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,
71 BIGNUM **kinvp, BIGNUM **rp,
72 const unsigned char *dgst, int dlen);
73 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
74 DSA *dsa);
75 static int dsa_init(DSA *dsa);
76 static int dsa_finish(DSA *dsa);
77
78 static DSA_METHOD openssl_dsa_meth = {
79 "OpenSSL DSA method",
80 dsa_do_sign,
81 dsa_sign_setup,
82 dsa_do_verify,
83 NULL, /* dsa_mod_exp, */
84 NULL, /* dsa_bn_mod_exp, */
85 dsa_init,
86 dsa_finish,
87 0,
88 NULL,
89 NULL,
90 NULL
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 {
148 reason=DSA_R_MISSING_PARAMETERS;
149 goto err;
150 }
151
152 s=BN_new();
153 if (s == NULL) goto err;
154 ctx=BN_CTX_new();
155 if (ctx == NULL) goto err;
156 redo:
157 if ((dsa->kinv == NULL) || (dsa->r == NULL))
158 {
159 if (!dsa->meth->dsa_sign_setup(dsa,ctx,&kinv,&r,dgst,dlen))
160 goto err;
161 }
162 else
163 {
164 kinv=dsa->kinv;
165 dsa->kinv=NULL;
166 r=dsa->r;
167 dsa->r=NULL;
168 noredo = 1;
169 }
170
171
172 if (dlen > BN_num_bytes(dsa->q))
173 /* if the digest length is greater than the size of q use the
174 * BN_num_bits(dsa->q) leftmost bits of the digest, see
175 * fips 186-3, 4.2 */
176 dlen = BN_num_bytes(dsa->q);
177 if (BN_bin2bn(dgst,dlen,&m) == NULL)
178 goto err;
179
180 /* Compute s = inv(k) (m + xr) mod q */
181 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
182 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */
183 if (BN_cmp(s,dsa->q) > 0)
184 if (!BN_sub(s,s,dsa->q)) goto err;
185 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
186
187 ret=DSA_SIG_new();
188 if (ret == NULL) goto err;
189 /* Redo if r or s is zero as required by FIPS 186-3: this is
190 * very unlikely.
191 */
192 if (BN_is_zero(r) || BN_is_zero(s))
193 {
194 if (noredo)
195 {
196 reason = DSA_R_NEED_NEW_SETUP_VALUES;
197 goto err;
198 }
199 goto redo;
200 }
201 ret->r = r;
202 ret->s = s;
203
204 err:
205 if (!ret)
206 {
207 DSAerr(DSA_F_DSA_DO_SIGN,reason);
208 BN_free(r);
209 BN_free(s);
210 }
211 if (ctx != NULL) BN_CTX_free(ctx);
212 BN_clear_free(&m);
213 BN_clear_free(&xr);
214 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
215 BN_clear_free(kinv);
216 return(ret);
217 }
218
dsa_sign_setup(DSA * dsa,BN_CTX * ctx_in,BIGNUM ** kinvp,BIGNUM ** rp,const unsigned char * dgst,int dlen)219 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
220 BIGNUM **kinvp, BIGNUM **rp,
221 const unsigned char *dgst, int dlen)
222 {
223 BN_CTX *ctx;
224 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
225 int ret=0;
226
227 if (!dsa->p || !dsa->q || !dsa->g)
228 {
229 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
230 return 0;
231 }
232
233 BN_init(&k);
234 BN_init(&kq);
235
236 if (ctx_in == NULL)
237 {
238 if ((ctx=BN_CTX_new()) == NULL) goto err;
239 }
240 else
241 ctx=ctx_in;
242
243 if ((r=BN_new()) == NULL) goto err;
244
245 /* Get random k */
246 do
247 {
248 #ifndef OPENSSL_NO_SHA512
249 if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH)
250 {
251 /* If DSA_FLAG_NONCE_FROM_HASH is set then we calculate k from
252 * SHA512(private_key + H(message) + random). This protects the
253 * private key from a weak PRNG. */
254 if (!BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, dgst,
255 dlen, ctx))
256 goto err;
257 }
258 else
259 #endif
260 if (!BN_rand_range(&k, dsa->q)) goto err;
261 } while (BN_is_zero(&k));
262 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
263 {
264 BN_set_flags(&k, BN_FLG_CONSTTIME);
265 }
266
267 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
268 {
269 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
270 CRYPTO_LOCK_DSA,
271 dsa->p, ctx))
272 goto err;
273 }
274
275 /* Compute r = (g^k mod p) mod q */
276
277 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
278 {
279 if (!BN_copy(&kq, &k)) goto err;
280
281 /* We do not want timing information to leak the length of k,
282 * so we compute g^k using an equivalent exponent of fixed length.
283 *
284 * (This is a kludge that we need because the BN_mod_exp_mont()
285 * does not let us specify the desired timing behaviour.) */
286
287 if (!BN_add(&kq, &kq, dsa->q)) goto err;
288 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
289 {
290 if (!BN_add(&kq, &kq, dsa->q)) goto err;
291 }
292
293 K = &kq;
294 }
295 else
296 {
297 K = &k;
298 }
299 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
300 dsa->method_mont_p);
301 if (!BN_mod(r,r,dsa->q,ctx)) goto err;
302
303 /* Compute part of 's = inv(k) (m + xr) mod q' */
304 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
305
306 if (*kinvp != NULL) BN_clear_free(*kinvp);
307 *kinvp=kinv;
308 kinv=NULL;
309 if (*rp != NULL) BN_clear_free(*rp);
310 *rp=r;
311 ret=1;
312 err:
313 if (!ret)
314 {
315 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
316 if (r != NULL)
317 BN_clear_free(r);
318 }
319 if (ctx_in == NULL) BN_CTX_free(ctx);
320 BN_clear_free(&k);
321 BN_clear_free(&kq);
322 return(ret);
323 }
324
dsa_do_verify(const unsigned char * dgst,int dgst_len,DSA_SIG * sig,DSA * dsa)325 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
326 DSA *dsa)
327 {
328 BN_CTX *ctx;
329 BIGNUM u1,u2,t1;
330 BN_MONT_CTX *mont=NULL;
331 int ret = -1, i;
332 if (!dsa->p || !dsa->q || !dsa->g)
333 {
334 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
335 return -1;
336 }
337
338 i = BN_num_bits(dsa->q);
339 /* fips 186-3 allows only different sizes for q */
340 if (i != 160 && i != 224 && i != 256)
341 {
342 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
343 return -1;
344 }
345
346 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
347 {
348 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
349 return -1;
350 }
351 BN_init(&u1);
352 BN_init(&u2);
353 BN_init(&t1);
354
355 if ((ctx=BN_CTX_new()) == NULL) goto err;
356
357 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
358 BN_ucmp(sig->r, dsa->q) >= 0)
359 {
360 ret = 0;
361 goto err;
362 }
363 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
364 BN_ucmp(sig->s, dsa->q) >= 0)
365 {
366 ret = 0;
367 goto err;
368 }
369
370 /* Calculate W = inv(S) mod Q
371 * save W in u2 */
372 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
373
374 /* save M in u1 */
375 if (dgst_len > (i >> 3))
376 /* if the digest length is greater than the size of q use the
377 * BN_num_bits(dsa->q) leftmost bits of the digest, see
378 * fips 186-3, 4.2 */
379 dgst_len = (i >> 3);
380 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
381
382 /* u1 = M * w mod q */
383 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
384
385 /* u2 = r * w mod q */
386 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
387
388
389 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
390 {
391 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
392 CRYPTO_LOCK_DSA, dsa->p, ctx);
393 if (!mont)
394 goto err;
395 }
396
397
398 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
399 /* BN_copy(&u1,&t1); */
400 /* let u1 = u1 mod q */
401 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
402
403 /* V is now in u1. If the signature is correct, it will be
404 * equal to R. */
405 ret=(BN_ucmp(&u1, sig->r) == 0);
406
407 err:
408 /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
409 there is no error in BN. Test should be ret == -1 (Ben) */
410 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
411 if (ctx != NULL) BN_CTX_free(ctx);
412 BN_free(&u1);
413 BN_free(&u2);
414 BN_free(&t1);
415 return(ret);
416 }
417
dsa_init(DSA * dsa)418 static int dsa_init(DSA *dsa)
419 {
420 dsa->flags|=DSA_FLAG_CACHE_MONT_P;
421 return(1);
422 }
423
dsa_finish(DSA * dsa)424 static int dsa_finish(DSA *dsa)
425 {
426 if(dsa->method_mont_p)
427 BN_MONT_CTX_free(dsa->method_mont_p);
428 return(1);
429 }
430
431