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use std::io::{stdin, BufRead};
use std::{net::SocketAddr, time::Duration};
use anyhow::{Context, Result};
use futures::{Sink, SinkExt, Stream, StreamExt};
use tokio::net::TcpListener;
use tokio::sync::mpsc::{unbounded_channel, UnboundedReceiver, UnboundedSender};
use tokio_tungstenite::{tungstenite::Error as WsError, tungstenite::Message};
use url::Url;
const USAGE: &str = "\
Usage: webcat <url> Connect to a ws:// URL
Usage: webcat -l <port> Listen to the given port
You can use FIFOs to create a debugging man-in-the-middle setup:
mkfifo client-in server-in
webcat ws://example.com:3000/ < client-in > server-in
webcat -l 4000 < server-in > client-in
echo > server-in # unblock the FIFO deadlock\
";
#[tokio::main]
async fn main() -> Result<()> {
let args: Vec<_> = std::env::args().skip(1).collect();
if args.len() == 1 {
start_client(args[0].parse().context("failed to parse URL")?).await?;
} else if args.len() == 2 && args[0] == "-l" {
start_server(args[1].parse().context("failed to parse port")?).await?;
} else {
println!("{}", USAGE);
}
Ok(())
}
async fn start_client(url: Url) -> Result<()> {
// stdio is blocking so we do it in a dedicated task
let (stdin_sender, mut stdin_receiver) = unbounded_channel::<String>();
tokio::spawn(send_stdin_to_channel(stdin_sender));
loop {
match tokio_tungstenite::connect_async(&url).await {
Ok((stream, _resp)) => {
eprintln!("connected to server");
webcat(Mode::Client, stream, &mut stdin_receiver).await?;
}
Err(err) => {
eprintln!("failed to connect to server: {}", err);
let mut reconnect_timer = tokio::time::interval(Duration::from_secs(1));
eprint!("reconnecting in ");
for i in (1..6).rev() {
reconnect_timer.tick().await;
eprint!("... {}", i);
}
eprintln!();
}
}
}
}
const SERVER_ACCEPTED_NEW_CONN: &str = "accepted new client";
async fn start_server(port: u16) -> Result<()> {
let listen_addr: SocketAddr = ([127, 0, 0, 1], port).into();
let listener = TcpListener::bind(listen_addr).await?;
// stdio is blocking so we do it in a dedicated task
let (stdin_sender, mut stdin_receiver) = unbounded_channel::<String>();
tokio::spawn(send_stdin_to_channel(stdin_sender));
eprintln!("listening for connections on {}", listen_addr);
loop {
let (stream, _client_addr) = listener.accept().await?;
match tokio_tungstenite::accept_async(stream).await {
Ok(stream) => {
println!("{}", SERVER_ACCEPTED_NEW_CONN);
webcat(Mode::Server, stream, &mut stdin_receiver).await?;
}
Err(err) => {
eprintln!("failed to upgrade {}", err);
}
}
}
}
async fn send_stdin_to_channel(sender: UnboundedSender<String>) -> Result<()> {
for line in stdin().lock().lines().flatten() {
sender.send(line)?;
}
Ok(())
}
#[derive(PartialEq)]
enum Mode {
Server,
Client,
}
async fn webcat<S: Stream<Item = Result<Message, WsError>> + Sink<Message>>(
mode: Mode,
stream: S,
receiver: &mut UnboundedReceiver<String>,
) -> Result<()> {
let (mut write, mut read) = stream.split();
loop {
tokio::select! {
Some(line) = receiver.recv() => {
if atty::isnt(atty::Stream::Stdin) && mode == Mode::Client && line == SERVER_ACCEPTED_NEW_CONN {
// Assuming the MITM setup described in the README, we
// disconnect and reconnect the client to prevent the
// application client and server from desynchronizing.
return Ok(());
} else if write.send(Message::Text(line)).await.is_err() {
eprintln!("failed to send message");
}
}
msg = read.next() => {
match msg {
Some(Ok(msg)) => {
match msg {
Message::Text(text) => {
println!("{}", text);
if !atty::is(atty::Stream::Stdout) {
// if stdout is redirected we also print the
// messages to stderr for convenience
eprintln!("{} {}", match mode {
Mode::Server => "server <<<",
Mode::Client => "client >>>",
}, text);
}
}
other => {
eprintln!("received: {:?}", other);
}
}
}
Some(Err(err)) => {
eprintln!("error: {:?}", err);
}
None => {
return Ok(());
}
}
}
};
}
}
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