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/sha.h>
  65 #include <openssl/dsa.h>
  66 #include <openssl/rand.h>
  67 #include <openssl/asn1.h>
  68
  69 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
  70 static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
  71                                     BIGNUM **rp);
  72 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
  73                           BIGNUM **rp, const unsigned char *dgst, int dlen);
  74 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
  75                          DSA_SIG *sig, DSA *dsa);
  76 static int dsa_init(DSA *dsa);
  77 static int dsa_finish(DSA *dsa);
  78
  79 static DSA_METHOD openssl_dsa_meth = {
  80     "OpenSSL DSA method",
  81     dsa_do_sign,
  82     dsa_sign_setup_no_digest,
  83     dsa_do_verify,
  84     NULL,                       /* dsa_mod_exp, */
  85     NULL,                       /* dsa_bn_mod_exp, */
  86     dsa_init,
  87     dsa_finish,
  88     DSA_FLAG_FIPS_METHOD,
  89     NULL,
  90     NULL,
  91     NULL
  92 };
  93
  94 /*-
  95  * These macro wrappers replace attempts to use the dsa_mod_exp() and
  96  * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
  97  * having a the macro work as an expression by bundling an "err_instr". So;
  98  *
  99  *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
 100  *                 dsa->method_mont_p)) goto err;
 101  *
 102  * can be replaced by;
 103  *
 104  *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
 105  *                 dsa->method_mont_p);
 106  */
 107
 108 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
 109         do { \
 110         int _tmp_res53; \
 111         if((dsa)->meth->dsa_mod_exp) \
 112                 _tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
 113                                 (a2), (p2), (m), (ctx), (in_mont)); \
 114         else \
 115                 _tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
 116                                 (m), (ctx), (in_mont)); \
 117         if(!_tmp_res53) err_instr; \
 118         } while(0)
 119 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
 120         do { \
 121         int _tmp_res53; \
 122         if((dsa)->meth->bn_mod_exp) \
 123                 _tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
 124                                 (m), (ctx), (m_ctx)); \
 125         else \
 126                 _tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
 127         if(!_tmp_res53) err_instr; \
 128         } while(0)
 129
 130 const DSA_METHOD *DSA_OpenSSL(void)
 131 {
 132     return &openssl_dsa_meth;
 133 }
 134
 135 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
 136 {
 137     BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
 138     BIGNUM *m;
 139     BIGNUM *xr;
 140     BN_CTX *ctx = NULL;
 141     int reason = ERR_R_BN_LIB;
 142     DSA_SIG *ret = NULL;
 143     int noredo = 0;
 144
 145     m = BN_new();
 146     xr = BN_new();
 147     if (!m || !xr)
 148         goto err;
 149
 150     if (!dsa->p || !dsa->q || !dsa->g) {
 151         reason = DSA_R_MISSING_PARAMETERS;
 152         goto err;
 153     }
 154
 155     s = BN_new();
 156     if (s == NULL)
 157         goto err;
 158     ctx = BN_CTX_new();
 159     if (ctx == NULL)
 160         goto err;
 161  redo:
 162     if ((dsa->kinv == NULL) || (dsa->r == NULL)) {
 163         if (!dsa_sign_setup(dsa, ctx, &kinv, &r, dgst, dlen))
 164             goto err;
 165     } else {
 166         kinv = dsa->kinv;
 167         dsa->kinv = NULL;
 168         r = dsa->r;
 169         dsa->r = NULL;
 170         noredo = 1;
 171     }
 172
 173     if (dlen > BN_num_bytes(dsa->q))
 174         /*
 175          * if the digest length is greater than the size of q use the
 176          * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
 177          * 4.2
 178          */
 179         dlen = BN_num_bytes(dsa->q);
 180     if (BN_bin2bn(dgst, dlen, m) == NULL)
 181         goto err;
 182
 183     /* Compute  s = inv(k) (m + xr) mod q */
 184     if (!BN_mod_mul(xr, dsa->priv_key, r, dsa->q, ctx))
 185         goto err;               /* s = xr */
 186     if (!BN_add(s, xr, m))
 187         goto err;               /* s = m + xr */
 188     if (BN_cmp(s, dsa->q) > 0)
 189         if (!BN_sub(s, s, dsa->q))
 190             goto err;
 191     if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
 192         goto err;
 193
 194     ret = DSA_SIG_new();
 195     if (ret == NULL)
 196         goto err;
 197     /*
 198      * Redo if r or s is zero as required by FIPS 186-3: this is very
 199      * unlikely.
 200      */
 201     if (BN_is_zero(r) || BN_is_zero(s)) {
 202         if (noredo) {
 203             reason = DSA_R_NEED_NEW_SETUP_VALUES;
 204             goto err;
 205         }
 206         goto redo;
 207     }
 208     ret->r = r;
 209     ret->s = s;
 210
 211  err:
 212     if (!ret) {
 213         DSAerr(DSA_F_DSA_DO_SIGN, reason);
 214         BN_free(r);
 215         BN_free(s);
 216     }
 217     if (ctx != NULL)
 218         BN_CTX_free(ctx);
 219     BN_clear_free(m);
 220     BN_clear_free(xr);
 221     if (kinv != NULL)           /* dsa->kinv is NULL now if we used it */
 222         BN_clear_free(kinv);
 223     return (ret);
 224 }
 225
 226 static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
 227                                     BIGNUM **kinvp, BIGNUM **rp)
 228 {
 229     return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
 230 }
 231
 232 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
 233                           BIGNUM **kinvp, BIGNUM **rp,
 234                           const unsigned char *dgst, int dlen)
 235 {
 236     BN_CTX *ctx = NULL;
 237     BIGNUM *k, *kq, *K, *kinv = NULL, *r = NULL;
 238     int ret = 0;
 239
 240     if (!dsa->p || !dsa->q || !dsa->g) {
 241         DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
 242         return 0;
 243     }
 244
 245     k = BN_new();
 246     kq = BN_new();
 247     if (!k || !kq)
 248         goto err;
 249
 250     if (ctx_in == NULL) {
 251         if ((ctx = BN_CTX_new()) == NULL)
 252             goto err;
 253     } else
 254         ctx = ctx_in;
 255
 256     if ((r = BN_new()) == NULL)
 257         goto err;
 258
 259     /* Get random k */
 260     do {
 261         if (dgst != NULL) {
 262             /*
 263              * We calculate k from SHA512(private_key + H(message) + random).
 264              * This protects the private key from a weak PRNG.
 265              */
 266             if (!BN_generate_dsa_nonce(k, dsa->q, dsa->priv_key, dgst,
 267                                        dlen, ctx))
 268                 goto err;
 269         } else if (!BN_rand_range(k, dsa->q))
 270             goto err;
 271     } while (BN_is_zero(k));
 272
 273     if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
 274         BN_set_flags(k, BN_FLG_CONSTTIME);
 275     }
 276
 277     if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
 278         if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 279                                     CRYPTO_LOCK_DSA, dsa->p, ctx))
 280             goto err;
 281     }
 282
 283     /* Compute r = (g^k mod p) mod q */
 284
 285     if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
 286         if (!BN_copy(kq, k))
 287             goto err;
 288
 289         /*
 290          * We do not want timing information to leak the length of k, so we
 291          * compute g^k using an equivalent exponent of fixed length. (This
 292          * is a kludge that we need because the BN_mod_exp_mont() does not
 293          * let us specify the desired timing behaviour.)
 294          */
 295
 296         if (!BN_add(kq, kq, dsa->q))
 297             goto err;
 298         if (BN_num_bits(kq) <= BN_num_bits(dsa->q)) {
 299             if (!BN_add(kq, kq, dsa->q))
 300                 goto err;
 301         }
 302
 303         K = kq;
 304     } else {
 305         K = k;
 306     }
 307     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
 308                    dsa->method_mont_p);
 309     if (!BN_mod(r, r, dsa->q, ctx))
 310         goto err;
 311
 312     /* Compute  part of 's = inv(k) (m + xr) mod q' */
 313     if ((kinv = BN_mod_inverse(NULL, k, dsa->q, ctx)) == NULL)
 314         goto err;
 315
 316     if (*kinvp != NULL)
 317         BN_clear_free(*kinvp);
 318     *kinvp = kinv;
 319     kinv = NULL;
 320     if (*rp != NULL)
 321         BN_clear_free(*rp);
 322     *rp = r;
 323     ret = 1;
 324  err:
 325     if (!ret) {
 326         DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
 327         if (r != NULL)
 328             BN_clear_free(r);
 329     }
 330     if (ctx_in == NULL)
 331         BN_CTX_free(ctx);
 332     BN_clear_free(k);
 333     BN_clear_free(kq);
 334     return (ret);
 335 }
 336
 337 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
 338                          DSA_SIG *sig, DSA *dsa)
 339 {
 340     BN_CTX *ctx;
 341     BIGNUM *u1, *u2, *t1;
 342     BN_MONT_CTX *mont = NULL;
 343     int ret = -1, i;
 344     if (!dsa->p || !dsa->q || !dsa->g) {
 345         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
 346         return -1;
 347     }
 348
 349     i = BN_num_bits(dsa->q);
 350     /* fips 186-3 allows only different sizes for q */
 351     if (i != 160 && i != 224 && i != 256) {
 352         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
 353         return -1;
 354     }
 355
 356     if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
 357         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
 358         return -1;
 359     }
 360     u1 = BN_new();
 361     u2 = BN_new();
 362     t1 = BN_new();
 363     ctx = BN_CTX_new();
 364     if (!u1 || !u2 || !t1 || !ctx)
 365         goto err;
 366
 367     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 368         BN_ucmp(sig->r, dsa->q) >= 0) {
 369         ret = 0;
 370         goto err;
 371     }
 372     if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
 373         BN_ucmp(sig->s, dsa->q) >= 0) {
 374         ret = 0;
 375         goto err;
 376     }
 377
 378     /*
 379      * Calculate W = inv(S) mod Q save W in u2
 380      */
 381     if ((BN_mod_inverse(u2, sig->s, dsa->q, ctx)) == NULL)
 382         goto err;
 383
 384     /* save M in u1 */
 385     if (dgst_len > (i >> 3))
 386         /*
 387          * if the digest length is greater than the size of q use the
 388          * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
 389          * 4.2
 390          */
 391         dgst_len = (i >> 3);
 392     if (BN_bin2bn(dgst, dgst_len, u1) == NULL)
 393         goto err;
 394
 395     /* u1 = M * w mod q */
 396     if (!BN_mod_mul(u1, u1, u2, dsa->q, ctx))
 397         goto err;
 398
 399     /* u2 = r * w mod q */
 400     if (!BN_mod_mul(u2, sig->r, u2, dsa->q, ctx))
 401         goto err;
 402
 403     if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
 404         mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 405                                       CRYPTO_LOCK_DSA, dsa->p, ctx);
 406         if (!mont)
 407             goto err;
 408     }
 409
 410     DSA_MOD_EXP(goto err, dsa, t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx,
 411                 mont);
 412     /* BN_copy(&u1,&t1); */
 413     /* let u1 = u1 mod q */
 414     if (!BN_mod(u1, t1, dsa->q, ctx))
 415         goto err;
 416
 417     /*
 418      * V is now in u1.  If the signature is correct, it will be equal to R.
 419      */
 420     ret = (BN_ucmp(u1, sig->r) == 0);
 421
 422  err:
 423     if (ret < 0)
 424         DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
 425     if (ctx != NULL)
 426         BN_CTX_free(ctx);
 427     if (u1)
 428         BN_free(u1);
 429     if (u2)
 430         BN_free(u2);
 431     if (t1)
 432         BN_free(t1);
 433     return (ret);
 434 }
 435
 436 static int dsa_init(DSA *dsa)
 437 {
 438     dsa->flags |= DSA_FLAG_CACHE_MONT_P;
 439     return (1);
 440 }
 441
 442 static int dsa_finish(DSA *dsa)
 443 {
 444     if (dsa->method_mont_p)
 445         BN_MONT_CTX_free(dsa->method_mont_p);
 446     return (1);
 447 }