2 * Copyright 1995-2020 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,
26 unsigned char *buf = NULL;
27 int b, ret = 0, bit, bytes, mask;
28 OPENSSL_CTX *libctx = bn_get_lib_ctx(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);
45 BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
49 /* make a random number and set the top and bottom bits */
50 b = flag == NORMAL ? RAND_bytes_ex(libctx, buf, bytes)
51 : RAND_priv_bytes_ex(libctx, buf, bytes);
55 if (flag == TESTING) {
57 * generate patterns that are more likely to trigger BN library bugs
62 for (i = 0; i < bytes; i++) {
63 if (RAND_bytes_ex(libctx, &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 BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL);
102 int BN_rand_ex(BIGNUM *rnd, int bits, int top, int bottom, BN_CTX *ctx)
104 return bnrand(NORMAL, rnd, bits, top, bottom, ctx);
107 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
109 return bnrand(NORMAL, rnd, bits, top, bottom, NULL);
112 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
114 return bnrand(TESTING, rnd, bits, top, bottom, NULL);
118 int BN_priv_rand_ex(BIGNUM *rnd, int bits, int top, int bottom, BN_CTX *ctx)
120 return bnrand(PRIVATE, rnd, bits, top, bottom, ctx);
124 int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom)
126 return bnrand(PRIVATE, rnd, bits, top, bottom, NULL);
130 /* random number r: 0 <= r < range */
131 static int bnrand_range(BNRAND_FLAG flag, BIGNUM *r, const BIGNUM *range,
137 if (range->neg || BN_is_zero(range)) {
138 BNerr(BN_F_BNRAND_RANGE, BN_R_INVALID_RANGE);
142 n = BN_num_bits(range); /* n > 0 */
144 /* BN_is_bit_set(range, n - 1) always holds */
148 else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
150 * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
154 if (!bnrand(flag, r, n + 1, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY,
159 * If r < 3*range, use r := r MOD range (which is either r, r -
160 * range, or r - 2*range). Otherwise, iterate once more. Since
161 * 3*range = 11..._2, each iteration succeeds with probability >=
164 if (BN_cmp(r, range) >= 0) {
165 if (!BN_sub(r, r, range))
167 if (BN_cmp(r, range) >= 0)
168 if (!BN_sub(r, r, range))
173 BNerr(BN_F_BNRAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
178 while (BN_cmp(r, range) >= 0);
181 /* range = 11..._2 or range = 101..._2 */
182 if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY, ctx))
186 BNerr(BN_F_BNRAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
190 while (BN_cmp(r, range) >= 0);
197 int BN_rand_range_ex(BIGNUM *r, const BIGNUM *range, BN_CTX *ctx)
199 return bnrand_range(NORMAL, r, range, ctx);
203 int BN_rand_range(BIGNUM *r, const BIGNUM *range)
205 return bnrand_range(NORMAL, r, range, NULL);
209 int BN_priv_rand_range_ex(BIGNUM *r, const BIGNUM *range, BN_CTX *ctx)
211 return bnrand_range(PRIVATE, r, range, ctx);
215 int BN_priv_rand_range(BIGNUM *r, const BIGNUM *range)
217 return bnrand_range(PRIVATE, r, range, NULL);
220 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
222 return BN_rand(rnd, bits, top, bottom);
225 int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
227 return BN_rand_range(r, range);
232 * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
233 * BN_rand_range, it also includes the contents of |priv| and |message| in
234 * the generation so that an RNG failure isn't fatal as long as |priv|
235 * remains secret. This is intended for use in DSA and ECDSA where an RNG
236 * weakness leads directly to private key exposure unless this function is
239 int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
240 const BIGNUM *priv, const unsigned char *message,
241 size_t message_len, BN_CTX *ctx)
243 EVP_MD_CTX *mdctx = EVP_MD_CTX_new();
245 * We use 512 bits of random data per iteration to ensure that we have at
246 * least |range| bits of randomness.
248 unsigned char random_bytes[64];
249 unsigned char digest[SHA512_DIGEST_LENGTH];
251 /* We generate |range|+8 bytes of random output. */
252 const unsigned num_k_bytes = BN_num_bytes(range) + 8;
253 unsigned char private_bytes[96];
254 unsigned char *k_bytes = NULL;
257 OPENSSL_CTX *libctx = bn_get_lib_ctx(ctx);
262 k_bytes = OPENSSL_malloc(num_k_bytes);
266 /* We copy |priv| into a local buffer to avoid exposing its length. */
267 if (BN_bn2binpad(priv, private_bytes, sizeof(private_bytes)) < 0) {
269 * No reasonable DSA or ECDSA key should have a private key this
270 * large and we don't handle this case in order to avoid leaking the
271 * length of the private key.
273 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
277 md = EVP_MD_fetch(libctx, "SHA512", NULL);
279 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_NO_SUITABLE_DIGEST);
282 for (done = 0; done < num_k_bytes;) {
283 if (!RAND_priv_bytes_ex(libctx, random_bytes, sizeof(random_bytes)))
286 if (!EVP_DigestInit_ex(mdctx, md, NULL)
287 || !EVP_DigestUpdate(mdctx, &done, sizeof(done))
288 || !EVP_DigestUpdate(mdctx, private_bytes,
289 sizeof(private_bytes))
290 || !EVP_DigestUpdate(mdctx, message, message_len)
291 || !EVP_DigestUpdate(mdctx, random_bytes, sizeof(random_bytes))
292 || !EVP_DigestFinal_ex(mdctx, digest, NULL))
295 todo = num_k_bytes - done;
296 if (todo > SHA512_DIGEST_LENGTH)
297 todo = SHA512_DIGEST_LENGTH;
298 memcpy(k_bytes + done, digest, todo);
302 if (!BN_bin2bn(k_bytes, num_k_bytes, out))
304 if (BN_mod(out, out, range, ctx) != 1)
309 EVP_MD_CTX_free(mdctx);
311 OPENSSL_free(k_bytes);
312 OPENSSL_cleanse(private_bytes, sizeof(private_bytes));