ssl: Handle really big handshake packages

If a handshake message is really big it could happen that the ssl
process would hang due to failing of requesting more data from the
socket. This has been fixed.

Also added option to limit max handshake size. It has a default
value that should be big enough to handle normal usage and small
enough to mitigate DoS attacks.

1 files changed, 39 insertions, 11 deletions

diff --git a/lib/ssl/src/tls_connection.erl b/lib/ssl/src/tls_connection.erl
index 32991d3079..77606911be 100644
--- a/lib/ssl/src/tls_connection.erl
+++ b/lib/ssl/src/tls_connection.erl
@@ -424,18 +424,26 @@ handle_common_event(internal,  #ssl_tls{type = ?HANDSHAKE, fragment = Data},
 				      ssl_options = Options} = State0) ->
     try
 	{Packets, Buf} = tls_handshake:get_tls_handshake(Version,Data,Buf0, Options),
-	State =
+	State1 =
 	    State0#state{protocol_buffers =
 			     Buffers#protocol_buffers{tls_handshake_buffer = Buf}},
-	Events = tls_handshake_events(Packets),
-	case StateName of
-	    connection ->
-		ssl_connection:hibernate_after(StateName, State, Events);
-	    _ ->
-		{next_state, StateName, State#state{unprocessed_handshake_events = unprocessed_events(Events)}, Events}
-	end
+	case Packets of
+            [] -> 
+                assert_buffer_sanity(Buf, Options),
+                {Record, State} = next_record(State1),
+                next_event(StateName, Record, State);
+            _ ->                
+                Events = tls_handshake_events(Packets),
+                case StateName of
+                    connection ->
+                        ssl_connection:hibernate_after(StateName, State1, Events);
+                    _ ->
+                        {next_state, StateName, 
+                         State1#state{unprocessed_handshake_events = unprocessed_events(Events)}, Events}
+                end
+        end
     catch throw:#alert{} = Alert ->
-	    ssl_connection:handle_own_alert(Alert, Version, StateName, State0)
+            ssl_connection:handle_own_alert(Alert, Version, StateName, State0)
     end;
 %%% TLS record protocol level application data messages 
 handle_common_event(internal, #ssl_tls{type = ?APPLICATION_DATA, fragment = Data}, StateName, State) ->
@@ -615,8 +623,6 @@ next_event(StateName, Record, State, Actions) ->
 	    {next_state, StateName, State, [{next_event, internal, Alert} | Actions]}
     end.
 
-tls_handshake_events([]) ->
-    throw(?ALERT_REC(?FATAL, ?HANDSHAKE_FAILURE, malformed_handshake));
 tls_handshake_events(Packets) ->
     lists:map(fun(Packet) ->
 		      {next_event, internal, {handshake, Packet}}
@@ -735,3 +741,25 @@ unprocessed_events(Events) ->
     %% handshake events left to process before we should
     %% process more TLS-records received on the socket. 
     erlang:length(Events)-1.
+
+
+assert_buffer_sanity(<<?BYTE(_Type), ?UINT24(Length), Rest/binary>>, #ssl_options{max_handshake_size = Max}) when 
+      Length =< Max ->  
+    case size(Rest) of
+        N when N < Length ->
+            true;
+        N when N > Length ->       
+            throw(?ALERT_REC(?FATAL, ?HANDSHAKE_FAILURE, 
+                             too_big_handshake_data));
+        _ ->
+            throw(?ALERT_REC(?FATAL, ?HANDSHAKE_FAILURE, 
+                             malformed_handshake_data))  
+    end;  
+assert_buffer_sanity(Bin, _) ->
+    case size(Bin) of
+        N when N < 3 ->
+            true;
+        _ ->       
+            throw(?ALERT_REC(?FATAL, ?HANDSHAKE_FAILURE, 
+                             malformed_handshake_data))
+    end.