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);
48 if (RAND_bytes(buf, bytes) <= 0)
51 if (RAND_bytes(buf, bytes) <= 0)
55 if (pseudorand == 2) {
57 * generate patterns that are more likely to trigger BN library bugs
62 for (i = 0; i < bytes; i++) {
63 if (RAND_bytes(&c, 1) <= 0)
65 if (c >= 128 && i > 0)
80 buf[0] |= (3 << (bit - 1));
87 if (bottom) /* set bottom bit if requested */
89 if (!BN_bin2bn(buf, bytes, rnd))
93 OPENSSL_clear_free(buf, bytes);
98 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
100 return bnrand(0, rnd, bits, top, bottom);
103 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
105 return bnrand(1, rnd, bits, top, bottom);
108 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
110 return bnrand(2, rnd, bits, top, bottom);
113 /* random number r: 0 <= r < range */
114 static int bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
116 int (*bn_rand) (BIGNUM *, int, int, int) =
117 pseudo ? BN_pseudo_rand : BN_rand;
121 if (range->neg || BN_is_zero(range)) {
122 BNerr(BN_F_BN_RAND_RANGE, BN_R_INVALID_RANGE);
126 n = BN_num_bits(range); /* n > 0 */
128 /* BN_is_bit_set(range, n - 1) always holds */
132 else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
134 * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
138 if (!bn_rand(r, n + 1, -1, 0))
141 * If r < 3*range, use r := r MOD range (which is either r, r -
142 * range, or r - 2*range). Otherwise, iterate once more. Since
143 * 3*range = 11..._2, each iteration succeeds with probability >=
146 if (BN_cmp(r, range) >= 0) {
147 if (!BN_sub(r, r, range))
149 if (BN_cmp(r, range) >= 0)
150 if (!BN_sub(r, r, range))
155 BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
160 while (BN_cmp(r, range) >= 0);
163 /* range = 11..._2 or range = 101..._2 */
164 if (!bn_rand(r, n, -1, 0))
168 BNerr(BN_F_BN_RAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
172 while (BN_cmp(r, range) >= 0);
179 int BN_rand_range(BIGNUM *r, const BIGNUM *range)
181 return bn_rand_range(0, r, range);
184 int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
186 return bn_rand_range(1, r, range);
190 * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
191 * BN_rand_range, it also includes the contents of |priv| and |message| in
192 * the generation so that an RNG failure isn't fatal as long as |priv|
193 * remains secret. This is intended for use in DSA and ECDSA where an RNG
194 * weakness leads directly to private key exposure unless this function is
197 int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
198 const BIGNUM *priv, const unsigned char *message,
199 size_t message_len, BN_CTX *ctx)
203 * We use 512 bits of random data per iteration to ensure that we have at
204 * least |range| bits of randomness.
206 unsigned char random_bytes[64];
207 unsigned char digest[SHA512_DIGEST_LENGTH];
209 /* We generate |range|+8 bytes of random output. */
210 const unsigned num_k_bytes = BN_num_bytes(range) + 8;
211 unsigned char private_bytes[96];
212 unsigned char *k_bytes;
215 k_bytes = OPENSSL_malloc(num_k_bytes);
219 /* We copy |priv| into a local buffer to avoid exposing its length. */
220 todo = sizeof(priv->d[0]) * priv->top;
221 if (todo > sizeof(private_bytes)) {
223 * No reasonable DSA or ECDSA key should have a private key this
224 * large and we don't handle this case in order to avoid leaking the
225 * length of the private key.
227 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
230 memcpy(private_bytes, priv->d, todo);
231 memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);
233 for (done = 0; done < num_k_bytes;) {
234 if (RAND_bytes(random_bytes, sizeof(random_bytes)) != 1)
237 SHA512_Update(&sha, &done, sizeof(done));
238 SHA512_Update(&sha, private_bytes, sizeof(private_bytes));
239 SHA512_Update(&sha, message, message_len);
240 SHA512_Update(&sha, random_bytes, sizeof(random_bytes));
241 SHA512_Final(digest, &sha);
243 todo = num_k_bytes - done;
244 if (todo > SHA512_DIGEST_LENGTH)
245 todo = SHA512_DIGEST_LENGTH;
246 memcpy(k_bytes + done, digest, todo);
250 if (!BN_bin2bn(k_bytes, num_k_bytes, out))
252 if (BN_mod(out, out, range, ctx) != 1)
257 OPENSSL_free(k_bytes);