nonce level and another for the other levels of randomness.
*/
struct fips_ctx {
struct drbg_aes_ctx nonce_context;
struct drbg_aes_ctx normal_context;
unsigned int forkid;
};
static int _rngfips_ctx_reinit(struct fips_ctx *fctx);
static int _rngfips_ctx_init(struct fips_ctx *fctx);
static int drbg_reseed(struct drbg_aes_ctx *ctx);
static int get_random(struct drbg_aes_ctx *ctx, struct fips_ctx *fctx,
void *buffer, size_t length)
{
int ret;
if ( _gnutls_detect_fork(fctx->forkid) != 0) {
ret = _rngfips_ctx_reinit(fctx);
if (ret < 0)
return gnutls_assert_val(ret);
}
if (ctx->reseed_counter > DRBG_AES_RESEED_TIME) {
ret = drbg_reseed(ctx);
if (ret < 0)
return gnutls_assert_val(ret);
}
ret = drbg_aes_random(ctx, length, buffer);
if (ret == 0)
return gnutls_assert_val(GNUTLS_E_RANDOM_FAILED);
return 0;
}
#define PSTRING "gnutls-rng"
#define PSTRING_SIZE (sizeof(PSTRING)-1)
static int drbg_init(struct drbg_aes_ctx *ctx)
{
uint8_t buffer[DRBG_AES_SEED_SIZE];
int ret;
/* Get a key from the standard RNG or from the entropy source. */
ret = _rnd_get_system_entropy(buffer, sizeof(buffer));
if (ret < 0)
return gnutls_assert_val(ret);
ret = drbg_aes_init(ctx, sizeof(buffer), buffer, PSTRING_SIZE, (void*)PSTRING);
if (ret == 0)
return gnutls_assert_val(GNUTLS_E_RANDOM_FAILED);
zeroize_key(buffer, sizeof(buffer));
return 0;
}
/* Reseed a generator. */
static int drbg_reseed(struct drbg_aes_ctx *ctx)
{
uint8_t buffer[DRBG_AES_SEED_SIZE];
int ret;
/* The other two generators are seeded from /dev/random. */
ret = _rnd_get_system_entropy(buffer, sizeof(buffer));
if (ret < 0)
return gnutls_assert_val(ret);
drbg_aes_reseed(ctx, sizeof(buffer), buffer, 0, NULL);
return 0;
}
static int _rngfips_ctx_init(struct fips_ctx *fctx)
{
int ret;
/* normal */
ret = drbg_init(&fctx->normal_context);
if (ret < 0)
return gnutls_assert_val(ret);
/* nonce */
ret = drbg_init(&fctx->nonce_context);
if (ret < 0)
return gnutls_assert_val(ret);
fctx->forkid = _gnutls_get_forkid();
return 0;
}
static int _rngfips_ctx_reinit(struct fips_ctx *fctx)
{
int ret;
/* normal */
ret = drbg_reseed(&fctx->normal_context);
if (ret < 0)
return gnutls_assert_val(ret);
/* nonce */
ret = drbg_reseed(&fctx->nonce_context);
if (ret < 0)
return gnutls_assert_val(ret);
fctx->forkid = _gnutls_get_forkid();
return 0;
}
/* Initialize this random subsystem. */
static int _rngfips_init(void **_ctx)
{
/* Basic initialization is required to
do a few checks on the implementation. */
struct fips_ctx *ctx;
int ret;
ctx = gnutls_calloc(1, sizeof(*ctx));
if (ctx == NULL)
return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);
ret = _rngfips_ctx_init(ctx);
if (ret < 0) {
gnutls_free(ctx);
return gnutls_assert_val(ret);
}
*_ctx = ctx;
return 0;
}
static int _rngfips_rnd(void *_ctx, int level, void *buffer, size_t length)
{
struct fips_ctx *ctx = _ctx;
int ret;
switch (level) {
case GNUTLS_RND_RANDOM:
case GNUTLS_RND_KEY:
/* Unlike the chacha generator in rnd.c we do not need
* to explicitly protect against backtracking in GNUTLS_RND_KEY
* level. This protection is part of the DRBG generator. */
ret = get_random(&ctx->normal_context, ctx, buffer, length);
break;
default:
ret = get_random(&ctx->nonce_context, ctx, buffer, length);
break;
}
return ret;
}
static void _rngfips_deinit(void *_ctx)
{
struct fips_ctx *ctx = _ctx;
zeroize_key(ctx, sizeof(*ctx));
free(ctx);
}
static void _rngfips_refresh(void *_ctx)
{
/* this is predictable RNG. Don't refresh */
return;
}
static int selftest_kat(void)
{
int ret;
ret = drbg_aes_self_test();
if (ret == 0) {
_gnutls_debug_log("DRBG-AES self test failed\n");
return gnutls_assert_val(GNUTLS_E_RANDOM_FAILED);
} else
_gnutls_debug_log("DRBG-AES self test succeeded\n");
return 0;
}
gnutls_crypto_rnd_st _gnutls_fips_rnd_ops = {
.init = _rngfips_init,
.deinit = _rngfips_deinit,
.rnd = _rngfips_rnd,
.rnd_refresh = _rngfips_refresh,
.self_test = selftest_kat,
};
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