net: allow fallback down to TLS 1.0 in the event of a bad-record-MAC alert.

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 a984f581faf0036589fbe00c37b75f81f76c4ef9..ee29fdeada6e6dbb3bc42cb9c0da5e51ee912c66 100644
--- a/net/socket/ssl_client_socket_nss.cc
+++ b/net/socket/ssl_client_socket_nss.cc
@@ -1861,6 +1861,15 @@ int SSLClientSocketNSS::Core::DoHandshake() {
       net_error = ERR_SSL_PROTOCOL_ERROR;
     }
 
+    // Some broken SSL devices negotiate TLS 1.0 when sent a TLS 1.1 or 1.2
+    // ClientHello, but then return a bad-record-MAC alert. See
+    // crbug.com/260358. In order to make the fallback as minimal as possible,
+    // this fallback is only triggered for >= TLS 1.1.
+    if (net_error == ERR_SSL_BAD_RECORD_MAC_ALERT &&
+        ssl_config_.version_max >= SSL_PROTOCOL_VERSION_TLS1_1) {
+      net_error = ERR_SSL_PROTOCOL_ERROR;
+    }
+
     // If not done, stay in this state
     if (net_error == ERR_IO_PENDING) {
       GotoState(STATE_HANDSHAKE);