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* Copyright 2014 The WebRTC project authors. All Rights Reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
// External libsrtp HMAC auth module which implements methods defined in
// auth_type_t.
// The default auth module will be replaced only when the ENABLE_EXTERNAL_AUTH
// flag is enabled. This allows us to access to authentication keys,
// as the default auth implementation doesn't provide access and avoids
// hashing each packet twice.
// How will libsrtp select this module?
// Libsrtp defines authentication function types identified by an unsigned
// integer, e.g. SRTP_HMAC_SHA1 is 3. Using authentication ids, the
// application can plug any desired authentication modules into libsrtp.
// libsrtp also provides a mechanism to select different auth functions for
// individual streams. This can be done by setting the right value in
// the auth_type of srtp_policy_t. The application must first register auth
// functions and the corresponding authentication id using
// crypto_kernel_replace_auth_type function.
#include <stdint.h>
#include "third_party/libsrtp/crypto/include/auth.h"
#include "third_party/libsrtp/crypto/include/crypto_types.h"
#include "third_party/libsrtp/include/srtp.h"
#define HMAC_KEY_LENGTH 20
// The HMAC context structure used to store authentication keys.
// The pointer to the key will be allocated in the external_hmac_init function.
// This pointer is owned by srtp_t in a template context.
typedef struct {
uint8_t key[HMAC_KEY_LENGTH];
int key_length;
} ExternalHmacContext;
srtp_err_status_t external_hmac_alloc(srtp_auth_t** a,
int key_len,
int out_len);
srtp_err_status_t external_hmac_dealloc(srtp_auth_t* a);
srtp_err_status_t external_hmac_init(void* state,
const uint8_t* key,
int key_len);
srtp_err_status_t external_hmac_start(void* state);
srtp_err_status_t external_hmac_update(void* state,
const uint8_t* message,
int msg_octets);
srtp_err_status_t external_hmac_compute(void* state,
const uint8_t* message,
int msg_octets,
int tag_len,
uint8_t* result);
srtp_err_status_t external_crypto_init();