/* 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> */

#include <stdio.h>
#include <openssl/bn.h>
#include <openssl/dsa.h>
#include <openssl/rand.h>
#include <openssl/asn1.h>
#include <openssl/err.h>
#ifndef OPENSSL_NO_ENGINE
#include <openssl/engine.h>
#endif
#include <openssl/fips.h>

#ifdef OPENSSL_FIPS

static DSA_SIG *dsa_do_sign(const unsigned char *dgst, FIPS_DSA_SIZE_T 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, FIPS_DSA_SIZE_T dgst_len, DSA_SIG *sig,
		  DSA *dsa);
static int dsa_init(DSA *dsa);
static int dsa_finish(DSA *dsa);
static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
		BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
		BN_MONT_CTX *in_mont);
static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
				const BIGNUM *m, BN_CTX *ctx,
				BN_MONT_CTX *m_ctx);

static const DSA_METHOD openssl_dsa_meth = {
"OpenSSL FIPS DSA method",
dsa_do_sign,
dsa_sign_setup,
dsa_do_verify,
dsa_mod_exp,
dsa_bn_mod_exp,
dsa_init,
dsa_finish,
DSA_FLAG_FIPS_METHOD,
NULL
};
#if 0
int FIPS_dsa_check(struct dsa_st *dsa)
    {
    if(dsa->meth != &openssl_dsa_meth || dsa->meth->dsa_do_sign != dsa_do_sign
       || dsa->meth->dsa_sign_setup != dsa_sign_setup
       || dsa->meth->dsa_mod_exp != dsa_mod_exp
       || dsa->meth->bn_mod_exp != dsa_bn_mod_exp
       || dsa->meth->init != dsa_init
       || dsa->meth->finish != dsa_finish)
	{
	FIPSerr(FIPS_F_FIPS_DSA_CHECK,FIPS_R_NON_FIPS_METHOD);
	return 0;
	}
    return 1;
    }
#endif

const DSA_METHOD *DSA_OpenSSL(void)
{
	return &openssl_dsa_meth;
}

static DSA_SIG *dsa_do_sign(const unsigned char *dgst, FIPS_DSA_SIZE_T 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;

	if(FIPS_selftest_failed())
	    {
	    FIPSerr(FIPS_F_DSA_DO_SIGN,FIPS_R_FIPS_SELFTEST_FAILED);
	    return NULL;
	    }

	if (FIPS_mode() && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
		{
		DSAerr(DSA_F_DSA_DO_SIGN, DSA_R_KEY_SIZE_TOO_SMALL);
		return 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->meth->dsa_sign_setup(dsa,ctx,&kinv,&r)) goto err;

	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((BN_MONT_CTX **)&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;
		}
	if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,K,dsa->p,ctx,
		(BN_MONT_CTX *)dsa->method_mont_p)) goto err;
	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, FIPS_DSA_SIZE_T 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(FIPS_selftest_failed())
	    {
	    FIPSerr(FIPS_F_DSA_DO_VERIFY,FIPS_R_FIPS_SELFTEST_FAILED);
	    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;
		}

	if (FIPS_mode() && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS))
		{
		DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_KEY_SIZE_TOO_SMALL);
		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) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0)
		{
		ret = 0;
		goto err;
		}
	if (BN_is_zero(sig->s) || sig->s->neg || 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(
					(BN_MONT_CTX **)&dsa->method_mont_p,
					CRYPTO_LOCK_DSA, dsa->p, ctx);
		if (!mont)
			goto err;
		}

#if 0
	{
	BIGNUM t2;

	BN_init(&t2);
	/* v = ( g^u1 * y^u2 mod p ) mod q */
	/* let t1 = g ^ u1 mod p */
	if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err;
	/* let t2 = y ^ u2 mod p */
	if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err;
	/* let u1 = t1 * t2 mod p */
	if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn;
	BN_free(&t2);
	}
	/* let u1 = u1 mod q */
	if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err;
#else
	{
	if (!dsa->meth->dsa_mod_exp(dsa, &t1,dsa->g,&u1,dsa->pub_key,&u2,
						dsa->p,ctx,mont)) goto err;
	/* BN_copy(&u1,&t1); */
	/* let u1 = u1 mod q */
	if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
	}
#endif
	/* V is now in u1.  If the signature is correct, it will be
	 * equal to R. */
	ret=(BN_ucmp(&u1, sig->r) == 0);

	err:
	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)
{
	FIPS_selftest_check();
	dsa->flags|=DSA_FLAG_CACHE_MONT_P;
	return(1);
}

static int dsa_finish(DSA *dsa)
{
	if(dsa->method_mont_p)
		BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p);
	return(1);
}

static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
		BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
		BN_MONT_CTX *in_mont)
{
	return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont);
}
	
static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
				const BIGNUM *m, BN_CTX *ctx,
				BN_MONT_CTX *m_ctx)
{
	return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
}

#else /* ndef OPENSSL_FIPS */

static void *dummy=&dummy;

#endif /* ndef OPENSSL_FIPS */