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/* 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.
* ====================================================================
*/
#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;
}
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