Add support for GCM cipher suites from RFC 7714.

webrtc/base/sslstreamadapter.cc

Index: webrtc/base/sslstreamadapter.cc
diff --git a/webrtc/base/sslstreamadapter.cc b/webrtc/base/sslstreamadapter.cc
index e0fce3ad2f2642090e818a963972e03e1712317d..2fec2479bb0ae1c0137620afc9f36bba63e09dad 100644
--- a/webrtc/base/sslstreamadapter.cc
+++ b/webrtc/base/sslstreamadapter.cc
@@ -25,13 +25,22 @@ namespace rtc {
 // webrtc:5043.
 const char CS_AES_CM_128_HMAC_SHA1_80[] = "AES_CM_128_HMAC_SHA1_80";
 const char CS_AES_CM_128_HMAC_SHA1_32[] = "AES_CM_128_HMAC_SHA1_32";
+const char CS_AEAD_AES_128_GCM[] = "AEAD_AES_128_GCM";
+const char CS_AEAD_AES_256_GCM[] = "AEAD_AES_256_GCM";
 
 std::string SrtpCryptoSuiteToName(int crypto_suite) {
-  if (crypto_suite == SRTP_AES128_CM_SHA1_32)
+  switch (crypto_suite) {
+  case SRTP_AES128_CM_SHA1_32:
     return CS_AES_CM_128_HMAC_SHA1_32;
-  if (crypto_suite == SRTP_AES128_CM_SHA1_80)
+  case SRTP_AES128_CM_SHA1_80:
     return CS_AES_CM_128_HMAC_SHA1_80;
-  return std::string();
+  case SRTP_AEAD_AES_128_GCM:
+    return CS_AEAD_AES_128_GCM;
+  case SRTP_AEAD_AES_256_GCM:
+    return CS_AEAD_AES_256_GCM;
+  default:
+    return std::string();
+  }
 }
 
 int SrtpCryptoSuiteFromName(const std::string& crypto_suite) {
@@ -39,9 +48,58 @@ int SrtpCryptoSuiteFromName(const std::string& crypto_suite) {
     return SRTP_AES128_CM_SHA1_32;
   if (crypto_suite == CS_AES_CM_128_HMAC_SHA1_80)
     return SRTP_AES128_CM_SHA1_80;
+  if (crypto_suite == CS_AEAD_AES_128_GCM)
+    return SRTP_AEAD_AES_128_GCM;
+  if (crypto_suite == CS_AEAD_AES_256_GCM)
+    return SRTP_AEAD_AES_256_GCM;
   return SRTP_INVALID_CRYPTO_SUITE;
 }
 
+bool GetSrtpKeyAndSaltLengths(int crypto_suite, int *key_length,
+    int *salt_length) {
+  switch (crypto_suite) {
+  case SRTP_AES128_CM_SHA1_32:
+  case SRTP_AES128_CM_SHA1_80:
+    // SRTP_AES128_CM_HMAC_SHA1_32 and SRTP_AES128_CM_HMAC_SHA1_80 are defined
+    // in RFC 5764 to use a 128 bits key and 112 bits salt for the cipher.
+    *key_length = 16;
+    *salt_length = 14;
+    break;
+  case SRTP_AEAD_AES_128_GCM:
+    // SRTP_AEAD_AES_128_GCM is defined in RFC 7714 to use a 128 bits key and
+    // a 96 bits salt for the cipher.
+    *key_length = 16;
+    *salt_length = 12;
+    break;
+  case SRTP_AEAD_AES_256_GCM:
+    // SRTP_AEAD_AES_256_GCM is defined in RFC 7714 to use a 256 bits key and
+    // a 96 bits salt for the cipher.
+    *key_length = 32;
+    *salt_length = 12;
+    break;
+  default:
+    return false;
+  }
+  return true;
+}
+
+bool IsGcmCryptoSuite(int crypto_suite) {
+  return (crypto_suite == SRTP_AEAD_AES_256_GCM ||
+          crypto_suite == SRTP_AEAD_AES_128_GCM);
+}
+
+bool IsGcmCryptoSuiteName(const std::string& crypto_suite) {
+  return (crypto_suite == CS_AEAD_AES_256_GCM ||
+          crypto_suite == CS_AEAD_AES_128_GCM);
+}
+
+// static
+CryptoOptions CryptoOptions::NoGcm() {
+  CryptoOptions options;
+  options.enable_gcm_crypto_suites = false;
+  return options;
+}
+
 SSLStreamAdapter* SSLStreamAdapter::Create(StreamInterface* stream) {
 #if SSL_USE_OPENSSL
   return new OpenSSLStreamAdapter(stream);