crypto/dsa/dsa_ossl.c

   1 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   2  * All rights reserved.
   3  *
   4  * This package is an SSL implementation written
   5  * by Eric Young (eay@cryptsoft.com).
   6  * The implementation was written so as to conform with Netscapes SSL.
   7  *
   8  * This library is free for commercial and non-commercial use as long as
   9  * the following conditions are aheared to.  The following conditions
  10  * apply to all code found in this distribution, be it the RC4, RSA,
  11  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  12  * included with this distribution is covered by the same copyright terms
  13  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  14  *
  15  * Copyright remains Eric Young's, and as such any Copyright notices in
  16  * the code are not to be removed.
  17  * If this package is used in a product, Eric Young should be given attribution
  18  * as the author of the parts of the library used.
  19  * This can be in the form of a textual message at program startup or
  20  * in documentation (online or textual) provided with the package.
  21  *
  22  * Redistribution and use in source and binary forms, with or without
  23  * modification, are permitted provided that the following conditions
  24  * are met:
  25  * 1. Redistributions of source code must retain the copyright
  26  *    notice, this list of conditions and the following disclaimer.
  27  * 2. Redistributions in binary form must reproduce the above copyright
  28  *    notice, this list of conditions and the following disclaimer in the
  29  *    documentation and/or other materials provided with the distribution.
  30  * 3. All advertising materials mentioning features or use of this software
  31  *    must display the following acknowledgement:
  32  *    "This product includes cryptographic software written by
  33  *     Eric Young (eay@cryptsoft.com)"
  34  *    The word 'cryptographic' can be left out if the rouines from the library
  35  *    being used are not cryptographic related :-).
  36  * 4. If you include any Windows specific code (or a derivative thereof) from
  37  *    the apps directory (application code) you must include an acknowledgement:
  38  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  39  *
  40  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  41  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  43  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  44  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  45  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  46  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  47  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  48  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  49  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  50  * SUCH DAMAGE.
  51  *
  52  * The licence and distribution terms for any publically available version or
  53  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  54  * copied and put under another distribution licence
  55  * [including the GNU Public Licence.]
  56  */
  57
  58 /* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
  59
  60 #include <stdio.h>
  61 #include "internal/cryptlib.h"
  62 #include <openssl/bn.h>
  63 #include <openssl/sha.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 static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
  70                                     BIGNUM **rp);
  71 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
  72                           BIGNUM **rp, const unsigned char *dgst, int dlen);
  73 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
  74                          DSA_SIG *sig, DSA *dsa);
  75 static int dsa_init(DSA *dsa);
  76 static int dsa_finish(DSA *dsa);
  77
  78 static DSA_METHOD openssl_dsa_meth = {
  79     "OpenSSL DSA method",
  80     dsa_do_sign,
  81     dsa_sign_setup_no_digest,
  82     dsa_do_verify,
  83     NULL,                       /* dsa_mod_exp, */
  84     NULL,                       /* dsa_bn_mod_exp, */
  85     dsa_init,
  86     dsa_finish,
  87     DSA_FLAG_FIPS_METHOD,
  88     NULL,
  89     NULL,
  90     NULL
  91 };
  92
  93 /*-
  94  * These macro wrappers replace attempts to use the dsa_mod_exp() and
  95  * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
  96  * having a the macro work as an expression by bundling an "err_instr". So;
  97  *
  98  *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
  99  *                 dsa->method_mont_p)) goto err;
 100  *
 101  * can be replaced by;
 102  *
 103  *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
 104  *                 dsa->method_mont_p);
 105  */
 106
 107 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
 108         do { \
 109         int _tmp_res53; \
 110         if ((dsa)->meth->dsa_mod_exp) \
 111                 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
 112                                 (a2), (p2), (m), (ctx), (in_mont)); \
 113         else \
 114                 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
 115                                 (m), (ctx), (in_mont)); \
 116         if (!_tmp_res53) err_instr; \
 117         } while(0)
 118 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
 119         do { \
 120         int _tmp_res53; \
 121         if ((dsa)->meth->bn_mod_exp) \
 122                 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
 123                                 (m), (ctx), (m_ctx)); \
 124         else \
 125                 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
 126         if (!_tmp_res53) err_instr; \
 127         } while(0)
 128
 129 const DSA_METHOD *DSA_OpenSSL(void)
 130 {
 131     return &openssl_dsa_meth;
 132 }
 133
 134 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 135 {
 136     BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
 137     BIGNUM *m;
 138     BIGNUM *xr;
 139     BN_CTX *ctx = NULL;
 140     int reason = ERR_R_BN_LIB;
 141     DSA_SIG *ret = NULL;
 142     int noredo = 0;
 143
 144     m = BN_new();
 145     xr = BN_new();
 146     if (m == NULL || xr == NULL)
 147         goto err;
 148
 149     if (!dsa->p || !dsa->q || !dsa->g) {
 150         reason = DSA_R_MISSING_PARAMETERS;
 151         goto err;
 152     }
 153
 154     s = BN_new();
 155     if (s == NULL)
 156         goto err;
 157     ctx = BN_CTX_new();
 158     if (ctx == NULL)
 159         goto err;
 160  redo:
 161     if (!dsa_sign_setup(dsa, ctx, &kinv, &r, dgst, dlen))
 162         goto err;
 163
 164     if (dlen > BN_num_bytes(dsa->q))
 165         /*
 166          * if the digest length is greater than the size of q use the
 167          * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
 168          * 4.2
 169          */
 170         dlen = BN_num_bytes(dsa->q);
 171     if (BN_bin2bn(dgst, dlen, m) == NULL)
 172         goto err;
 173
 174     /* Compute  s = inv(k) (m + xr) mod q */
 175     if (!BN_mod_mul(xr, dsa->priv_key, r, dsa->q, ctx))
 176         goto err;               /* s = xr */
 177     if (!BN_add(s, xr, m))
 178         goto err;               /* s = m + xr */
 179     if (BN_cmp(s, dsa->q) > 0)
 180         if (!BN_sub(s, s, dsa->q))
 181             goto err;
 182     if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
 183         goto err;
 184
 185     /*
 186      * Redo if r or s is zero as required by FIPS 186-3: this is very
 187      * unlikely.
 188      */
 189     if (BN_is_zero(r) || BN_is_zero(s)) {
 190         if (noredo) {
 191             reason = DSA_R_NEED_NEW_SETUP_VALUES;
 192             goto err;
 193         }
 194         goto redo;
 195     }
 196     ret = DSA_SIG_new();
 197     if (ret == NULL)
 198         goto err;
 199     ret->r = r;
 200     ret->s = s;
 201
 202  err:
 203     if (ret == NULL) {
 204         DSAerr(DSA_F_DSA_DO_SIGN, reason);
 205         BN_free(r);
 206         BN_free(s);
 207     }
 208     BN_CTX_free(ctx);
 209     BN_clear_free(m);
 210     BN_clear_free(xr);
 211     BN_clear_free(kinv);
 212     return (ret);
 213 }
 214
 215 static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
 216                                     BIGNUM **kinvp, BIGNUM **rp)
 217 {
 218     return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
 219 }
 220
 221 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
 222                           BIGNUM **kinvp, BIGNUM **rp,
 223                           const unsigned char *dgst, int dlen)
 224 {
 225     BN_CTX *ctx = NULL;
 226     BIGNUM *k, *kq, *K, *kinv = NULL, *r = NULL;
 227     int ret = 0;
 228
 229     if (!dsa->p || !dsa->q || !dsa->g) {
 230         DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
 231         return 0;
 232     }
 233
 234     k = BN_new();
 235     kq = BN_new();
 236     if (k == NULL || kq == NULL)
 237         goto err;
 238
 239     if (ctx_in == NULL) {
 240         if ((ctx = BN_CTX_new()) == NULL)
 241             goto err;
 242     } else
 243         ctx = ctx_in;
 244
 245     if ((r = BN_new()) == NULL)
 246         goto err;
 247
 248     /* Get random k */
 249     do {
 250         if (dgst != NULL) {
 251             /*
 252              * We calculate k from SHA512(private_key + H(message) + random).
 253              * This protects the private key from a weak PRNG.
 254              */
 255             if (!BN_generate_dsa_nonce(k, dsa->q, dsa->priv_key, dgst,
 256                                        dlen, ctx))
 257                 goto err;
 258         } else if (!BN_rand_range(k, dsa->q))
 259             goto err;
 260     } while (BN_is_zero(k));
 261
 262     if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
 263         BN_set_flags(k, BN_FLG_CONSTTIME);
 264     }
 265
 266     if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
 267         if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 268                                     dsa->lock, dsa->p, ctx))
 269             goto err;
 270     }
 271
 272     /* Compute r = (g^k mod p) mod q */
 273
 274     if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
 275         if (!BN_copy(kq, k))
 276             goto err;
 277
 278         /*
 279          * We do not want timing information to leak the length of k, so we
 280          * compute g^k using an equivalent exponent of fixed length. (This
 281          * is a kludge that we need because the BN_mod_exp_mont() does not
 282          * let us specify the desired timing behaviour.)
 283          */
 284
 285         if (!BN_add(kq, kq, dsa->q))
 286             goto err;
 287         if (BN_num_bits(kq) <= BN_num_bits(dsa->q)) {
 288             if (!BN_add(kq, kq, dsa->q))
 289                 goto err;
 290         }
 291
 292         K = kq;
 293     } else {
 294         K = k;
 295     }
 296     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
 297                    dsa->method_mont_p);
 298     if (!BN_mod(r, r, dsa->q, ctx))
 299         goto err;
 300
 301     /* Compute  part of 's = inv(k) (m + xr) mod q' */
 302     if ((kinv = BN_mod_inverse(NULL, k, dsa->q, ctx)) == NULL)
 303         goto err;
 304
 305     BN_clear_free(*kinvp);
 306     *kinvp = kinv;
 307     kinv = NULL;
 308     BN_clear_free(*rp);
 309     *rp = r;
 310     ret = 1;
 311  err:
 312     if (!ret) {
 313         DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
 314         BN_clear_free(r);
 315     }
 316     if (ctx != ctx_in)
 317         BN_CTX_free(ctx);
 318     BN_clear_free(k);
 319     BN_clear_free(kq);
 320     return (ret);
 321 }
 322
 323 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
 324                          DSA_SIG *sig, DSA *dsa)
 325 {
 326     BN_CTX *ctx;
 327     BIGNUM *u1, *u2, *t1;
 328     BN_MONT_CTX *mont = NULL;
 329     int ret = -1, i;
 330     if (!dsa->p || !dsa->q || !dsa->g) {
 331         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
 332         return -1;
 333     }
 334
 335     i = BN_num_bits(dsa->q);
 336     /* fips 186-3 allows only different sizes for q */
 337     if (i != 160 && i != 224 && i != 256) {
 338         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
 339         return -1;
 340     }
 341
 342     if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
 343         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
 344         return -1;
 345     }
 346     u1 = BN_new();
 347     u2 = BN_new();
 348     t1 = BN_new();
 349     ctx = BN_CTX_new();
 350     if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
 351         goto err;
 352
 353     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 354         BN_ucmp(sig->r, dsa->q) >= 0) {
 355         ret = 0;
 356         goto err;
 357     }
 358     if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
 359         BN_ucmp(sig->s, dsa->q) >= 0) {
 360         ret = 0;
 361         goto err;
 362     }
 363
 364     /*
 365      * Calculate W = inv(S) mod Q save W in u2
 366      */
 367     if ((BN_mod_inverse(u2, sig->s, dsa->q, ctx)) == NULL)
 368         goto err;
 369
 370     /* save M in u1 */
 371     if (dgst_len > (i >> 3))
 372         /*
 373          * if the digest length is greater than the size of q use the
 374          * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
 375          * 4.2
 376          */
 377         dgst_len = (i >> 3);
 378     if (BN_bin2bn(dgst, dgst_len, u1) == NULL)
 379         goto err;
 380
 381     /* u1 = M * w mod q */
 382     if (!BN_mod_mul(u1, u1, u2, dsa->q, ctx))
 383         goto err;
 384
 385     /* u2 = r * w mod q */
 386     if (!BN_mod_mul(u2, sig->r, u2, dsa->q, ctx))
 387         goto err;
 388
 389     if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
 390         mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 391                                       dsa->lock, dsa->p, ctx);
 392         if (!mont)
 393             goto err;
 394     }
 395
 396     DSA_MOD_EXP(goto err, dsa, t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx,
 397                 mont);
 398     /* BN_copy(&u1,&t1); */
 399     /* let u1 = u1 mod q */
 400     if (!BN_mod(u1, t1, dsa->q, ctx))
 401         goto err;
 402
 403     /*
 404      * V is now in u1.  If the signature is correct, it will be equal to R.
 405      */
 406     ret = (BN_ucmp(u1, sig->r) == 0);
 407
 408  err:
 409     if (ret < 0)
 410         DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
 411     BN_CTX_free(ctx);
 412     BN_free(u1);
 413     BN_free(u2);
 414     BN_free(t1);
 415     return (ret);
 416 }
 417
 418 static int dsa_init(DSA *dsa)
 419 {
 420     dsa->flags |= DSA_FLAG_CACHE_MONT_P;
 421     return (1);
 422 }
 423
 424 static int dsa_finish(DSA *dsa)
 425 {
 426     BN_MONT_CTX_free(dsa->method_mont_p);
 427     return (1);
 428 }