dsa_ossl.c revision 280304 
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,
71                          BIGNUM **rp);
72static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
73                         DSA_SIG *sig, DSA *dsa);
74static int dsa_init(DSA *dsa);
75static int dsa_finish(DSA *dsa);
76
77static DSA_METHOD openssl_dsa_meth = {
78    "OpenSSL DSA method",
79    dsa_do_sign,
80    dsa_sign_setup,
81    dsa_do_verify,
82    NULL,                       /* dsa_mod_exp, */
83    NULL,                       /* dsa_bn_mod_exp, */
84    dsa_init,
85    dsa_finish,
86    0,
87    NULL,
88    NULL,
89    NULL
90};
91
92/*-
93 * These macro wrappers replace attempts to use the dsa_mod_exp() and
94 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
95 * having a the macro work as an expression by bundling an "err_instr". So;
96 *
97 *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
98 *                 dsa->method_mont_p)) goto err;
99 *
100 * can be replaced by;
101 *
102 *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
103 *                 dsa->method_mont_p);
104 */
105
106#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
107        do { \
108        int _tmp_res53; \
109        if((dsa)->meth->dsa_mod_exp) \
110                _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
111                                (a2), (p2), (m), (ctx), (in_mont)); \
112        else \
113                _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
114                                (m), (ctx), (in_mont)); \
115        if(!_tmp_res53) err_instr; \
116        } while(0)
117#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
118        do { \
119        int _tmp_res53; \
120        if((dsa)->meth->bn_mod_exp) \
121                _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
122                                (m), (ctx), (m_ctx)); \
123        else \
124                _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
125        if(!_tmp_res53) err_instr; \
126        } while(0)
127
128const DSA_METHOD *DSA_OpenSSL(void)
129{
130    return &openssl_dsa_meth;
131}
132
133static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
134{
135    BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
136    BIGNUM m;
137    BIGNUM xr;
138    BN_CTX *ctx = NULL;
139    int reason = ERR_R_BN_LIB;
140    DSA_SIG *ret = NULL;
141    int noredo = 0;
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    ctx = BN_CTX_new();
155    if (ctx == NULL)
156        goto err;
157 redo:
158    if ((dsa->kinv == NULL) || (dsa->r == NULL)) {
159        if (!DSA_sign_setup(dsa, ctx, &kinv, &r))
160            goto err;
161    } else {
162        kinv = dsa->kinv;
163        dsa->kinv = NULL;
164        r = dsa->r;
165        dsa->r = NULL;
166        noredo = 1;
167    }
168
169    if (dlen > BN_num_bytes(dsa->q))
170        /*
171         * if the digest length is greater than the size of q use the
172         * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
173         * 4.2
174         */
175        dlen = BN_num_bytes(dsa->q);
176    if (BN_bin2bn(dgst, dlen, &m) == NULL)
177        goto err;
178
179    /* Compute  s = inv(k) (m + xr) mod q */
180    if (!BN_mod_mul(&xr, dsa->priv_key, r, dsa->q, ctx))
181        goto err;               /* s = xr */
182    if (!BN_add(s, &xr, &m))
183        goto err;               /* s = m + xr */
184    if (BN_cmp(s, dsa->q) > 0)
185        if (!BN_sub(s, s, dsa->q))
186            goto err;
187    if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
188        goto err;
189
190    ret = DSA_SIG_new();
191    if (ret == NULL)
192        goto err;
193    /*
194     * Redo if r or s is zero as required by FIPS 186-3: this is very
195     * unlikely.
196     */
197    if (BN_is_zero(r) || BN_is_zero(s)) {
198        if (noredo) {
199            reason = DSA_R_NEED_NEW_SETUP_VALUES;
200            goto err;
201        }
202        goto redo;
203    }
204    ret->r = r;
205    ret->s = s;
206
207 err:
208    if (!ret) {
209        DSAerr(DSA_F_DSA_DO_SIGN, reason);
210        BN_free(r);
211        BN_free(s);
212    }
213    if (ctx != NULL)
214        BN_CTX_free(ctx);
215    BN_clear_free(&m);
216    BN_clear_free(&xr);
217    if (kinv != NULL)           /* dsa->kinv is NULL now if we used it */
218        BN_clear_free(kinv);
219    return (ret);
220}
221
222static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
223                          BIGNUM **rp)
224{
225    BN_CTX *ctx;
226    BIGNUM k, kq, *K, *kinv = NULL, *r = NULL;
227    int ret = 0;
228
229    if (!dsa->p || !dsa->q || !dsa->g) {
230        DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
231        return 0;
232    }
233
234    BN_init(&k);
235    BN_init(&kq);
236
237    if (ctx_in == NULL) {
238        if ((ctx = BN_CTX_new()) == NULL)
239            goto err;
240    } else
241        ctx = ctx_in;
242
243    if ((r = BN_new()) == NULL)
244        goto err;
245
246    /* Get random k */
247    do
248        if (!BN_rand_range(&k, dsa->q))
249            goto err;
250    while (BN_is_zero(&k)) ;
251    if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
252        BN_set_flags(&k, BN_FLG_CONSTTIME);
253    }
254
255    if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
256        if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
257                                    CRYPTO_LOCK_DSA, dsa->p, ctx))
258            goto err;
259    }
260
261    /* Compute r = (g^k mod p) mod q */
262
263    if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
264        if (!BN_copy(&kq, &k))
265            goto err;
266
267        /*
268         * We do not want timing information to leak the length of k, so we
269         * compute g^k using an equivalent exponent of fixed length. (This
270         * is a kludge that we need because the BN_mod_exp_mont() does not
271         * let us specify the desired timing behaviour.)
272         */
273
274        if (!BN_add(&kq, &kq, dsa->q))
275            goto err;
276        if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) {
277            if (!BN_add(&kq, &kq, dsa->q))
278                goto err;
279        }
280
281        K = &kq;
282    } else {
283        K = &k;
284    }
285    DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
286                   dsa->method_mont_p);
287    if (!BN_mod(r, r, dsa->q, ctx))
288        goto err;
289
290    /* Compute  part of 's = inv(k) (m + xr) mod q' */
291    if ((kinv = BN_mod_inverse(NULL, &k, dsa->q, ctx)) == NULL)
292        goto err;
293
294    if (*kinvp != NULL)
295        BN_clear_free(*kinvp);
296    *kinvp = kinv;
297    kinv = NULL;
298    if (*rp != NULL)
299        BN_clear_free(*rp);
300    *rp = r;
301    ret = 1;
302 err:
303    if (!ret) {
304        DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
305        if (r != NULL)
306            BN_clear_free(r);
307    }
308    if (ctx_in == NULL)
309        BN_CTX_free(ctx);
310    BN_clear_free(&k);
311    BN_clear_free(&kq);
312    return (ret);
313}
314
315static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
316                         DSA_SIG *sig, DSA *dsa)
317{
318    BN_CTX *ctx;
319    BIGNUM u1, u2, t1;
320    BN_MONT_CTX *mont = NULL;
321    int ret = -1, i;
322    if (!dsa->p || !dsa->q || !dsa->g) {
323        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
324        return -1;
325    }
326
327    i = BN_num_bits(dsa->q);
328    /* fips 186-3 allows only different sizes for q */
329    if (i != 160 && i != 224 && i != 256) {
330        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
331        return -1;
332    }
333
334    if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
335        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
336        return -1;
337    }
338    BN_init(&u1);
339    BN_init(&u2);
340    BN_init(&t1);
341
342    if ((ctx = BN_CTX_new()) == NULL)
343        goto err;
344
345    if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
346        BN_ucmp(sig->r, dsa->q) >= 0) {
347        ret = 0;
348        goto err;
349    }
350    if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
351        BN_ucmp(sig->s, dsa->q) >= 0) {
352        ret = 0;
353        goto err;
354    }
355
356    /*
357     * Calculate W = inv(S) mod Q save W in u2
358     */
359    if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL)
360        goto err;
361
362    /* save M in u1 */
363    if (dgst_len > (i >> 3))
364        /*
365         * if the digest length is greater than the size of q use the
366         * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
367         * 4.2
368         */
369        dgst_len = (i >> 3);
370    if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
371        goto err;
372
373    /* u1 = M * w mod q */
374    if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
375        goto err;
376
377    /* u2 = r * w mod q */
378    if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
379        goto err;
380
381    if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
382        mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
383                                      CRYPTO_LOCK_DSA, dsa->p, ctx);
384        if (!mont)
385            goto err;
386    }
387
388    DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p,
389                ctx, mont);
390    /* BN_copy(&u1,&t1); */
391    /* let u1 = u1 mod q */
392    if (!BN_mod(&u1, &t1, dsa->q, ctx))
393        goto err;
394
395    /*
396     * V is now in u1.  If the signature is correct, it will be equal to R.
397     */
398    ret = (BN_ucmp(&u1, sig->r) == 0);
399
400 err:
401    /*
402     * XXX: surely this is wrong - if ret is 0, it just didn't verify; there
403     * is no error in BN. Test should be ret == -1 (Ben)
404     */
405    if (ret != 1)
406        DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
407    if (ctx != NULL)
408        BN_CTX_free(ctx);
409    BN_free(&u1);
410    BN_free(&u2);
411    BN_free(&t1);
412    return (ret);
413}
414
415static int dsa_init(DSA *dsa)
416{
417    dsa->flags |= DSA_FLAG_CACHE_MONT_P;
418    return (1);
419}
420
421static int dsa_finish(DSA *dsa)
422{
423    if (dsa->method_mont_p)
424        BN_MONT_CTX_free(dsa->method_mont_p);
425    return (1);
426}
427