crypto/dsa/dsa_ossl.c

   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/dsa.h>
  65 #include <openssl/rand.h>
  66 #include <openssl/asn1.h>
  67
  68 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
  69 int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);
  70 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
  71                   DSA *dsa);
  72 static int dsa_init(DSA *dsa);
  73 static int dsa_finish(DSA *dsa);
  74 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
  75                 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
  76                 BN_MONT_CTX *in_mont);
  77 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
  78                                 const BIGNUM *m, BN_CTX *ctx,
  79                                 BN_MONT_CTX *m_ctx);
  80
  81 static DSA_METHOD openssl_dsa_meth = {
  82 "OpenSSL DSA method",
  83 dsa_do_sign,
  84 dsa_sign_setup,
  85 dsa_do_verify,
  86 dsa_mod_exp,
  87 dsa_bn_mod_exp,
  88 dsa_init,
  89 dsa_finish,
  90 0,
  91 NULL
  92 };
  93
  94 DSA_METHOD *DSA_OpenSSL(void)
  95 {
  96         return &openssl_dsa_meth;
  97 }
  98
  99 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 100         {
 101         BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
 102         BIGNUM m;
 103         BIGNUM xr;
 104         BN_CTX *ctx=NULL;
 105         int i,reason=ERR_R_BN_LIB;
 106         DSA_SIG *ret=NULL;
 107
 108         BN_init(&m);
 109         BN_init(&xr);
 110         s=BN_new();
 111         if (s == NULL) goto err;
 112
 113         i=BN_num_bytes(dsa->q); /* should be 20 */
 114         if ((dlen > i) || (dlen > 50))
 115                 {
 116                 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
 117                 goto err;
 118                 }
 119
 120         ctx=BN_CTX_new();
 121         if (ctx == NULL) goto err;
 122
 123         if ((dsa->kinv == NULL) || (dsa->r == NULL))
 124                 {
 125                 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
 126                 }
 127         else
 128                 {
 129                 kinv=dsa->kinv;
 130                 dsa->kinv=NULL;
 131                 r=dsa->r;
 132                 dsa->r=NULL;
 133                 }
 134
 135         if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err;
 136
 137         /* Compute  s = inv(k) (m + xr) mod q */
 138         if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
 139         if (!BN_add(s, &xr, &m)) goto err;              /* s = m + xr */
 140         if (BN_cmp(s,dsa->q) > 0)
 141                 BN_sub(s,s,dsa->q);
 142         if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
 143
 144         ret=DSA_SIG_new();
 145         if (ret == NULL) goto err;
 146         ret->r = r;
 147         ret->s = s;
 148
 149 err:
 150         if (!ret)
 151                 {
 152                 DSAerr(DSA_F_DSA_DO_SIGN,reason);
 153                 BN_free(r);
 154                 BN_free(s);
 155                 }
 156         if (ctx != NULL) BN_CTX_free(ctx);
 157         BN_clear_free(&m);
 158         BN_clear_free(&xr);
 159         if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
 160             BN_clear_free(kinv);
 161         return(ret);
 162         }
 163
 164 int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
 165         {
 166         BN_CTX *ctx;
 167         BIGNUM k,*kinv=NULL,*r=NULL;
 168         int ret=0;
 169
 170         if (ctx_in == NULL)
 171                 {
 172                 if ((ctx=BN_CTX_new()) == NULL) goto err;
 173                 }
 174         else
 175                 ctx=ctx_in;
 176
 177         BN_init(&k);
 178         if ((r=BN_new()) == NULL) goto err;
 179         kinv=NULL;
 180
 181         /* Get random k */
 182         for (;;)
 183                 {
 184                 if (!BN_rand(&k, BN_num_bits(dsa->q), 1, 0)) goto err;
 185                 if (BN_cmp(&k,dsa->q) >= 0)
 186                         BN_sub(&k,&k,dsa->q);
 187                 if (!BN_is_zero(&k)) break;
 188                 }
 189
 190         if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
 191                 {
 192                 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 193                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
 194                                 dsa->p,ctx)) goto err;
 195                 }
 196
 197         /* Compute r = (g^k mod p) mod q */
 198         if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
 199                 (BN_MONT_CTX *)dsa->method_mont_p)) goto err;
 200         if (!BN_mod(r,r,dsa->q,ctx)) goto err;
 201
 202         /* Compute  part of 's = inv(k) (m + xr) mod q' */
 203         if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
 204
 205         if (*kinvp != NULL) BN_clear_free(*kinvp);
 206         *kinvp=kinv;
 207         kinv=NULL;
 208         if (*rp != NULL) BN_clear_free(*rp);
 209         *rp=r;
 210         ret=1;
 211 err:
 212         if (!ret)
 213                 {
 214                 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
 215                 if (kinv != NULL) BN_clear_free(kinv);
 216                 if (r != NULL) BN_clear_free(r);
 217                 }
 218         if (ctx_in == NULL) BN_CTX_free(ctx);
 219         if (kinv != NULL) BN_clear_free(kinv);
 220         BN_clear_free(&k);
 221         return(ret);
 222         }
 223
 224 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
 225                   DSA *dsa)
 226         {
 227         BN_CTX *ctx;
 228         BIGNUM u1,u2,t1;
 229         BN_MONT_CTX *mont=NULL;
 230         int ret = -1;
 231
 232         if ((ctx=BN_CTX_new()) == NULL) goto err;
 233         BN_init(&u1);
 234         BN_init(&u2);
 235         BN_init(&t1);
 236
 237         /* Calculate W = inv(S) mod Q
 238          * save W in u2 */
 239         if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
 240
 241         /* save M in u1 */
 242         if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
 243
 244         /* u1 = M * w mod q */
 245         if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
 246
 247         /* u2 = r * w mod q */
 248         if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
 249
 250         if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
 251                 {
 252                 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
 253                         if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
 254                                 dsa->p,ctx)) goto err;
 255                 }
 256         mont=(BN_MONT_CTX *)dsa->method_mont_p;
 257
 258 #if 0
 259         {
 260         BIGNUM t2;
 261
 262         BN_init(&t2);
 263         /* v = ( g^u1 * y^u2 mod p ) mod q */
 264         /* let t1 = g ^ u1 mod p */
 265         if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err;
 266         /* let t2 = y ^ u2 mod p */
 267         if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err;
 268         /* let u1 = t1 * t2 mod p */
 269         if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn;
 270         BN_free(&t2);
 271         }
 272         /* let u1 = u1 mod q */
 273         if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err;
 274 #else
 275         {
 276         if (!dsa->meth->dsa_mod_exp(dsa, &t1,dsa->g,&u1,dsa->pub_key,&u2,
 277                                                 dsa->p,ctx,mont)) goto err;
 278         /* BN_copy(&u1,&t1); */
 279         /* let u1 = u1 mod q */
 280         if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
 281         }
 282 #endif
 283         /* V is now in u1.  If the signature is correct, it will be
 284          * equal to R. */
 285         ret=(BN_ucmp(&u1, sig->r) == 0);
 286
 287         err:
 288         if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
 289         if (ctx != NULL) BN_CTX_free(ctx);
 290         BN_free(&u1);
 291         BN_free(&u2);
 292         BN_free(&t1);
 293         return(ret);
 294         }
 295
 296 static int dsa_init(DSA *dsa)
 297 {
 298         dsa->flags=DSA_FLAG_CACHE_MONT_P;
 299         return(1);
 300 }
 301
 302 static int dsa_finish(DSA *dsa)
 303 {
 304         return(1);
 305 }
 306
 307 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
 308                 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
 309                 BN_MONT_CTX *in_mont)
 310 {
 311         return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont);
 312 }
 313
 314 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
 315                                 const BIGNUM *m, BN_CTX *ctx,
 316                                 BN_MONT_CTX *m_ctx)
 317 {
 318         return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
 319 }