2 * Copyright 1995-2019 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 typedef enum bnrand_flag_e {
18 NORMAL, TESTING, PRIVATE
21 static int bnrand(BNRAND_FLAG flag, BIGNUM *rnd, int bits, int top, int bottom)
23 unsigned char *buf = NULL;
24 int b, ret = 0, bit, bytes, mask;
27 if (top != BN_RAND_TOP_ANY || bottom != BN_RAND_BOTTOM_ANY)
32 if (bits < 0 || (bits == 1 && top > 0))
35 bytes = (bits + 7) / 8;
37 mask = 0xff << (bit + 1);
39 buf = OPENSSL_malloc(bytes);
41 BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
45 /* make a random number and set the top and bottom bits */
46 b = flag == NORMAL ? RAND_bytes(buf, bytes) : RAND_priv_bytes(buf, bytes);
50 if (flag == TESTING) {
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 BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL);
97 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
99 return bnrand(NORMAL, rnd, bits, top, bottom);
102 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
104 return bnrand(TESTING, rnd, bits, top, bottom);
107 int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom)
109 return bnrand(PRIVATE, rnd, bits, top, bottom);
112 /* random number r: 0 <= r < range */
113 static int bnrand_range(BNRAND_FLAG flag, BIGNUM *r, const BIGNUM *range)
118 if (range->neg || BN_is_zero(range)) {
119 BNerr(BN_F_BNRAND_RANGE, BN_R_INVALID_RANGE);
123 n = BN_num_bits(range); /* n > 0 */
125 /* BN_is_bit_set(range, n - 1) always holds */
129 else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
131 * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
135 if (!bnrand(flag, r, n + 1, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
139 * If r < 3*range, use r := r MOD range (which is either r, r -
140 * range, or r - 2*range). Otherwise, iterate once more. Since
141 * 3*range = 11..._2, each iteration succeeds with probability >=
144 if (BN_cmp(r, range) >= 0) {
145 if (!BN_sub(r, r, range))
147 if (BN_cmp(r, range) >= 0)
148 if (!BN_sub(r, r, range))
153 BNerr(BN_F_BNRAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
158 while (BN_cmp(r, range) >= 0);
161 /* range = 11..._2 or range = 101..._2 */
162 if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
166 BNerr(BN_F_BNRAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
170 while (BN_cmp(r, range) >= 0);
177 int BN_rand_range(BIGNUM *r, const BIGNUM *range)
179 return bnrand_range(NORMAL, r, range);
182 int BN_priv_rand_range(BIGNUM *r, const BIGNUM *range)
184 return bnrand_range(PRIVATE, r, range);
187 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
189 return BN_rand(rnd, bits, top, bottom);
192 int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
194 return BN_rand_range(r, range);
198 * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
199 * BN_rand_range, it also includes the contents of |priv| and |message| in
200 * the generation so that an RNG failure isn't fatal as long as |priv|
201 * remains secret. This is intended for use in DSA and ECDSA where an RNG
202 * weakness leads directly to private key exposure unless this function is
205 int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
206 const BIGNUM *priv, const unsigned char *message,
207 size_t message_len, BN_CTX *ctx)
211 * We use 512 bits of random data per iteration to ensure that we have at
212 * least |range| bits of randomness.
214 unsigned char random_bytes[64];
215 unsigned char digest[SHA512_DIGEST_LENGTH];
217 /* We generate |range|+8 bytes of random output. */
218 const unsigned num_k_bytes = BN_num_bytes(range) + 8;
219 unsigned char private_bytes[96];
220 unsigned char *k_bytes;
223 k_bytes = OPENSSL_malloc(num_k_bytes);
227 /* We copy |priv| into a local buffer to avoid exposing its length. */
228 if (BN_bn2binpad(priv, private_bytes, sizeof(private_bytes)) < 0) {
230 * No reasonable DSA or ECDSA key should have a private key this
231 * large and we don't handle this case in order to avoid leaking the
232 * length of the private key.
234 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
238 for (done = 0; done < num_k_bytes;) {
239 if (RAND_priv_bytes(random_bytes, sizeof(random_bytes)) != 1)
242 SHA512_Update(&sha, &done, sizeof(done));
243 SHA512_Update(&sha, private_bytes, sizeof(private_bytes));
244 SHA512_Update(&sha, message, message_len);
245 SHA512_Update(&sha, random_bytes, sizeof(random_bytes));
246 SHA512_Final(digest, &sha);
248 todo = num_k_bytes - done;
249 if (todo > SHA512_DIGEST_LENGTH)
250 todo = SHA512_DIGEST_LENGTH;
251 memcpy(k_bytes + done, digest, todo);
255 if (!BN_bin2bn(k_bytes, num_k_bytes, out))
257 if (BN_mod(out, out, range, ctx) != 1)
262 OPENSSL_free(k_bytes);
263 OPENSSL_cleanse(private_bytes, sizeof(private_bytes));