Add support for GCM cipher suites from RFC 7714.

talk/session/media/srtpfilter.cc

 /*
  * libjingle
  * Copyright 2009 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 55 matching lines @@
 extern "C" debug_module_t mod_aes_icm;
 extern "C" debug_module_t mod_aes_hmac;
 #endif
 #else
 // SrtpFilter needs that constant.
 #define SRTP_MASTER_KEY_LEN 30
 #endif  // HAVE_SRTP
 
 namespace cricket {
 
-const int SRTP_MASTER_KEY_BASE64_LEN = SRTP_MASTER_KEY_LEN * 4 / 3;
-const int SRTP_MASTER_KEY_KEY_LEN = 16;
-const int SRTP_MASTER_KEY_SALT_LEN = 14;
-
 #ifndef HAVE_SRTP
 
 // This helper function is used on systems that don't (yet) have SRTP,
 // to log that the functions that require it won't do anything.
 namespace {
 bool SrtpNotAvailable(const char *func) {
   LOG(LS_ERROR) << func << ": SRTP is not available on your system.";
   return false;
 }
 }  // anonymous namespace
@@ skipping 577 matching lines @@
     return false;
   }
 
   if (!Init()) {
     return false;
   }
 
   srtp_policy_t policy;
   memset(&policy, 0, sizeof(policy));
 
+  int expected_key_len;
   if (cs == rtc::SRTP_AES128_CM_SHA1_80) {
     crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtp);
     crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtcp);
+    // Master key is 128 bits key + 112 bits salt.
+    expected_key_len = 16 + 14;
   } else if (cs == rtc::SRTP_AES128_CM_SHA1_32) {
     crypto_policy_set_aes_cm_128_hmac_sha1_32(&policy.rtp);   // rtp is 32,
     crypto_policy_set_aes_cm_128_hmac_sha1_80(&policy.rtcp);  // rtcp still 80
+    // Master key is 128 bits key + 112 bits salt.
+    expected_key_len = 16 + 14;
+  } else if (cs == rtc::SRTP_AEAD_AES_128_GCM) {
+    crypto_policy_set_aes_gcm_128_16_auth(&policy.rtp);
+    crypto_policy_set_aes_gcm_128_16_auth(&policy.rtcp);
+    // Master key is 128 bits key + 96 bits salt.
+    expected_key_len = 16 + 12;
+  } else if (cs == rtc::SRTP_AEAD_AES_256_GCM) {
+    crypto_policy_set_aes_gcm_256_16_auth(&policy.rtp);
+    crypto_policy_set_aes_gcm_256_16_auth(&policy.rtcp);
+    // Master key is 256 bits key + 96 bits salt.
+    expected_key_len = 32 + 12;

[pthatcher1, 2015/12/18 20:31:32]

This seems duplicative with the new SrtpCryptoSuiteParams function you added. 
Can you use that here to avoid duplicating information in the code base?

[joachim, 2015/12/19 15:26:23]

Right, I wrote that code before adding the new function. Changed.

   } else {
     LOG(LS_WARNING) << "Failed to create SRTP session: unsupported"
                     << " cipher_suite " << cs;
     return false;
   }
 
-  if (!key || len != SRTP_MASTER_KEY_LEN) {
+  if (!key || len != expected_key_len) {
     LOG(LS_WARNING) << "Failed to create SRTP session: invalid key";
     return false;
   }
 
   policy.ssrc.type = static_cast<ssrc_type_t>(type);
   policy.ssrc.value = 0;
   policy.key = const_cast<uint8_t*>(key);
   // TODO(astor) parse window size from WSH session-param
   policy.window_size = 1024;
   policy.allow_repeat_tx = 1;
   // If external authentication option is enabled, supply custom auth module
   // id EXTERNAL_HMAC_SHA1 in the policy structure.
   // We want to set this option only for rtp packets.
   // By default policy structure is initialized to HMAC_SHA1.
 #if defined(ENABLE_EXTERNAL_AUTH)
   // Enable external HMAC authentication only for outgoing streams.
   if (type == ssrc_any_outbound) {
     policy.rtp.auth_type = EXTERNAL_HMAC_SHA1;
   }
 #endif
   policy.next = NULL;
 
   int err = srtp_create(&session_, &policy);
   if (err != err_status_ok) {
     session_ = NULL;
     LOG(LS_ERROR) << "Failed to create SRTP session, err=" << err;
     return false;
   }
 
-
   rtp_auth_tag_len_ = policy.rtp.auth_tag_len;
   rtcp_auth_tag_len_ = policy.rtcp.auth_tag_len;
   return true;
 }
 
 bool SrtpSession::Init() {
   rtc::GlobalLockScope ls(&lock_);
 
   if (!inited_) {
     int err;
@@ skipping 211 matching lines @@
   SrtpNotAvailable(__FUNCTION__);
 }
 
 void SrtpStat::HandleSrtpResult(const SrtpStat::FailureKey& key) {
   SrtpNotAvailable(__FUNCTION__);
 }
 
 #endif  // HAVE_SRTP
 
 }  // namespace cricket