hmac.c

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/*
 * Copyright (c) 2006 - 2007 Kungliga Tekniska H鰃skolan
 * (Royal Institute of Technology, Stockholm, Sweden). 
 * 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. Neither the name of the Institute nor the names of its contributors 
 *    may be used to endorse or promote products derived from this software 
 *    without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``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 INSTITUTE 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. 
 */

#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <hmac.h>

void
HMAC_CTX_init(HMAC_CTX *ctx)
{
    memset(ctx, 0, sizeof(*ctx));
}

void
HMAC_CTX_cleanup(HMAC_CTX *ctx)
{
    if (ctx->buf) {
	memset(ctx->buf, 0, ctx->key_length);
	free(ctx->buf);
	ctx->buf = NULL;
    }
    if (ctx->opad) {
	memset(ctx->ipad, 0, ctx->key_length);
	free(ctx->opad);
	ctx->opad = NULL;
    }
    if (ctx->ipad) {
	memset(ctx->ipad, 0, ctx->key_length);
	free(ctx->ipad);
	ctx->ipad = NULL;
    }
    if (ctx->ctx) {
	EVP_MD_CTX_destroy(ctx->ctx);
	ctx->ctx = NULL;
    }
}

size_t
HMAC_size(const HMAC_CTX *ctx)
{
    return EVP_MD_size(ctx->md);
}

void
HMAC_Init_ex(HMAC_CTX *ctx,
	     const void *key,
	     size_t keylen,
	     const EVP_MD *md,
	     ENGINE *engine)
{
    unsigned char *p;
    size_t i;

    if (ctx->md != md) {
	ctx->md = md;
	if (ctx->buf) {
	    memset(ctx->buf, 0, ctx->key_length);
	    free (ctx->buf);
	}
	ctx->key_length = EVP_MD_size(ctx->md);
	ctx->buf = malloc(ctx->key_length);
    }
#if 0
    ctx->engine = engine;
#endif

    if (keylen > EVP_MD_block_size(ctx->md)) {
	EVP_Digest(key, keylen, ctx->buf, NULL, ctx->md, engine);
	key = ctx->buf;
	keylen = EVP_MD_size(ctx->md);
    }

    if (ctx->opad) {
	memset(ctx->opad, 0, ctx->key_length);
	free(ctx->opad);
    }
    if (ctx->ipad) {
	memset(ctx->ipad, 0, ctx->key_length);
	free(ctx->ipad);
    }

    ctx->opad = malloc(EVP_MD_block_size(ctx->md));
    ctx->ipad = malloc(EVP_MD_block_size(ctx->md));
    memset(ctx->ipad, 0x36, EVP_MD_block_size(ctx->md));
    memset(ctx->opad, 0x5c, EVP_MD_block_size(ctx->md));

    for (i = 0, p = ctx->ipad; i < keylen; i++)
	p[i] ^= ((const unsigned char *)key)[i];
    for (i = 0, p = ctx->opad; i < keylen; i++)
	p[i] ^= ((const unsigned char *)key)[i];

    ctx->ctx = EVP_MD_CTX_create();

    EVP_DigestInit_ex(ctx->ctx, ctx->md, ctx->engine);
    EVP_DigestUpdate(ctx->ctx, ctx->ipad, EVP_MD_block_size(ctx->md));
}

void
HMAC_Update(HMAC_CTX *ctx, const void *data, size_t len)
{
    EVP_DigestUpdate(ctx->ctx, data, len);
}

void
HMAC_Final(HMAC_CTX *ctx, void *md, unsigned int *len)
{
    EVP_DigestFinal_ex(ctx->ctx, ctx->buf, NULL);

    EVP_DigestInit_ex(ctx->ctx, ctx->md, ctx->engine);
    EVP_DigestUpdate(ctx->ctx, ctx->opad, EVP_MD_block_size(ctx->md));
    EVP_DigestUpdate(ctx->ctx, ctx->buf, ctx->key_length);
    EVP_DigestFinal_ex(ctx->ctx, md, len);
}

void *
HMAC(const EVP_MD *md,
     const void *key, size_t key_size,
     const void *data, size_t data_size, 
     void *hash, unsigned int *hash_len)
{
    HMAC_CTX ctx;

    HMAC_CTX_init(&ctx);
    HMAC_Init_ex(&ctx, key, key_size, md, NULL);
    HMAC_Update(&ctx, data, data_size);
    HMAC_Final(&ctx, hash, hash_len);
    HMAC_CTX_cleanup(&ctx);
    return hash;
}