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