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 "internal/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 == NULL || xr == NULL)
 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     /*
 195      * Redo if r or s is zero as required by FIPS 186-3: this is very
 196      * unlikely.
 197      */
 198     if (BN_is_zero(r) || BN_is_zero(s)) {
 199         if (noredo) {
 200             reason = DSA_R_NEED_NEW_SETUP_VALUES;
 201             goto err;
 202         }
 203         goto redo;
 204     }
 205     ret = DSA_SIG_new();
 206     if (ret == NULL)
 207         goto err;
 208     ret->r = r;
 209     ret->s = s;
 210
 211  err:
 212     if (ret == NULL) {
 213         DSAerr(DSA_F_DSA_DO_SIGN, reason);
 214         BN_free(r);
 215         BN_free(s);
 216     }
 217     BN_CTX_free(ctx);
 218     BN_clear_free(m);
 219     BN_clear_free(xr);
 220     BN_clear_free(kinv);
 221     return (ret);
 222 }
 223
 224 static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
 225                                     BIGNUM **kinvp, BIGNUM **rp)
 226 {
 227     return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
 228 }
 229
 230 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
 231                           BIGNUM **kinvp, BIGNUM **rp,
 232                           const unsigned char *dgst, int dlen)
 233 {
 234     BN_CTX *ctx = NULL;
 235     BIGNUM *k, *kq, *K, *kinv = NULL, *r = NULL;
 236     int ret = 0;
 237
 238     if (!dsa->p || !dsa->q || !dsa->g) {
 239         DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
 240         return 0;
 241     }
 242
 243     k = BN_new();
 244     kq = BN_new();
 245     if (k == NULL || kq == NULL)
 246         goto err;
 247
 248     if (ctx_in == NULL) {
 249         if ((ctx = BN_CTX_new()) == NULL)
 250             goto err;
 251     } else
 252         ctx = ctx_in;
 253
 254     if ((r = BN_new()) == NULL)
 255         goto err;
 256
 257     /* Get random k */
 258     do {
 259         if (dgst != NULL) {
 260             /*
 261              * We calculate k from SHA512(private_key + H(message) + random).
 262              * This protects the private key from a weak PRNG.
 263              */
 264             if (!BN_generate_dsa_nonce(k, dsa->q, dsa->priv_key, dgst,
 265                                        dlen, ctx))
 266                 goto err;
 267         } else if (!BN_rand_range(k, dsa->q))
 268             goto err;
 269     } while (BN_is_zero(k));
 270
 271     if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
 272         BN_set_flags(k, BN_FLG_CONSTTIME);
 273     }
 274
 275     if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
 276         if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 277                                     CRYPTO_LOCK_DSA, dsa->p, ctx))
 278             goto err;
 279     }
 280
 281     /* Compute r = (g^k mod p) mod q */
 282
 283     if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
 284         if (!BN_copy(kq, k))
 285             goto err;
 286
 287         /*
 288          * We do not want timing information to leak the length of k, so we
 289          * compute g^k using an equivalent exponent of fixed length. (This
 290          * is a kludge that we need because the BN_mod_exp_mont() does not
 291          * let us specify the desired timing behaviour.)
 292          */
 293
 294         if (!BN_add(kq, kq, dsa->q))
 295             goto err;
 296         if (BN_num_bits(kq) <= BN_num_bits(dsa->q)) {
 297             if (!BN_add(kq, kq, dsa->q))
 298                 goto err;
 299         }
 300
 301         K = kq;
 302     } else {
 303         K = k;
 304     }
 305     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
 306                    dsa->method_mont_p);
 307     if (!BN_mod(r, r, dsa->q, ctx))
 308         goto err;
 309
 310     /* Compute  part of 's = inv(k) (m + xr) mod q' */
 311     if ((kinv = BN_mod_inverse(NULL, k, dsa->q, ctx)) == NULL)
 312         goto err;
 313
 314     BN_clear_free(*kinvp);
 315     *kinvp = kinv;
 316     kinv = NULL;
 317     BN_clear_free(*rp);
 318     *rp = r;
 319     ret = 1;
 320  err:
 321     if (!ret) {
 322         DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
 323         BN_clear_free(r);
 324     }
 325     if (ctx != ctx_in)
 326         BN_CTX_free(ctx);
 327     BN_clear_free(k);
 328     BN_clear_free(kq);
 329     return (ret);
 330 }
 331
 332 static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
 333                          DSA_SIG *sig, DSA *dsa)
 334 {
 335     BN_CTX *ctx;
 336     BIGNUM *u1, *u2, *t1;
 337     BN_MONT_CTX *mont = NULL;
 338     int ret = -1, i;
 339     if (!dsa->p || !dsa->q || !dsa->g) {
 340         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
 341         return -1;
 342     }
 343
 344     i = BN_num_bits(dsa->q);
 345     /* fips 186-3 allows only different sizes for q */
 346     if (i != 160 && i != 224 && i != 256) {
 347         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
 348         return -1;
 349     }
 350
 351     if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
 352         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
 353         return -1;
 354     }
 355     u1 = BN_new();
 356     u2 = BN_new();
 357     t1 = BN_new();
 358     ctx = BN_CTX_new();
 359     if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
 360         goto err;
 361
 362     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 363         BN_ucmp(sig->r, dsa->q) >= 0) {
 364         ret = 0;
 365         goto err;
 366     }
 367     if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
 368         BN_ucmp(sig->s, dsa->q) >= 0) {
 369         ret = 0;
 370         goto err;
 371     }
 372
 373     /*
 374      * Calculate W = inv(S) mod Q save W in u2
 375      */
 376     if ((BN_mod_inverse(u2, sig->s, dsa->q, ctx)) == NULL)
 377         goto err;
 378
 379     /* save M in u1 */
 380     if (dgst_len > (i >> 3))
 381         /*
 382          * if the digest length is greater than the size of q use the
 383          * BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
 384          * 4.2
 385          */
 386         dgst_len = (i >> 3);
 387     if (BN_bin2bn(dgst, dgst_len, u1) == NULL)
 388         goto err;
 389
 390     /* u1 = M * w mod q */
 391     if (!BN_mod_mul(u1, u1, u2, dsa->q, ctx))
 392         goto err;
 393
 394     /* u2 = r * w mod q */
 395     if (!BN_mod_mul(u2, sig->r, u2, dsa->q, ctx))
 396         goto err;
 397
 398     if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
 399         mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
 400                                       CRYPTO_LOCK_DSA, dsa->p, ctx);
 401         if (!mont)
 402             goto err;
 403     }
 404
 405     DSA_MOD_EXP(goto err, dsa, t1, dsa->g, u1, dsa->pub_key, u2, dsa->p, ctx,
 406                 mont);
 407     /* BN_copy(&u1,&t1); */
 408     /* let u1 = u1 mod q */
 409     if (!BN_mod(u1, t1, dsa->q, ctx))
 410         goto err;
 411
 412     /*
 413      * V is now in u1.  If the signature is correct, it will be equal to R.
 414      */
 415     ret = (BN_ucmp(u1, sig->r) == 0);
 416
 417  err:
 418     if (ret < 0)
 419         DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
 420     BN_CTX_free(ctx);
 421     BN_free(u1);
 422     BN_free(u2);
 423     BN_free(t1);
 424     return (ret);
 425 }
 426
 427 static int dsa_init(DSA *dsa)
 428 {
 429     dsa->flags |= DSA_FLAG_CACHE_MONT_P;
 430     return (1);
 431 }
 432
 433 static int dsa_finish(DSA *dsa)
 434 {
 435     BN_MONT_CTX_free(dsa->method_mont_p);
 436     return (1);
 437 }