engines/ccgost/gost_sign.c

   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
  21 void dump_signature(const char *message,const unsigned char *buffer,size_t len)
  22         {
  23         size_t i;
  24         fprintf(stderr,"signature %s Length=%d",message,len);
  25         for (i=0; i<len; i++)
  26                 {
  27                 if (i% 16 ==0) fputc('\n',stderr);
  28                 fprintf (stderr," %02x",buffer[i]);
  29                 }
  30         fprintf(stderr,"\nEnd of signature\n");
  31         }
  32
  33 void dump_dsa_sig(const char *message, DSA_SIG *sig)
  34         {
  35         fprintf(stderr,"%s\nR=",message);
  36         BN_print_fp(stderr,sig->r);
  37         fprintf(stderr,"\nS=");
  38         BN_print_fp(stderr,sig->s);
  39         fprintf(stderr,"\n");
  40         }
  41
  42 #else
  43
  44 #define dump_signature(a,b,c)
  45 #define dump_dsa_sig(a,b)
  46 #endif
  47
  48 /*
  49  * Computes signature and returns it as DSA_SIG structure
  50  */
  51 DSA_SIG *gost_do_sign(const unsigned char *dgst,int dlen, DSA *dsa)
  52         {
  53         BIGNUM *k=NULL,*tmp=NULL,*tmp2=NULL;
  54         DSA_SIG *newsig = DSA_SIG_new();
  55         BIGNUM *md = hashsum2bn(dgst);
  56         /* check if H(M) mod q is zero */
  57         BN_CTX *ctx=BN_CTX_new();
  58         BN_CTX_start(ctx);
  59         if (!newsig)
  60                 {
  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                 {
  70                 BN_one(md);
  71                 }
  72         do
  73                 {
  74                 do
  75                         {
  76                         /*Generate random number k less than q*/
  77                         BN_rand_range(k,dsa->q);
  78                         /* generate r = (a^x mod p) mod q */
  79                         BN_mod_exp(tmp,dsa->g, k, dsa->p,ctx);
  80                         if (!(newsig->r)) 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) newsig->s=BN_new();
  88                 BN_mod_add(newsig->s,tmp,tmp2,dsa->q,ctx);
  89                 }
  90         while (BN_is_zero(newsig->s));
  91         err:
  92         BN_free(md);
  93         BN_CTX_end(ctx);
  94         BN_CTX_free(ctx);
  95         return newsig;
  96         }
  97
  98
  99 /*
 100  * Packs signature according to Cryptocom rules
 101  * and frees up DSA_SIG structure
 102  */
 103 /*
 104 int 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  */
 119 int 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
 135 int 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||
 147                 BN_cmp(sig->r,dsa->q)>=1)
 148                 {
 149                 GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
 150                 return 0;
 151                 }
 152         md=hashsum2bn(dgst);
 153
 154         tmp=BN_CTX_get(ctx);
 155         v=BN_CTX_get(ctx);
 156         q2=BN_CTX_get(ctx);
 157         z1=BN_CTX_get(ctx);
 158         z2=BN_CTX_get(ctx);
 159         tmp2=BN_CTX_get(ctx);
 160         tmp3=BN_CTX_get(ctx);
 161         u = BN_CTX_get(ctx);
 162
 163         BN_mod(tmp,md,dsa->q,ctx);
 164         if (BN_is_zero(tmp))
 165                 {
 166                 BN_one(md);
 167                 }
 168         BN_copy(q2,dsa->q);
 169         BN_sub_word(q2,2);
 170         BN_mod_exp(v,md,q2,dsa->q,ctx);
 171         BN_mod_mul(z1,sig->s,v,dsa->q,ctx);
 172         BN_sub(tmp,dsa->q,sig->r);
 173         BN_mod_mul(z2,tmp,v,dsa->p,ctx);
 174         BN_mod_exp(tmp,dsa->g,z1,dsa->p,ctx);
 175         BN_mod_exp(tmp2,dsa->pub_key,z2,dsa->p,ctx);
 176         BN_mod_mul(tmp3,tmp,tmp2,dsa->p,ctx);
 177         BN_mod(u,tmp3,dsa->q,ctx);
 178         ok= BN_cmp(u,sig->r);
 179
 180         BN_free(md);
 181         BN_CTX_end(ctx);
 182         BN_CTX_free(ctx);
 183         if (ok!=0)
 184                 {
 185                 GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_MISMATCH);
 186                 }
 187         return (ok==0);
 188         }
 189
 190 /*
 191  * Computes public keys for GOST R 34.10-94 algorithm
 192  *
 193  */
 194 int gost94_compute_public(DSA *dsa)
 195         {
 196         /* Now fill algorithm parameters with correct values */
 197         BN_CTX *ctx = BN_CTX_new();
 198         if (!dsa->g)
 199                 {
 200                 GOSTerr(GOST_F_GOST94_COMPUTE_PUBLIC,GOST_R_KEY_IS_NOT_INITALIZED);
 201                 return 0;
 202                 }
 203         /* Compute public key  y = a^x mod p */
 204         dsa->pub_key=BN_new();
 205         BN_mod_exp(dsa->pub_key, dsa->g,dsa->priv_key,dsa->p,ctx);
 206         BN_CTX_free(ctx);
 207         return 1;
 208         }
 209
 210 /*
 211  * Fill GOST 94 params, searching them in R3410_paramset array
 212  * by nid of paramset
 213  *
 214  */
 215 int fill_GOST94_params(DSA *dsa,int nid)
 216         {
 217         R3410_params *params=R3410_paramset;
 218         while (params->nid!=NID_undef && params->nid !=nid) params++;
 219         if (params->nid == NID_undef)
 220                 {
 221                 GOSTerr(GOST_F_FILL_GOST94_PARAMS,GOST_R_UNSUPPORTED_PARAMETER_SET);
 222                 return 0;
 223                 }
 224 #define dump_signature(a,b,c)
 225         if (dsa->p) { BN_free(dsa->p); }
 226         dsa->p=NULL;
 227         BN_dec2bn(&(dsa->p),params->p);
 228         if (dsa->q) { BN_free(dsa->q); }
 229         dsa->q=NULL;
 230         BN_dec2bn(&(dsa->q),params->q);
 231         if (dsa->g) { BN_free(dsa->g); }
 232         dsa->g=NULL;
 233         BN_dec2bn(&(dsa->g),params->a);
 234         return 1;
 235         }
 236
 237 /*
 238  *  Generate GOST R 34.10-94 keypair
 239  *
 240  *
 241  */
 242 int gost_sign_keygen(DSA *dsa)
 243         {
 244         dsa->priv_key = BN_new();
 245         BN_rand_range(dsa->priv_key,dsa->q);
 246         return gost94_compute_public( dsa);
 247         }
 248
 249 /* Unpack signature according to cryptocom rules  */
 250 /*
 251 DSA_SIG *unpack_cc_signature(const unsigned char *sig,size_t siglen)
 252         {
 253         DSA_SIG *s;
 254         s = DSA_SIG_new();
 255         if (s == NULL)
 256                 {
 257                 GOSTerr(GOST_F_UNPACK_CC_SIGNATURE,GOST_R_NO_MEMORY);
 258                 return(NULL);
 259                 }
 260         s->r = getbnfrombuf(sig, siglen/2);
 261         s->s = getbnfrombuf(sig + siglen/2, siglen/2);
 262         return s;
 263         }
 264 */
 265 /* Unpack signature according to cryptopro rules  */
 266 DSA_SIG *unpack_cp_signature(const unsigned char *sig,size_t siglen)
 267         {
 268         DSA_SIG *s;
 269
 270         s = DSA_SIG_new();
 271         if (s == NULL)
 272                 {
 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 */
 282 BIGNUM *hashsum2bn(const unsigned char *dgst)
 283         {
 284         unsigned char buf[32];
 285         int i;
 286         for (i=0;i<32;i++)
 287                 {
 288                 buf[31-i]=dgst[i];
 289                 }
 290         return getbnfrombuf(buf,32);
 291         }
 292
 293 /* Convert byte buffer to bignum, skipping leading zeros*/
 294 BIGNUM *getbnfrombuf(const unsigned char *buf,size_t len)
 295         {
 296         while (*buf==0&&len>0)
 297                 {
 298                 buf++; len--;
 299                 }
 300         if (len)
 301                 {
 302                 return BN_bin2bn(buf,len,NULL);
 303                 }
 304         else
 305                 {
 306                 BIGNUM *b=BN_new();
 307                 BN_zero(b);
 308                 return b;
 309                 }
 310         }
 311
 312 /* Pack bignum into byte buffer of given size, filling all leading bytes
 313  * by zeros */
 314 int store_bignum(BIGNUM *bn, unsigned char *buf,int len)
 315         {
 316         int bytes = BN_num_bytes(bn);
 317         if (bytes>len) return 0;
 318         memset(buf,0,len);
 319         BN_bn2bin(bn,buf+len-bytes);
 320         return 1;
 321         }