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/*
* hmac.c
*
* implementation of hmac auth_type_t
*
* David A. McGrew
* Cisco Systems, Inc.
*/
/*
*
* Copyright(c) 2001-2006 Cisco Systems, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 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.
*
* Neither the name of the Cisco Systems, Inc. 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 COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDERS 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 "hmac.h"
#include "alloc.h"
/* the debug module for authentiation */
debug_module_t mod_hmac = {
0, /* debugging is off by default */
"hmac sha-1" /* printable name for module */
};
err_status_t
hmac_alloc(auth_t **a, int key_len, int out_len) {
extern auth_type_t hmac;
uint8_t *pointer;
debug_print(mod_hmac, "allocating auth func with key length %d", key_len);
debug_print(mod_hmac, " tag length %d", out_len);
/*
* check key length - note that we don't support keys larger
* than 20 bytes yet
*/
if (key_len > 20)
return err_status_bad_param;
/* check output length - should be less than 20 bytes */
if (out_len > 20)
return err_status_bad_param;
/* allocate memory for auth and hmac_ctx_t structures */
pointer = (uint8_t*)crypto_alloc(sizeof(hmac_ctx_t) + sizeof(auth_t));
if (pointer == NULL)
return err_status_alloc_fail;
/* set pointers */
*a = (auth_t *)pointer;
(*a)->type = &hmac;
(*a)->state = pointer + sizeof(auth_t);
(*a)->out_len = out_len;
(*a)->key_len = key_len;
(*a)->prefix_len = 0;
/* increment global count of all hmac uses */
hmac.ref_count++;
return err_status_ok;
}
err_status_t
hmac_dealloc(auth_t *a) {
extern auth_type_t hmac;
/* zeroize entire state*/
octet_string_set_to_zero((uint8_t *)a,
sizeof(hmac_ctx_t) + sizeof(auth_t));
/* free memory */
crypto_free(a);
/* decrement global count of all hmac uses */
hmac.ref_count--;
return err_status_ok;
}
err_status_t
hmac_init(hmac_ctx_t *state, const uint8_t *key, int key_len) {
int i;
uint8_t ipad[64];
/*
* check key length - note that we don't support keys larger
* than 20 bytes yet
*/
if (key_len > 20)
return err_status_bad_param;
/*
* set values of ipad and opad by exoring the key into the
* appropriate constant values
*/
for (i=0; i < key_len; i++) {
ipad[i] = key[i] ^ 0x36;
state->opad[i] = key[i] ^ 0x5c;
}
/* set the rest of ipad, opad to constant values */
for ( ; i < 64; i++) {
ipad[i] = 0x36;
((uint8_t *)state->opad)[i] = 0x5c;
}
debug_print(mod_hmac, "ipad: %s", octet_string_hex_string(ipad, 64));
/* initialize sha1 context */
sha1_init(&state->init_ctx);
/* hash ipad ^ key */
sha1_update(&state->init_ctx, ipad, 64);
memcpy(&state->ctx, &state->init_ctx, sizeof(sha1_ctx_t));
return err_status_ok;
}
err_status_t
hmac_start(hmac_ctx_t *state) {
memcpy(&state->ctx, &state->init_ctx, sizeof(sha1_ctx_t));
return err_status_ok;
}
err_status_t
hmac_update(hmac_ctx_t *state, const uint8_t *message, int msg_octets) {
debug_print(mod_hmac, "input: %s",
octet_string_hex_string(message, msg_octets));
/* hash message into sha1 context */
sha1_update(&state->ctx, message, msg_octets);
return err_status_ok;
}
err_status_t
hmac_compute(hmac_ctx_t *state, const void *message,
int msg_octets, int tag_len, uint8_t *result) {
uint32_t hash_value[5];
uint32_t H[5];
int i;
/* check tag length, return error if we can't provide the value expected */
if (tag_len > 20)
return err_status_bad_param;
/* hash message, copy output into H */
hmac_update(state, (const uint8_t*)message, msg_octets);
sha1_final(&state->ctx, H);
/*
* note that we don't need to debug_print() the input, since the
* function hmac_update() already did that for us
*/
debug_print(mod_hmac, "intermediate state: %s",
octet_string_hex_string((uint8_t *)H, 20));
/* re-initialize hash context */
sha1_init(&state->ctx);
/* hash opad ^ key */
sha1_update(&state->ctx, (uint8_t *)state->opad, 64);
/* hash the result of the inner hash */
sha1_update(&state->ctx, (uint8_t *)H, 20);
/* the result is returned in the array hash_value[] */
sha1_final(&state->ctx, hash_value);
/* copy hash_value to *result */
for (i=0; i < tag_len; i++)
result[i] = ((uint8_t *)hash_value)[i];
debug_print(mod_hmac, "output: %s",
octet_string_hex_string((uint8_t *)hash_value, tag_len));
return err_status_ok;
}
/* begin test case 0 */
uint8_t
hmac_test_case_0_key[20] = {
0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
0x0b, 0x0b, 0x0b, 0x0b
};
uint8_t
hmac_test_case_0_data[8] = {
0x48, 0x69, 0x20, 0x54, 0x68, 0x65, 0x72, 0x65 /* "Hi There" */
};
uint8_t
hmac_test_case_0_tag[20] = {
0xb6, 0x17, 0x31, 0x86, 0x55, 0x05, 0x72, 0x64,
0xe2, 0x8b, 0xc0, 0xb6, 0xfb, 0x37, 0x8c, 0x8e,
0xf1, 0x46, 0xbe, 0x00
};
auth_test_case_t
hmac_test_case_0 = {
20, /* octets in key */
hmac_test_case_0_key, /* key */
8, /* octets in data */
hmac_test_case_0_data, /* data */
20, /* octets in tag */
hmac_test_case_0_tag, /* tag */
NULL /* pointer to next testcase */
};
/* end test case 0 */
char hmac_description[] = "hmac sha-1 authentication function";
/*
* auth_type_t hmac is the hmac metaobject
*/
auth_type_t
hmac = {
(auth_alloc_func) hmac_alloc,
(auth_dealloc_func) hmac_dealloc,
(auth_init_func) hmac_init,
(auth_compute_func) hmac_compute,
(auth_update_func) hmac_update,
(auth_start_func) hmac_start,
(char *) hmac_description,
(int) 0, /* instance count */
(auth_test_case_t *) &hmac_test_case_0,
(debug_module_t *) &mod_hmac
};
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