267 lines
7.8 KiB
C
267 lines
7.8 KiB
C
/*
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* hmac.c
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*
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* implementation of hmac srtp_auth_type_t
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*
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* David A. McGrew
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* Cisco Systems, Inc.
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*/
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/*
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*
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* Copyright(c) 2001-2017 Cisco Systems, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* Neither the name of the Cisco Systems, Inc. nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include "hmac.h"
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#include "alloc.h"
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/* the debug module for authentiation */
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srtp_debug_module_t srtp_mod_hmac = {
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0, /* debugging is off by default */
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"hmac sha-1" /* printable name for module */
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};
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static srtp_err_status_t srtp_hmac_alloc (srtp_auth_t **a, int key_len, int out_len)
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{
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extern const srtp_auth_type_t srtp_hmac;
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uint8_t *pointer;
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debug_print(srtp_mod_hmac, "allocating auth func with key length %d", key_len);
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debug_print(srtp_mod_hmac, " tag length %d", out_len);
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/*
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* check key length - note that we don't support keys larger
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* than 20 bytes yet
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*/
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if (key_len > 20) {
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return srtp_err_status_bad_param;
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}
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/* check output length - should be less than 20 bytes */
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if (out_len > 20) {
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return srtp_err_status_bad_param;
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}
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/* allocate memory for auth and srtp_hmac_ctx_t structures */
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pointer = (uint8_t*)srtp_crypto_alloc(sizeof(srtp_hmac_ctx_t) + sizeof(srtp_auth_t));
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if (pointer == NULL) {
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return srtp_err_status_alloc_fail;
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}
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/* set pointers */
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*a = (srtp_auth_t*)pointer;
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(*a)->type = &srtp_hmac;
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(*a)->state = pointer + sizeof(srtp_auth_t);
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(*a)->out_len = out_len;
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(*a)->key_len = key_len;
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(*a)->prefix_len = 0;
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return srtp_err_status_ok;
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}
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static srtp_err_status_t srtp_hmac_dealloc (srtp_auth_t *a)
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{
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/* zeroize entire state*/
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octet_string_set_to_zero(a, sizeof(srtp_hmac_ctx_t) + sizeof(srtp_auth_t));
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/* free memory */
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srtp_crypto_free(a);
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return srtp_err_status_ok;
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}
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static srtp_err_status_t srtp_hmac_init (void *statev, const uint8_t *key, int key_len)
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{
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srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
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int i;
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uint8_t ipad[64];
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/*
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* check key length - note that we don't support keys larger
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* than 20 bytes yet
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*/
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if (key_len > 20) {
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return srtp_err_status_bad_param;
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}
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/*
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* set values of ipad and opad by exoring the key into the
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* appropriate constant values
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*/
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for (i = 0; i < key_len; i++) {
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ipad[i] = key[i] ^ 0x36;
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state->opad[i] = key[i] ^ 0x5c;
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}
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/* set the rest of ipad, opad to constant values */
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for (; i < 64; i++) {
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ipad[i] = 0x36;
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((uint8_t*)state->opad)[i] = 0x5c;
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}
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debug_print(srtp_mod_hmac, "ipad: %s", srtp_octet_string_hex_string(ipad, 64));
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/* initialize sha1 context */
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srtp_sha1_init(&state->init_ctx);
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/* hash ipad ^ key */
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srtp_sha1_update(&state->init_ctx, ipad, 64);
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memcpy(&state->ctx, &state->init_ctx, sizeof(srtp_sha1_ctx_t));
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return srtp_err_status_ok;
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}
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static srtp_err_status_t srtp_hmac_start (void *statev)
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{
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srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
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memcpy(&state->ctx, &state->init_ctx, sizeof(srtp_sha1_ctx_t));
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return srtp_err_status_ok;
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}
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static srtp_err_status_t srtp_hmac_update (void *statev, const uint8_t *message, int msg_octets)
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{
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srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
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debug_print(srtp_mod_hmac, "input: %s",
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srtp_octet_string_hex_string(message, msg_octets));
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/* hash message into sha1 context */
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srtp_sha1_update(&state->ctx, message, msg_octets);
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return srtp_err_status_ok;
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}
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static srtp_err_status_t srtp_hmac_compute (void *statev, const uint8_t *message,
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int msg_octets, int tag_len, uint8_t *result)
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{
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srtp_hmac_ctx_t *state = (srtp_hmac_ctx_t *)statev;
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uint32_t hash_value[5];
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uint32_t H[5];
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int i;
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/* check tag length, return error if we can't provide the value expected */
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if (tag_len > 20) {
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return srtp_err_status_bad_param;
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}
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/* hash message, copy output into H */
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srtp_hmac_update(state, message, msg_octets);
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srtp_sha1_final(&state->ctx, H);
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/*
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* note that we don't need to debug_print() the input, since the
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* function hmac_update() already did that for us
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*/
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debug_print(srtp_mod_hmac, "intermediate state: %s",
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srtp_octet_string_hex_string((uint8_t*)H, 20));
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/* re-initialize hash context */
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srtp_sha1_init(&state->ctx);
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/* hash opad ^ key */
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srtp_sha1_update(&state->ctx, (uint8_t*)state->opad, 64);
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/* hash the result of the inner hash */
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srtp_sha1_update(&state->ctx, (uint8_t*)H, 20);
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/* the result is returned in the array hash_value[] */
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srtp_sha1_final(&state->ctx, hash_value);
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/* copy hash_value to *result */
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for (i = 0; i < tag_len; i++) {
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result[i] = ((uint8_t*)hash_value)[i];
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}
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debug_print(srtp_mod_hmac, "output: %s",
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srtp_octet_string_hex_string((uint8_t*)hash_value, tag_len));
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return srtp_err_status_ok;
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}
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/* begin test case 0 */
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static const uint8_t srtp_hmac_test_case_0_key[20] = {
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0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
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0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b, 0x0b,
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0x0b, 0x0b, 0x0b, 0x0b
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};
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static const uint8_t srtp_hmac_test_case_0_data[8] = {
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0x48, 0x69, 0x20, 0x54, 0x68, 0x65, 0x72, 0x65 /* "Hi There" */
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};
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static const uint8_t srtp_hmac_test_case_0_tag[20] = {
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0xb6, 0x17, 0x31, 0x86, 0x55, 0x05, 0x72, 0x64,
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0xe2, 0x8b, 0xc0, 0xb6, 0xfb, 0x37, 0x8c, 0x8e,
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0xf1, 0x46, 0xbe, 0x00
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};
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static const srtp_auth_test_case_t srtp_hmac_test_case_0 = {
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20, /* octets in key */
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srtp_hmac_test_case_0_key, /* key */
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8, /* octets in data */
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srtp_hmac_test_case_0_data, /* data */
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20, /* octets in tag */
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srtp_hmac_test_case_0_tag, /* tag */
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NULL /* pointer to next testcase */
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};
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/* end test case 0 */
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static const char srtp_hmac_description[] = "hmac sha-1 authentication function";
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/*
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* srtp_auth_type_t hmac is the hmac metaobject
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*/
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const srtp_auth_type_t srtp_hmac = {
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srtp_hmac_alloc,
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srtp_hmac_dealloc,
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srtp_hmac_init,
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srtp_hmac_compute,
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srtp_hmac_update,
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srtp_hmac_start,
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srtp_hmac_description,
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&srtp_hmac_test_case_0,
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SRTP_HMAC_SHA1
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};
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