gost_sign.c revision 296341 
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#include <openssl/err.h>
16
17#include "gost_params.h"
18#include "gost_lcl.h"
19#include "e_gost_err.h"
20
21#ifdef DEBUG_SIGN
22void dump_signature(const char *message, const unsigned char *buffer,
23                    size_t len)
24{
25    size_t i;
26    fprintf(stderr, "signature %s Length=%d", message, len);
27    for (i = 0; i < len; i++) {
28        if (i % 16 == 0)
29            fputc('\n', stderr);
30        fprintf(stderr, " %02x", buffer[i]);
31    }
32    fprintf(stderr, "\nEnd of signature\n");
33}
34
35void dump_dsa_sig(const char *message, DSA_SIG *sig)
36{
37    fprintf(stderr, "%s\nR=", message);
38    BN_print_fp(stderr, sig->r);
39    fprintf(stderr, "\nS=");
40    BN_print_fp(stderr, sig->s);
41    fprintf(stderr, "\n");
42}
43
44#else
45
46# define dump_signature(a,b,c)
47# define dump_dsa_sig(a,b)
48#endif
49
50/*
51 * Computes signature and returns it as DSA_SIG structure
52 */
53DSA_SIG *gost_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
54{
55    BIGNUM *k = NULL, *tmp = NULL, *tmp2 = NULL;
56    DSA_SIG *newsig = NULL, *ret = NULL;
57    BIGNUM *md = hashsum2bn(dgst);
58    /* check if H(M) mod q is zero */
59    BN_CTX *ctx = BN_CTX_new();
60    if(!ctx) {
61        GOSTerr(GOST_F_GOST_DO_SIGN, ERR_R_MALLOC_FAILURE);
62        goto err;
63    }
64    BN_CTX_start(ctx);
65    newsig = DSA_SIG_new();
66    if (!newsig) {
67        GOSTerr(GOST_F_GOST_DO_SIGN, GOST_R_NO_MEMORY);
68        goto err;
69    }
70    tmp = BN_CTX_get(ctx);
71    k = BN_CTX_get(ctx);
72    tmp2 = BN_CTX_get(ctx);
73    if(!tmp || !k || !tmp2) {
74        GOSTerr(GOST_F_GOST_DO_SIGN, ERR_R_MALLOC_FAILURE);
75        goto err;
76    }
77    BN_mod(tmp, md, dsa->q, ctx);
78    if (BN_is_zero(tmp)) {
79        BN_one(md);
80    }
81    do {
82        do {
83            /*
84             * Generate random number k less than q
85             */
86            BN_rand_range(k, dsa->q);
87            /* generate r = (a^x mod p) mod q */
88            BN_mod_exp(tmp, dsa->g, k, dsa->p, ctx);
89            if (!(newsig->r)) {
90                newsig->r = BN_new();
91                if(!newsig->r) {
92                    GOSTerr(GOST_F_GOST_DO_SIGN, ERR_R_MALLOC_FAILURE);
93                    goto err;
94                }
95            }
96            BN_mod(newsig->r, tmp, dsa->q, ctx);
97        }
98        while (BN_is_zero(newsig->r));
99        /* generate s = (xr + k(Hm)) mod q */
100        BN_mod_mul(tmp, dsa->priv_key, newsig->r, dsa->q, ctx);
101        BN_mod_mul(tmp2, k, md, dsa->q, ctx);
102        if (!newsig->s) {
103            newsig->s = BN_new();
104            if(!newsig->s) {
105                GOSTerr(GOST_F_GOST_DO_SIGN, ERR_R_MALLOC_FAILURE);
106                goto err;
107            }
108        }
109        BN_mod_add(newsig->s, tmp, tmp2, dsa->q, ctx);
110    }
111    while (BN_is_zero(newsig->s));
112
113    ret = newsig;
114 err:
115    BN_free(md);
116    if(ctx) {
117        BN_CTX_end(ctx);
118        BN_CTX_free(ctx);
119    }
120    if(!ret && newsig) {
121        DSA_SIG_free(newsig);
122    }
123    return ret;
124}
125
126/*
127 * Packs signature according to Cryptocom rules
128 * and frees up DSA_SIG structure
129 */
130/*-
131int pack_sign_cc(DSA_SIG *s,int order,unsigned char *sig, size_t *siglen)
132        {
133        *siglen = 2*order;
134        memset(sig,0,*siglen);
135        store_bignum(s->r, sig,order);
136        store_bignum(s->s, sig + order,order);
137        dump_signature("serialized",sig,*siglen);
138        DSA_SIG_free(s);
139        return 1;
140        }
141*/
142/*
143 * Packs signature according to Cryptopro rules
144 * and frees up DSA_SIG structure
145 */
146int pack_sign_cp(DSA_SIG *s, int order, unsigned char *sig, size_t *siglen)
147{
148    *siglen = 2 * order;
149    memset(sig, 0, *siglen);
150    store_bignum(s->s, sig, order);
151    store_bignum(s->r, sig + order, order);
152    dump_signature("serialized", sig, *siglen);
153    DSA_SIG_free(s);
154    return 1;
155}
156
157/*
158 * Verifies signature passed as DSA_SIG structure
159 *
160 */
161
162int gost_do_verify(const unsigned char *dgst, int dgst_len,
163                   DSA_SIG *sig, DSA *dsa)
164{
165    BIGNUM *md = NULL, *tmp = NULL;
166    BIGNUM *q2 = NULL;
167    BIGNUM *u = NULL, *v = NULL, *z1 = NULL, *z2 = NULL;
168    BIGNUM *tmp2 = NULL, *tmp3 = NULL;
169    int ok = 0;
170    BN_CTX *ctx = BN_CTX_new();
171    if(!ctx) {
172        GOSTerr(GOST_F_GOST_DO_VERIFY, ERR_R_MALLOC_FAILURE);
173        goto err;
174    }
175
176    BN_CTX_start(ctx);
177    if (BN_cmp(sig->s, dsa->q) >= 1 || BN_cmp(sig->r, dsa->q) >= 1) {
178        GOSTerr(GOST_F_GOST_DO_VERIFY, GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
179        goto err;
180    }
181    md = hashsum2bn(dgst);
182
183    tmp = BN_CTX_get(ctx);
184    v = BN_CTX_get(ctx);
185    q2 = BN_CTX_get(ctx);
186    z1 = BN_CTX_get(ctx);
187    z2 = BN_CTX_get(ctx);
188    tmp2 = BN_CTX_get(ctx);
189    tmp3 = BN_CTX_get(ctx);
190    u = BN_CTX_get(ctx);
191    if(!tmp || !v || !q2 || !z1 || !z2 || !tmp2 || !tmp3 || !u) {
192        GOSTerr(GOST_F_GOST_DO_VERIFY, ERR_R_MALLOC_FAILURE);
193        goto err;
194    }
195
196    BN_mod(tmp, md, dsa->q, ctx);
197    if (BN_is_zero(tmp)) {
198        BN_one(md);
199    }
200    BN_copy(q2, dsa->q);
201    BN_sub_word(q2, 2);
202    BN_mod_exp(v, md, q2, dsa->q, ctx);
203    BN_mod_mul(z1, sig->s, v, dsa->q, ctx);
204    BN_sub(tmp, dsa->q, sig->r);
205    BN_mod_mul(z2, tmp, v, dsa->p, ctx);
206    BN_mod_exp(tmp, dsa->g, z1, dsa->p, ctx);
207    BN_mod_exp(tmp2, dsa->pub_key, z2, dsa->p, ctx);
208    BN_mod_mul(tmp3, tmp, tmp2, dsa->p, ctx);
209    BN_mod(u, tmp3, dsa->q, ctx);
210    ok = (BN_cmp(u, sig->r) == 0);
211
212    if (!ok) {
213        GOSTerr(GOST_F_GOST_DO_VERIFY, GOST_R_SIGNATURE_MISMATCH);
214    }
215err:
216    if(md) BN_free(md);
217    if(ctx) {
218        BN_CTX_end(ctx);
219        BN_CTX_free(ctx);
220    }
221    return ok;
222}
223
224/*
225 * Computes public keys for GOST R 34.10-94 algorithm
226 *
227 */
228int gost94_compute_public(DSA *dsa)
229{
230    /* Now fill algorithm parameters with correct values */
231    BN_CTX *ctx;
232    if (!dsa->g) {
233        GOSTerr(GOST_F_GOST94_COMPUTE_PUBLIC, GOST_R_KEY_IS_NOT_INITALIZED);
234        return 0;
235    }
236    ctx = BN_CTX_new();
237    if(!ctx) {
238        GOSTerr(GOST_F_GOST94_COMPUTE_PUBLIC, ERR_R_MALLOC_FAILURE);
239        return 0;
240    }
241
242    dsa->pub_key = BN_new();
243    if(!dsa->pub_key) {
244        GOSTerr(GOST_F_GOST94_COMPUTE_PUBLIC, ERR_R_MALLOC_FAILURE);
245        BN_CTX_free(ctx);
246        return 0;
247    }
248    /* Compute public key  y = a^x mod p */
249    BN_mod_exp(dsa->pub_key, dsa->g, dsa->priv_key, dsa->p, ctx);
250    BN_CTX_free(ctx);
251    return 1;
252}
253
254/*
255 * Fill GOST 94 params, searching them in R3410_paramset array
256 * by nid of paramset
257 *
258 */
259int fill_GOST94_params(DSA *dsa, int nid)
260{
261    R3410_params *params = R3410_paramset;
262    while (params->nid != NID_undef && params->nid != nid)
263        params++;
264    if (params->nid == NID_undef) {
265        GOSTerr(GOST_F_FILL_GOST94_PARAMS, GOST_R_UNSUPPORTED_PARAMETER_SET);
266        return 0;
267    }
268#define dump_signature(a,b,c)
269    if (dsa->p) {
270        BN_free(dsa->p);
271    }
272    dsa->p = NULL;
273    BN_dec2bn(&(dsa->p), params->p);
274    if (dsa->q) {
275        BN_free(dsa->q);
276    }
277    dsa->q = NULL;
278    BN_dec2bn(&(dsa->q), params->q);
279    if (dsa->g) {
280        BN_free(dsa->g);
281    }
282    dsa->g = NULL;
283    BN_dec2bn(&(dsa->g), params->a);
284    return 1;
285}
286
287/*
288 *  Generate GOST R 34.10-94 keypair
289 *
290 *
291 */
292int gost_sign_keygen(DSA *dsa)
293{
294    dsa->priv_key = BN_new();
295    if(!dsa->priv_key) {
296        GOSTerr(GOST_F_GOST_SIGN_KEYGEN, ERR_R_MALLOC_FAILURE);
297        return 0;
298    }
299    BN_rand_range(dsa->priv_key, dsa->q);
300    return gost94_compute_public(dsa);
301}
302
303/* Unpack signature according to cryptocom rules  */
304/*-
305DSA_SIG *unpack_cc_signature(const unsigned char *sig,size_t siglen)
306        {
307        DSA_SIG *s;
308        s = DSA_SIG_new();
309        if (s == NULL)
310                {
311                GOSTerr(GOST_F_UNPACK_CC_SIGNATURE,GOST_R_NO_MEMORY);
312                return(NULL);
313                }
314        s->r = getbnfrombuf(sig, siglen/2);
315        s->s = getbnfrombuf(sig + siglen/2, siglen/2);
316        return s;
317        }
318*/
319/* Unpack signature according to cryptopro rules  */
320DSA_SIG *unpack_cp_signature(const unsigned char *sig, size_t siglen)
321{
322    DSA_SIG *s;
323
324    s = DSA_SIG_new();
325    if (s == NULL) {
326        GOSTerr(GOST_F_UNPACK_CP_SIGNATURE, GOST_R_NO_MEMORY);
327        return NULL;
328    }
329    s->s = getbnfrombuf(sig, siglen / 2);
330    s->r = getbnfrombuf(sig + siglen / 2, siglen / 2);
331    return s;
332}
333
334/* Convert little-endian byte array into bignum */
335BIGNUM *hashsum2bn(const unsigned char *dgst)
336{
337    unsigned char buf[32];
338    int i;
339    for (i = 0; i < 32; i++) {
340        buf[31 - i] = dgst[i];
341    }
342    return getbnfrombuf(buf, 32);
343}
344
345/* Convert byte buffer to bignum, skipping leading zeros*/
346BIGNUM *getbnfrombuf(const unsigned char *buf, size_t len)
347{
348    while (*buf == 0 && len > 0) {
349        buf++;
350        len--;
351    }
352    if (len) {
353        return BN_bin2bn(buf, len, NULL);
354    } else {
355        BIGNUM *b = BN_new();
356        BN_zero(b);
357        return b;
358    }
359}
360
361/*
362 * Pack bignum into byte buffer of given size, filling all leading bytes by
363 * zeros
364 */
365int store_bignum(BIGNUM *bn, unsigned char *buf, int len)
366{
367    int bytes = BN_num_bytes(bn);
368    if (bytes > len)
369        return 0;
370    memset(buf, 0, len);
371    BN_bn2bin(bn, buf + len - bytes);
372    return 1;
373}
374