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/err.h>
  15 #include <openssl/evp.h>
  16
  17 #include "gost_params.h"
  18 #include "gost_lcl.h"
  19 #include "e_gost_err.h"
  20
  21 #ifdef DEBUG_SIGN
  22 void dump_signature(const char *message,const unsigned char *buffer,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                 {
  28                 if (i% 16 ==0) fputc('\n',stderr);
  29                 fprintf (stderr," %02x",buffer[i]);
  30                 }
  31         fprintf(stderr,"\nEnd of signature\n");
  32         }
  33
  34 void 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  */
  52 DSA_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                 {
  62                 GOSTerr(GOST_F_GOST_DO_SIGN,ERR_R_MALLOC_FAILURE);
  63                 goto err;
  64                 }
  65         tmp=BN_CTX_get(ctx);
  66         k = BN_CTX_get(ctx);
  67         tmp2 = BN_CTX_get(ctx);
  68         BN_mod(tmp,md,dsa->q,ctx);
  69         if (BN_is_zero(tmp))
  70                 {
  71                 BN_one(md);
  72                 }
  73         do
  74                 {
  75                 do
  76                         {
  77                         /*Generate random number k less than q*/
  78                         BN_rand_range(k,dsa->q);
  79                         /* generate r = (a^x mod p) mod q */
  80                         BN_mod_exp(tmp,dsa->g, k, dsa->p,ctx);
  81                         if (!(newsig->r)) newsig->r=BN_new();
  82                         BN_mod(newsig->r,tmp,dsa->q,ctx);
  83                         }
  84                 while (BN_is_zero(newsig->r));
  85                 /* generate s = (xr + k(Hm)) mod q */
  86                 BN_mod_mul(tmp,dsa->priv_key,newsig->r,dsa->q,ctx);
  87                 BN_mod_mul(tmp2,k,md,dsa->q,ctx);
  88                 if (!newsig->s) 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 /*
 101  * Packs signature according to Cryptocom rules
 102  * and frees up DSA_SIG structure
 103  */
 104 /*
 105 int pack_sign_cc(DSA_SIG *s,int order,unsigned char *sig, size_t *siglen)
 106         {
 107         *siglen = 2*order;
 108         memset(sig,0,*siglen);
 109         store_bignum(s->r, sig,order);
 110         store_bignum(s->s, sig + order,order);
 111         dump_signature("serialized",sig,*siglen);
 112         DSA_SIG_free(s);
 113         return 1;
 114         }
 115 */
 116 /*
 117  * Packs signature according to Cryptopro rules
 118  * and frees up DSA_SIG structure
 119  */
 120 int pack_sign_cp(DSA_SIG *s,int order,unsigned char *sig, size_t *siglen)
 121         {
 122         *siglen = 2*order;
 123         memset(sig,0,*siglen);
 124         store_bignum(s->s, sig, order);
 125         store_bignum(s->r, sig+order,order);
 126         dump_signature("serialized",sig,*siglen);
 127         DSA_SIG_free(s);
 128         return 1;
 129         }
 130
 131 /*
 132  * Verifies signature passed as DSA_SIG structure
 133  *
 134  */
 135
 136 int gost_do_verify(const unsigned char *dgst, int dgst_len,
 137         DSA_SIG *sig, DSA *dsa)
 138         {
 139         BIGNUM *md, *tmp=NULL;
 140         BIGNUM *q2=NULL;
 141         BIGNUM *u=NULL,*v=NULL,*z1=NULL,*z2=NULL;
 142         BIGNUM *tmp2=NULL,*tmp3=NULL;
 143         int ok;
 144         BN_CTX *ctx = BN_CTX_new();
 145
 146         BN_CTX_start(ctx);
 147         if (BN_cmp(sig->s,dsa->q)>=1||
 148                 BN_cmp(sig->r,dsa->q)>=1)
 149                 {
 150                 GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
 151                 return 0;
 152                 }
 153         md=hashsum2bn(dgst);
 154
 155         tmp=BN_CTX_get(ctx);
 156         v=BN_CTX_get(ctx);
 157         q2=BN_CTX_get(ctx);
 158         z1=BN_CTX_get(ctx);
 159         z2=BN_CTX_get(ctx);
 160         tmp2=BN_CTX_get(ctx);
 161         tmp3=BN_CTX_get(ctx);
 162         u = BN_CTX_get(ctx);
 163
 164         BN_mod(tmp,md,dsa->q,ctx);
 165         if (BN_is_zero(tmp))
 166                 {
 167                 BN_one(md);
 168                 }
 169         BN_copy(q2,dsa->q);
 170         BN_sub_word(q2,2);
 171         BN_mod_exp(v,md,q2,dsa->q,ctx);
 172         BN_mod_mul(z1,sig->s,v,dsa->q,ctx);
 173         BN_sub(tmp,dsa->q,sig->r);
 174         BN_mod_mul(z2,tmp,v,dsa->p,ctx);
 175         BN_mod_exp(tmp,dsa->g,z1,dsa->p,ctx);
 176         BN_mod_exp(tmp2,dsa->pub_key,z2,dsa->p,ctx);
 177         BN_mod_mul(tmp3,tmp,tmp2,dsa->p,ctx);
 178         BN_mod(u,tmp3,dsa->q,ctx);
 179         ok= BN_cmp(u,sig->r);
 180
 181         BN_free(md);
 182         BN_CTX_end(ctx);
 183         BN_CTX_free(ctx);
 184         if (ok!=0)
 185                 {
 186                 GOSTerr(GOST_F_GOST_DO_VERIFY,GOST_R_SIGNATURE_MISMATCH);
 187                 }
 188         return (ok==0);
 189         }
 190
 191 /*
 192  * Computes public keys for GOST R 34.10-94 algorithm
 193  *
 194  */
 195 int gost94_compute_public(DSA *dsa)
 196         {
 197         /* Now fill algorithm parameters with correct values */
 198         BN_CTX *ctx = BN_CTX_new();
 199         if (!dsa->g)
 200                 {
 201                 GOSTerr(GOST_F_GOST94_COMPUTE_PUBLIC,GOST_R_KEY_IS_NOT_INITALIZED);
 202                 return 0;
 203                 }
 204         /* Compute public key  y = a^x mod p */
 205         dsa->pub_key=BN_new();
 206         BN_mod_exp(dsa->pub_key, dsa->g,dsa->priv_key,dsa->p,ctx);
 207         BN_CTX_free(ctx);
 208         return 1;
 209         }
 210
 211 /*
 212  * Fill GOST 94 params, searching them in R3410_paramset array
 213  * by nid of paramset
 214  *
 215  */
 216 int fill_GOST94_params(DSA *dsa,int nid)
 217         {
 218         R3410_params *params=R3410_paramset;
 219         while (params->nid!=NID_undef && params->nid !=nid) params++;
 220         if (params->nid == NID_undef)
 221                 {
 222                 GOSTerr(GOST_F_FILL_GOST94_PARAMS,GOST_R_UNSUPPORTED_PARAMETER_SET);
 223                 return 0;
 224                 }
 225 #define dump_signature(a,b,c)
 226         if (dsa->p) { BN_free(dsa->p); }
 227         dsa->p=NULL;
 228         BN_dec2bn(&(dsa->p),params->p);
 229         if (dsa->q) { BN_free(dsa->q); }
 230         dsa->q=NULL;
 231         BN_dec2bn(&(dsa->q),params->q);
 232         if (dsa->g) { BN_free(dsa->g); }
 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  */
 243 int 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 /*
 252 DSA_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,ERR_R_MALLOC_FAILURE);
 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  */
 267 DSA_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                 {
 274                 GOSTerr(GOST_F_UNPACK_CP_SIGNATURE,ERR_R_MALLOC_FAILURE);
 275                 return NULL;
 276                 }
 277         s->s = getbnfrombuf(sig , siglen/2);
 278         s->r = getbnfrombuf(sig + siglen/2, siglen/2);
 279         return s;
 280         }
 281
 282 /* Convert little-endian byte array into bignum */
 283 BIGNUM *hashsum2bn(const unsigned char *dgst)
 284         {
 285         unsigned char buf[32];
 286         int i;
 287         for (i=0;i<32;i++)
 288                 {
 289                 buf[31-i]=dgst[i];
 290                 }
 291         return getbnfrombuf(buf,32);
 292         }
 293
 294 /* Convert byte buffer to bignum, skipping leading zeros*/
 295 BIGNUM *getbnfrombuf(const unsigned char *buf,size_t len)
 296         {
 297         while (*buf==0&&len>0)
 298                 {
 299                 buf++; len--;
 300                 }
 301         if (len)
 302                 {
 303                 return BN_bin2bn(buf,len,NULL);
 304                 }
 305         else
 306                 {
 307                 BIGNUM *b=BN_new();
 308                 BN_zero(b);
 309                 return b;
 310                 }
 311         }
 312
 313 /* Pack bignum into byte buffer of given size, filling all leading bytes
 314  * by zeros */
 315 int store_bignum(BIGNUM *bn, unsigned char *buf,int len)
 316         {
 317         int bytes = BN_num_bytes(bn);
 318         if (bytes>len) return 0;
 319         memset(buf,0,len);
 320         BN_bn2bin(bn,buf+len-bytes);
 321         return 1;
 322         }