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/*
* Copyright (C) 2005-2006 Martin Willi
* Copyright (C) 2005 Jan Hutter
* Hochschule fuer Technik Rapperswil
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General hmac License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General hmac License
* for more details.
*
* $Id: hmac.c 3488 2008-02-21 15:10:02Z martin $
*/
#include <string.h>
#include "hmac.h"
typedef struct private_hmac_t private_hmac_t;
/**
* Private data of a hmac_t object.
*
* The variable names are the same as in the RFC.
*/
struct private_hmac_t {
/**
* Public hmac_t interface.
*/
hmac_t hmac;
/**
* Block size, as in RFC.
*/
u_int8_t b;
/**
* Hash function.
*/
hasher_t *h;
/**
* Previously xor'ed key using opad.
*/
chunk_t opaded_key;
/**
* Previously xor'ed key using ipad.
*/
chunk_t ipaded_key;
};
/**
* Implementation of hmac_t.get_mac.
*/
static void get_mac(private_hmac_t *this, chunk_t data, u_int8_t *out)
{
/* H(K XOR opad, H(K XOR ipad, text))
*
* if out is NULL, we append text to the inner hash.
* else, we complete the inner and do the outer.
*
*/
u_int8_t buffer[this->h->get_hash_size(this->h)];
chunk_t inner;
if (out == NULL)
{
/* append data to inner */
this->h->get_hash(this->h, data, NULL);
}
else
{
/* append and do outer hash */
inner.ptr = buffer;
inner.len = this->h->get_hash_size(this->h);
/* complete inner */
this->h->get_hash(this->h, data, buffer);
/* do outer */
this->h->get_hash(this->h, this->opaded_key, NULL);
this->h->get_hash(this->h, inner, out);
/* reinit for next call */
this->h->get_hash(this->h, this->ipaded_key, NULL);
}
}
/**
* Implementation of hmac_t.allocate_mac.
*/
static void allocate_mac(private_hmac_t *this, chunk_t data, chunk_t *out)
{
/* allocate space and use get_mac */
if (out == NULL)
{
/* append mode */
this->hmac.get_mac(&(this->hmac), data, NULL);
}
else
{
out->len = this->h->get_hash_size(this->h);
out->ptr = malloc(out->len);
this->hmac.get_mac(&(this->hmac), data, out->ptr);
}
}
/**
* Implementation of hmac_t.get_block_size.
*/
static size_t get_block_size(private_hmac_t *this)
{
return this->h->get_hash_size(this->h);
}
/**
* Implementation of hmac_t.set_key.
*/
static void set_key(private_hmac_t *this, chunk_t key)
{
int i;
u_int8_t buffer[this->b];
memset(buffer, 0, this->b);
if (key.len > this->b)
{
/* if key is too long, it will be hashed */
this->h->get_hash(this->h, key, buffer);
}
else
{
/* if not, just copy it in our pre-padded k */
memcpy(buffer, key.ptr, key.len);
}
/* apply ipad and opad to key */
for (i = 0; i < this->b; i++)
{
this->ipaded_key.ptr[i] = buffer[i] ^ 0x36;
this->opaded_key.ptr[i] = buffer[i] ^ 0x5C;
}
/* begin hashing of inner pad */
this->h->reset(this->h);
this->h->get_hash(this->h, this->ipaded_key, NULL);
}
/**
* Implementation of hmac_t.destroy.
*/
static void destroy(private_hmac_t *this)
{
this->h->destroy(this->h);
free(this->opaded_key.ptr);
free(this->ipaded_key.ptr);
free(this);
}
/*
* Described in header
*/
hmac_t *hmac_create(hash_algorithm_t hash_algorithm)
{
private_hmac_t *this = malloc_thing(private_hmac_t);
/* set hmac_t methods */
this->hmac.get_mac = (void (*)(hmac_t *,chunk_t,u_int8_t*))get_mac;
this->hmac.allocate_mac = (void (*)(hmac_t *,chunk_t,chunk_t*))allocate_mac;
this->hmac.get_block_size = (size_t (*)(hmac_t *))get_block_size;
this->hmac.set_key = (void (*)(hmac_t *,chunk_t))set_key;
this->hmac.destroy = (void (*)(hmac_t *))destroy;
/* set b, according to hasher */
switch (hash_algorithm)
{
case HASH_SHA1:
case HASH_MD5:
case HASH_SHA256:
this->b = 64;
break;
case HASH_SHA384:
case HASH_SHA512:
this->b = 128;
break;
default:
free(this);
return NULL;
}
/* build the hasher */
this->h = lib->crypto->create_hasher(lib->crypto, hash_algorithm);
if (this->h == NULL)
{
free(this);
return NULL;
}
/* build ipad and opad */
this->opaded_key.ptr = malloc(this->b);
this->opaded_key.len = this->b;
this->ipaded_key.ptr = malloc(this->b);
this->ipaded_key.len = this->b;
return &(this->hmac);
}
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