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, BIGNUM **rp);
71 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
72 DSA *dsa);
73 static int dsa_init(DSA *dsa);
74 static int dsa_finish(DSA *dsa);
75
76 static DSA_METHOD openssl_dsa_meth = {
77 "OpenSSL DSA method",
78 dsa_do_sign,
79 dsa_sign_setup,
80 dsa_do_verify,
81 NULL, /* dsa_mod_exp, */
82 NULL, /* dsa_bn_mod_exp, */
83 dsa_init,
84 dsa_finish,
85 0,
86 NULL,
87 NULL,
88 NULL
89 };
90
91 /* These macro wrappers replace attempts to use the dsa_mod_exp() and
92 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
93 * having a the macro work as an expression by bundling an "err_instr". So;
94 *
95 * if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
96 * dsa->method_mont_p)) goto err;
97 *
98 * can be replaced by;
99 *
100 * DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
101 * dsa->method_mont_p);
102 */
103
104 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
105 do { \
106 int _tmp_res53; \
107 if((dsa)->meth->dsa_mod_exp) \
108 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
109 (a2), (p2), (m), (ctx), (in_mont)); \
110 else \
111 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
112 (m), (ctx), (in_mont)); \
113 if(!_tmp_res53) err_instr; \
114 } while(0)
115 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
116 do { \
117 int _tmp_res53; \
118 if((dsa)->meth->bn_mod_exp) \
119 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
120 (m), (ctx), (m_ctx)); \
121 else \
122 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
123 if(!_tmp_res53) err_instr; \
124 } while(0)
125
126 const DSA_METHOD *DSA_OpenSSL(void)
127 {
128 return &openssl_dsa_meth;
129 }
130
131 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
132 {
133 BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
134 BIGNUM m;
135 BIGNUM xr;
136 BN_CTX *ctx=NULL;
137 int reason=ERR_R_BN_LIB;
138 DSA_SIG *ret=NULL;
139 int noredo = 0;
140
141 BN_init(&m);
142 BN_init(&xr);
143
144 if (!dsa->p || !dsa->q || !dsa->g)
145 {
146 reason=DSA_R_MISSING_PARAMETERS;
147 goto err;
148 }
149
150 s=BN_new();
151 if (s == NULL) goto err;
152 ctx=BN_CTX_new();
153 if (ctx == NULL) goto err;
154 redo:
155 if ((dsa->kinv == NULL) || (dsa->r == NULL))
156 {
157 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
158 }
159 else
160 {
161 kinv=dsa->kinv;
162 dsa->kinv=NULL;
163 r=dsa->r;
164 dsa->r=NULL;
165 noredo = 1;
166 }
167
168
169 if (dlen > BN_num_bytes(dsa->q))
170 /* if the digest length is greater than the size of q use the
171 * BN_num_bits(dsa->q) leftmost bits of the digest, see
172 * fips 186-3, 4.2 */
173 dlen = BN_num_bytes(dsa->q);
174 if (BN_bin2bn(dgst,dlen,&m) == NULL)
175 goto err;
176
177 /* Compute s = inv(k) (m + xr) mod q */
178 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
179 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */
180 if (BN_cmp(s,dsa->q) > 0)
181 if (!BN_sub(s,s,dsa->q)) goto err;
182 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
183
184 ret=DSA_SIG_new();
185 if (ret == NULL) goto err;
186 /* Redo if r or s is zero as required by FIPS 186-3: this is
187 * very unlikely.
188 */
189 if (BN_is_zero(r) || BN_is_zero(s))
190 {
191 if (noredo)
192 {
193 reason = DSA_R_NEED_NEW_SETUP_VALUES;
194 goto err;
195 }
196 goto redo;
197 }
198 ret->r = r;
199 ret->s = s;
200
201 err:
202 if (!ret)
203 {
204 DSAerr(DSA_F_DSA_DO_SIGN,reason);
205 BN_free(r);
206 BN_free(s);
207 }
208 if (ctx != NULL) BN_CTX_free(ctx);
209 BN_clear_free(&m);
210 BN_clear_free(&xr);
211 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
212 BN_clear_free(kinv);
213 return(ret);
214 }
215
216 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
217 {
218 BN_CTX *ctx;
219 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
220 int ret=0;
221
222 if (!dsa->p || !dsa->q || !dsa->g)
223 {
224 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
225 return 0;
226 }
227
228 BN_init(&k);
229 BN_init(&kq);
230
231 if (ctx_in == NULL)
232 {
233 if ((ctx=BN_CTX_new()) == NULL) goto err;
234 }
235 else
236 ctx=ctx_in;
237
238 if ((r=BN_new()) == NULL) goto err;
239
240 /* Get random k */
241 do
242 if (!BN_rand_range(&k, dsa->q)) goto err;
243 while (BN_is_zero(&k));
244 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
245 {
246 BN_set_flags(&k, BN_FLG_CONSTTIME);
247 }
248
249 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
250 {
251 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
252 CRYPTO_LOCK_DSA,
253 dsa->p, ctx))
254 goto err;
255 }
256
257 /* Compute r = (g^k mod p) mod q */
258
259 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
260 {
261 if (!BN_copy(&kq, &k)) goto err;
262
263 /* We do not want timing information to leak the length of k,
264 * so we compute g^k using an equivalent exponent of fixed length.
265 *
266 * (This is a kludge that we need because the BN_mod_exp_mont()
267 * does not let us specify the desired timing behaviour.) */
268
269 if (!BN_add(&kq, &kq, dsa->q)) goto err;
270 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
271 {
272 if (!BN_add(&kq, &kq, dsa->q)) goto err;
273 }
274
275 K = &kq;
276 }
277 else
278 {
279 K = &k;
280 }
281 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
282 dsa->method_mont_p);
283 if (!BN_mod(r,r,dsa->q,ctx)) goto err;
284
285 /* Compute part of 's = inv(k) (m + xr) mod q' */
286 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
287
288 if (*kinvp != NULL) BN_clear_free(*kinvp);
289 *kinvp=kinv;
290 kinv=NULL;
291 if (*rp != NULL) BN_clear_free(*rp);
292 *rp=r;
293 ret=1;
294 err:
295 if (!ret)
296 {
297 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
298 if (r != NULL)
299 BN_clear_free(r);
300 }
301 if (ctx_in == NULL) BN_CTX_free(ctx);
302 BN_clear_free(&k);
303 BN_clear_free(&kq);
304 return(ret);
305 }
306
307 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
308 DSA *dsa)
309 {
310 BN_CTX *ctx;
311 BIGNUM u1,u2,t1;
312 BN_MONT_CTX *mont=NULL;
313 int ret = -1, i;
314 if (!dsa->p || !dsa->q || !dsa->g)
315 {
316 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
317 return -1;
318 }
319
320 i = BN_num_bits(dsa->q);
321 /* fips 186-3 allows only different sizes for q */
322 if (i != 160 && i != 224 && i != 256)
323 {
324 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
325 return -1;
326 }
327
328 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
329 {
330 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
331 return -1;
332 }
333 BN_init(&u1);
334 BN_init(&u2);
335 BN_init(&t1);
336
337 if ((ctx=BN_CTX_new()) == NULL) goto err;
338
339 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
340 BN_ucmp(sig->r, dsa->q) >= 0)
341 {
342 ret = 0;
343 goto err;
344 }
345 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
346 BN_ucmp(sig->s, dsa->q) >= 0)
347 {
348 ret = 0;
349 goto err;
350 }
351
352 /* Calculate W = inv(S) mod Q
353 * save W in u2 */
354 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
355
356 /* save M in u1 */
357 if (dgst_len > (i >> 3))
358 /* if the digest length is greater than the size of q use the
359 * BN_num_bits(dsa->q) leftmost bits of the digest, see
360 * fips 186-3, 4.2 */
361 dgst_len = (i >> 3);
362 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
363
364 /* u1 = M * w mod q */
365 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
366
367 /* u2 = r * w mod q */
368 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
369
370
371 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
372 {
373 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
374 CRYPTO_LOCK_DSA, dsa->p, ctx);
375 if (!mont)
376 goto err;
377 }
378
379
380 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
381 /* BN_copy(&u1,&t1); */
382 /* let u1 = u1 mod q */
383 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
384
385 /* V is now in u1. If the signature is correct, it will be
386 * equal to R. */
387 ret=(BN_ucmp(&u1, sig->r) == 0);
388
389 err:
390 /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
391 there is no error in BN. Test should be ret == -1 (Ben) */
392 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
393 if (ctx != NULL) BN_CTX_free(ctx);
394 BN_free(&u1);
395 BN_free(&u2);
396 BN_free(&t1);
397 return(ret);
398 }
399
400 static int dsa_init(DSA *dsa)
401 {
402 dsa->flags|=DSA_FLAG_CACHE_MONT_P;
403 return(1);
404 }
405
406 static int dsa_finish(DSA *dsa)
407 {
408 if(dsa->method_mont_p)
409 BN_MONT_CTX_free(dsa->method_mont_p);
410 return(1);
411 }