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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 
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 
DSA_OpenSSL(void)126 const DSA_METHOD *DSA_OpenSSL(void)
127 {
128 	return &openssl_dsa_meth;
129 }
130 
dsa_do_sign(const unsigned char * dgst,int dlen,DSA * dsa)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 
dsa_sign_setup(DSA * dsa,BN_CTX * ctx_in,BIGNUM ** kinvp,BIGNUM ** rp)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 
dsa_do_verify(const unsigned char * dgst,int dgst_len,DSA_SIG * sig,DSA * dsa)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 
dsa_init(DSA * dsa)400 static int dsa_init(DSA *dsa)
401 {
402 	dsa->flags|=DSA_FLAG_CACHE_MONT_P;
403 	return(1);
404 }
405 
dsa_finish(DSA * dsa)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 }
412 
413