net: allow False Start only for >= TLS 1.2 && AEAD && forward-secure && ALPN/NPN.

net/socket/ssl_client_socket_nss.cc

Index: net/socket/ssl_client_socket_nss.cc
diff --git a/net/socket/ssl_client_socket_nss.cc b/net/socket/ssl_client_socket_nss.cc
index e20b28a3512b05b67dbfbbc2a9a4d05a9f7fc206..efcac80c5ddcce158a5c497bb50ab3c0f39cbb01 100644
--- a/net/socket/ssl_client_socket_nss.cc
+++ b/net/socket/ssl_client_socket_nss.cc
@@ -107,6 +107,7 @@
 #include "net/socket/client_socket_handle.h"
 #include "net/socket/nss_ssl_util.h"
 #include "net/ssl/ssl_cert_request_info.h"
+#include "net/ssl/ssl_cipher_suite_names.h"
 #include "net/ssl/ssl_connection_status_flags.h"
 #include "net/ssl/ssl_info.h"
 
@@ -1601,6 +1602,17 @@ SECStatus SSLClientSocketNSS::Core::CanFalseStartCallback(
     return SECSuccess;
   }
 
+  SSLChannelInfo channel_info;
+  SECStatus ok = SSL_GetChannelInfo(socket,
+                                    &channel_info, sizeof(channel_info));
+  if (ok != SECSuccess ||
+      channel_info.length != sizeof(channel_info) ||
+      channel_info.protocolVersion < SSL_LIBRARY_VERSION_TLS_1_2 ||
+      !IsSecureTLSCipherSuite(channel_info.cipherSuite)) {
+    *can_false_start = PR_FALSE;
+    return SECSuccess;
+  }
+
   return SSL_RecommendedCanFalseStart(socket, can_false_start);
 }