From 73c332ec49e12e4587f2f462bb929d68fbab1324 Mon Sep 17 00:00:00 2001
From: Naitik Shah <n@daaku.org>
Date: Fri, 31 May 2024 11:21:49 +0400
Subject: [PATCH] kill and reap ProxyCommand

The wrapper struct ensures ensures the child process spawned for
the ProxyCommand is cleaned up under all the various error scenarios
(such as auth failures etc), as well as in the normal successful use
case. This includes killing it if necessary, and then waiting for it.
---
 wezterm-ssh/src/sessioninner.rs | 34 ++++++++++++++++++++++++++-------
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/wezterm-ssh/src/sessioninner.rs b/wezterm-ssh/src/sessioninner.rs
index bbc145a1572..4ff213ad29b 100644
--- a/wezterm-ssh/src/sessioninner.rs
+++ b/wezterm-ssh/src/sessioninner.rs
@@ -205,7 +205,7 @@ impl SessionInner {
             sess.set_option(libssh_rs::SshOption::HostKeys(host_key.to_string()))?;
         }
 
-        let sock =
+        let (sock, _child) =
             self.connect_to_host(&hostname, port, verbose, self.config.get("proxycommand"))?;
         let raw = {
             #[cfg(unix)]
@@ -288,7 +288,7 @@ impl SessionInner {
             ))))
             .context("notifying user of banner")?;
 
-        let sock =
+        let (sock, _child) =
             self.connect_to_host(&hostname, port, verbose, self.config.get("proxycommand"))?;
 
         let mut sess = ssh2::Session::new()?;
@@ -332,7 +332,7 @@ impl SessionInner {
         port: u16,
         verbose: bool,
         proxy_command: Option<&String>,
-    ) -> anyhow::Result<Socket> {
+    ) -> anyhow::Result<(Socket, Option<KillOnDropChild>)> {
         match proxy_command.map(|s| s.as_str()) {
             Some("none") | None => {}
             Some(proxy_command) => {
@@ -351,19 +351,25 @@ impl SessionInner {
                 cmd.stdin(b.as_stdio()?);
                 cmd.stdout(b.as_stdio()?);
                 cmd.stderr(std::process::Stdio::inherit());
-                let _child = cmd
+                let child = cmd
                     .spawn()
                     .with_context(|| format!("spawning ProxyCommand {}", proxy_command))?;
 
                 #[cfg(unix)]
                 unsafe {
                     use std::os::unix::io::{FromRawFd, IntoRawFd};
-                    return Ok(Socket::from_raw_fd(a.into_raw_fd()));
+                    return Ok((
+                        Socket::from_raw_fd(a.into_raw_fd()),
+                        Some(KillOnDropChild(child)),
+                    ));
                 }
                 #[cfg(windows)]
                 unsafe {
                     use std::os::windows::io::{FromRawSocket, IntoRawSocket};
-                    return Ok(Socket::from_raw_socket(a.into_raw_socket()));
+                    return Ok((
+                        Socket::from_raw_socket(a.into_raw_socket()),
+                        Some(KillOnDropChild(child)),
+                    ));
                 }
             }
         }
@@ -392,7 +398,7 @@ impl SessionInner {
 
         sock.connect(&addr.into())
             .with_context(|| format!("Connecting to {hostname}:{port} ({addr:?})"))?;
-        Ok(sock)
+        Ok((sock, None))
     }
 
     /// Used to restrict to_socket_addrs results to the address
@@ -1086,3 +1092,17 @@ where
     }
     Ok(true)
 }
+
+/// A little helper to ensure the Child process is killed on Drop.
+struct KillOnDropChild(std::process::Child);
+
+impl Drop for KillOnDropChild {
+    fn drop(&mut self) {
+        if let Err(err) = self.0.kill() {
+            log::error!("Error killing ProxyCommand: {}", err);
+        }
+        if let Err(err) = self.0.wait() {
+            log::error!("Error waiting for ProxyCommand to finish: {}", err);
+        }
+    }
+}