Copy stdin/stdout while waiting for sync

This should allow password authentication on ssh connect

src/lib.rs

@@ -161,22 +161,38 @@ async fn server_main<Reader: AsyncRead + Unpin, Writer: AsyncWrite + Unpin>(
     }
 }
 
-async fn client_sync<T: AsyncRead + Unpin>(reader: &mut T) -> Result<()> {
-    // TODO: While we're waiting here we should be echoing everything we read.
-    //       We should also be proxying *our* stdin to the processes stdin,
-    //       and turn that off when we've synchronized. That way we can
-    //       handle passwords and the like for authentication.
+async fn client_sync<Read: AsyncRead + Unpin, Write: AsyncWrite + Unpin>(
+    reader: &mut Read,
+    writer: &mut Write,
+) -> Result<(), tokio::io::Error> {
     eprintln!("> Waiting for synchronization marker...");
-    let mut seen = 0;
-    while seen < 8 {
-        let byte = reader.read_u8().await?;
-        if byte == 0 {
-            seen += 1;
-        } else {
-            tokio::io::stdout().write_u8(byte).await?;
-        }
+
+    // Run these two loops in parallel; the copy of stdin should stop when
+    // we've seen the marker from the client. If the pipe closes for whatever
+    // reason then obviously we quit.
+    let mut stdout = tokio::io::stdout();
+    tokio::select! {
+        result = async {
+            let mut stdin = tokio::io::stdin();
+            tokio::io::copy(&mut stdin, writer).await
+        } => match result {
+            Ok(_) => Ok(()),
+            Err(e) => Err(e),
+        },
+        result = async {
+            let mut seen = 0;
+            while seen < 8 {
+                let byte = reader.read_u8().await?;
+                if byte == 0 {
+                    seen += 1;
+                } else {
+                    stdout.write_u8(byte).await?;
+                }
+            }
+
+            Ok::<_, tokio::io::Error>(())
+        } => result,
     }
-    Ok(())
 }
 
 async fn client_handle_connection(
@@ -388,12 +404,10 @@ pub async fn run_client(remote: &str) {
     // TODO: Drive a reconnect loop
     let mut child = spawn_ssh(remote).await.expect("failed to spawn");
 
-    let mut writer = MessageWriter::new(BufWriter::new(
-        child
-            .stdin
-            .take()
-            .expect("child did not have a handle to stdout"),
-    ));
+    let mut writer = child
+        .stdin
+        .take()
+        .expect("child did not have a handle to stdin");
 
     let mut reader = BufReader::new(
         child
@@ -402,11 +416,12 @@ pub async fn run_client(remote: &str) {
             .expect("child did not have a handle to stdout"),
     );
 
-    if let Err(e) = client_sync(&mut reader).await {
+    if let Err(e) = client_sync(&mut reader, &mut writer).await {
         eprintln!("Error synchronizing: {:?}", e);
         return;
     }
 
+    let mut writer = MessageWriter::new(BufWriter::new(writer));
     let mut reader = MessageReader::new(reader);
     if let Err(e) = client_main(&mut reader, &mut writer).await {
         eprintln!("Error: {:?}", e);