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
));