deterministic.c

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/* Copyright (c) 2016, Google Inc.
 *
 * Permission to use, copy, modify, and/or 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 <openssl/rand.h>
 
#if defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
 
#include <string.h>
 
#include <openssl/chacha.h>
 
#include "../internal.h"
#include "../fipsmodule/rand/internal.h"
 
 
// g_num_calls is the number of calls to |CRYPTO_sysrand| that have occurred.
//
// This is intentionally not thread-safe. If the fuzzer mode is ever used in a
// multi-threaded program, replace this with a thread-local. (A mutex would not
// be deterministic.)
static uint64_t g_num_calls = 0;
static struct CRYPTO_STATIC_MUTEX g_num_calls_lock = CRYPTO_STATIC_MUTEX_INIT;
 
void RAND_reset_for_fuzzing(void) { g_num_calls = 0; }
 
void CRYPTO_sysrand(uint8_t *out, size_t requested) {
  static const uint8_t kZeroKey[32];
 
  CRYPTO_STATIC_MUTEX_lock_write(&g_num_calls_lock);
  uint64_t num_calls = g_num_calls++;
  CRYPTO_STATIC_MUTEX_unlock_write(&g_num_calls_lock);
 
  uint8_t nonce[12];
  OPENSSL_memset(nonce, 0, sizeof(nonce));
  OPENSSL_memcpy(nonce, &num_calls, sizeof(num_calls));
 
  OPENSSL_memset(out, 0, requested);
  CRYPTO_chacha_20(out, out, requested, kZeroKey, nonce, 0);
}
 
void CRYPTO_sysrand_for_seed(uint8_t *out, size_t requested) {
  CRYPTO_sysrand(out, requested);
}
 
#endif  // BORINGSSL_UNSAFE_DETERMINISTIC_MODE