1 /* crypto/dsa/dsa_ossl.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
59 /* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
63 #include <openssl/bn.h>
64 #include <openssl/sha.h>
65 #include <openssl/dsa.h>
66 #include <openssl/rand.h>
67 #include <openssl/asn1.h>
69 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
70 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
72 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
73 DSA_SIG *sig, DSA *dsa);
74 static int dsa_init(DSA *dsa);
75 static int dsa_finish(DSA *dsa);
77 static DSA_METHOD openssl_dsa_meth = {
82 NULL, /* dsa_mod_exp, */
83 NULL, /* dsa_bn_mod_exp, */
93 * These macro wrappers replace attempts to use the dsa_mod_exp() and
94 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
95 * having a the macro work as an expression by bundling an "err_instr". So;
97 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
98 * dsa->method_mont_p)) goto err;
100 * can be replaced by;
102 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
103 * dsa->method_mont_p);
106 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
109 if ((dsa)->meth->dsa_mod_exp) \
110 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
111 (a2), (p2), (m), (ctx), (in_mont)); \
113 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
114 (m), (ctx), (in_mont)); \
115 if (!_tmp_res53) err_instr; \
117 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
120 if ((dsa)->meth->bn_mod_exp) \
121 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
122 (m), (ctx), (m_ctx)); \
124 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
125 if (!_tmp_res53) err_instr; \
128 const DSA_METHOD *DSA_OpenSSL(void)
130 return &openssl_dsa_meth;
133 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
135 BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
136 BIGNUM *m, *blind, *blindm, *tmp;
138 int reason = ERR_R_BN_LIB;
142 if (dsa->p == NULL || dsa->q == NULL || dsa->g == NULL) {
143 reason = DSA_R_MISSING_PARAMETERS;
154 blind = BN_CTX_get(ctx);
155 blindm = BN_CTX_get(ctx);
156 tmp = BN_CTX_get(ctx);
161 if ((dsa->kinv == NULL) || (dsa->r == NULL)) {
162 if (!DSA_sign_setup(dsa, ctx, &kinv, &r))
172 if (dlen > BN_num_bytes(dsa->q))
174 * if the digest length is greater than the size of q use the
175 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
178 dlen = BN_num_bytes(dsa->q);
179 if (BN_bin2bn(dgst, dlen, m) == NULL)
183 * The normal signature calculation is:
185 * s := k^-1 * (m + r * priv_key) mod q
187 * We will blind this to protect against side channel attacks
189 * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod q
192 /* Generate a blinding value */
194 if (!BN_rand(blind, BN_num_bits(dsa->q) - 1, -1, 0))
196 } while (BN_is_zero(blind));
197 BN_set_flags(blind, BN_FLG_CONSTTIME);
198 BN_set_flags(blindm, BN_FLG_CONSTTIME);
199 BN_set_flags(tmp, BN_FLG_CONSTTIME);
201 /* tmp := blind * priv_key * r mod q */
202 if (!BN_mod_mul(tmp, blind, dsa->priv_key, dsa->q, ctx))
204 if (!BN_mod_mul(tmp, tmp, r, dsa->q, ctx))
207 /* blindm := blind * m mod q */
208 if (!BN_mod_mul(blindm, blind, m, dsa->q, ctx))
211 /* s : = (blind * priv_key * r) + (blind * m) mod q */
212 if (!BN_mod_add_quick(s, tmp, blindm, dsa->q))
215 /* s := s * k^-1 mod q */
216 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
219 /* s:= s * blind^-1 mod q */
220 if (BN_mod_inverse(blind, blind, dsa->q, ctx) == NULL)
222 if (!BN_mod_mul(s, s, blind, dsa->q, ctx))
226 * Redo if r or s is zero as required by FIPS 186-3: this is very
229 if (BN_is_zero(r) || BN_is_zero(s)) {
231 reason = DSA_R_NEED_NEW_SETUP_VALUES;
244 DSAerr(DSA_F_DSA_DO_SIGN, reason);
253 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
257 BIGNUM k, kq, *K, *kinv = NULL, *r = NULL;
262 if (!dsa->p || !dsa->q || !dsa->g) {
263 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
272 if (ctx_in == NULL) {
273 if ((ctx = BN_CTX_new()) == NULL)
278 if ((r = BN_new()) == NULL)
281 /* Preallocate space */
282 q_bits = BN_num_bits(dsa->q) + sizeof(dsa->q->d[0]) * 16;
283 if (!BN_set_bit(&k, q_bits)
284 || !BN_set_bit(&l, q_bits)
285 || !BN_set_bit(&m, q_bits))
290 if (!BN_rand_range(&k, dsa->q))
292 while (BN_is_zero(&k));
294 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
295 BN_set_flags(&k, BN_FLG_CONSTTIME);
299 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
300 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
301 CRYPTO_LOCK_DSA, dsa->p, ctx))
305 /* Compute r = (g^k mod p) mod q */
307 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
309 * We do not want timing information to leak the length of k, so we
310 * compute G^k using an equivalent scalar of fixed bit-length.
312 * We unconditionally perform both of these additions to prevent a
313 * small timing information leakage. We then choose the sum that is
314 * one bit longer than the modulus.
316 * TODO: revisit the BN_copy aiming for a memory access agnostic
319 if (!BN_add(&l, &k, dsa->q)
320 || !BN_add(&m, &l, dsa->q)
321 || !BN_copy(&kq, BN_num_bits(&l) > q_bits ? &l : &m))
324 BN_set_flags(&kq, BN_FLG_CONSTTIME);
331 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
333 if (!BN_mod(r, r, dsa->q, ctx))
336 /* Compute part of 's = inv(k) (m + xr) mod q' */
337 if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL)
341 BN_clear_free(*kinvp);
350 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
363 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
364 DSA_SIG *sig, DSA *dsa)
368 BN_MONT_CTX *mont = NULL;
370 if (!dsa->p || !dsa->q || !dsa->g) {
371 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
375 i = BN_num_bits(dsa->q);
376 /* fips 186-3 allows only different sizes for q */
377 if (i != 160 && i != 224 && i != 256) {
378 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
382 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
383 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
390 if ((ctx = BN_CTX_new()) == NULL)
393 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
394 BN_ucmp(sig->r, dsa->q) >= 0) {
398 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
399 BN_ucmp(sig->s, dsa->q) >= 0) {
405 * Calculate W = inv(S) mod Q save W in u2
407 if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL)
411 if (dgst_len > (i >> 3))
413 * if the digest length is greater than the size of q use the
414 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
418 if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
421 /* u1 = M * w mod q */
422 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
425 /* u2 = r * w mod q */
426 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
429 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
430 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
431 CRYPTO_LOCK_DSA, dsa->p, ctx);
436 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p,
438 /* BN_copy(&u1,&t1); */
439 /* let u1 = u1 mod q */
440 if (!BN_mod(&u1, &t1, dsa->q, ctx))
444 * V is now in u1. If the signature is correct, it will be equal to R.
446 ret = (BN_ucmp(&u1, sig->r) == 0);
450 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
459 static int dsa_init(DSA *dsa)
461 dsa->flags |= DSA_FLAG_CACHE_MONT_P;
465 static int dsa_finish(DSA *dsa)
467 if (dsa->method_mont_p)
468 BN_MONT_CTX_free(dsa->method_mont_p);