+ if (TLSProxy::Proxy->is_tls13()) {
+ #A TLS1.3 client, when processing the server's initial flight, could
+ #respond with either an encrypted or an unencrypted alert.
+ if ($self->content_type() == RT_ALERT) {
+ #TODO(TLS1.3): Eventually it is sufficient just to check the record
+ #content type. If an alert is encrypted it will have a record
+ #content type of application data. However we haven't done the
+ #record layer changes yet, so it's a bit more complicated. For now
+ #we will additionally check if the data length is 2 (1 byte for
+ #alert level, 1 byte for alert description). If it is, then this is
+ #an unecrypted alert, so don't try to decrypt
+ return $data if (length($data) == 2);
+ }