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diff --git a/src/lib/libcrypto/dsa/dsa_ossl.c b/src/lib/libcrypto/dsa/dsa_ossl.c
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1/* $OpenBSD: dsa_ossl.c,v 1.26 2016/06/21 04:16:53 bcook Exp $ */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
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.
8 *
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).
15 *
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.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
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)"
40 *
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
51 * SUCH DAMAGE.
52 *
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.]
57 */
58
59/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
60
61#include <stdio.h>
62
63#include <openssl/asn1.h>
64#include <openssl/bn.h>
65#include <openssl/dsa.h>
66#include <openssl/err.h>
67#include <openssl/sha.h>
68
69static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
70static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
71 BIGNUM **rp);
72static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
73 DSA *dsa);
74static int dsa_init(DSA *dsa);
75static int dsa_finish(DSA *dsa);
76
77static DSA_METHOD openssl_dsa_meth = {
78 .name = "OpenSSL DSA method",
79 .dsa_do_sign = dsa_do_sign,
80 .dsa_sign_setup = dsa_sign_setup,
81 .dsa_do_verify = dsa_do_verify,
82 .init = dsa_init,
83 .finish = dsa_finish
84};
85
86const DSA_METHOD *
87DSA_OpenSSL(void)
88{
89 return &openssl_dsa_meth;
90}
91
92static DSA_SIG *
93dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
94{
95 BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
96 BIGNUM m;
97 BIGNUM xr;
98 BN_CTX *ctx = NULL;
99 int reason = ERR_R_BN_LIB;
100 DSA_SIG *ret = NULL;
101 int noredo = 0;
102
103 BN_init(&m);
104 BN_init(&xr);
105
106 if (!dsa->p || !dsa->q || !dsa->g) {
107 reason = DSA_R_MISSING_PARAMETERS;
108 goto err;
109 }
110
111 s = BN_new();
112 if (s == NULL)
113 goto err;
114 ctx = BN_CTX_new();
115 if (ctx == NULL)
116 goto err;
117redo:
118 if (dsa->kinv == NULL || dsa->r == NULL) {
119 if (!DSA_sign_setup(dsa, ctx, &kinv, &r))
120 goto err;
121 } else {
122 kinv = dsa->kinv;
123 dsa->kinv = NULL;
124 r = dsa->r;
125 dsa->r = NULL;
126 noredo = 1;
127 }
128
129
130 /*
131 * If the digest length is greater than the size of q use the
132 * BN_num_bits(dsa->q) leftmost bits of the digest, see
133 * fips 186-3, 4.2
134 */
135 if (dlen > BN_num_bytes(dsa->q))
136 dlen = BN_num_bytes(dsa->q);
137 if (BN_bin2bn(dgst,dlen,&m) == NULL)
138 goto err;
139
140 /* Compute s = inv(k) (m + xr) mod q */
141 if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx)) /* s = xr */
142 goto err;
143 if (!BN_add(s, &xr, &m)) /* s = m + xr */
144 goto err;
145 if (BN_cmp(s, dsa->q) > 0)
146 if (!BN_sub(s, s, dsa->q))
147 goto err;
148 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
149 goto err;
150
151 ret = DSA_SIG_new();
152 if (ret == NULL)
153 goto err;
154 /*
155 * Redo if r or s is zero as required by FIPS 186-3: this is
156 * very unlikely.
157 */
158 if (BN_is_zero(r) || BN_is_zero(s)) {
159 if (noredo) {
160 reason = DSA_R_NEED_NEW_SETUP_VALUES;
161 goto err;
162 }
163 goto redo;
164 }
165 ret->r = r;
166 ret->s = s;
167
168err:
169 if (!ret) {
170 DSAerr(DSA_F_DSA_DO_SIGN, reason);
171 BN_free(r);
172 BN_free(s);
173 }
174 BN_CTX_free(ctx);
175 BN_clear_free(&m);
176 BN_clear_free(&xr);
177 BN_clear_free(kinv);
178 return ret;
179}
180
181static int
182dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
183{
184 BN_CTX *ctx;
185 BIGNUM k, *kinv = NULL, *r = NULL;
186 int ret = 0;
187
188 if (!dsa->p || !dsa->q || !dsa->g) {
189 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
190 return 0;
191 }
192
193 BN_init(&k);
194
195 if (ctx_in == NULL) {
196 if ((ctx = BN_CTX_new()) == NULL)
197 goto err;
198 } else
199 ctx = ctx_in;
200
201 if ((r = BN_new()) == NULL)
202 goto err;
203
204 /* Get random k */
205 do {
206 if (!BN_rand_range(&k, dsa->q))
207 goto err;
208 } while (BN_is_zero(&k));
209
210 BN_set_flags(&k, BN_FLG_CONSTTIME);
211
212 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
213 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
214 CRYPTO_LOCK_DSA, dsa->p, ctx))
215 goto err;
216 }
217
218 /* Compute r = (g^k mod p) mod q */
219
220 /*
221 * We do not want timing information to leak the length of k,
222 * so we compute g^k using an equivalent exponent of fixed
223 * length.
224 *
225 * (This is a kludge that we need because the BN_mod_exp_mont()
226 * does not let us specify the desired timing behaviour.)
227 */
228
229 if (!BN_add(&k, &k, dsa->q))
230 goto err;
231 if (BN_num_bits(&k) <= BN_num_bits(dsa->q)) {
232 if (!BN_add(&k, &k, dsa->q))
233 goto err;
234 }
235
236 if (dsa->meth->bn_mod_exp != NULL) {
237 if (!dsa->meth->bn_mod_exp(dsa, r, dsa->g, &k, dsa->p, ctx,
238 dsa->method_mont_p))
239 goto err;
240 } else {
241 if (!BN_mod_exp_mont(r, dsa->g, &k, dsa->p, ctx, dsa->method_mont_p))
242 goto err;
243 }
244
245 if (!BN_mod(r,r,dsa->q,ctx))
246 goto err;
247
248 /* Compute part of 's = inv(k) (m + xr) mod q' */
249 if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL)
250 goto err;
251
252 BN_clear_free(*kinvp);
253 *kinvp = kinv;
254 kinv = NULL;
255 BN_clear_free(*rp);
256 *rp = r;
257 ret = 1;
258err:
259 if (!ret) {
260 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
261 BN_clear_free(r);
262 }
263 if (ctx_in == NULL)
264 BN_CTX_free(ctx);
265 BN_clear_free(&k);
266 return ret;
267}
268
269static int
270dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig, DSA *dsa)
271{
272 BN_CTX *ctx;
273 BIGNUM u1, u2, t1;
274 BN_MONT_CTX *mont = NULL;
275 int ret = -1, i;
276
277 if (!dsa->p || !dsa->q || !dsa->g) {
278 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
279 return -1;
280 }
281
282 i = BN_num_bits(dsa->q);
283 /* fips 186-3 allows only different sizes for q */
284 if (i != 160 && i != 224 && i != 256) {
285 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
286 return -1;
287 }
288
289 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
290 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
291 return -1;
292 }
293 BN_init(&u1);
294 BN_init(&u2);
295 BN_init(&t1);
296
297 if ((ctx = BN_CTX_new()) == NULL)
298 goto err;
299
300 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
301 BN_ucmp(sig->r, dsa->q) >= 0) {
302 ret = 0;
303 goto err;
304 }
305 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
306 BN_ucmp(sig->s, dsa->q) >= 0) {
307 ret = 0;
308 goto err;
309 }
310
311 /* Calculate W = inv(S) mod Q
312 * save W in u2 */
313 if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL)
314 goto err;
315
316 /* save M in u1 */
317 /*
318 * If the digest length is greater than the size of q use the
319 * BN_num_bits(dsa->q) leftmost bits of the digest, see
320 * fips 186-3, 4.2
321 */
322 if (dgst_len > (i >> 3))
323 dgst_len = (i >> 3);
324 if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
325 goto err;
326
327 /* u1 = M * w mod q */
328 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
329 goto err;
330
331 /* u2 = r * w mod q */
332 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
333 goto err;
334
335
336 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
337 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
338 CRYPTO_LOCK_DSA, dsa->p, ctx);
339 if (!mont)
340 goto err;
341 }
342
343 if (dsa->meth->dsa_mod_exp != NULL) {
344 if (!dsa->meth->dsa_mod_exp(dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2,
345 dsa->p, ctx, mont))
346 goto err;
347 } else {
348 if (!BN_mod_exp2_mont(&t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx,
349 mont))
350 goto err;
351 }
352
353 /* BN_copy(&u1,&t1); */
354 /* let u1 = u1 mod q */
355 if (!BN_mod(&u1, &t1, dsa->q, ctx))
356 goto err;
357
358 /* V is now in u1. If the signature is correct, it will be
359 * equal to R. */
360 ret = BN_ucmp(&u1, sig->r) == 0;
361
362err:
363 if (ret < 0)
364 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
365 BN_CTX_free(ctx);
366 BN_free(&u1);
367 BN_free(&u2);
368 BN_free(&t1);
369 return ret;
370}
371
372static int
373dsa_init(DSA *dsa)
374{
375 dsa->flags |= DSA_FLAG_CACHE_MONT_P;
376 return 1;
377}
378
379static int
380dsa_finish(DSA *dsa)
381{
382 BN_MONT_CTX_free(dsa->method_mont_p);
383 return 1;
384}
385
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