Support setting HTTP headers for WebSocket connection

[wolfman42]

Proposed change

Support setting of (additional) HTTP headers for WebSocket connection. This could be a new part of NatsOpts class. Useful for providing an Authorization header. Perhaps along the following lines:

        var opts = new NatsOpts {
            Url = $"wss://localhost:8181"
        };
        opts.SetWebSocketHeader("authorization", $"Bearer {accessToken}");
        await using var nats = new NatsConnection(opts);
        await nats.PingAsync();

OnConnectingAsync callback should allow updating the headers, so that an authorization token could be refreshed.

Use case

JWT based authorization outside of NATS server.

Contribution

yes, interested.

[caleblloyd]

I don't think that WebSockets support HTTP Headers. I've been frustrated by this before :smile:

https://stackoverflow.com/a/4361358

SignalR Core uses a query string parameter to transmit bearer tokens over websockets

[wolfman42]

I don't think that WebSockets support HTTP Headers. I've been frustrated by this before 😄

https://stackoverflow.com/a/4361358

SignalR Core uses a query string parameter to transmit bearer tokens over websockets

WebSockets in C# (and most other languages / frameworks) do support HTTP headers. The only situation when it's not supported (AFAIK) is when you try to connect a WebSocket from a browser application.

Here's a C# example:

            using (var socket = new ClientWebSocket())
                try
                {
                    socket.Options.SetRequestHeader("authorization", $"Bearer {accessToken}");
                    await socket.ConnectAsync(new Uri($"wss://localhost:8181"), CancellationToken.None);

                    await Send(socket, "data");
                    if (!await Receive(socket)) return;

                }
                catch (Exception ex)
                {
                    Console.WriteLine($"ERROR - {ex.Message}");
                    return;
                }

[caleblloyd]

Good to know. Maybe we could have a callback in NatsOpts:

Func<Uri, ValueTask<ClientWebSocketOptions>>? ConfigureWebSocketOpts

Where the Uri argument is the URI of the NATS Server we are attempting to connect to

[adamreed90]

👍 I could see this being extremely useful with Blazor WebAssembly, specifically with being able to securely emit events from the frontend without the need for SignalR

[caleblloyd]

I think that Blazor WebAssembly running in the browser will use the Browser's websocket implementation, which doesn't support headers.