2 * Copyright 1995-2016 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
10 /* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
13 #include "internal/cryptlib.h"
14 #include <openssl/bn.h>
15 #include <openssl/sha.h>
17 #include <openssl/rand.h>
18 #include <openssl/asn1.h>
20 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
21 static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
23 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
24 BIGNUM **rp, const unsigned char *dgst, int dlen);
25 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
26 DSA_SIG *sig, DSA *dsa);
27 static int dsa_init(DSA *dsa);
28 static int dsa_finish(DSA *dsa);
30 static DSA_METHOD openssl_dsa_meth = {
33 dsa_sign_setup_no_digest,
35 NULL, /* dsa_mod_exp, */
36 NULL, /* dsa_bn_mod_exp, */
45 const DSA_METHOD *DSA_OpenSSL(void)
47 return &openssl_dsa_meth;
50 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
57 int reason = ERR_R_BN_LIB;
63 if (m == NULL || xr == NULL)
66 if (!dsa->p || !dsa->q || !dsa->g) {
67 reason = DSA_R_MISSING_PARAMETERS;
75 DSA_SIG_get0(&r, &s, ret);
81 if (!dsa_sign_setup(dsa, ctx, &kinv, &r, dgst, dlen))
84 if (dlen > BN_num_bytes(dsa->q))
86 * if the digest length is greater than the size of q use the
87 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
90 dlen = BN_num_bytes(dsa->q);
91 if (BN_bin2bn(dgst, dlen, m) == NULL)
94 /* Compute s = inv(k) (m + xr) mod q */
95 if (!BN_mod_mul(xr, dsa->priv_key, r, dsa->q, ctx))
96 goto err; /* s = xr */
97 if (!BN_add(s, xr, m))
98 goto err; /* s = m + xr */
99 if (BN_cmp(s, dsa->q) > 0)
100 if (!BN_sub(s, s, dsa->q))
102 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
106 * Redo if r or s is zero as required by FIPS 186-3: this is very
109 if (BN_is_zero(r) || BN_is_zero(s))
116 DSAerr(DSA_F_DSA_DO_SIGN, reason);
127 static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
128 BIGNUM **kinvp, BIGNUM **rp)
130 return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
133 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
134 BIGNUM **kinvp, BIGNUM **rp,
135 const unsigned char *dgst, int dlen)
138 BIGNUM *k, *kinv = NULL, *r = *rp;
141 if (!dsa->p || !dsa->q || !dsa->g) {
142 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
150 if (ctx_in == NULL) {
151 if ((ctx = BN_CTX_new()) == NULL)
160 * We calculate k from SHA512(private_key + H(message) + random).
161 * This protects the private key from a weak PRNG.
163 if (!BN_generate_dsa_nonce(k, dsa->q, dsa->priv_key, dgst,
166 } else if (!BN_rand_range(k, dsa->q))
168 } while (BN_is_zero(k));
170 BN_set_flags(k, BN_FLG_CONSTTIME);
172 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
173 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
174 dsa->lock, dsa->p, ctx))
178 /* Compute r = (g^k mod p) mod q */
181 * We do not want timing information to leak the length of k, so we
182 * compute g^k using an equivalent exponent of fixed length. (This
183 * is a kludge that we need because the BN_mod_exp_mont() does not
184 * let us specify the desired timing behaviour.)
187 if (!BN_add(k, k, dsa->q))
189 if (BN_num_bits(k) <= BN_num_bits(dsa->q)) {
190 if (!BN_add(k, k, dsa->q))
194 if ((dsa)->meth->bn_mod_exp != NULL) {
195 if (!dsa->meth->bn_mod_exp(dsa, r, dsa->g, k, dsa->p, ctx,
199 if (!BN_mod_exp_mont(r, dsa->g, k, dsa->p, ctx, dsa->method_mont_p))
203 if (!BN_mod(r, r, dsa->q, ctx))
206 /* Compute part of 's = inv(k) (m + xr) mod q' */
207 if ((kinv = BN_mod_inverse(NULL, k, dsa->q, ctx)) == NULL)
210 BN_clear_free(*kinvp);
216 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
223 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
224 DSA_SIG *sig, DSA *dsa)
227 BIGNUM *u1, *u2, *t1;
228 BN_MONT_CTX *mont = NULL;
231 if (!dsa->p || !dsa->q || !dsa->g) {
232 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
236 i = BN_num_bits(dsa->q);
237 /* fips 186-3 allows only different sizes for q */
238 if (i != 160 && i != 224 && i != 256) {
239 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
243 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
244 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
251 if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
254 DSA_SIG_get0(&r, &s, sig);
256 if (BN_is_zero(r) || BN_is_negative(r) ||
257 BN_ucmp(r, dsa->q) >= 0) {
261 if (BN_is_zero(s) || BN_is_negative(s) ||
262 BN_ucmp(s, dsa->q) >= 0) {
268 * Calculate W = inv(S) mod Q save W in u2
270 if ((BN_mod_inverse(u2, s, dsa->q, ctx)) == NULL)
274 if (dgst_len > (i >> 3))
276 * if the digest length is greater than the size of q use the
277 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
281 if (BN_bin2bn(dgst, dgst_len, u1) == NULL)
284 /* u1 = M * w mod q */
285 if (!BN_mod_mul(u1, u1, u2, dsa->q, ctx))
288 /* u2 = r * w mod q */
289 if (!BN_mod_mul(u2, r, u2, dsa->q, ctx))
292 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
293 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
294 dsa->lock, dsa->p, ctx);
299 if (dsa->meth->dsa_mod_exp != NULL) {
300 if (!dsa->meth->dsa_mod_exp(dsa, t1, dsa->g, u1, dsa->pub_key, u2,
304 if (!BN_mod_exp2_mont(t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx,
309 /* let u1 = u1 mod q */
310 if (!BN_mod(u1, t1, dsa->q, ctx))
314 * V is now in u1. If the signature is correct, it will be equal to R.
316 ret = (BN_ucmp(u1, r) == 0);
320 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
328 static int dsa_init(DSA *dsa)
330 dsa->flags |= DSA_FLAG_CACHE_MONT_P;
334 static int dsa_finish(DSA *dsa)
336 BN_MONT_CTX_free(dsa->method_mont_p);