dtls: Implement replay protection

See RFC 6347 section 3.3

1 files changed, 23 insertions, 9 deletions

diff --git a/lib/ssl/src/dtls_connection.erl b/lib/ssl/src/dtls_connection.erl
index 9937373e6e..b52896a458 100644
--- a/lib/ssl/src/dtls_connection.erl
+++ b/lib/ssl/src/dtls_connection.erl
@@ -688,16 +688,19 @@ next_record(#state{unprocessed_handshake_events = N} = State) when N > 0 ->
     {no_record, State#state{unprocessed_handshake_events = N-1}};
 					 
 next_record(#state{protocol_buffers =
-		       #protocol_buffers{dtls_cipher_texts = [CT | Rest]}
+		       #protocol_buffers{dtls_cipher_texts = [#ssl_tls{epoch = Epoch} = CT | Rest]}
 		   = Buffers,
-		   connection_states = ConnStates0} = State) ->
-    case dtls_record:decode_cipher_text(CT, ConnStates0) of
-	{Plain, ConnStates} ->		      
-	    {Plain, State#state{protocol_buffers =
-				    Buffers#protocol_buffers{dtls_cipher_texts = Rest},
-				connection_states = ConnStates}};
-	#alert{} = Alert ->
-	    {Alert, State}
+		   connection_states = ConnectionStates} = State) ->
+    CurrentRead = dtls_record:get_connection_state_by_epoch(Epoch, ConnectionStates, read),
+    case dtls_record:replay_detect(CT, CurrentRead) of
+        false ->
+            decode_cipher_text(State#state{connection_states = ConnectionStates}) ;
+        true ->
+            ct:pal("Replay detect", []),            
+            %% Ignore replayed record
+            next_record(State#state{protocol_buffers =
+                                        Buffers#protocol_buffers{dtls_cipher_texts = Rest},
+                                    connection_states = ConnectionStates})
     end;
 next_record(#state{role = server,
 		   socket = {Listener, {Client, _}},
@@ -770,6 +773,17 @@ next_event(StateName, Record,
 	    {next_state, StateName, State, [{next_event, internal, Alert} | Actions]}
     end.
 
+decode_cipher_text(#state{protocol_buffers = #protocol_buffers{dtls_cipher_texts = [ CT | Rest]} = Buffers,
+                          connection_states = ConnStates0} = State) ->
+    case dtls_record:decode_cipher_text(CT, ConnStates0) of
+	{Plain, ConnStates} ->		      
+	    {Plain, State#state{protocol_buffers =
+				    Buffers#protocol_buffers{dtls_cipher_texts = Rest},
+				connection_states = ConnStates}};
+	#alert{} = Alert ->
+	    {Alert, State}
+    end.
+
 dtls_version(hello, Version, #state{role = server} = State) ->
     State#state{negotiated_version = Version}; %%Inital version
 dtls_version(_,_, State) ->