2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
12 #include "internal/cryptlib.h"
14 #include <openssl/rand.h>
15 #include <openssl/sha.h>
17 static int bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
19 unsigned char *buf = NULL;
20 int ret = 0, bit, bytes, mask;
23 if (bits < 0 || (bits == 1 && top > 0)) {
24 BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL);
33 bytes = (bits + 7) / 8;
35 mask = 0xff << (bit + 1);
37 buf = OPENSSL_malloc(bytes);
39 BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
43 /* make a random number and set the top and bottom bits */
45 RAND_add(&tim, sizeof(tim), 0.0);
47 if (RAND_bytes(buf, bytes) <= 0)
50 if (pseudorand == 2) {
52 * generate patterns that are more likely to trigger BN library bugs
57 for (i = 0; i < bytes; i++) {
58 if (RAND_bytes(&c, 1) <= 0)
60 if (c >= 128 && i > 0)
75 buf[0] |= (3 << (bit - 1));
82 if (bottom) /* set bottom bit if requested */
84 if (!BN_bin2bn(buf, bytes, rnd))
88 OPENSSL_clear_free(buf, bytes);
93 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
95 return bnrand(0, rnd, bits, top, bottom);
98 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
100 return bnrand(1, rnd, bits, top, bottom);
103 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
105 return bnrand(2, rnd, bits, top, bottom);
108 /* random number r: 0 <= r < range */
109 static int bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
111 int (*bn_rand) (BIGNUM *, int, int, int) =
112 pseudo ? BN_pseudo_rand : BN_rand;
116 if (range->neg || BN_is_zero(range)) {
117 BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
121 n = BN_num_bits(range); /* n > 0 */
123 /* BN_is_bit_set(range, n - 1) always holds */
127 else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
129 * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
133 if (!bn_rand(r, n + 1, -1, 0))
136 * If r < 3*range, use r := r MOD range (which is either r, r -
137 * range, or r - 2*range). Otherwise, iterate once more. Since
138 * 3*range = 11..._2, each iteration succeeds with probability >=
141 if (BN_cmp(r, range) >= 0) {
142 if (!BN_sub(r, r, range))
144 if (BN_cmp(r, range) >= 0)
145 if (!BN_sub(r, r, range))
150 BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
155 while (BN_cmp(r, range) >= 0);
158 /* range = 11..._2 or range = 101..._2 */
159 if (!bn_rand(r, n, -1, 0))
163 BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
167 while (BN_cmp(r, range) >= 0);
174 int BN_rand_range(BIGNUM *r, const BIGNUM *range)
176 return bn_rand_range(0, r, range);
179 int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
181 return bn_rand_range(1, r, range);
185 * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
186 * BN_rand_range, it also includes the contents of |priv| and |message| in
187 * the generation so that an RNG failure isn't fatal as long as |priv|
188 * remains secret. This is intended for use in DSA and ECDSA where an RNG
189 * weakness leads directly to private key exposure unless this function is
192 int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
193 const BIGNUM *priv, const unsigned char *message,
194 size_t message_len, BN_CTX *ctx)
198 * We use 512 bits of random data per iteration to ensure that we have at
199 * least |range| bits of randomness.
201 unsigned char random_bytes[64];
202 unsigned char digest[SHA512_DIGEST_LENGTH];
204 /* We generate |range|+8 bytes of random output. */
205 const unsigned num_k_bytes = BN_num_bytes(range) + 8;
206 unsigned char private_bytes[96];
207 unsigned char *k_bytes;
210 k_bytes = OPENSSL_malloc(num_k_bytes);
214 /* We copy |priv| into a local buffer to avoid exposing its length. */
215 todo = sizeof(priv->d[0]) * priv->top;
216 if (todo > sizeof(private_bytes)) {
218 * No reasonable DSA or ECDSA key should have a private key this
219 * large and we don't handle this case in order to avoid leaking the
220 * length of the private key.
222 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
225 memcpy(private_bytes, priv->d, todo);
226 memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);
228 for (done = 0; done < num_k_bytes;) {
229 if (RAND_bytes(random_bytes, sizeof(random_bytes)) != 1)
232 SHA512_Update(&sha, &done, sizeof(done));
233 SHA512_Update(&sha, private_bytes, sizeof(private_bytes));
234 SHA512_Update(&sha, message, message_len);
235 SHA512_Update(&sha, random_bytes, sizeof(random_bytes));
236 SHA512_Final(digest, &sha);
238 todo = num_k_bytes - done;
239 if (todo > SHA512_DIGEST_LENGTH)
240 todo = SHA512_DIGEST_LENGTH;
241 memcpy(k_bytes + done, digest, todo);
245 if (!BN_bin2bn(k_bytes, num_k_bytes, out))
247 if (BN_mod(out, out, range, ctx) != 1)
252 OPENSSL_free(k_bytes);