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/dsa.h>
65#include <openssl/rand.h>
66#include <openssl/asn1.h>
67
68#ifndef OPENSSL_FIPS
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);
75static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
76		BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
77		BN_MONT_CTX *in_mont);
78static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
79				const BIGNUM *m, BN_CTX *ctx,
80				BN_MONT_CTX *m_ctx);
81
82static DSA_METHOD openssl_dsa_meth = {
83"OpenSSL DSA method",
84dsa_do_sign,
85dsa_sign_setup,
86dsa_do_verify,
87dsa_mod_exp,
88dsa_bn_mod_exp,
89dsa_init,
90dsa_finish,
910,
92NULL
93};
94
95const DSA_METHOD *DSA_OpenSSL(void)
96{
97	return &openssl_dsa_meth;
98}
99
100static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
101	{
102	BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
103	BIGNUM m;
104	BIGNUM xr;
105	BN_CTX *ctx=NULL;
106	int i,reason=ERR_R_BN_LIB;
107	DSA_SIG *ret=NULL;
108
109	BN_init(&m);
110	BN_init(&xr);
111
112	if (!dsa->p || !dsa->q || !dsa->g)
113		{
114		reason=DSA_R_MISSING_PARAMETERS;
115		goto err;
116		}
117
118	s=BN_new();
119	if (s == NULL) goto err;
120
121	i=BN_num_bytes(dsa->q); /* should be 20 */
122	if ((dlen > i) || (dlen > 50))
123		{
124		reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
125		goto err;
126		}
127
128	ctx=BN_CTX_new();
129	if (ctx == NULL) goto err;
130
131	if ((dsa->kinv == NULL) || (dsa->r == NULL))
132		{
133		if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
134		}
135	else
136		{
137		kinv=dsa->kinv;
138		dsa->kinv=NULL;
139		r=dsa->r;
140		dsa->r=NULL;
141		}
142
143	if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err;
144
145	/* Compute  s = inv(k) (m + xr) mod q */
146	if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
147	if (!BN_add(s, &xr, &m)) goto err;		/* s = m + xr */
148	if (BN_cmp(s,dsa->q) > 0)
149		BN_sub(s,s,dsa->q);
150	if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
151
152	ret=DSA_SIG_new();
153	if (ret == NULL) goto err;
154	ret->r = r;
155	ret->s = s;
156
157err:
158	if (!ret)
159		{
160		DSAerr(DSA_F_DSA_DO_SIGN,reason);
161		BN_free(r);
162		BN_free(s);
163		}
164	if (ctx != NULL) BN_CTX_free(ctx);
165	BN_clear_free(&m);
166	BN_clear_free(&xr);
167	if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
168	    BN_clear_free(kinv);
169	return(ret);
170	}
171
172static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
173	{
174	BN_CTX *ctx;
175	BIGNUM k,*kinv=NULL,*r=NULL;
176	int ret=0;
177
178	if (!dsa->p || !dsa->q || !dsa->g)
179		{
180		DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
181		return 0;
182		}
183
184	BN_init(&k);
185
186	if (ctx_in == NULL)
187		{
188		if ((ctx=BN_CTX_new()) == NULL) goto err;
189		}
190	else
191		ctx=ctx_in;
192
193	if ((r=BN_new()) == NULL) goto err;
194	kinv=NULL;
195
196	/* Get random k */
197	do
198		if (!BN_rand_range(&k, dsa->q)) goto err;
199	while (BN_is_zero(&k));
200
201	if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
202		{
203		if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
204			if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
205				dsa->p,ctx)) goto err;
206		}
207
208	/* Compute r = (g^k mod p) mod q */
209	if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
210		(BN_MONT_CTX *)dsa->method_mont_p)) goto err;
211	if (!BN_mod(r,r,dsa->q,ctx)) goto err;
212
213	/* Compute  part of 's = inv(k) (m + xr) mod q' */
214	if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
215
216	if (*kinvp != NULL) BN_clear_free(*kinvp);
217	*kinvp=kinv;
218	kinv=NULL;
219	if (*rp != NULL) BN_clear_free(*rp);
220	*rp=r;
221	ret=1;
222err:
223	if (!ret)
224		{
225		DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
226		if (kinv != NULL) BN_clear_free(kinv);
227		if (r != NULL) BN_clear_free(r);
228		}
229	if (ctx_in == NULL) BN_CTX_free(ctx);
230	if (kinv != NULL) BN_clear_free(kinv);
231	BN_clear_free(&k);
232	return(ret);
233	}
234
235static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
236		  DSA *dsa)
237	{
238	BN_CTX *ctx;
239	BIGNUM u1,u2,t1;
240	BN_MONT_CTX *mont=NULL;
241	int ret = -1;
242	if (!dsa->p || !dsa->q || !dsa->g)
243		{
244		DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
245		return -1;
246		}
247
248	BN_init(&u1);
249	BN_init(&u2);
250	BN_init(&t1);
251
252	if ((ctx=BN_CTX_new()) == NULL) goto err;
253
254	if (BN_is_zero(sig->r) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0)
255		{
256		ret = 0;
257		goto err;
258		}
259	if (BN_is_zero(sig->s) || sig->s->neg || BN_ucmp(sig->s, dsa->q) >= 0)
260		{
261		ret = 0;
262		goto err;
263		}
264
265	/* Calculate W = inv(S) mod Q
266	 * save W in u2 */
267	if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
268
269	/* save M in u1 */
270	if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
271
272	/* u1 = M * w mod q */
273	if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
274
275	/* u2 = r * w mod q */
276	if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
277
278	if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
279		{
280		if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
281			if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
282				dsa->p,ctx)) goto err;
283		}
284	mont=(BN_MONT_CTX *)dsa->method_mont_p;
285
286#if 0
287	{
288	BIGNUM t2;
289
290	BN_init(&t2);
291	/* v = ( g^u1 * y^u2 mod p ) mod q */
292	/* let t1 = g ^ u1 mod p */
293	if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err;
294	/* let t2 = y ^ u2 mod p */
295	if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err;
296	/* let u1 = t1 * t2 mod p */
297	if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn;
298	BN_free(&t2);
299	}
300	/* let u1 = u1 mod q */
301	if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err;
302#else
303	{
304	if (!dsa->meth->dsa_mod_exp(dsa, &t1,dsa->g,&u1,dsa->pub_key,&u2,
305						dsa->p,ctx,mont)) goto err;
306	/* BN_copy(&u1,&t1); */
307	/* let u1 = u1 mod q */
308	if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
309	}
310#endif
311	/* V is now in u1.  If the signature is correct, it will be
312	 * equal to R. */
313	ret=(BN_ucmp(&u1, sig->r) == 0);
314
315	err:
316	if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
317	if (ctx != NULL) BN_CTX_free(ctx);
318	BN_free(&u1);
319	BN_free(&u2);
320	BN_free(&t1);
321	return(ret);
322	}
323
324static int dsa_init(DSA *dsa)
325{
326	dsa->flags|=DSA_FLAG_CACHE_MONT_P;
327	return(1);
328}
329
330static int dsa_finish(DSA *dsa)
331{
332	if(dsa->method_mont_p)
333		BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p);
334	return(1);
335}
336
337static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
338		BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
339		BN_MONT_CTX *in_mont)
340{
341	return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont);
342}
343
344static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
345				const BIGNUM *m, BN_CTX *ctx,
346				BN_MONT_CTX *m_ctx)
347{
348	return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
349}
350#endif
351