ASP.NET Bad Practices: Compression Over Encrypted WebSocket Connection

The application enables dangerous compression.

The application uses code that enables the permessage-deflate WebSocket extension which allows for compression over encrypted connections. Enabling this type of compression makes the application subject to the CRIME and BREACH type of attacks.

Example 1: The following code sets DangerousEnableCompression to true in order to enable the 'per-message-deflate' extension:

    app.Run(async context => {
        using var websocket = await context.WebSockets.AcceptWebSocketAsync(new WebSocketAcceptContext() { DangerousEnableCompression = true });
        await websocket.SendAsync(...);
        await websocket.ReceiveAsync(...);
        await websocket.CloseAsync(WebSocketCloseStatus.NormalClosure, null, default);
    });
    

Example 2: The following code uses DangerousDeflateOptions to set the options for the 'per-message-deflate' extension:

    using ClientWebSocket ws = new() {
        Options = {
            CollectHttpResponseDetails = true,
            DangerousDeflateOptions = new WebSocketDeflateOptions() {
                ClientMaxWindowBits = 10,
                ServerMaxWindowBits = 10
            }
        }
    };