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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
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, BIGNUM **rp);
71static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
72 DSA *dsa);
73static int dsa_init(DSA *dsa);
74static int dsa_finish(DSA *dsa);
75
76static DSA_METHOD openssl_dsa_meth = {
77"OpenSSL DSA method",
78dsa_do_sign,
79dsa_sign_setup,
80dsa_do_verify,
81NULL, /* dsa_mod_exp, */
82NULL, /* dsa_bn_mod_exp, */
83dsa_init,
84dsa_finish,
850,
86NULL,
87NULL,
88NULL
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
126const DSA_METHOD *DSA_OpenSSL(void)
127{
128 return &openssl_dsa_meth;
129}
130
131static 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
140 BN_init(&m);
141 BN_init(&xr);
142
143 if (!dsa->p || !dsa->q || !dsa->g)
144 {
145 reason=DSA_R_MISSING_PARAMETERS;
146 goto err;
147 }
148
149 s=BN_new();
150 if (s == NULL) goto err;
151 ctx=BN_CTX_new();
152 if (ctx == NULL) goto err;
153
154 if ((dsa->kinv == NULL) || (dsa->r == NULL))
155 {
156 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
157 }
158 else
159 {
160 kinv=dsa->kinv;
161 dsa->kinv=NULL;
162 r=dsa->r;
163 dsa->r=NULL;
164 }
165
166
167 if (dlen > BN_num_bytes(dsa->q))
168 /* if the digest length is greater than the size of q use the
169 * BN_num_bits(dsa->q) leftmost bits of the digest, see
170 * fips 186-3, 4.2 */
171 dlen = BN_num_bytes(dsa->q);
172 if (BN_bin2bn(dgst,dlen,&m) == NULL)
173 goto err;
174
175 /* Compute s = inv(k) (m + xr) mod q */
176 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
177 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */
178 if (BN_cmp(s,dsa->q) > 0)
179 if (!BN_sub(s,s,dsa->q)) goto err;
180 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
181
182 ret=DSA_SIG_new();
183 if (ret == NULL) goto err;
184 ret->r = r;
185 ret->s = s;
186
187err:
188 if (!ret)
189 {
190 DSAerr(DSA_F_DSA_DO_SIGN,reason);
191 BN_free(r);
192 BN_free(s);
193 }
194 if (ctx != NULL) BN_CTX_free(ctx);
195 BN_clear_free(&m);
196 BN_clear_free(&xr);
197 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
198 BN_clear_free(kinv);
199 return(ret);
200 }
201
202static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
203 {
204 BN_CTX *ctx;
205 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
206 int ret=0;
207
208 if (!dsa->p || !dsa->q || !dsa->g)
209 {
210 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
211 return 0;
212 }
213
214 BN_init(&k);
215 BN_init(&kq);
216
217 if (ctx_in == NULL)
218 {
219 if ((ctx=BN_CTX_new()) == NULL) goto err;
220 }
221 else
222 ctx=ctx_in;
223
224 if ((r=BN_new()) == NULL) goto err;
225
226 /* Get random k */
227 do
228 if (!BN_rand_range(&k, dsa->q)) goto err;
229 while (BN_is_zero(&k));
230 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
231 {
232 BN_set_flags(&k, BN_FLG_CONSTTIME);
233 }
234
235 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
236 {
237 if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
238 CRYPTO_LOCK_DSA,
239 dsa->p, ctx))
240 goto err;
241 }
242
243 /* Compute r = (g^k mod p) mod q */
244
245 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
246 {
247 if (!BN_copy(&kq, &k)) goto err;
248
249 /* We do not want timing information to leak the length of k,
250 * so we compute g^k using an equivalent exponent of fixed length.
251 *
252 * (This is a kludge that we need because the BN_mod_exp_mont()
253 * does not let us specify the desired timing behaviour.) */
254
255 if (!BN_add(&kq, &kq, dsa->q)) goto err;
256 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
257 {
258 if (!BN_add(&kq, &kq, dsa->q)) goto err;
259 }
260
261 K = &kq;
262 }
263 else
264 {
265 K = &k;
266 }
267 DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
268 dsa->method_mont_p);
269 if (!BN_mod(r,r,dsa->q,ctx)) goto err;
270
271 /* Compute part of 's = inv(k) (m + xr) mod q' */
272 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
273
274 if (*kinvp != NULL) BN_clear_free(*kinvp);
275 *kinvp=kinv;
276 kinv=NULL;
277 if (*rp != NULL) BN_clear_free(*rp);
278 *rp=r;
279 ret=1;
280err:
281 if (!ret)
282 {
283 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
284 if (r != NULL)
285 BN_clear_free(r);
286 }
287 if (ctx_in == NULL) BN_CTX_free(ctx);
288 BN_clear_free(&k);
289 BN_clear_free(&kq);
290 return(ret);
291 }
292
293static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
294 DSA *dsa)
295 {
296 BN_CTX *ctx;
297 BIGNUM u1,u2,t1;
298 BN_MONT_CTX *mont=NULL;
299 int ret = -1, i;
300 if (!dsa->p || !dsa->q || !dsa->g)
301 {
302 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
303 return -1;
304 }
305
306 i = BN_num_bits(dsa->q);
307 /* fips 186-3 allows only different sizes for q */
308 if (i != 160 && i != 224 && i != 256)
309 {
310 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
311 return -1;
312 }
313
314 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
315 {
316 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
317 return -1;
318 }
319 BN_init(&u1);
320 BN_init(&u2);
321 BN_init(&t1);
322
323 if ((ctx=BN_CTX_new()) == NULL) goto err;
324
325 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
326 BN_ucmp(sig->r, dsa->q) >= 0)
327 {
328 ret = 0;
329 goto err;
330 }
331 if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
332 BN_ucmp(sig->s, dsa->q) >= 0)
333 {
334 ret = 0;
335 goto err;
336 }
337
338 /* Calculate W = inv(S) mod Q
339 * save W in u2 */
340 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
341
342 /* save M in u1 */
343 if (dgst_len > (i >> 3))
344 /* if the digest length is greater than the size of q use the
345 * BN_num_bits(dsa->q) leftmost bits of the digest, see
346 * fips 186-3, 4.2 */
347 dgst_len = (i >> 3);
348 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
349
350 /* u1 = M * w mod q */
351 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
352
353 /* u2 = r * w mod q */
354 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
355
356
357 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
358 {
359 mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
360 CRYPTO_LOCK_DSA, dsa->p, ctx);
361 if (!mont)
362 goto err;
363 }
364
365
366 DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
367 /* BN_copy(&u1,&t1); */
368 /* let u1 = u1 mod q */
369 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
370
371 /* V is now in u1. If the signature is correct, it will be
372 * equal to R. */
373 ret=(BN_ucmp(&u1, sig->r) == 0);
374
375 err:
376 /* XXX: surely this is wrong - if ret is 0, it just didn't verify;
377 there is no error in BN. Test should be ret == -1 (Ben) */
378 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
379 if (ctx != NULL) BN_CTX_free(ctx);
380 BN_free(&u1);
381 BN_free(&u2);
382 BN_free(&t1);
383 return(ret);
384 }
385
386static int dsa_init(DSA *dsa)
387{
388 dsa->flags|=DSA_FLAG_CACHE_MONT_P;
389 return(1);
390}
391
392static int dsa_finish(DSA *dsa)
393{
394 if(dsa->method_mont_p)
395 BN_MONT_CTX_free(dsa->method_mont_p);
396 return(1);
397}
398
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