allow blocking local addresses

server/src/main.rs

@@ -1,4 +1,4 @@
-#![feature(let_chains)]
+#![feature(let_chains, ip)]
 use std::io::Error;
 
 use bytes::Bytes;
@@ -12,7 +12,7 @@ use hyper::{
     body::Incoming, server::conn::http1, service::service_fn, Request, Response, StatusCode,
 };
 use hyper_util::rt::TokioIo;
-use tokio::net::{TcpListener, TcpStream, UdpSocket};
+use tokio::net::{lookup_host, TcpListener, TcpStream, UdpSocket};
 #[cfg(unix)]
 use tokio::net::{UnixListener, UnixStream};
 use tokio_util::codec::{BytesCodec, Framed};
@@ -23,17 +23,29 @@ use wisp_mux::{CloseReason, ConnectPacket, MuxStream, ServerMux, StreamType, Wis
 
 type HttpBody = http_body_util::Full<hyper::body::Bytes>;
 
+/// Server implementation of the Wisp protocol in Rust, made for epoxy
 #[derive(Parser)]
-#[command(version = clap::crate_version!(), about = "Server implementation of the Wisp protocol in Rust, made for epoxy.")]
+#[command(version = clap::crate_version!())]
 struct Cli {
+    /// URL prefix the server should serve on
     #[arg(long, default_value = "")]
     prefix: String,
+    /// Port the server should bind to
     #[arg(long, short, default_value = "4000")]
     port: String,
+    /// Host the server should bind to
     #[arg(long = "host", short, value_name = "HOST", default_value = "0.0.0.0")]
     bind_host: String,
+    /// Whether the server should listen on a Unix socket located at the value of the bind_host
+    /// argument
     #[arg(long, short)]
     unix_socket: bool,
+    /// Whether the server should block IP addresses that are not globally reachable
+    ///
+    /// See https://doc.rust-lang.org/std/net/struct.Ipv4Addr.html#method.is_global for which IP
+    /// addresses are blocked
+    #[arg(long, short)]
+    block_local: bool,
 }
 
 #[cfg(not(unix))]
@@ -107,11 +119,12 @@ async fn main() -> Result<(), Error> {
 
     println!("listening on `{}`", addr);
     while let Ok((stream, addr)) = socket.accept().await {
-        let prefix_cloned = opt.prefix.clone();
+        let prefix = opt.prefix.clone();
         tokio::spawn(async move {
             let io = TokioIo::new(stream);
-            let service =
-                service_fn(move |res| accept_http(res, addr.clone(), prefix_cloned.clone()));
+            let service = service_fn(move |res| {
+                accept_http(res, addr.clone(), prefix.clone(), opt.block_local)
+            });
             let conn = http1::Builder::new()
                 .serve_connection(io, service)
                 .with_upgrades();
@@ -128,17 +141,18 @@ async fn accept_http(
     mut req: Request<Incoming>,
     addr: String,
     prefix: String,
+    block_local: bool,
 ) -> Result<Response<HttpBody>, WebSocketError> {
-    let uri = req.uri().clone().path().to_string();
+    let uri = req.uri().path().to_string();
     if upgrade::is_upgrade_request(&req)
         && let Some(uri) = uri.strip_prefix(&prefix)
     {
         let (res, fut) = upgrade::upgrade(&mut req)?;
 
-        if uri.is_empty() || uri == "/" {
-            tokio::spawn(async move { accept_ws(fut, addr.clone()).await });
+        if uri == "/" {
+            tokio::spawn(async move { accept_ws(fut, addr.clone(), block_local).await });
         } else if let Some(uri) = uri.strip_prefix('/').map(|x| x.to_string()) {
-            tokio::spawn(async move { accept_wsproxy(fut, uri, addr.clone()).await });
+            tokio::spawn(async move { accept_wsproxy(fut, uri, addr.clone(), block_local).await });
         }
 
         Ok(Response::from_parts(
@@ -202,6 +216,7 @@ async fn handle_mux(packet: ConnectPacket, mut stream: MuxStream) -> Result<bool
 async fn accept_ws(
     fut: upgrade::UpgradeFut,
     addr: String,
+    block_local: bool,
 ) -> Result<(), Box<dyn std::error::Error + Sync + Send>> {
     let (rx, tx) = fut.await?.split(tokio::io::split);
     let rx = FragmentCollectorRead::new(rx);
@@ -218,6 +233,29 @@ async fn accept_ws(
 
     while let Some((packet, stream)) = mux.server_new_stream().await {
         tokio::spawn(async move {
+            if block_local {
+                match lookup_host(format!(
+                    "{}:{}",
+                    packet.destination_hostname, packet.destination_port
+                ))
+                .await
+                .ok()
+                .and_then(|mut x| x.next())
+                .map(|x| !x.ip().is_global())
+                {
+                    Some(true) => {
+                        let _ = stream.close(CloseReason::ServerStreamBlockedAddress).await;
+                        return;
+                    }
+                    Some(false) => {}
+                    None => {
+                        let _ = stream
+                            .close(CloseReason::ServerStreamConnectionRefused)
+                            .await;
+                        return;
+                    }
+                }
+            }
             let close_err = stream.get_close_handle();
             let close_ok = stream.get_close_handle();
             let _ = handle_mux(packet, stream)
@@ -244,18 +282,35 @@ async fn accept_wsproxy(
     fut: upgrade::UpgradeFut,
     incoming_uri: String,
     addr: String,
+    block_local: bool,
 ) -> Result<(), Box<dyn std::error::Error + Sync + Send>> {
     let mut ws_stream = FragmentCollector::new(fut.await?);
 
     println!("{:?}: connected (wsproxy): {:?}", addr, incoming_uri);
 
-    match hyper::Uri::try_from(incoming_uri.clone()) {
-        Ok(_) => (),
-        Err(err) => {
-            ws_stream
-                .write_frame(Frame::close(CloseCode::Away.into(), b"invalid uri"))
-                .await?;
-            return Err(Box::new(err));
+    if block_local {
+        match lookup_host(&incoming_uri)
+            .await
+            .ok()
+            .and_then(|mut x| x.next())
+            .map(|x| !x.ip().is_global())
+        {
+            Some(true) => {
+                ws_stream
+                    .write_frame(Frame::close(CloseCode::Error.into(), b"blocked uri"))
+                    .await?;
+                return Ok(());
+            }
+            Some(false) => {}
+            None => {
+                ws_stream
+                    .write_frame(Frame::close(
+                        CloseCode::Error.into(),
+                        b"failed to resolve uri",
+                    ))
+                    .await?;
+                return Ok(());
+            }
         }
     }
 
@@ -263,7 +318,7 @@ async fn accept_wsproxy(
         Ok(stream) => stream,
         Err(err) => {
             ws_stream
-                .write_frame(Frame::close(CloseCode::Away.into(), b"failed to connect"))
+                .write_frame(Frame::close(CloseCode::Error.into(), b"failed to connect"))
                 .await?;
             return Err(Box::new(err));
         }