/* crypto/ecdh/ech_ossl.c */

/* ====================================================================

 * Copyright 2002 Sun Microsystems, Inc. ALL RIGHTS RESERVED.

 *

 * The Elliptic Curve Public-Key Crypto Library (ECC Code) included

 * herein is developed by SUN MICROSYSTEMS, INC., and is contributed

 * to the OpenSSL project.

 *

 * The ECC Code is licensed pursuant to the OpenSSL open source

 * license provided below.

 *

 * The ECDH software is originally written by Douglas Stebila of

 * Sun Microsystems Laboratories.

 *

 */

/* ====================================================================

 * Copyright (c) 1998-2003 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 <string.h>

#include <limits.h>

#include "cryptlib.h"

#include "ech_locl.h"

#include <openssl/err.h>

#include <openssl/sha.h>

#include <openssl/obj_mac.h>

#include <openssl/bn.h>

static int ecdh_compute_key(void *out, size_t len, const EC_POINT *pub_key,

                            EC_KEY *ecdh,

                            void *(*KDF) (const void *in, size_t inlen,

                                          void *out, size_t *outlen));

static ECDH_METHOD openssl_ecdh_meth = {

    "OpenSSL ECDH method",

    ecdh_compute_key,

#if 0

    NULL,                       /* init */

    NULL,                       /* finish */

#endif

    0,                          /* flags */

    NULL                        /* app_data */

};

const ECDH_METHOD *ECDH_OpenSSL(void)

{

    return &openssl_ecdh_meth;

}

/*-

 * This implementation is based on the following primitives in the IEEE 1363 standard:

 *  - ECKAS-DH1

 *  - ECSVDP-DH

 * Finally an optional KDF is applied.

 */

static int ecdh_compute_key(void *out, size_t outlen, const EC_POINT *pub_key,

                            EC_KEY *ecdh,

                            void *(*KDF) (const void *in, size_t inlen,

                                          void *out, size_t *outlen))

{

    BN_CTX *ctx;

    EC_POINT *tmp = NULL;

    BIGNUM *x = NULL, *y = NULL;

    const BIGNUM *priv_key;

    const EC_GROUP *group;

    int ret = -1;

    size_t buflen, len;

    unsigned char *buf = NULL;

    if (outlen > INT_MAX) {

        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE); /* sort of,

                                                                 * anyway */

        return -1;

    }

    if ((ctx = BN_CTX_new()) == NULL)

        goto err;

    BN_CTX_start(ctx);

    x = BN_CTX_get(ctx);

    y = BN_CTX_get(ctx);

    priv_key = EC_KEY_get0_private_key(ecdh);

    if (priv_key == NULL) {

        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_NO_PRIVATE_VALUE);

        goto err;

    }

    group = EC_KEY_get0_group(ecdh);

    if (EC_KEY_get_flags(ecdh) & EC_FLAG_COFACTOR_ECDH) {

        if (!EC_GROUP_get_cofactor(group, x, ctx) ||

            !BN_mul(x, x, priv_key, ctx)) {

            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);

            goto err;

        }

        priv_key = x;

    }

    if ((tmp = EC_POINT_new(group)) == NULL) {

        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    if (!EC_POINT_mul(group, tmp, NULL, pub_key, priv_key, ctx)) {

        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);

        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, x, y, ctx)) {

            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);

            goto err;

        }

    }

#ifndef OPENSSL_NO_EC2M

    else {

        if (!EC_POINT_get_affine_coordinates_GF2m(group, tmp, x, y, ctx)) {

            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_POINT_ARITHMETIC_FAILURE);

            goto err;

        }

    }

#endif

    buflen = (EC_GROUP_get_degree(group) + 7) / 8;

    len = BN_num_bytes(x);

    if (len > buflen) {

        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_INTERNAL_ERROR);

        goto err;

    }

    if ((buf = OPENSSL_malloc(buflen)) == NULL) {

        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    memset(buf, 0, buflen - len);

    if (len != (size_t)BN_bn2bin(x, buf + buflen - len)) {

        ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ERR_R_BN_LIB);

        goto err;

    }

    if (KDF != 0) {

        if (KDF(buf, buflen, out, &outlen) == NULL) {

            ECDHerr(ECDH_F_ECDH_COMPUTE_KEY, ECDH_R_KDF_FAILED);

            goto err;

        }

        ret = outlen;

    } else {

        /* no KDF, just copy as much as we can */

        if (outlen > buflen)

            outlen = buflen;

        memcpy(out, buf, outlen);

        ret = outlen;

    }

 err:

    if (tmp)

        EC_POINT_free(tmp);

    if (ctx)

        BN_CTX_end(ctx);

    if (ctx)

        BN_CTX_free(ctx);

    if (buf) {

        OPENSSL_cleanse(buf, buflen);

        OPENSSL_free(buf);

    }

    return (ret);

}