Fix a hard to find problem in DeviceRedirection

Specifc file transfers would hang. A minimal reproducer was hard to create. It turns out that the issue was in the encapsulation of the TLSSecurityLayer. If a virtual channel packet at a specific length (0x80), it would confuse the next layer into thinking it was the Security Header's licensing bytes causing the payload to be skipped from its usual processing.

See the recv() method of the TLSSecurityLayer class in `pyrdp/layer/rdp/security.py`.

Turns out that the security layer is not required if we are using modern RDP access mechanisms (anything more recent than RC4) so we can just remove the layer when the MITM is setup.

This fix happens to fix #139 as well.

pyrdp/mitm/RDPMITM.py

@@ -330,18 +330,22 @@ def buildClipboardChannel(self, client: MCSServerChannel, server: MCSClientChann
         :param server: MCS channel for the server side
         """
 
-        clientSecurity = self.state.createSecurityLayer(ParserMode.SERVER, True)
         clientVirtualChannel = VirtualChannelLayer()
         clientLayer = ClipboardLayer()
-        serverSecurity = self.state.createSecurityLayer(ParserMode.CLIENT, True)
         serverVirtualChannel = VirtualChannelLayer()
         serverLayer = ClipboardLayer()
 
         clientLayer.addObserver(LayerLogger(self.getClientLog(MCSChannelName.CLIPBOARD)))
         serverLayer.addObserver(LayerLogger(self.getServerLog(MCSChannelName.CLIPBOARD)))
 
-        LayerChainItem.chain(client, clientSecurity, clientVirtualChannel, clientLayer)
-        LayerChainItem.chain(server, serverSecurity, serverVirtualChannel, serverLayer)
+        if self.state.useTLS:
+            LayerChainItem.chain(client, clientVirtualChannel, clientLayer)
+            LayerChainItem.chain(server, serverVirtualChannel, serverLayer)
+        else:
+            clientSecurity = self.state.createSecurityLayer(ParserMode.SERVER, True)
+            serverSecurity = self.state.createSecurityLayer(ParserMode.CLIENT, True)
+            LayerChainItem.chain(client, clientSecurity, clientVirtualChannel, clientLayer)
+            LayerChainItem.chain(server, serverSecurity, serverVirtualChannel, serverLayer)
 
         if self.config.disableActiveClipboardStealing:
             mitm = PassiveClipboardStealer(self.config, clientLayer, serverLayer, self.getLog(MCSChannelName.CLIPBOARD),
@@ -358,18 +362,22 @@ def buildDeviceChannel(self, client: MCSServerChannel, server: MCSClientChannel)
         :param server: MCS channel for the server side
         """
 
-        clientSecurity = self.state.createSecurityLayer(ParserMode.SERVER, True)
         clientVirtualChannel = VirtualChannelLayer(activateShowProtocolFlag=False)
         clientLayer = DeviceRedirectionLayer()
-        serverSecurity = self.state.createSecurityLayer(ParserMode.CLIENT, True)
         serverVirtualChannel = VirtualChannelLayer(activateShowProtocolFlag=False)
         serverLayer = DeviceRedirectionLayer()
 
         clientLayer.addObserver(LayerLogger(self.getClientLog(MCSChannelName.DEVICE_REDIRECTION)))
         serverLayer.addObserver(LayerLogger(self.getServerLog(MCSChannelName.DEVICE_REDIRECTION)))
 
-        LayerChainItem.chain(client, clientSecurity, clientVirtualChannel, clientLayer)
-        LayerChainItem.chain(server, serverSecurity, serverVirtualChannel, serverLayer)
+        if self.state.useTLS:
+            LayerChainItem.chain(client, clientVirtualChannel, clientLayer)
+            LayerChainItem.chain(server, serverVirtualChannel, serverLayer)
+        else:
+            clientSecurity = self.state.createSecurityLayer(ParserMode.SERVER, True)
+            serverSecurity = self.state.createSecurityLayer(ParserMode.CLIENT, True)
+            LayerChainItem.chain(client, clientSecurity, clientVirtualChannel, clientLayer)
+            LayerChainItem.chain(server, serverSecurity, serverVirtualChannel, serverLayer)
 
         deviceRedirection = DeviceRedirectionMITM(clientLayer, serverLayer, self.getLog(MCSChannelName.DEVICE_REDIRECTION), self.statCounter, self.state, self.tcp)
         self.channelMITMs[client.channelID] = deviceRedirection
@@ -387,13 +395,17 @@ def buildVirtualChannel(self, client: MCSServerChannel, server: MCSClientChannel
         :param server: MCS channel for the server side
         """
 
-        clientSecurity = self.state.createSecurityLayer(ParserMode.SERVER, True)
         clientLayer = RawLayer()
-        serverSecurity = self.state.createSecurityLayer(ParserMode.CLIENT, True)
         serverLayer = RawLayer()
 
-        LayerChainItem.chain(client, clientSecurity, clientLayer)
-        LayerChainItem.chain(server, serverSecurity, serverLayer)
+        if self.state.useTLS:
+            LayerChainItem.chain(client, clientLayer)
+            LayerChainItem.chain(server, serverLayer)
+        else:
+            clientSecurity = self.state.createSecurityLayer(ParserMode.SERVER, True)
+            serverSecurity = self.state.createSecurityLayer(ParserMode.CLIENT, True)
+            LayerChainItem.chain(client, clientSecurity, clientLayer)
+            LayerChainItem.chain(server, serverSecurity, serverLayer)
 
         mitm = VirtualChannelMITM(clientLayer, serverLayer, self.statCounter)
         self.channelMITMs[client.channelID] = mitm