dsa_ossl.c revision 296465 
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
69
70static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
71static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
72                          BIGNUM **rp);
73static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
74                         DSA_SIG *sig, DSA *dsa);
75static int dsa_init(DSA *dsa);
76static int dsa_finish(DSA *dsa);
77
78static 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/*-
94 * These macro wrappers replace attempts to use the dsa_mod_exp() and
95 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
96 * having a the macro work as an expression by bundling an "err_instr". So;
97 *
98 *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
99 *                 dsa->method_mont_p)) goto err;
100 *
101 * can be replaced by;
102 *
103 *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
104 *                 dsa->method_mont_p);
105 */
106
107# define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
108        do { \
109        int _tmp_res53; \
110        if ((dsa)->meth->dsa_mod_exp) \
111                _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
112                                (a2), (p2), (m), (ctx), (in_mont)); \
113        else \
114                _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
115                                (m), (ctx), (in_mont)); \
116        if (!_tmp_res53) err_instr; \
117        } while(0)
118# define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
119        do { \
120        int _tmp_res53; \
121        if ((dsa)->meth->bn_mod_exp) \
122                _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
123                                (m), (ctx), (m_ctx)); \
124        else \
125                _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
126        if (!_tmp_res53) err_instr; \
127        } while(0)
128
129const DSA_METHOD *DSA_OpenSSL(void)
130{
131    return &openssl_dsa_meth;
132}
133
134static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
135{
136    BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
137    BIGNUM m;
138    BIGNUM xr;
139    BN_CTX *ctx = NULL;
140    int i, reason = ERR_R_BN_LIB;
141    DSA_SIG *ret = NULL;
142
143    BN_init(&m);
144    BN_init(&xr);
145
146    if (!dsa->p || !dsa->q || !dsa->g) {
147        reason = DSA_R_MISSING_PARAMETERS;
148        goto err;
149    }
150
151    s = BN_new();
152    if (s == NULL)
153        goto err;
154
155    i = BN_num_bytes(dsa->q);   /* should be 20 */
156    if ((dlen > i) || (dlen > 50)) {
157        reason = DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
158        goto err;
159    }
160
161    ctx = BN_CTX_new();
162    if (ctx == NULL)
163        goto err;
164
165    if ((dsa->kinv == NULL) || (dsa->r == NULL)) {
166        if (!DSA_sign_setup(dsa, ctx, &kinv, &r))
167            goto err;
168    } else {
169        kinv = dsa->kinv;
170        dsa->kinv = NULL;
171        r = dsa->r;
172        dsa->r = NULL;
173    }
174
175    if (BN_bin2bn(dgst, dlen, &m) == NULL)
176        goto err;
177
178    /* Compute  s = inv(k) (m + xr) mod q */
179    if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx))
180        goto err;               /* s = xr */
181    if (!BN_add(s, &xr, &m))
182        goto err;               /* s = m + xr */
183    if (BN_cmp(s, dsa->q) > 0)
184        if (!BN_sub(s, s, dsa->q))
185            goto err;
186    if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
187        goto err;
188
189    ret = DSA_SIG_new();
190    if (ret == NULL)
191        goto err;
192    ret->r = r;
193    ret->s = s;
194
195 err:
196    if (!ret) {
197        DSAerr(DSA_F_DSA_DO_SIGN, reason);
198        BN_free(r);
199        BN_free(s);
200    }
201    if (ctx != NULL)
202        BN_CTX_free(ctx);
203    BN_clear_free(&m);
204    BN_clear_free(&xr);
205    if (kinv != NULL)           /* dsa->kinv is NULL now if we used it */
206        BN_clear_free(kinv);
207    return (ret);
208}
209
210static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
211                          BIGNUM **rp)
212{
213    BN_CTX *ctx;
214    BIGNUM k, kq, *K, *kinv = NULL, *r = NULL;
215    int ret = 0;
216
217    if (!dsa->p || !dsa->q || !dsa->g) {
218        DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
219        return 0;
220    }
221
222    BN_init(&k);
223    BN_init(&kq);
224
225    if (ctx_in == NULL) {
226        if ((ctx = BN_CTX_new()) == NULL)
227            goto err;
228    } else
229        ctx = ctx_in;
230
231    if ((r = BN_new()) == NULL)
232        goto err;
233
234    /* Get random k */
235    do
236        if (!BN_rand_range(&k, dsa->q))
237            goto err;
238    while (BN_is_zero(&k)) ;
239    if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
240        BN_set_flags(&k, BN_FLG_CONSTTIME);
241    }
242
243    if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
244        if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
245                                    CRYPTO_LOCK_DSA, dsa->p, ctx))
246            goto err;
247    }
248
249    /* Compute r = (g^k mod p) mod q */
250
251    if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
252        if (!BN_copy(&kq, &k))
253            goto err;
254
255        /*
256         * We do not want timing information to leak the length of k, so we
257         * compute g^k using an equivalent exponent of fixed length. (This
258         * is a kludge that we need because the BN_mod_exp_mont() does not
259         * let us specify the desired timing behaviour.)
260         */
261
262        if (!BN_add(&kq, &kq, dsa->q))
263            goto err;
264        if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) {
265            if (!BN_add(&kq, &kq, dsa->q))
266                goto err;
267        }
268
269        K = &kq;
270    } else {
271        K = &k;
272    }
273    DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
274                   dsa->method_mont_p);
275    if (!BN_mod(r, r, dsa->q, ctx))
276        goto err;
277
278    /* Compute  part of 's = inv(k) (m + xr) mod q' */
279    if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL)
280        goto err;
281
282    if (*kinvp != NULL)
283        BN_clear_free(*kinvp);
284    *kinvp = kinv;
285    kinv = NULL;
286    if (*rp != NULL)
287        BN_clear_free(*rp);
288    *rp = r;
289    ret = 1;
290 err:
291    if (!ret) {
292        DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
293        if (kinv != NULL)
294            BN_clear_free(kinv);
295        if (r != NULL)
296            BN_clear_free(r);
297    }
298    if (ctx_in == NULL)
299        BN_CTX_free(ctx);
300    if (kinv != NULL)
301        BN_clear_free(kinv);
302    BN_clear_free(&k);
303    BN_clear_free(&kq);
304    return (ret);
305}
306
307static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
308                         DSA_SIG *sig, DSA *dsa)
309{
310    BN_CTX *ctx;
311    BIGNUM u1, u2, t1;
312    BN_MONT_CTX *mont = NULL;
313    int ret = -1;
314    if (!dsa->p || !dsa->q || !dsa->g) {
315        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
316        return -1;
317    }
318
319    if (BN_num_bits(dsa->q) != 160) {
320        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
321        return -1;
322    }
323
324    if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
325        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
326        return -1;
327    }
328
329    BN_init(&u1);
330    BN_init(&u2);
331    BN_init(&t1);
332
333    if ((ctx = BN_CTX_new()) == NULL)
334        goto err;
335
336    if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
337        BN_ucmp(sig->r, dsa->q) >= 0) {
338        ret = 0;
339        goto err;
340    }
341    if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
342        BN_ucmp(sig->s, dsa->q) >= 0) {
343        ret = 0;
344        goto err;
345    }
346
347    /*
348     * Calculate W = inv(S) mod Q save W in u2
349     */
350    if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL)
351        goto err;
352
353    /* save M in u1 */
354    if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
355        goto err;
356
357    /* u1 = M * w mod q */
358    if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
359        goto err;
360
361    /* u2 = r * w mod q */
362    if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
363        goto err;
364
365    if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
366        mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
367                                      CRYPTO_LOCK_DSA, dsa->p, ctx);
368        if (!mont)
369            goto err;
370    }
371
372    DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p,
373                ctx, mont);
374    /* BN_copy(&u1,&t1); */
375    /* let u1 = u1 mod q */
376    if (!BN_mod(&u1, &t1, dsa->q, ctx))
377        goto err;
378
379    /*
380     * V is now in u1.  If the signature is correct, it will be equal to R.
381     */
382    ret = (BN_ucmp(&u1, sig->r) == 0);
383
384 err:
385    /*
386     * XXX: surely this is wrong - if ret is 0, it just didn't verify; there
387     * is no error in BN. Test should be ret == -1 (Ben)
388     */
389    if (ret != 1)
390        DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
391    if (ctx != NULL)
392        BN_CTX_free(ctx);
393    BN_free(&u1);
394    BN_free(&u2);
395    BN_free(&t1);
396    return (ret);
397}
398
399static int dsa_init(DSA *dsa)
400{
401    dsa->flags |= DSA_FLAG_CACHE_MONT_P;
402    return (1);
403}
404
405static int dsa_finish(DSA *dsa)
406{
407    if (dsa->method_mont_p)
408        BN_MONT_CTX_free(dsa->method_mont_p);
409    return (1);
410}
411
412#endif
413