1 /*
2  *  Copyright 2014 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef PC_EXTERNAL_HMAC_H_
12 #define PC_EXTERNAL_HMAC_H_
13 
14 // External libsrtp HMAC auth module which implements methods defined in
15 // auth_type_t.
16 // The default auth module will be replaced only when the ENABLE_EXTERNAL_AUTH
17 // flag is enabled. This allows us to access to authentication keys,
18 // as the default auth implementation doesn't provide access and avoids
19 // hashing each packet twice.
20 
21 // How will libsrtp select this module?
22 // Libsrtp defines authentication function types identified by an unsigned
23 // integer, e.g. SRTP_HMAC_SHA1 is 3. Using authentication ids, the
24 // application can plug any desired authentication modules into libsrtp.
25 // libsrtp also provides a mechanism to select different auth functions for
26 // individual streams. This can be done by setting the right value in
27 // the auth_type of srtp_policy_t. The application must first register auth
28 // functions and the corresponding authentication id using
29 // crypto_kernel_replace_auth_type function.
30 
31 #include <stdint.h>
32 
33 #include "third_party/libsrtp/crypto/include/auth.h"
34 #include "third_party/libsrtp/crypto/include/crypto_types.h"
35 #include "third_party/libsrtp/include/srtp.h"
36 
37 #define EXTERNAL_HMAC_SHA1 SRTP_HMAC_SHA1 + 1
38 #define HMAC_KEY_LENGTH 20
39 
40 // The HMAC context structure used to store authentication keys.
41 // The pointer to the key  will be allocated in the external_hmac_init function.
42 // This pointer is owned by srtp_t in a template context.
43 typedef struct {
44   uint8_t key[HMAC_KEY_LENGTH];
45   int key_length;
46 } ExternalHmacContext;
47 
48 srtp_err_status_t external_hmac_alloc(srtp_auth_t** a,
49                                       int key_len,
50                                       int out_len);
51 
52 srtp_err_status_t external_hmac_dealloc(srtp_auth_t* a);
53 
54 srtp_err_status_t external_hmac_init(void* state,
55                                      const uint8_t* key,
56                                      int key_len);
57 
58 srtp_err_status_t external_hmac_start(void* state);
59 
60 srtp_err_status_t external_hmac_update(void* state,
61                                        const uint8_t* message,
62                                        int msg_octets);
63 
64 srtp_err_status_t external_hmac_compute(void* state,
65                                         const uint8_t* message,
66                                         int msg_octets,
67                                         int tag_len,
68                                         uint8_t* result);
69 
70 srtp_err_status_t external_crypto_init();
71 
72 #endif  // PC_EXTERNAL_HMAC_H_
73