2 * Copyright 1995-2018 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"
14 #include <openssl/rand.h>
15 #include <openssl/rand_drbg.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)
25 unsigned char *buf = NULL;
26 int b, ret = 0, bit, bytes, mask;
29 if (top != BN_RAND_TOP_ANY || bottom != BN_RAND_BOTTOM_ANY)
34 if (bits < 0 || (bits == 1 && top > 0))
37 bytes = (bits + 7) / 8;
39 mask = 0xff << (bit + 1);
41 buf = OPENSSL_malloc(bytes);
43 BNerr(BN_F_BNRAND, ERR_R_MALLOC_FAILURE);
47 /* make a random number and set the top and bottom bits */
48 b = flag == NORMAL ? RAND_bytes(buf, bytes) : RAND_priv_bytes(buf, bytes);
52 if (flag == TESTING) {
54 * generate patterns that are more likely to trigger BN library bugs
59 for (i = 0; i < bytes; i++) {
60 if (RAND_bytes(&c, 1) <= 0)
62 if (c >= 128 && i > 0)
77 buf[0] |= (3 << (bit - 1));
84 if (bottom) /* set bottom bit if requested */
86 if (!BN_bin2bn(buf, bytes, rnd))
90 OPENSSL_clear_free(buf, bytes);
95 BNerr(BN_F_BNRAND, BN_R_BITS_TOO_SMALL);
99 int BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
101 return bnrand(NORMAL, rnd, bits, top, bottom);
104 int BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
106 return bnrand(TESTING, rnd, bits, top, bottom);
109 int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom)
111 return bnrand(PRIVATE, rnd, bits, top, bottom);
114 /* random number r: 0 <= r < range */
115 static int bnrand_range(BNRAND_FLAG flag, BIGNUM *r, const BIGNUM *range)
120 if (range->neg || BN_is_zero(range)) {
121 BNerr(BN_F_BNRAND_RANGE, BN_R_INVALID_RANGE);
125 n = BN_num_bits(range); /* n > 0 */
127 /* BN_is_bit_set(range, n - 1) always holds */
131 else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
133 * range = 100..._2, so 3*range (= 11..._2) is exactly one bit longer
137 if (!bnrand(flag, r, n + 1, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
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_BNRAND_RANGE, BN_R_TOO_MANY_ITERATIONS);
160 while (BN_cmp(r, range) >= 0);
163 /* range = 11..._2 or range = 101..._2 */
164 if (!bnrand(flag, r, n, BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
168 BNerr(BN_F_BNRAND_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 bnrand_range(NORMAL, r, range);
184 int BN_priv_rand_range(BIGNUM *r, const BIGNUM *range)
186 return bnrand_range(PRIVATE, r, range);
189 int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
191 return BN_rand(rnd, bits, top, bottom);
194 int BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
196 return BN_rand_range(r, range);
200 * BN_generate_dsa_nonce generates a random number 0 <= out < range. Unlike
201 * BN_rand_range, it also includes the contents of |priv| and |message| in
202 * the generation so that an RNG failure isn't fatal as long as |priv|
203 * remains secret. This is intended for use in DSA and ECDSA where an RNG
204 * weakness leads directly to private key exposure unless this function is
207 int BN_generate_dsa_nonce(BIGNUM *out, const BIGNUM *range,
208 const BIGNUM *priv, const unsigned char *message,
209 size_t message_len, BN_CTX *ctx)
211 EVP_MD_CTX *mdctx = EVP_MD_CTX_new();
213 * We use 512 bits of random data per iteration to ensure that we have at
214 * least |range| bits of randomness.
216 unsigned char random_bytes[64];
217 unsigned char digest[SHA512_DIGEST_LENGTH];
219 /* We generate |range|+8 bytes of random output. */
220 const unsigned num_k_bytes = BN_num_bytes(range) + 8;
221 unsigned char private_bytes[96];
222 unsigned char *k_bytes = NULL;
225 OPENSSL_CTX *libctx = (ctx != NULL) ? bn_get_lib_ctx(ctx) : NULL;
226 RAND_DRBG *privdrbg = OPENSSL_CTX_get0_private_drbg(libctx);
228 if (mdctx == NULL || privdrbg == NULL)
231 k_bytes = OPENSSL_malloc(num_k_bytes);
235 /* We copy |priv| into a local buffer to avoid exposing its length. */
236 todo = sizeof(priv->d[0]) * priv->top;
237 if (todo > sizeof(private_bytes)) {
239 * No reasonable DSA or ECDSA key should have a private key this
240 * large and we don't handle this case in order to avoid leaking the
241 * length of the private key.
243 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_PRIVATE_KEY_TOO_LARGE);
246 memcpy(private_bytes, priv->d, todo);
247 memset(private_bytes + todo, 0, sizeof(private_bytes) - todo);
249 md = EVP_MD_fetch(libctx, "SHA512", NULL);
251 BNerr(BN_F_BN_GENERATE_DSA_NONCE, BN_R_NO_SUITABLE_DIGEST);
254 for (done = 0; done < num_k_bytes;) {
255 if (!RAND_DRBG_bytes(privdrbg, random_bytes, sizeof(random_bytes)))
258 if (!EVP_DigestInit_ex(mdctx, md, NULL)
259 || !EVP_DigestUpdate(mdctx, &done, sizeof(done))
260 || !EVP_DigestUpdate(mdctx, private_bytes,
261 sizeof(private_bytes))
262 || !EVP_DigestUpdate(mdctx, message, message_len)
263 || !EVP_DigestUpdate(mdctx, random_bytes, sizeof(random_bytes))
264 || !EVP_DigestFinal_ex(mdctx, digest, NULL))
267 todo = num_k_bytes - done;
268 if (todo > SHA512_DIGEST_LENGTH)
269 todo = SHA512_DIGEST_LENGTH;
270 memcpy(k_bytes + done, digest, todo);
274 if (!BN_bin2bn(k_bytes, num_k_bytes, out))
276 if (BN_mod(out, out, range, ctx) != 1)
281 EVP_MD_CTX_free(mdctx);
282 EVP_MD_meth_free(md);
283 OPENSSL_free(k_bytes);
284 OPENSSL_cleanse(private_bytes, sizeof(private_bytes));