exfiltrate_proxy

A WebSocket/TCP bridge that enables debugging of WebAssembly applications running in browsers using the exfiltrate crate.

Overview

WebAssembly applications running in a browser cannot open raw TCP sockets—they are restricted to WebSockets. The exfiltrate CLI, however, communicates via TCP.

This proxy bridges that gap by running two servers:

1. WebSocket Server (Port 1338): Accepts connections from the WASM application
2. TCP Server (Port 1337): Accepts connections from the exfiltrate CLI

Messages are forwarded bidirectionally between these endpoints, allowing the CLI to debug browser-based applications as if they were local native processes.

Usage

Start the proxy:

cargo run -p exfiltrate_proxy

Or if installed:

exfiltrate_proxy

The proxy will listen on:

• 127.0.0.1:1337 for TCP connections (CLI)
• 127.0.0.1:1338 for WebSocket connections (WASM app)

Architecture

┌─────────────────┐     WebSocket      ┌─────────────────┐       TCP        ┌─────────────────┐
│   WASM App      │ ◄────────────────► │  exfiltrate     │ ◄──────────────► │  exfiltrate     │
│   (Browser)     │     Port 1338      │    _proxy       │    Port 1337     │     CLI         │
└─────────────────┘                    └─────────────────┘                  └─────────────────┘

Connection Flow

1. Start the proxy
2. Your WASM application connects to ws://127.0.0.1:1338
3. The CLI connects to 127.0.0.1:1337
4. Commands from the CLI are forwarded to the WASM app via WebSocket
5. Responses from the WASM app are forwarded back to the CLI via TCP

Multiple CLI Clients

The TCP server supports multiple concurrent CLI connections. Messages received from the WebSocket (WASM app) are broadcast to all connected TCP clients.

WASM Application Setup

Your WASM application should connect to the proxy's WebSocket endpoint instead of using the native TCP server. The exfiltrate library handles this automatically when compiled for wasm32-unknown-unknown targets.

Debugging Tips

The proxy outputs connection events and message sizes to stderr:

Listening on 127.0.0.1:1337
New WebSocket connection established: 127.0.0.1:xxxxx
Distributor: Received message of size 42
Distributor: Broadcasting to 1 clients

License

See LICENSE for details.