Fix externalhmac.h/.cc to compile with libsrtp 1 and 2

webrtc/pc/externalhmac.h

 /*
  *  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.
  */
 
 #ifndef WEBRTC_PC_EXTERNALHMAC_H_
 #define WEBRTC_PC_EXTERNALHMAC_H_
 
 // 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. HMAC_SHA1 is 3. Using authentication ids, the application
-// can plug any desired authentication modules into libsrtp.
+// 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 "webrtc/base/basictypes.h"
 #ifdef HAVE_SRTP
 extern "C" {
 #ifdef SRTP_RELATIVE_PATH
 #include "auth.h"  // NOLINT
 #else
 #include "third_party/libsrtp/crypto/include/auth.h"
 #endif  // SRTP_RELATIVE_PATH
 }
 #endif  // HAVE_SRTP
 
+#if defined(HAVE_SRTP) && !defined(SRTP_HMAC_SHA1)
+// Include compatibility shims to compile against libsrtp 1.x.
+// TODO(mattdr): Remove once Chromium uses libsrtp 2.
+
+// Remember that the definition of SRTP_HMAC_SHA1 is synthetic.
+#define COMPILING_AGAINST_LIBSRTP1 1
+
+#define SRTP_HMAC_SHA1 HMAC_SHA1
+#define srtp_auth_t auth_t
+#endif
+
 #if defined(HAVE_SRTP) && defined(ENABLE_EXTERNAL_AUTH)
 
-#define EXTERNAL_HMAC_SHA1 HMAC_SHA1 + 1
+#define EXTERNAL_HMAC_SHA1 SRTP_HMAC_SHA1 + 1
 #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;
 
-err_status_t external_hmac_alloc(auth_t** a, int key_len, int out_len);
+srtp_err_status_t external_hmac_alloc(srtp_auth_t** a,
+                                      int key_len,
+                                      int out_len);
 
-err_status_t external_hmac_dealloc(auth_t* a);
+srtp_err_status_t external_hmac_dealloc(srtp_auth_t* a);
 
-err_status_t external_hmac_init(ExternalHmacContext* state,
-                                const uint8_t* key,
-                                int key_len);
+srtp_err_status_t external_hmac_init(ExternalHmacContext* state,
+                                     const uint8_t* key,
+                                     int key_len);
 
-err_status_t external_hmac_start(ExternalHmacContext* state);
+srtp_err_status_t external_hmac_start(ExternalHmacContext* state);
 
-err_status_t external_hmac_update(ExternalHmacContext* state,
-                                  const uint8_t* message,
-                                  int msg_octets);
+srtp_err_status_t external_hmac_update(ExternalHmacContext* state,
+                                       const uint8_t* message,
+                                       int msg_octets);
 
-err_status_t external_hmac_compute(ExternalHmacContext* state,
-                                   const void* message,
-                                   int msg_octets,
-                                   int tag_len,
-                                   uint8_t* result);
+srtp_err_status_t external_hmac_compute(ExternalHmacContext* state,
+                                        const void* message,
+                                        int msg_octets,
+                                        int tag_len,
+                                        uint8_t* result);
 
-err_status_t external_crypto_init();
+srtp_err_status_t external_crypto_init();
 
 #endif  // defined(HAVE_SRTP) && defined(ENABLE_EXTERNAL_AUTH)
 #endif  // WEBRTC_PC_EXTERNALHMAC_H_