2 * Copyright 1995-2021 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (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"
13 #include "crypto/rand.h"
15 #include <openssl/rand.h>
16 #include <openssl/sha.h>
17 #include <openssl/evp.h>
19 typedef enum bnrand_flag_e {
20 NORMAL, TESTING, PRIVATE
23 static int bnrand(BNRAND_FLAG flag, BIGNUM *rnd, int bits, int top, int bottom,
24 unsigned int strength, BN_CTX *ctx)
26 unsigned char *buf = NULL;
27 int b, ret = 0, bit, bytes, mask;
28 OSSL_LIB_CTX *libctx = ossl_bn_get_libctx(ctx);
31 if (top != BN_RAND_TOP_ANY || bottom != BN_RAND_BOTTOM_ANY)
36 if (bits < 0 || (bits == 1 && top > 0))
39 bytes = (bits + 7) / 8;
41 mask = 0xff << (bit + 1);
43 buf = OPENSSL_malloc(bytes);
47 /* make a random number and set the top and bottom bits */
48 b = flag == NORMAL ? RAND_bytes_ex(libctx, buf, bytes, strength)
49 : RAND_priv_bytes_ex(libctx, buf, bytes, strength);
53 if (flag == TESTING) {
55 * generate patterns that are more likely to trigger BN library bugs
60 for (i = 0; i < bytes; i++) {
61 if (RAND_bytes_ex(libctx, &c, 1, strength) <= 0)
63 if (c >= 128 && i > 0)
78 buf[0] |= (3 << (bit - 1));
85 if (bottom) /* set bottom bit if requested */
87 if (!BN_bin2bn(buf, bytes, rnd))
91 OPENSSL_clear_free(buf, bytes);
96 ERR_raise(ERR_LIB_BN, BN_R_BITS_TOO_SMALL);
100 int BN_rand_ex(BIGNUM *rnd, int bits, int top, int bottom,
101 unsigned int strength, BN_CTX *ctx)
103 return bnrand(NORMAL, rnd, bits, top, bottom, strength, ctx);
106 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
108 return bnrand(NORMAL, rnd, bits, top, bottom, 0, NULL);
111 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
113 return bnrand(TESTING, rnd, bits, top, bottom, 0, NULL);
117 int BN_priv_rand_ex(BIGNUM *rnd, int bits, int top, int bottom,
118 unsigned int strength, BN_CTX *ctx)
120 return bnrand(PRIVATE, rnd, bits, top, bottom, strength, ctx);
124 int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom)
126 return bnrand(PRIVATE, rnd, bits, top, bottom, 0, NULL);
130 /* random number r: 0 <= r < range */
131 static int bnrand_range(BNRAND_FLAG flag, BIGNUM *r, const BIGNUM *range,
132 unsigned int strength, BN_CTX *ctx)
138 ERR_raise(ERR_LIB_BN, ERR_R_PASSED_NULL_PARAMETER);
142 if (range->neg || BN_is_zero(range)) {
143 ERR_raise(ERR_LIB_BN, BN_R_INVALID_RANGE);
147 n = BN_num_bits(range); /* n > 0 */
149 /* BN_is_bit_set(range, n - 1) always holds */
153 else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
155 * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
159 if (!bnrand(flag, r, n + 1, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY,
164 * If r < 3*range, use r := r MOD range (which is either r, r -
165 * range, or r - 2*range). Otherwise, iterate once more. Since
166 * 3*range = 11..._2, each iteration succeeds with probability >=
169 if (BN_cmp(r, range) >= 0) {
170 if (!BN_sub(r, r, range))
172 if (BN_cmp(r, range) >= 0)
173 if (!BN_sub(r, r, range))
178 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
183 while (BN_cmp(r, range) >= 0);
186 /* range = 11..._2 or range = 101..._2 */
187 if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, 0,
192 ERR_raise(ERR_LIB_BN, BN_R_TOO_MANY_ITERATIONS);
196 while (BN_cmp(r, range) >= 0);
203 int BN_rand_range_ex(BIGNUM *r, const BIGNUM *range, unsigned int strength,
206 return bnrand_range(NORMAL, r, range, strength, ctx);
210 int BN_rand_range(BIGNUM *r, const BIGNUM *range)
212 return bnrand_range(NORMAL, r, range, 0, NULL);
216 int BN_priv_rand_range_ex(BIGNUM *r, const BIGNUM *range, unsigned int strength,
219 return bnrand_range(PRIVATE, r, range, strength, ctx);
223 int BN_priv_rand_range(BIGNUM *r, const BIGNUM *range)
225 return bnrand_range(PRIVATE, r, range, 0, NULL);
228 # ifndef OPENSSL_NO_DEPRECATED_3_0
229 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
231 return BN_rand(rnd, bits, top, bottom);
234 int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
236 return BN_rand_range(r, range);
242 * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
243 * BN_rand_range, it also includes the contents of |priv| and |message| in
244 * the generation so that an RNG failure isn't fatal as long as |priv|
245 * remains secret. This is intended for use in DSA and ECDSA where an RNG
246 * weakness leads directly to private key exposure unless this function is
249 int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
250 const BIGNUM *priv, const unsigned char *message,
251 size_t message_len, BN_CTX *ctx)
253 EVP_MD_CTX *mdctx = EVP_MD_CTX_new();
255 * We use 512 bits of random data per iteration to ensure that we have at
256 * least |range| bits of randomness.
258 unsigned char random_bytes[64];
259 unsigned char digest[SHA512_DIGEST_LENGTH];
261 /* We generate |range|+8 bytes of random output. */
262 const unsigned num_k_bytes = BN_num_bytes(range) + 8;
263 unsigned char private_bytes[96];
264 unsigned char *k_bytes = NULL;
267 OSSL_LIB_CTX *libctx = ossl_bn_get_libctx(ctx);
272 k_bytes = OPENSSL_malloc(num_k_bytes);
276 /* We copy |priv| into a local buffer to avoid exposing its length. */
277 if (BN_bn2binpad(priv, private_bytes, sizeof(private_bytes)) < 0) {
279 * No reasonable DSA or ECDSA key should have a private key this
280 * large and we don't handle this case in order to avoid leaking the
281 * length of the private key.
283 ERR_raise(ERR_LIB_BN, BN_R_PRIVATE_KEY_TOO_LARGE);
287 md = EVP_MD_fetch(libctx, "SHA512", NULL);
289 ERR_raise(ERR_LIB_BN, BN_R_NO_SUITABLE_DIGEST);
292 for (done = 0; done < num_k_bytes;) {
293 if (RAND_priv_bytes_ex(libctx, random_bytes, sizeof(random_bytes), 0) <= 0)
296 if (!EVP_DigestInit_ex(mdctx, md, NULL)
297 || !EVP_DigestUpdate(mdctx, &done, sizeof(done))
298 || !EVP_DigestUpdate(mdctx, private_bytes,
299 sizeof(private_bytes))
300 || !EVP_DigestUpdate(mdctx, message, message_len)
301 || !EVP_DigestUpdate(mdctx, random_bytes, sizeof(random_bytes))
302 || !EVP_DigestFinal_ex(mdctx, digest, NULL))
305 todo = num_k_bytes - done;
306 if (todo > SHA512_DIGEST_LENGTH)
307 todo = SHA512_DIGEST_LENGTH;
308 memcpy(k_bytes + done, digest, todo);
312 if (!BN_bin2bn(k_bytes, num_k_bytes, out))
314 if (BN_mod(out, out, range, ctx) != 1)
319 EVP_MD_CTX_free(mdctx);
321 OPENSSL_clear_free(k_bytes, num_k_bytes);
322 OPENSSL_cleanse(digest, sizeof(digest));
323 OPENSSL_cleanse(random_bytes, sizeof(random_bytes));
324 OPENSSL_cleanse(private_bytes, sizeof(private_bytes));