/* crypto/ecdh/ec_kdf.c */

/*

 * Written by Stephen Henson for the OpenSSL project.

 */

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

 * Copyright (c) 2013 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.

 * ====================================================================

 */

#define OPENSSL_FIPSAPI

#include <string.h>

#include <openssl/ecdh.h>

#include <openssl/evp.h>

/* Key derivation function from X9.62/SECG */

/* Way more than we will ever need */

#define ECDH_KDF_MAX    (1 << 30)

int ECDH_KDF_X9_62(unsigned char *out, size_t outlen,

                   const unsigned char *Z, size_t Zlen,

                   const unsigned char *sinfo, size_t sinfolen,

                   const EVP_MD *md)

{

    EVP_MD_CTX mctx;

    int rv = 0;

    unsigned int i;

    size_t mdlen;

    unsigned char ctr[4];

    if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX

        || Zlen > ECDH_KDF_MAX)

        return 0;

    mdlen = EVP_MD_size(md);

    EVP_MD_CTX_init(&mctx);

    for (i = 1;; i++) {

        unsigned char mtmp[EVP_MAX_MD_SIZE];

        EVP_DigestInit_ex(&mctx, md, NULL);

        ctr[3] = i & 0xFF;

        ctr[2] = (i >> 8) & 0xFF;

        ctr[1] = (i >> 16) & 0xFF;

        ctr[0] = (i >> 24) & 0xFF;

        if (!EVP_DigestUpdate(&mctx, Z, Zlen))

            goto err;

        if (!EVP_DigestUpdate(&mctx, ctr, sizeof(ctr)))

            goto err;

        if (!EVP_DigestUpdate(&mctx, sinfo, sinfolen))

            goto err;

        if (outlen >= mdlen) {

            if (!EVP_DigestFinal(&mctx, out, NULL))

                goto err;

            outlen -= mdlen;

            if (outlen == 0)

                break;

            out += mdlen;

        } else {

            if (!EVP_DigestFinal(&mctx, mtmp, NULL))

                goto err;

            memcpy(out, mtmp, outlen);

            OPENSSL_cleanse(mtmp, mdlen);

            break;

        }

    }

    rv = 1;

 err:

    EVP_MD_CTX_cleanup(&mctx);

    return rv;

}