/*

 * hmac.c

 *

 * implementation of hmac srtp_auth_type_t

 *

 * David A. McGrew

 * Cisco Systems, Inc.

 */

/*

 *

 * Copyright(c) 2001-2017 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.

 *

 */

#ifdef HAVE_CONFIG_H

#include <config.h>

#endif

#include "hmac.h"

#include "alloc.h"

#include "cipher_types.h"

#include "auth_test_cases.h"

/* the debug module for authentiation */

srtp_debug_module_t srtp_mod_hmac = {

    false,       /* debugging is off by default */

    "hmac sha-1" /* printable name for module   */

};

static srtp_err_status_t srtp_hmac_alloc(srtp_auth_t **a,

                                         size_t key_len,

                                         size_t out_len)

{

    extern const srtp_auth_type_t srtp_hmac;

    uint8_t *pointer;

    debug_print(srtp_mod_hmac, "allocating auth func with key length %zu",

                key_len);

    debug_print(srtp_mod_hmac, "                          tag length %zu",

                out_len);

    /*

     * check key length - note that we don't support keys larger

     * than 20 bytes yet

     */

    if (key_len > 20) {

        return srtp_err_status_bad_param;

    }

    /* check output length - should be less than 20 bytes */

    if (out_len > 20) {

        return srtp_err_status_bad_param;

    }

    /* allocate memory for auth and srtp_hmac_ctx_t structures */

    pointer = (uint8_t *)srtp_crypto_alloc(sizeof(srtp_hmac_ctx_t) +

                                           sizeof(srtp_auth_t));

    if (pointer == NULL) {

        return srtp_err_status_alloc_fail;

    }

    /* set pointers */

    *a = (srtp_auth_t *)pointer;

    (*a)->type = &srtp_hmac;

    (*a)->state = pointer + sizeof(srtp_auth_t);

    (*a)->out_len = out_len;

    (*a)->key_len = key_len;

    (*a)->prefix_len = 0;

    return srtp_err_status_ok;

}

static srtp_err_status_t srtp_hmac_dealloc(srtp_auth_t *a)

{

    /* zeroize entire state*/

    octet_string_set_to_zero(a, sizeof(srtp_hmac_ctx_t) + sizeof(srtp_auth_t));

    /* free memory */

    srtp_crypto_free(a);

    return srtp_err_status_ok;

}

static srtp_err_status_t srtp_hmac_init(void *statev,

                                        const uint8_t *key,

                                        size_t key_len)

{

    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;

    uint8_t ipad[64];

    /*

     * check key length - note that we don't support keys larger

     * than 20 bytes yet

     */

    if (key_len > 20) {

        return srtp_err_status_bad_param;

    }

    /*

     * set values of ipad and opad by exoring the key into the

     * appropriate constant values

     */

    for (size_t 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 (size_t i = key_len; i < 64; i++) {

        ipad[i] = 0x36;

        ((uint8_t *)state->opad)[i] = 0x5c;

    }

    debug_print(srtp_mod_hmac, "ipad: %s",

                srtp_octet_string_hex_string(ipad, 64));

    /* initialize sha1 context */

    srtp_sha1_init(&state->init_ctx);

    /* hash ipad ^ key */

    srtp_sha1_update(&state->init_ctx, ipad, 64);

    memcpy(&state->ctx, &state->init_ctx, sizeof(srtp_sha1_ctx_t));

    return srtp_err_status_ok;

}

static srtp_err_status_t srtp_hmac_start(void *statev)

{

    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;

    memcpy(&state->ctx, &state->init_ctx, sizeof(srtp_sha1_ctx_t));

    return srtp_err_status_ok;

}

static srtp_err_status_t srtp_hmac_update(void *statev,

                                          const uint8_t *message,

                                          size_t msg_octets)

{

    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;

    debug_print(srtp_mod_hmac, "input: %s",

                srtp_octet_string_hex_string(message, msg_octets));

    /* hash message into sha1 context */

    srtp_sha1_update(&state->ctx, message, msg_octets);

    return srtp_err_status_ok;

}

static srtp_err_status_t srtp_hmac_compute(void *statev,

                                           const uint8_t *message,

                                           size_t msg_octets,

                                           size_t tag_len,

                                           uint8_t *result)

{

    srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;

    uint32_t hash_value[5];

    uint32_t H[5];

    size_t i;

    /* check tag length, return error if we can't provide the value expected */

    if (tag_len > 20) {

        return srtp_err_status_bad_param;

    }

    /* hash message, copy output into H */

    srtp_hmac_update(state, message, msg_octets);

    srtp_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(srtp_mod_hmac, "intermediate state: %s",

                srtp_octet_string_hex_string((uint8_t *)H, 20));

    /* re-initialize hash context */

    srtp_sha1_init(&state->ctx);

    /* hash opad ^ key  */

    srtp_sha1_update(&state->ctx, (uint8_t *)state->opad, 64);

    /* hash the result of the inner hash */

    srtp_sha1_update(&state->ctx, (uint8_t *)H, 20);

    /* the result is returned in the array hash_value[] */

    srtp_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(srtp_mod_hmac, "output: %s",

                srtp_octet_string_hex_string((uint8_t *)hash_value, tag_len));

    return srtp_err_status_ok;

}

static const char srtp_hmac_description[] =

    "hmac sha-1 authentication function";

/*

 * srtp_auth_type_t hmac is the hmac metaobject

 */

const srtp_auth_type_t srtp_hmac = {

    srtp_hmac_alloc,        /* */

    srtp_hmac_dealloc,      /* */

    srtp_hmac_init,         /* */

    srtp_hmac_compute,      /* */

    srtp_hmac_update,       /* */

    srtp_hmac_start,        /* */

    srtp_hmac_description,  /* */

    &srtp_hmac_test_case_0, /* */

    SRTP_HMAC_SHA1          /* */

};