1 /* crypto/dsa/dsa_ossl.c */
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 #include "cryptlib.h"
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>
68
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,
71 BIGNUM **rp);
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);
76
77 static DSA_METHOD openssl_dsa_meth = {
78 "OpenSSL DSA method",
79 dsa_do_sign,
80 dsa_sign_setup,
81 dsa_do_verify,
82 NULL, /* dsa_mod_exp, */
83 NULL, /* dsa_bn_mod_exp, */
84 dsa_init,
85 dsa_finish,
86 0,
87 NULL,
88 NULL,
89 NULL
90 };
91
92 /*-
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;
96 *
97 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
98 * dsa->method_mont_p)) goto err;
99 *
100 * can be replaced by;
101 *
102 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
103 * dsa->method_mont_p);
104 */
105
106 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
107 do { \
108 int _tmp_res53; \
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)); \
112 else \
113 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
114 (m), (ctx), (in_mont)); \
115 if (!_tmp_res53) err_instr; \
116 } while(0)
117 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
118 do { \
119 int _tmp_res53; \
120 if ((dsa)->meth->bn_mod_exp) \
121 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
122 (m), (ctx), (m_ctx)); \
123 else \
124 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
125 if (!_tmp_res53) err_instr; \
126 } while(0)
127
DSA_OpenSSL(void)128 const DSA_METHOD *DSA_OpenSSL(void)
129 {
130 return &openssl_dsa_meth;
131 }
132
dsa_do_sign(const unsigned char * dgst,int dlen,DSA * dsa)133 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
134 {
135 BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
136 BIGNUM m;
137 BIGNUM xr;
138 BN_CTX *ctx = NULL;
139 int reason = ERR_R_BN_LIB;
140 DSA_SIG *ret = NULL;
141 int noredo = 0;
142
143 BN_init(&m);
144 BN_init(&xr);
145
146 if (!dsa->p || !dsa->q || !dsa->g) {
147 reason = DSA_R_MISSING_PARAMETERS;
148 goto err;
149 }
150
151 s = BN_new();
152 if (s == NULL)
153 goto err;
154 ctx = BN_CTX_new();
155 if (ctx == NULL)
156 goto err;
157 redo:
158 if ((dsa->kinv == NULL) || (dsa->r == NULL)) {
159 if (!DSA_sign_setup(dsa, ctx, &kinv, &r))
160 goto err;
161 } else {
162 kinv = dsa->kinv;
163 dsa->kinv = NULL;
164 r = dsa->r;
165 dsa->r = NULL;
166 noredo = 1;
167 }
168
169 if (dlen > BN_num_bytes(dsa->q))
170 /*
171 * if the digest length is greater than the size of q use the
172 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
173 * 4.2
174 */
175 dlen = BN_num_bytes(dsa->q);
176 if (BN_bin2bn(dgst, dlen, &m) == NULL)
177 goto err;
178
179 /* Compute s = inv(k) (m + xr) mod q */
180 if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx))
181 goto err; /* s = xr */
182 if (!BN_add(s, &xr, &m))
183 goto err; /* s = m + xr */
184 if (BN_cmp(s, dsa->q) > 0)
185 if (!BN_sub(s, s, dsa->q))
186 goto err;
187 if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
188 goto err;
189
190 ret = DSA_SIG_new();
191 if (ret == NULL)
192 goto err;
193 /*
194 * Redo if r or s is zero as required by FIPS 186-3: this is very
195 * unlikely.
196 */
197 if (BN_is_zero(r) || BN_is_zero(s)) {
198 if (noredo) {
199 reason = DSA_R_NEED_NEW_SETUP_VALUES;
200 goto err;
201 }
202 goto redo;
203 }
204 ret->r = r;
205 ret->s = s;
206
207 err:
208 if (!ret) {
209 DSAerr(DSA_F_DSA_DO_SIGN, reason);
210 BN_free(r);
211 BN_free(s);
212 }
213 if (ctx != NULL)
214 BN_CTX_free(ctx);
215 BN_clear_free(&m);
216 BN_clear_free(&xr);
217 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
218 BN_clear_free(kinv);
219 return (ret);
220 }
221
dsa_sign_setup(DSA * dsa,BN_CTX * ctx_in,BIGNUM ** kinvp,BIGNUM ** rp)222 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
223 BIGNUM **rp)
224 {
225 BN_CTX *ctx;
226 BIGNUM k, kq, *K, *kinv = NULL, *r = NULL;
227 int ret = 0;
228
229 if (!dsa->p || !dsa->q || !dsa->g) {
230 DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
231 return 0;
232 }
233
234 BN_init(&k);
235 BN_init(&kq);
236
237 if (ctx_in == NULL) {
238 if ((ctx = BN_CTX_new()) == NULL)
239 goto err;
240 } else
241 ctx = ctx_in;
242
243 if ((r = BN_new()) == NULL)
244 goto err;
245
246 /* Get random k */
247 do
248 if (!BN_rand_range(&k, dsa->q))
249 goto err;
250 while (BN_is_zero(&k)) ;
251 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
252 BN_set_flags(&k, BN_FLG_CONSTTIME);
253 }
254
255 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
256 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
257 CRYPTO_LOCK_DSA, dsa->p, ctx))
258 goto err;
259 }
260
261 /* Compute r = (g^k mod p) mod q */
262
263 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
264 if (!BN_copy(&kq, &k))
265 goto err;
266
267 /*
268 * We do not want timing information to leak the length of k, so we
269 * compute g^k using an equivalent exponent of fixed length. (This
270 * is a kludge that we need because the BN_mod_exp_mont() does not
271 * let us specify the desired timing behaviour.)
272 */
273
274 if (!BN_add(&kq, &kq, dsa->q))
275 goto err;
276 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) {
277 if (!BN_add(&kq, &kq, dsa->q))
278 goto err;
279 }
280
281 K = &kq;
282 } else {
283 K = &k;
284 }
285 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
286 dsa->method_mont_p);
287 if (!BN_mod(r, r, dsa->q, ctx))
288 goto err;
289
290 /* Compute part of 's = inv(k) (m + xr) mod q' */
291 if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL)
292 goto err;
293
294 if (*kinvp != NULL)
295 BN_clear_free(*kinvp);
296 *kinvp = kinv;
297 kinv = NULL;
298 if (*rp != NULL)
299 BN_clear_free(*rp);
300 *rp = r;
301 ret = 1;
302 err:
303 if (!ret) {
304 DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
305 if (r != NULL)
306 BN_clear_free(r);
307 }
308 if (ctx_in == NULL)
309 BN_CTX_free(ctx);
310 BN_clear_free(&k);
311 BN_clear_free(&kq);
312 return (ret);
313 }
314
dsa_do_verify(const unsigned char * dgst,int dgst_len,DSA_SIG * sig,DSA * dsa)315 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
316 DSA_SIG *sig, DSA *dsa)
317 {
318 BN_CTX *ctx;
319 BIGNUM u1, u2, t1;
320 BN_MONT_CTX *mont = NULL;
321 int ret = -1, i;
322 if (!dsa->p || !dsa->q || !dsa->g) {
323 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
324 return -1;
325 }
326
327 i = BN_num_bits(dsa->q);
328 /* fips 186-3 allows only different sizes for q */
329 if (i != 160 && i != 224 && i != 256) {
330 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
331 return -1;
332 }
333
334 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
335 DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
336 return -1;
337 }
338 BN_init(&u1);
339 BN_init(&u2);
340 BN_init(&t1);
341
342 if ((ctx = BN_CTX_new()) == NULL)
343 goto err;
344
345 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
346 BN_ucmp(sig->r, dsa->q) >= 0) {
347 ret = 0;
348 goto err;
349 }
350 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
351 BN_ucmp(sig->s, dsa->q) >= 0) {
352 ret = 0;
353 goto err;
354 }
355
356 /*
357 * Calculate W = inv(S) mod Q save W in u2
358 */
359 if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL)
360 goto err;
361
362 /* save M in u1 */
363 if (dgst_len > (i >> 3))
364 /*
365 * if the digest length is greater than the size of q use the
366 * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
367 * 4.2
368 */
369 dgst_len = (i >> 3);
370 if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
371 goto err;
372
373 /* u1 = M * w mod q */
374 if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
375 goto err;
376
377 /* u2 = r * w mod q */
378 if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
379 goto err;
380
381 if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
382 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
383 CRYPTO_LOCK_DSA, dsa->p, ctx);
384 if (!mont)
385 goto err;
386 }
387
388 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p,
389 ctx, mont);
390 /* BN_copy(&u1,&t1); */
391 /* let u1 = u1 mod q */
392 if (!BN_mod(&u1, &t1, dsa->q, ctx))
393 goto err;
394
395 /*
396 * V is now in u1. If the signature is correct, it will be equal to R.
397 */
398 ret = (BN_ucmp(&u1, sig->r) == 0);
399
400 err:
401 /*
402 * XXX: surely this is wrong - if ret is 0, it just didn't verify; there
403 * is no error in BN. Test should be ret == -1 (Ben)
404 */
405 if (ret != 1)
406 DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
407 if (ctx != NULL)
408 BN_CTX_free(ctx);
409 BN_free(&u1);
410 BN_free(&u2);
411 BN_free(&t1);
412 return (ret);
413 }
414
dsa_init(DSA * dsa)415 static int dsa_init(DSA *dsa)
416 {
417 dsa->flags |= DSA_FLAG_CACHE_MONT_P;
418 return (1);
419 }
420
dsa_finish(DSA * dsa)421 static int dsa_finish(DSA *dsa)
422 {
423 if (dsa->method_mont_p)
424 BN_MONT_CTX_free(dsa->method_mont_p);
425 return (1);
426 }
427