gost_sign.c revision 280304 
1/**********************************************************************
2 *                          gost_sign.c                               *
3 *             Copyright (c) 2005-2006 Cryptocom LTD                  *
4 *         This file is distributed under the same license as OpenSSL *
5 *                                                                    *
6 *       Implementation of GOST R 34.10-94 signature algorithm        *
7 *       for OpenSSL                                                  *
8 *          Requires OpenSSL 0.9.9 for compilation                    *
9 **********************************************************************/
10#include <string.h>
11#include <openssl/rand.h>
12#include <openssl/bn.h>
13#include <openssl/dsa.h>
14#include <openssl/evp.h>
15
16#include "gost_params.h"
17#include "gost_lcl.h"
18#include "e_gost_err.h"
19
20#ifdef DEBUG_SIGN
21void dump_signature(const char *message, const unsigned char *buffer,
22                    size_t len)
23{
24    size_t i;
25    fprintf(stderr, "signature %s Length=%d", message, len);
26    for (i = 0; i < len; i++) {
27        if (i % 16 == 0)
28            fputc('\n', stderr);
29        fprintf(stderr, " %02x", buffer[i]);
30    }
31    fprintf(stderr, "\nEnd of signature\n");
32}
33
34void dump_dsa_sig(const char *message, DSA_SIG *sig)
35{
36    fprintf(stderr, "%s\nR=", message);
37    BN_print_fp(stderr, sig->r);
38    fprintf(stderr, "\nS=");
39    BN_print_fp(stderr, sig->s);
40    fprintf(stderr, "\n");
41}
42
43#else
44
45# define dump_signature(a,b,c)
46# define dump_dsa_sig(a,b)
47#endif
48
49/*
50 * Computes signature and returns it as DSA_SIG structure
51 */
52DSA_SIG *gost_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
53{
54    BIGNUM *k = NULL, *tmp = NULL, *tmp2 = NULL;
55    DSA_SIG *newsig = DSA_SIG_new();
56    BIGNUM *md = hashsum2bn(dgst);
57    /* check if H(M) mod q is zero */
58    BN_CTX *ctx = BN_CTX_new();
59    BN_CTX_start(ctx);
60    if (!newsig) {
61        GOSTerr(GOST_F_GOST_DO_SIGN, GOST_R_NO_MEMORY);
62        goto err;
63    }
64    tmp = BN_CTX_get(ctx);
65    k = BN_CTX_get(ctx);
66    tmp2 = BN_CTX_get(ctx);
67    BN_mod(tmp, md, dsa->q, ctx);
68    if (BN_is_zero(tmp)) {
69        BN_one(md);
70    }
71    do {
72        do {
73            /*
74             * Generate random number k less than q
75             */
76            BN_rand_range(k, dsa->q);
77            /* generate r = (a^x mod p) mod q */
78            BN_mod_exp(tmp, dsa->g, k, dsa->p, ctx);
79            if (!(newsig->r))
80                newsig->r = BN_new();
81            BN_mod(newsig->r, tmp, dsa->q, ctx);
82        }
83        while (BN_is_zero(newsig->r));
84        /* generate s = (xr + k(Hm)) mod q */
85        BN_mod_mul(tmp, dsa->priv_key, newsig->r, dsa->q, ctx);
86        BN_mod_mul(tmp2, k, md, dsa->q, ctx);
87        if (!newsig->s)
88            newsig->s = BN_new();
89        BN_mod_add(newsig->s, tmp, tmp2, dsa->q, ctx);
90    }
91    while (BN_is_zero(newsig->s));
92 err:
93    BN_free(md);
94    BN_CTX_end(ctx);
95    BN_CTX_free(ctx);
96    return newsig;
97}
98
99/*
100 * Packs signature according to Cryptocom rules
101 * and frees up DSA_SIG structure
102 */
103/*-
104int pack_sign_cc(DSA_SIG *s,int order,unsigned char *sig, size_t *siglen)
105        {
106        *siglen = 2*order;
107        memset(sig,0,*siglen);
108        store_bignum(s->r, sig,order);
109        store_bignum(s->s, sig + order,order);
110        dump_signature("serialized",sig,*siglen);
111        DSA_SIG_free(s);
112        return 1;
113        }
114*/
115/*
116 * Packs signature according to Cryptopro rules
117 * and frees up DSA_SIG structure
118 */
119int pack_sign_cp(DSA_SIG *s, int order, unsigned char *sig, size_t *siglen)
120{
121    *siglen = 2 * order;
122    memset(sig, 0, *siglen);
123    store_bignum(s->s, sig, order);
124    store_bignum(s->r, sig + order, order);
125    dump_signature("serialized", sig, *siglen);
126    DSA_SIG_free(s);
127    return 1;
128}
129
130/*
131 * Verifies signature passed as DSA_SIG structure
132 *
133 */
134
135int gost_do_verify(const unsigned char *dgst, int dgst_len,
136                   DSA_SIG *sig, DSA *dsa)
137{
138    BIGNUM *md, *tmp = NULL;
139    BIGNUM *q2 = NULL;
140    BIGNUM *u = NULL, *v = NULL, *z1 = NULL, *z2 = NULL;
141    BIGNUM *tmp2 = NULL, *tmp3 = NULL;
142    int ok;
143    BN_CTX *ctx = BN_CTX_new();
144
145    BN_CTX_start(ctx);
146    if (BN_cmp(sig->s, dsa->q) >= 1 || BN_cmp(sig->r, dsa->q) >= 1) {
147        GOSTerr(GOST_F_GOST_DO_VERIFY, GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
148        return 0;
149    }
150    md = hashsum2bn(dgst);
151
152    tmp = BN_CTX_get(ctx);
153    v = BN_CTX_get(ctx);
154    q2 = BN_CTX_get(ctx);
155    z1 = BN_CTX_get(ctx);
156    z2 = BN_CTX_get(ctx);
157    tmp2 = BN_CTX_get(ctx);
158    tmp3 = BN_CTX_get(ctx);
159    u = BN_CTX_get(ctx);
160
161    BN_mod(tmp, md, dsa->q, ctx);
162    if (BN_is_zero(tmp)) {
163        BN_one(md);
164    }
165    BN_copy(q2, dsa->q);
166    BN_sub_word(q2, 2);
167    BN_mod_exp(v, md, q2, dsa->q, ctx);
168    BN_mod_mul(z1, sig->s, v, dsa->q, ctx);
169    BN_sub(tmp, dsa->q, sig->r);
170    BN_mod_mul(z2, tmp, v, dsa->p, ctx);
171    BN_mod_exp(tmp, dsa->g, z1, dsa->p, ctx);
172    BN_mod_exp(tmp2, dsa->pub_key, z2, dsa->p, ctx);
173    BN_mod_mul(tmp3, tmp, tmp2, dsa->p, ctx);
174    BN_mod(u, tmp3, dsa->q, ctx);
175    ok = BN_cmp(u, sig->r);
176
177    BN_free(md);
178    BN_CTX_end(ctx);
179    BN_CTX_free(ctx);
180    if (ok != 0) {
181        GOSTerr(GOST_F_GOST_DO_VERIFY, GOST_R_SIGNATURE_MISMATCH);
182    }
183    return (ok == 0);
184}
185
186/*
187 * Computes public keys for GOST R 34.10-94 algorithm
188 *
189 */
190int gost94_compute_public(DSA *dsa)
191{
192    /* Now fill algorithm parameters with correct values */
193    BN_CTX *ctx = BN_CTX_new();
194    if (!dsa->g) {
195        GOSTerr(GOST_F_GOST94_COMPUTE_PUBLIC, GOST_R_KEY_IS_NOT_INITALIZED);
196        return 0;
197    }
198    /* Compute public key  y = a^x mod p */
199    dsa->pub_key = BN_new();
200    BN_mod_exp(dsa->pub_key, dsa->g, dsa->priv_key, dsa->p, ctx);
201    BN_CTX_free(ctx);
202    return 1;
203}
204
205/*
206 * Fill GOST 94 params, searching them in R3410_paramset array
207 * by nid of paramset
208 *
209 */
210int fill_GOST94_params(DSA *dsa, int nid)
211{
212    R3410_params *params = R3410_paramset;
213    while (params->nid != NID_undef && params->nid != nid)
214        params++;
215    if (params->nid == NID_undef) {
216        GOSTerr(GOST_F_FILL_GOST94_PARAMS, GOST_R_UNSUPPORTED_PARAMETER_SET);
217        return 0;
218    }
219#define dump_signature(a,b,c)
220    if (dsa->p) {
221        BN_free(dsa->p);
222    }
223    dsa->p = NULL;
224    BN_dec2bn(&(dsa->p), params->p);
225    if (dsa->q) {
226        BN_free(dsa->q);
227    }
228    dsa->q = NULL;
229    BN_dec2bn(&(dsa->q), params->q);
230    if (dsa->g) {
231        BN_free(dsa->g);
232    }
233    dsa->g = NULL;
234    BN_dec2bn(&(dsa->g), params->a);
235    return 1;
236}
237
238/*
239 *  Generate GOST R 34.10-94 keypair
240 *
241 *
242 */
243int gost_sign_keygen(DSA *dsa)
244{
245    dsa->priv_key = BN_new();
246    BN_rand_range(dsa->priv_key, dsa->q);
247    return gost94_compute_public(dsa);
248}
249
250/* Unpack signature according to cryptocom rules  */
251/*-
252DSA_SIG *unpack_cc_signature(const unsigned char *sig,size_t siglen)
253        {
254        DSA_SIG *s;
255        s = DSA_SIG_new();
256        if (s == NULL)
257                {
258                GOSTerr(GOST_F_UNPACK_CC_SIGNATURE,GOST_R_NO_MEMORY);
259                return(NULL);
260                }
261        s->r = getbnfrombuf(sig, siglen/2);
262        s->s = getbnfrombuf(sig + siglen/2, siglen/2);
263        return s;
264        }
265*/
266/* Unpack signature according to cryptopro rules  */
267DSA_SIG *unpack_cp_signature(const unsigned char *sig, size_t siglen)
268{
269    DSA_SIG *s;
270
271    s = DSA_SIG_new();
272    if (s == NULL) {
273        GOSTerr(GOST_F_UNPACK_CP_SIGNATURE, GOST_R_NO_MEMORY);
274        return NULL;
275    }
276    s->s = getbnfrombuf(sig, siglen / 2);
277    s->r = getbnfrombuf(sig + siglen / 2, siglen / 2);
278    return s;
279}
280
281/* Convert little-endian byte array into bignum */
282BIGNUM *hashsum2bn(const unsigned char *dgst)
283{
284    unsigned char buf[32];
285    int i;
286    for (i = 0; i < 32; i++) {
287        buf[31 - i] = dgst[i];
288    }
289    return getbnfrombuf(buf, 32);
290}
291
292/* Convert byte buffer to bignum, skipping leading zeros*/
293BIGNUM *getbnfrombuf(const unsigned char *buf, size_t len)
294{
295    while (*buf == 0 && len > 0) {
296        buf++;
297        len--;
298    }
299    if (len) {
300        return BN_bin2bn(buf, len, NULL);
301    } else {
302        BIGNUM *b = BN_new();
303        BN_zero(b);
304        return b;
305    }
306}
307
308/*
309 * Pack bignum into byte buffer of given size, filling all leading bytes by
310 * zeros
311 */
312int store_bignum(BIGNUM *bn, unsigned char *buf, int len)
313{
314    int bytes = BN_num_bytes(bn);
315    if (bytes > len)
316        return 0;
317    memset(buf, 0, len);
318    BN_bn2bin(bn, buf + len - bytes);
319    return 1;
320}
321