/* crypto/dsa/dsa_ossl.c */

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

 * All rights reserved.

 *

 * This package is an SSL implementation written

 * by Eric Young (eay@cryptsoft.com).

 * The implementation was written so as to conform with Netscapes SSL.

 * 

 * This library is free for commercial and non-commercial use as long as

 * the following conditions are aheared to.  The following conditions

 * apply to all code found in this distribution, be it the RC4, RSA,

 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

 * included with this distribution is covered by the same copyright terms

 * except that the holder is Tim Hudson (tjh@cryptsoft.com).

 * 

 * Copyright remains Eric Young's, and as such any Copyright notices in

 * the code are not to be removed.

 * If this package is used in a product, Eric Young should be given attribution

 * as the author of the parts of the library used.

 * This can be in the form of a textual message at program startup or

 * in documentation (online or textual) provided with the package.

 * 

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *    "This product includes cryptographic software written by

 *     Eric Young (eay@cryptsoft.com)"

 *    The word 'cryptographic' can be left out if the rouines from the library

 *    being used are not cryptographic related :-).

 * 4. If you include any Windows specific code (or a derivative thereof) from 

 *    the apps directory (application code) you must include an acknowledgement:

 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

 * 

 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 * 

 * The licence and distribution terms for any publically available version or

 * derivative of this code cannot be changed.  i.e. this code cannot simply be

 * copied and put under another distribution licence

 * [including the GNU Public Licence.]

 */

/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */

/*

 © Portions copyright (c) 2006 Nokia Corporation.  All rights reserved.

 */

#include <stdio.h>

#include "cryptlib.h"

#include <openssl/bn.h>

#include <openssl/dsa.h>

#include <openssl/rand.h>

#include <openssl/asn1.h>

#if (defined(SYMBIAN) && (defined(__WINSCW__) || defined(__WINS__)))

#include "libcrypto_wsd_macros.h"

#include "libcrypto_wsd.h"

#endif

static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);

static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);

static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,

		  DSA *dsa);

static int dsa_init(DSA *dsa);

static int dsa_finish(DSA *dsa);

#ifndef EMULATOR

static DSA_METHOD openssl_dsa_meth = {

"OpenSSL DSA method",

dsa_do_sign,

dsa_sign_setup,

dsa_do_verify,

NULL, /* dsa_mod_exp, */

NULL, /* dsa_bn_mod_exp, */

dsa_init,

dsa_finish,

0,

NULL,

NULL,

NULL

};

#else

GET_STATIC_VAR_FROM_TLS(openssl_dsa_meth,dsa_ossl,DSA_METHOD)

#define openssl_dsa_meth (*GET_WSD_VAR_NAME(openssl_dsa_meth,dsa_ossl, s)())

const DSA_METHOD temp_s_openssl_dsa_meth = {

"OpenSSL DSA method",

dsa_do_sign,

dsa_sign_setup,

dsa_do_verify,

NULL, /* dsa_mod_exp, */

NULL, /* dsa_bn_mod_exp, */

dsa_init,

dsa_finish,

0,

NULL,

NULL,

NULL

};

#endif

/* These macro wrappers replace attempts to use the dsa_mod_exp() and

 * bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of

 * having a the macro work as an expression by bundling an "err_instr". So;

 * 

 *     if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,

 *                 dsa->method_mont_p)) goto err;

 *

 * can be replaced by;

 *

 *     DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,

 *                 dsa->method_mont_p);

 */

#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \

	do { \

	int _tmp_res53; \

	if((dsa)->meth->dsa_mod_exp) \

		_tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \

				(a2), (p2), (m), (ctx), (in_mont)); \

	else \

		_tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \

				(m), (ctx), (in_mont)); \

	if(!_tmp_res53) err_instr; \

	} while(0)

#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \

	do { \

	int _tmp_res53; \

	if((dsa)->meth->bn_mod_exp) \

		_tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \

				(m), (ctx), (m_ctx)); \

	else \

		_tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \

	if(!_tmp_res53) err_instr; \

	} while(0)

EXPORT_C const DSA_METHOD *DSA_OpenSSL(void)

{

	return &openssl_dsa_meth;

}

static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)

	{

	BIGNUM *kinv=NULL,*r=NULL,*s=NULL;

	BIGNUM m;

	BIGNUM xr;

	BN_CTX *ctx=NULL;

	int i,reason=ERR_R_BN_LIB;

	DSA_SIG *ret=NULL;

	BN_init(&m);

	BN_init(&xr);

	if (!dsa->p || !dsa->q || !dsa->g)

		{

		reason=DSA_R_MISSING_PARAMETERS;

		goto err;

		}

	s=BN_new();

	if (s == NULL) goto err;

	i=BN_num_bytes(dsa->q); /* should be 20 */

	if ((dlen > i) || (dlen > 50))

		{

		reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;

		goto err;

		}

	ctx=BN_CTX_new();

	if (ctx == NULL) goto err;

	if ((dsa->kinv == NULL) || (dsa->r == NULL))

		{

		if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;

		}

	else

		{

		kinv=dsa->kinv;

		dsa->kinv=NULL;

		r=dsa->r;

		dsa->r=NULL;

		}

	if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err;

	/* Compute  s = inv(k) (m + xr) mod q */

	if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */

	if (!BN_add(s, &xr, &m)) goto err;		/* s = m + xr */

	if (BN_cmp(s,dsa->q) > 0)

		BN_sub(s,s,dsa->q);

	if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;

	ret=DSA_SIG_new();

	if (ret == NULL) goto err;

	ret->r = r;

	ret->s = s;

err:

	if (!ret)

		{

		DSAerr(DSA_F_DSA_DO_SIGN,reason);

		BN_free(r);

		BN_free(s);

		}

	if (ctx != NULL) BN_CTX_free(ctx);

	BN_clear_free(&m);

	BN_clear_free(&xr);

	if (kinv != NULL) /* dsa->kinv is NULL now if we used it */

	    BN_clear_free(kinv);

	return(ret);

	}

static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)

	{

	BN_CTX *ctx;

	BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;

	int ret=0;

	if (!dsa->p || !dsa->q || !dsa->g)

		{

		DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);

		return 0;

		}

	BN_init(&k);

	BN_init(&kq);

	if (ctx_in == NULL)

		{

		if ((ctx=BN_CTX_new()) == NULL) goto err;

		}

	else

		ctx=ctx_in;

	if ((r=BN_new()) == NULL) goto err;

	/* Get random k */

	do

		if (!BN_rand_range(&k, dsa->q)) goto err;

	while (BN_is_zero(&k));

	if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)

		{

		BN_set_flags(&k, BN_FLG_CONSTTIME);

		}

	if (dsa->flags & DSA_FLAG_CACHE_MONT_P)

		{

		if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,

						CRYPTO_LOCK_DSA,

						dsa->p, ctx))

			goto err;

		}

	/* Compute r = (g^k mod p) mod q */

	if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)

		{

		if (!BN_copy(&kq, &k)) goto err;

		/* We do not want timing information to leak the length of k,

		 * so we compute g^k using an equivalent exponent of fixed length.

		 *

		 * (This is a kludge that we need because the BN_mod_exp_mont()

		 * does not let us specify the desired timing behaviour.) */

		if (!BN_add(&kq, &kq, dsa->q)) goto err;

		if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))

			{

			if (!BN_add(&kq, &kq, dsa->q)) goto err;

			}

		K = &kq;

		}

	else

		{

		K = &k;

		}

	DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,

			dsa->method_mont_p);

	if (!BN_mod(r,r,dsa->q,ctx)) goto err;

	/* Compute  part of 's = inv(k) (m + xr) mod q' */

	if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;

	if (*kinvp != NULL) BN_clear_free(*kinvp);

	*kinvp=kinv;

	kinv=NULL;

	if (*rp != NULL) BN_clear_free(*rp);

	*rp=r;

	ret=1;

err:

	if (!ret)

		{

		DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);

		if (kinv != NULL) BN_clear_free(kinv);

		if (r != NULL) BN_clear_free(r);

		}

	if (ctx_in == NULL) BN_CTX_free(ctx);

	if (kinv != NULL) BN_clear_free(kinv);

	BN_clear_free(&k);

	BN_clear_free(&kq);

	return(ret);

	}

static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,

		  DSA *dsa)

	{

	BN_CTX *ctx;

	BIGNUM u1,u2,t1;

	BN_MONT_CTX *mont=NULL;

	int ret = -1;

	if (!dsa->p || !dsa->q || !dsa->g)

		{

		DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);

		return -1;

		}

	if (BN_num_bits(dsa->q) != 160)

		{

		DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);

		return -1;

		}

	if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)

		{

		DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);

		return -1;

		}

	BN_init(&u1);

	BN_init(&u2);

	BN_init(&t1);

	if ((ctx=BN_CTX_new()) == NULL) goto err;

	if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||

	    BN_ucmp(sig->r, dsa->q) >= 0)

		{

		ret = 0;

		goto err;

		}

	if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||

	    BN_ucmp(sig->s, dsa->q) >= 0)

		{

		ret = 0;

		goto err;

		}

	/* Calculate W = inv(S) mod Q

	 * save W in u2 */

	if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;

	/* save M in u1 */

	if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;

	/* u1 = M * w mod q */

	if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;

	/* u2 = r * w mod q */

	if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;

	if (dsa->flags & DSA_FLAG_CACHE_MONT_P)

		{

		mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,

					CRYPTO_LOCK_DSA, dsa->p, ctx);

		if (!mont)

			goto err;

		}

	DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);

	/* BN_copy(&u1,&t1); */

	/* let u1 = u1 mod q */

	if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;

	/* V is now in u1.  If the signature is correct, it will be

	 * equal to R. */

	ret=(BN_ucmp(&u1, sig->r) == 0);

	err:

	/* XXX: surely this is wrong - if ret is 0, it just didn't verify;

	   there is no error in BN. Test should be ret == -1 (Ben) */

	if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);

	if (ctx != NULL) BN_CTX_free(ctx);

	BN_free(&u1);

	BN_free(&u2);

	BN_free(&t1);

	return(ret);

	}

static int dsa_init(DSA *dsa)

{

	dsa->flags|=DSA_FLAG_CACHE_MONT_P;

	return(1);

}

static int dsa_finish(DSA *dsa)

{

	if(dsa->method_mont_p)

		BN_MONT_CTX_free(dsa->method_mont_p);

	return(1);

}