mirror of
https://github.com/openssl/openssl.git
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367ace6870
[skip ci] Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7777)
269 lines
7.4 KiB
C
269 lines
7.4 KiB
C
/*
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* Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <stdio.h>
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#include <time.h>
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#include "internal/cryptlib.h"
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#include "bn_lcl.h"
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#include <openssl/rand.h>
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#include <openssl/sha.h>
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typedef enum bnrand_flag_e {
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NORMAL, TESTING, PRIVATE
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} BNRAND_FLAG;
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static int bnrand(BNRAND_FLAG flag, BIGNUM *rnd, int bits, int top, int bottom)
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{
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unsigned char *buf = NULL;
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int b, ret = 0, bit, bytes, mask;
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if (bits == 0) {
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if (top != BN_RAND_TOP_ANY || bottom != BN_RAND_BOTTOM_ANY)
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goto toosmall;
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BN_zero(rnd);
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return 1;
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}
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if (bits < 0 || (bits == 1 && top > 0))
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goto toosmall;
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bytes = (bits + 7) / 8;
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bit = (bits - 1) % 8;
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mask = 0xff << (bit + 1);
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buf = OPENSSL_malloc(bytes);
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if (buf == NULL) {
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BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
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goto err;
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}
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/* make a random number and set the top and bottom bits */
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b = flag == NORMAL ? RAND_bytes(buf, bytes) : RAND_priv_bytes(buf, bytes);
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if (b <= 0)
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goto err;
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if (flag == TESTING) {
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/*
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* generate patterns that are more likely to trigger BN library bugs
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*/
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int i;
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unsigned char c;
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for (i = 0; i < bytes; i++) {
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if (RAND_bytes(&c, 1) <= 0)
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goto err;
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if (c >= 128 && i > 0)
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buf[i] = buf[i - 1];
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else if (c < 42)
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buf[i] = 0;
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else if (c < 84)
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buf[i] = 255;
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}
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}
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if (top >= 0) {
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if (top) {
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if (bit == 0) {
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buf[0] = 1;
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buf[1] |= 0x80;
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} else {
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buf[0] |= (3 << (bit - 1));
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}
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} else {
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buf[0] |= (1 << bit);
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}
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}
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buf[0] &= ~mask;
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if (bottom) /* set bottom bit if requested */
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buf[bytes - 1] |= 1;
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if (!BN_bin2bn(buf, bytes, rnd))
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goto err;
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ret = 1;
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err:
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OPENSSL_clear_free(buf, bytes);
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bn_check_top(rnd);
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return ret;
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toosmall:
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BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL);
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return 0;
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}
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int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
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{
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return bnrand(NORMAL, rnd, bits, top, bottom);
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}
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int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
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{
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return bnrand(TESTING, rnd, bits, top, bottom);
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}
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int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom)
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{
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return bnrand(PRIVATE, rnd, bits, top, bottom);
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}
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/* random number r: 0 <= r < range */
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static int bnrand_range(BNRAND_FLAG flag, BIGNUM *r, const BIGNUM *range)
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{
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int n;
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int count = 100;
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if (range->neg || BN_is_zero(range)) {
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BNerr(BN_F_BNRAND_RANGE, BN_R_INVALID_RANGE);
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return 0;
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}
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n = BN_num_bits(range); /* n > 0 */
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/* BN_is_bit_set(range, n - 1) always holds */
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if (n == 1)
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BN_zero(r);
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else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
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/*
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* range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
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* than range
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*/
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do {
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if (!bnrand(flag, r, n + 1, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
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return 0;
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/*
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* If r < 3*range, use r := r MOD range (which is either r, r -
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* range, or r - 2*range). Otherwise, iterate once more. Since
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* 3*range = 11..._2, each iteration succeeds with probability >=
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* .75.
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*/
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if (BN_cmp(r, range) >= 0) {
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if (!BN_sub(r, r, range))
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return 0;
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if (BN_cmp(r, range) >= 0)
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if (!BN_sub(r, r, range))
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return 0;
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}
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if (!--count) {
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BNerr(BN_F_BNRAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
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return 0;
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}
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}
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while (BN_cmp(r, range) >= 0);
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} else {
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do {
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/* range = 11..._2 or range = 101..._2 */
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if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
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return 0;
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if (!--count) {
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BNerr(BN_F_BNRAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
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return 0;
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}
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}
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while (BN_cmp(r, range) >= 0);
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}
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bn_check_top(r);
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return 1;
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}
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int BN_rand_range(BIGNUM *r, const BIGNUM *range)
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{
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return bnrand_range(NORMAL, r, range);
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}
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int BN_priv_rand_range(BIGNUM *r, const BIGNUM *range)
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{
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return bnrand_range(PRIVATE, r, range);
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}
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int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
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{
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return BN_rand(rnd, bits, top, bottom);
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}
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int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
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{
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return BN_rand_range(r, range);
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}
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/*
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* BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
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* BN_rand_range, it also includes the contents of |priv| and |message| in
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* the generation so that an RNG failure isn't fatal as long as |priv|
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* remains secret. This is intended for use in DSA and ECDSA where an RNG
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* weakness leads directly to private key exposure unless this function is
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* used.
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*/
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int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
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const BIGNUM *priv, const unsigned char *message,
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size_t message_len, BN_CTX *ctx)
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{
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SHA512_CTX sha;
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/*
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* We use 512 bits of random data per iteration to ensure that we have at
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* least |range| bits of randomness.
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*/
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unsigned char random_bytes[64];
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unsigned char digest[SHA512_DIGEST_LENGTH];
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unsigned done, todo;
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/* We generate |range|+8 bytes of random output. */
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const unsigned num_k_bytes = BN_num_bytes(range) + 8;
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unsigned char private_bytes[96];
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unsigned char *k_bytes;
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int ret = 0;
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k_bytes = OPENSSL_malloc(num_k_bytes);
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if (k_bytes == NULL)
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goto err;
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/* We copy |priv| into a local buffer to avoid exposing its length. */
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todo = sizeof(priv->d[0]) * priv->top;
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if (todo > sizeof(private_bytes)) {
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/*
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* No reasonable DSA or ECDSA key should have a private key this
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* large and we don't handle this case in order to avoid leaking the
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* length of the private key.
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*/
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BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
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goto err;
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}
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memcpy(private_bytes, priv->d, todo);
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memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);
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for (done = 0; done < num_k_bytes;) {
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if (RAND_priv_bytes(random_bytes, sizeof(random_bytes)) != 1)
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goto err;
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SHA512_Init(&sha);
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SHA512_Update(&sha, &done, sizeof(done));
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SHA512_Update(&sha, private_bytes, sizeof(private_bytes));
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SHA512_Update(&sha, message, message_len);
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SHA512_Update(&sha, random_bytes, sizeof(random_bytes));
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SHA512_Final(digest, &sha);
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todo = num_k_bytes - done;
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if (todo > SHA512_DIGEST_LENGTH)
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todo = SHA512_DIGEST_LENGTH;
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memcpy(k_bytes + done, digest, todo);
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done += todo;
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}
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if (!BN_bin2bn(k_bytes, num_k_bytes, out))
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goto err;
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if (BN_mod(out, out, range, ctx) != 1)
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goto err;
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ret = 1;
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err:
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OPENSSL_free(k_bytes);
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OPENSSL_cleanse(private_bytes, sizeof(private_bytes));
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return ret;
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}
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