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      1 /* crypto/dsa/dsa_ossl.c */
      2 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com)
      3  * All rights reserved.
      4  *
      5  * This package is an SSL implementation written
      6  * by Eric Young (eay (at) 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 (at) 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 (at) 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 (at) 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 (at) 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(DSA *dsa, BN_CTX *ctx_in,
     71 			  BIGNUM **kinvp, BIGNUM **rp,
     72 			  const unsigned char *dgst, int dlen);
     73 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
     74 			 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,
     82 dsa_do_verify,
     83 NULL, /* dsa_mod_exp, */
     84 NULL, /* dsa_bn_mod_exp, */
     85 dsa_init,
     86 dsa_finish,
     87 0,
     88 NULL,
     89 NULL,
     90 NULL
     91 };
     92 
     93 /* These macro wrappers replace attempts to use the dsa_mod_exp() and
     94  * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
     95  * having a the macro work as an expression by bundling an "err_instr". So;
     96  *
     97  *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
     98  *                 dsa->method_mont_p)) goto err;
     99  *
    100  * can be replaced by;
    101  *
    102  *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
    103  *                 dsa->method_mont_p);
    104  */
    105 
    106 #define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
    107 	do { \
    108 	int _tmp_res53; \
    109 	if((dsa)->meth->dsa_mod_exp) \
    110 		_tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
    111 				(a2), (p2), (m), (ctx), (in_mont)); \
    112 	else \
    113 		_tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
    114 				(m), (ctx), (in_mont)); \
    115 	if(!_tmp_res53) err_instr; \
    116 	} while(0)
    117 #define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
    118 	do { \
    119 	int _tmp_res53; \
    120 	if((dsa)->meth->bn_mod_exp) \
    121 		_tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
    122 				(m), (ctx), (m_ctx)); \
    123 	else \
    124 		_tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
    125 	if(!_tmp_res53) err_instr; \
    126 	} while(0)
    127 
    128 const DSA_METHOD *DSA_OpenSSL(void)
    129 {
    130 	return &openssl_dsa_meth;
    131 }
    132 
    133 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
    134 	{
    135 	BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
    136 	BIGNUM m;
    137 	BIGNUM xr;
    138 	BN_CTX *ctx=NULL;
    139 	int reason=ERR_R_BN_LIB;
    140 	DSA_SIG *ret=NULL;
    141 	int noredo = 0;
    142 
    143 	BN_init(&m);
    144 	BN_init(&xr);
    145 
    146 	if (!dsa->p || !dsa->q || !dsa->g)
    147 		{
    148 		reason=DSA_R_MISSING_PARAMETERS;
    149 		goto err;
    150 		}
    151 
    152 	s=BN_new();
    153 	if (s == NULL) goto err;
    154 	ctx=BN_CTX_new();
    155 	if (ctx == NULL) goto err;
    156 redo:
    157 	if ((dsa->kinv == NULL) || (dsa->r == NULL))
    158 		{
    159 		if (!dsa->meth->dsa_sign_setup(dsa,ctx,&kinv,&r,dgst,dlen))
    160 			goto err;
    161 		}
    162 	else
    163 		{
    164 		kinv=dsa->kinv;
    165 		dsa->kinv=NULL;
    166 		r=dsa->r;
    167 		dsa->r=NULL;
    168 		noredo = 1;
    169 		}
    170 
    171 
    172 	if (dlen > BN_num_bytes(dsa->q))
    173 		/* if the digest length is greater than the size of q use the
    174 		 * BN_num_bits(dsa->q) leftmost bits of the digest, see
    175 		 * fips 186-3, 4.2 */
    176 		dlen = BN_num_bytes(dsa->q);
    177 	if (BN_bin2bn(dgst,dlen,&m) == NULL)
    178 		goto err;
    179 
    180 	/* Compute  s = inv(k) (m + xr) mod q */
    181 	if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
    182 	if (!BN_add(s, &xr, &m)) goto err;		/* s = m + xr */
    183 	if (BN_cmp(s,dsa->q) > 0)
    184 		if (!BN_sub(s,s,dsa->q)) goto err;
    185 	if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
    186 
    187 	ret=DSA_SIG_new();
    188 	if (ret == NULL) goto err;
    189 	/* Redo if r or s is zero as required by FIPS 186-3: this is
    190 	 * very unlikely.
    191 	 */
    192 	if (BN_is_zero(r) || BN_is_zero(s))
    193 		{
    194 		if (noredo)
    195 			{
    196 			reason = DSA_R_NEED_NEW_SETUP_VALUES;
    197 			goto err;
    198 			}
    199 		goto redo;
    200 		}
    201 	ret->r = r;
    202 	ret->s = s;
    203 
    204 err:
    205 	if (!ret)
    206 		{
    207 		DSAerr(DSA_F_DSA_DO_SIGN,reason);
    208 		BN_free(r);
    209 		BN_free(s);
    210 		}
    211 	if (ctx != NULL) BN_CTX_free(ctx);
    212 	BN_clear_free(&m);
    213 	BN_clear_free(&xr);
    214 	if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
    215 	    BN_clear_free(kinv);
    216 	return(ret);
    217 	}
    218 
    219 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
    220 			  BIGNUM **kinvp, BIGNUM **rp,
    221 			  const unsigned char *dgst, int dlen)
    222 	{
    223 	BN_CTX *ctx;
    224 	BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
    225 	int ret=0;
    226 
    227 	if (!dsa->p || !dsa->q || !dsa->g)
    228 		{
    229 		DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
    230 		return 0;
    231 		}
    232 
    233 	BN_init(&k);
    234 	BN_init(&kq);
    235 
    236 	if (ctx_in == NULL)
    237 		{
    238 		if ((ctx=BN_CTX_new()) == NULL) goto err;
    239 		}
    240 	else
    241 		ctx=ctx_in;
    242 
    243 	if ((r=BN_new()) == NULL) goto err;
    244 
    245 	/* Get random k */
    246 	do
    247 		{
    248 #ifndef OPENSSL_NO_SHA512
    249 		if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH)
    250 			{
    251 			/* If DSA_FLAG_NONCE_FROM_HASH is set then we calculate k from
    252 			 * SHA512(private_key + H(message) + random). This protects the
    253 			 * private key from a weak PRNG. */
    254 			if (!BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, dgst,
    255 						   dlen, ctx))
    256 				goto err;
    257 			}
    258 		else
    259 #endif
    260 			if (!BN_rand_range(&k, dsa->q)) goto err;
    261 		} while (BN_is_zero(&k));
    262 	if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
    263 		{
    264 		BN_set_flags(&k, BN_FLG_CONSTTIME);
    265 		}
    266 
    267 	if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
    268 		{
    269 		if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
    270 						CRYPTO_LOCK_DSA,
    271 						dsa->p, ctx))
    272 			goto err;
    273 		}
    274 
    275 	/* Compute r = (g^k mod p) mod q */
    276 
    277 	if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
    278 		{
    279 		if (!BN_copy(&kq, &k)) goto err;
    280 
    281 		/* We do not want timing information to leak the length of k,
    282 		 * so we compute g^k using an equivalent exponent of fixed length.
    283 		 *
    284 		 * (This is a kludge that we need because the BN_mod_exp_mont()
    285 		 * does not let us specify the desired timing behaviour.) */
    286 
    287 		if (!BN_add(&kq, &kq, dsa->q)) goto err;
    288 		if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
    289 			{
    290 			if (!BN_add(&kq, &kq, dsa->q)) goto err;
    291 			}
    292 
    293 		K = &kq;
    294 		}
    295 	else
    296 		{
    297 		K = &k;
    298 		}
    299 	DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
    300 			dsa->method_mont_p);
    301 	if (!BN_mod(r,r,dsa->q,ctx)) goto err;
    302 
    303 	/* Compute  part of 's = inv(k) (m + xr) mod q' */
    304 	if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
    305 
    306 	if (*kinvp != NULL) BN_clear_free(*kinvp);
    307 	*kinvp=kinv;
    308 	kinv=NULL;
    309 	if (*rp != NULL) BN_clear_free(*rp);
    310 	*rp=r;
    311 	ret=1;
    312 err:
    313 	if (!ret)
    314 		{
    315 		DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
    316 		if (r != NULL)
    317 			BN_clear_free(r);
    318 		}
    319 	if (ctx_in == NULL) BN_CTX_free(ctx);
    320 	BN_clear_free(&k);
    321 	BN_clear_free(&kq);
    322 	return(ret);
    323 	}
    324 
    325 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
    326 			 DSA *dsa)
    327 	{
    328 	BN_CTX *ctx;
    329 	BIGNUM u1,u2,t1;
    330 	BN_MONT_CTX *mont=NULL;
    331 	int ret = -1, i;
    332 	if (!dsa->p || !dsa->q || !dsa->g)
    333 		{
    334 		DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
    335 		return -1;
    336 		}
    337 
    338 	i = BN_num_bits(dsa->q);
    339 	/* fips 186-3 allows only different sizes for q */
    340 	if (i != 160 && i != 224 && i != 256)
    341 		{
    342 		DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
    343 		return -1;
    344 		}
    345 
    346 	if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
    347 		{
    348 		DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
    349 		return -1;
    350 		}
    351 	BN_init(&u1);
    352 	BN_init(&u2);
    353 	BN_init(&t1);
    354 
    355 	if ((ctx=BN_CTX_new()) == NULL) goto err;
    356 
    357 	if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
    358 	    BN_ucmp(sig->r, dsa->q) >= 0)
    359 		{
    360 		ret = 0;
    361 		goto err;
    362 		}
    363 	if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
    364 	    BN_ucmp(sig->s, dsa->q) >= 0)
    365 		{
    366 		ret = 0;
    367 		goto err;
    368 		}
    369 
    370 	/* Calculate W = inv(S) mod Q
    371 	 * save W in u2 */
    372 	if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
    373 
    374 	/* save M in u1 */
    375 	if (dgst_len > (i >> 3))
    376 		/* if the digest length is greater than the size of q use the
    377 		 * BN_num_bits(dsa->q) leftmost bits of the digest, see
    378 		 * fips 186-3, 4.2 */
    379 		dgst_len = (i >> 3);
    380 	if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
    381 
    382 	/* u1 = M * w mod q */
    383 	if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
    384 
    385 	/* u2 = r * w mod q */
    386 	if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
    387 
    388 
    389 	if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
    390 		{
    391 		mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
    392 					CRYPTO_LOCK_DSA, dsa->p, ctx);
    393 		if (!mont)
    394 			goto err;
    395 		}
    396 
    397 
    398 	DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
    399 	/* BN_copy(&u1,&t1); */
    400 	/* let u1 = u1 mod q */
    401 	if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
    402 
    403 	/* V is now in u1.  If the signature is correct, it will be
    404 	 * equal to R. */
    405 	ret=(BN_ucmp(&u1, sig->r) == 0);
    406 
    407 	err:
    408 	/* XXX: surely this is wrong - if ret is 0, it just didn't verify;
    409 	   there is no error in BN. Test should be ret == -1 (Ben) */
    410 	if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
    411 	if (ctx != NULL) 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 	if(dsa->method_mont_p)
    427 		BN_MONT_CTX_free(dsa->method_mont_p);
    428 	return(1);
    429 }
    430 
    431