/* $OpenBSD: ecs_ossl.c,v 1.9 2017/01/29 17:49:23 beck Exp $ */
/*
 * Written by Nils Larsch for the OpenSSL project
 */
/* ====================================================================
 * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.
 *
 * 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 above 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 acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@OpenSSL.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED 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 OpenSSL PROJECT OR
 * ITS 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.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * (eay@cryptsoft.com).  This product includes software written by Tim
 * Hudson (tjh@cryptsoft.com).
 *
 */

#include <openssl/opensslconf.h>

#include <openssl/err.h>
#include <openssl/obj_mac.h>
#include <openssl/bn.h>

#include "bn_lcl.h"
#include "ecs_locl.h"

static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen,
    const BIGNUM *, const BIGNUM *, EC_KEY *eckey);
static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
    BIGNUM **rp);
static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
    const ECDSA_SIG *sig, EC_KEY *eckey);

static ECDSA_METHOD openssl_ecdsa_meth = {
	.name = "OpenSSL ECDSA method",
	.ecdsa_do_sign = ecdsa_do_sign,
	.ecdsa_sign_setup = ecdsa_sign_setup,
	.ecdsa_do_verify = ecdsa_do_verify
};

const ECDSA_METHOD *
ECDSA_OpenSSL(void)
{
	return &openssl_ecdsa_meth;
}

static int
ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
{
	BN_CTX   *ctx = NULL;
	BIGNUM	 *k = NULL, *r = NULL, *order = NULL, *X = NULL;
	EC_POINT *tmp_point = NULL;
	const EC_GROUP *group;
	int 	 ret = 0;

	if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
		ECDSAerror(ERR_R_PASSED_NULL_PARAMETER);
		return 0;
	}

	if (ctx_in == NULL) {
		if ((ctx = BN_CTX_new()) == NULL) {
			ECDSAerror(ERR_R_MALLOC_FAILURE);
			return 0;
		}
	} else
		ctx = ctx_in;

	k = BN_new();	/* this value is later returned in *kinvp */
	r = BN_new();	/* this value is later returned in *rp    */
	order = BN_new();
	X = BN_new();
	if (!k || !r || !order || !X) {
		ECDSAerror(ERR_R_MALLOC_FAILURE);
		goto err;
	}
	if ((tmp_point = EC_POINT_new(group)) == NULL) {
		ECDSAerror(ERR_R_EC_LIB);
		goto err;
	}
	if (!EC_GROUP_get_order(group, order, ctx)) {
		ECDSAerror(ERR_R_EC_LIB);
		goto err;
	}

	do {
		/* get random k */
		do
			if (!BN_rand_range(k, order)) {
				ECDSAerror(ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);
				goto err;
			}
		while (BN_is_zero(k));

		/* We do not want timing information to leak the length of k,
		 * so we compute G*k using an equivalent scalar of fixed
		 * bit-length. */
		if (!BN_add(k, k, order))
			goto err;
		if (BN_num_bits(k) <= BN_num_bits(order))
			if (!BN_add(k, k, order))
				goto err;

		BN_set_flags(k, BN_FLG_CONSTTIME);

		/* compute r the x-coordinate of generator * k */
		if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
			ECDSAerror(ERR_R_EC_LIB);
			goto err;
		}
		if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
		    NID_X9_62_prime_field) {
			if (!EC_POINT_get_affine_coordinates_GFp(group,
			    tmp_point, X, NULL, ctx)) {
				ECDSAerror(ERR_R_EC_LIB);
				goto err;
			}
		}
#ifndef OPENSSL_NO_EC2M
		else /* NID_X9_62_characteristic_two_field */
		{
			if (!EC_POINT_get_affine_coordinates_GF2m(group,
			    tmp_point, X, NULL, ctx)) {
				ECDSAerror(ERR_R_EC_LIB);
				goto err;
			}
		}
#endif
		if (!BN_nnmod(r, X, order, ctx)) {
			ECDSAerror(ERR_R_BN_LIB);
			goto err;
		}
	} while (BN_is_zero(r));

	/* compute the inverse of k */
	if (!BN_mod_inverse_ct(k, k, order, ctx)) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	/* clear old values if necessary */
	BN_clear_free(*rp);
	BN_clear_free(*kinvp);
	/* save the pre-computed values  */
	*rp = r;
	*kinvp = k;
	ret = 1;

err:
	if (!ret) {
		BN_clear_free(k);
		BN_clear_free(r);
	}
	if (ctx_in == NULL)
		BN_CTX_free(ctx);
	BN_free(order);
	EC_POINT_free(tmp_point);
	BN_clear_free(X);
	return (ret);
}


static ECDSA_SIG *
ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
    const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey)
{
	int     ok = 0, i;
	BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;
	const BIGNUM *ckinv;
	BN_CTX     *ctx = NULL;
	const EC_GROUP   *group;
	ECDSA_SIG  *ret;
	ECDSA_DATA *ecdsa;
	const BIGNUM *priv_key;

	ecdsa = ecdsa_check(eckey);
	group = EC_KEY_get0_group(eckey);
	priv_key = EC_KEY_get0_private_key(eckey);

	if (group == NULL || priv_key == NULL || ecdsa == NULL) {
		ECDSAerror(ERR_R_PASSED_NULL_PARAMETER);
		return NULL;
	}

	ret = ECDSA_SIG_new();
	if (!ret) {
		ECDSAerror(ERR_R_MALLOC_FAILURE);
		return NULL;
	}
	s = ret->s;

	if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
	    (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
		ECDSAerror(ERR_R_MALLOC_FAILURE);
		goto err;
	}

	if (!EC_GROUP_get_order(group, order, ctx)) {
		ECDSAerror(ERR_R_EC_LIB);
		goto err;
	}
	i = BN_num_bits(order);
	/* Need to truncate digest if it is too long: first truncate whole
	 * bytes.
	 */
	if (8 * dgst_len > i)
		dgst_len = (i + 7)/8;
	if (!BN_bin2bn(dgst, dgst_len, m)) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	/* If still too long truncate remaining bits with a shift */
	if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	do {
		if (in_kinv == NULL || in_r == NULL) {
			if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) {
				ECDSAerror(ERR_R_ECDSA_LIB);
				goto err;
			}
			ckinv = kinv;
		} else {
			ckinv = in_kinv;
			if (BN_copy(ret->r, in_r) == NULL) {
				ECDSAerror(ERR_R_MALLOC_FAILURE);
				goto err;
			}
		}

		if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
			ECDSAerror(ERR_R_BN_LIB);
			goto err;
		}
		if (!BN_mod_add_quick(s, tmp, m, order)) {
			ECDSAerror(ERR_R_BN_LIB);
			goto err;
		}
		if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
			ECDSAerror(ERR_R_BN_LIB);
			goto err;
		}
		if (BN_is_zero(s)) {
			/* if kinv and r have been supplied by the caller
			 * don't to generate new kinv and r values */
			if (in_kinv != NULL && in_r != NULL) {
				ECDSAerror(ECDSA_R_NEED_NEW_SETUP_VALUES);
				goto err;
			}
		} else
			/* s != 0 => we have a valid signature */
			break;
	} while (1);

	ok = 1;

err:
	if (!ok) {
		ECDSA_SIG_free(ret);
		ret = NULL;
	}
	BN_CTX_free(ctx);
	BN_clear_free(m);
	BN_clear_free(tmp);
	BN_free(order);
	BN_clear_free(kinv);
	return ret;
}

static int
ecdsa_do_verify(const unsigned char *dgst, int dgst_len, const ECDSA_SIG *sig,
    EC_KEY *eckey)
{
	int ret = -1, i;
	BN_CTX   *ctx;
	BIGNUM   *order, *u1, *u2, *m, *X;
	EC_POINT *point = NULL;
	const EC_GROUP *group;
	const EC_POINT *pub_key;

	/* check input values */
	if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
	    (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
		ECDSAerror(ECDSA_R_MISSING_PARAMETERS);
		return -1;
	}

	ctx = BN_CTX_new();
	if (!ctx) {
		ECDSAerror(ERR_R_MALLOC_FAILURE);
		return -1;
	}
	BN_CTX_start(ctx);
	order = BN_CTX_get(ctx);
	u1 = BN_CTX_get(ctx);
	u2 = BN_CTX_get(ctx);
	m = BN_CTX_get(ctx);
	X = BN_CTX_get(ctx);
	if (!X) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}

	if (!EC_GROUP_get_order(group, order, ctx)) {
		ECDSAerror(ERR_R_EC_LIB);
		goto err;
	}

	if (BN_is_zero(sig->r)          || BN_is_negative(sig->r) ||
	    BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s)  ||
	    BN_is_negative(sig->s)      || BN_ucmp(sig->s, order) >= 0) {
		ECDSAerror(ECDSA_R_BAD_SIGNATURE);
		ret = 0;	/* signature is invalid */
		goto err;
	}
	/* calculate tmp1 = inv(S) mod order */
	if (!BN_mod_inverse_ct(u2, sig->s, order, ctx)) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	/* digest -> m */
	i = BN_num_bits(order);
	/* Need to truncate digest if it is too long: first truncate whole
	 * bytes.
	 */
	if (8 * dgst_len > i)
		dgst_len = (i + 7)/8;
	if (!BN_bin2bn(dgst, dgst_len, m)) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	/* If still too long truncate remaining bits with a shift */
	if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	/* u1 = m * tmp mod order */
	if (!BN_mod_mul(u1, m, u2, order, ctx)) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	/* u2 = r * w mod q */
	if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}

	if ((point = EC_POINT_new(group)) == NULL) {
		ECDSAerror(ERR_R_MALLOC_FAILURE);
		goto err;
	}
	if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
		ECDSAerror(ERR_R_EC_LIB);
		goto err;
	}
	if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
	    NID_X9_62_prime_field) {
		if (!EC_POINT_get_affine_coordinates_GFp(group,
		    point, X, NULL, ctx)) {
			ECDSAerror(ERR_R_EC_LIB);
			goto err;
		}
	}
#ifndef OPENSSL_NO_EC2M
	else /* NID_X9_62_characteristic_two_field */
	{
		if (!EC_POINT_get_affine_coordinates_GF2m(group,
		    point, X, NULL, ctx)) {
			ECDSAerror(ERR_R_EC_LIB);
			goto err;
		}
	}
#endif
	if (!BN_nnmod(u1, X, order, ctx)) {
		ECDSAerror(ERR_R_BN_LIB);
		goto err;
	}
	/*  if the signature is correct u1 is equal to sig->r */
	ret = (BN_ucmp(u1, sig->r) == 0);

err:
	BN_CTX_end(ctx);
	BN_CTX_free(ctx);
	EC_POINT_free(point);
	return ret;
}