Isolate interactive terminal session ownership

crates/lazaret-linux/src/process.rs

@@ -33,6 +33,7 @@ pub struct TargetCommand {
     parent_edge: ParentEdge,
     executable: Option<OwnedFd>,
     stdin: Option<File>,
+    terminal: bool,
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
@@ -106,6 +107,7 @@ impl TargetCommand {
             parent_edge: ParentEdge::ParentDeathKill,
             executable: None,
             stdin: None,
+            terminal: false,
         }
     }
 
@@ -124,6 +126,7 @@ impl TargetCommand {
             parent_edge: ParentEdge::ParentDeathKill,
             executable: Some(executable),
             stdin: None,
+            terminal: false,
         })
     }
 
@@ -156,6 +159,12 @@ impl TargetCommand {
         Ok(self)
     }
 
+    #[must_use]
+    pub fn with_controlling_terminal(mut self) -> Self {
+        self.terminal = true;
+        self
+    }
+
     #[must_use]
     pub const fn parent_edge(&self) -> ParentEdge {
         self.parent_edge
@@ -180,6 +189,7 @@ impl TargetCommand {
                 ParentEdge::ParentDeathKill => "kill",
                 ParentEdge::LifetimePipe => "lifetime-pipe",
             })
+            .args(self.terminal.then_some("--target-terminal"))
             .args(
                 self.stdin
                     .as_ref()

crates/lazaret-linux/src/process/broker.rs

@@ -16,6 +16,7 @@ use super::{
 use crate::ipc::private_stream_pair;
 use crate::user_namespace::UserNamespaceMap;
 use std::io::{Read as _, Write as _};
+use std::os::unix::process::CommandExt as _;
 
 impl ChildBroker {
     /// Spawns the private Host Coordinator bootstrap with exact pipe ownership and pidfd reaping.
@@ -44,7 +45,8 @@ impl ChildBroker {
             .args(&target.arguments)
             .stdin(Stdio::from(lifetime_reader))
             .stdout(Stdio::piped())
-            .stderr(Stdio::inherit());
+            .stderr(Stdio::inherit())
+            .process_group(0);
         let mut child = command.spawn()?;
         let status = child
             .stdout
@@ -743,6 +745,7 @@ fn run_mapped_wrapper_role(arguments: Vec<OsString>) -> io::Result<()> {
         rustix::process::Uid::ROOT,
         rustix::process::Uid::ROOT,
     )?;
+    establish_controlling_terminal(&target)?;
     if let Some(stdin) = target.stdin.as_ref() {
         rustix::stdio::dup2_stdin(stdin)?;
     }
@@ -761,12 +764,27 @@ fn run_wrapper_role(arguments: Vec<OsString>) -> io::Result<()> {
             require_lifetime_pipe_and_recheck(expected_parent)?;
         }
     }
+    establish_controlling_terminal(&target)?;
     if let Some(stdin) = target.stdin.as_ref() {
         rustix::stdio::dup2_stdin(stdin)?;
     }
     Err(exec_target(target))
 }
 
+fn establish_controlling_terminal(target: &TargetCommand) -> io::Result<()> {
+    if !target.terminal {
+        return Ok(());
+    }
+    let stdin = target
+        .stdin
+        .as_ref()
+        .ok_or_else(|| io::Error::other("terminal target stdin is missing"))?;
+    rustix::process::setsid()?;
+    rustix::process::ioctl_tiocsctty(stdin)?;
+    rustix::termios::tcsetpgrp(stdin, rustix::process::getpgrp())?;
+    Ok(())
+}
+
 fn require_lifetime_pipe_and_recheck(
     expected_parent: PidfsProcessIdentityV1,
 ) -> io::Result<RetainedProcess> {

crates/lazaret-linux/src/process/launch.rs

@@ -91,7 +91,11 @@ pub fn parse_wrapper_arguments(
         Some("lifetime-pipe") => ParentEdge::LifetimePipe,
         _ => return Err(io::Error::other("wrapper parent action is invalid")),
     };
-    let next = arguments.next();
+    let mut next = arguments.next();
+    let terminal = next.as_deref() == Some(OsStr::new("--target-terminal"));
+    if terminal {
+        next = arguments.next();
+    }
     let stdin = if next.as_deref() == Some(OsStr::new("--target-stdin-fd")) {
         let descriptor = arguments
             .next()
@@ -117,6 +121,7 @@ pub fn parse_wrapper_arguments(
         parent_edge,
         executable: None,
         stdin,
+        terminal,
     };
     let boot = parse_boot_hex(&boot)?;
     Ok((

crates/lazaret-linux/tests/acquisition.rs

@@ -5,6 +5,7 @@ use std::os::fd::AsFd;
 use std::process::{ExitCode, Stdio};
 use std::sync::atomic::{AtomicU64, AtomicUsize, Ordering};
 use std::sync::{Arc, Barrier};
+use std::time::{Duration, Instant};
 
 use lazaret_core::identity::{
     CoordinatorId, DomainId, GenerationId, HostPidLocator, PidfsProcessIdentityV1,
@@ -13,14 +14,14 @@ use lazaret_core::records::{
     HostProcessOwnershipSlot, ProcessOwnershipCommitAck, StagedProcessOwnership,
 };
 use lazaret_linux::process::{
-    AcknowledgedChildAcquisition, ChildStandardIo, ProcessOwnershipContext, TargetCommand,
-    append_parent_identity, child_broker, current_process_identity, dispatch_private_process_role,
-    verify_direct_child_pidfd,
+    AcknowledgedChildAcquisition, ChildStandardIo, ProcessOwnershipContext, RetainedProcess,
+    TargetCommand, append_parent_identity, child_broker, current_process_identity,
+    dispatch_private_process_role, verify_direct_child_pidfd,
 };
 use lazaret_linux::user_namespace::UserNamespaceMap;
 use rustix::fs::{OFlags, fcntl_getfl, fcntl_setfl};
 use rustix::pipe::{PipeFlags, pipe_with};
-use rustix::process::{PidfdFlags, pidfd_open};
+use rustix::process::{PidfdFlags, Signal, pidfd_open};
 use rustix::pty::{OpenptFlags, grantpt, ioctl_tiocgptpeer, openpt, unlockpt};
 use rustix::termios::{Winsize, tcgetwinsize, tcsetwinsize};
 
@@ -52,6 +53,8 @@ fn run_all() -> std::io::Result<()> {
     mapped_transient_uses_configured_subordinates()?;
     transient_captured_child_preserves_streams_and_exit()?;
     terminal_child_restores_slave_stdin_and_merges_output()?;
+    terminal_children_isolate_window_signals()?;
+    bootstrap_child_uses_a_distinct_process_group()?;
     target_stdin_does_not_gain_write_authority()?;
     acknowledged_transition_precedes_exact_wrapper_release()?;
     failed_acknowledged_transition_refuses_exact_wrapper_release()?;
@@ -64,6 +67,33 @@ fn run_all() -> std::io::Result<()> {
     concurrent_acquisitions_serialize()
 }
 
+fn bootstrap_child_uses_a_distinct_process_group() -> std::io::Result<()> {
+    let (reader, writer) = pipe_with(PipeFlags::CLOEXEC)?;
+    let target = TargetCommand::new("/bin/sh")
+        .argument("-c")
+        .argument(
+            "if [ \"$(ps -o pgid= -p $$)\" = \"$(ps -o pgid= -p $PPID)\" ]; then printf E; else printf R; fi; read value || exit 0",
+        )
+        .with_lifetime_pipe_parent_edge();
+    let mut child = child_broker().spawn_bootstrap(&target, File::from(reader))?;
+    if child.bootstrap_status()? != b'R' {
+        return Err(std::io::Error::other(
+            "bootstrap child shared the client process group",
+        ));
+    }
+    drop(writer);
+    while !child.has_exited()? {
+        std::thread::yield_now();
+    }
+    let exit = child.reap()?;
+    if exit.exit_code != Some(0) || exit.terminating_signal.is_some() {
+        return Err(std::io::Error::other(format!(
+            "bootstrap process-group probe failed: {exit:?}"
+        )));
+    }
+    Ok(())
+}
+
 fn mapped_transient_uses_configured_subordinates() -> std::io::Result<()> {
     let map = UserNamespaceMap::resolve_current()?;
     child_broker()
@@ -149,7 +179,8 @@ fn terminal_child_restores_slave_stdin_and_merges_output() -> std::io::Result<()
         .argument(
             "read value; printf 'stdin-fd\\n' >&0; printf 'out:%s\\n' \"$value\"; printf 'err\\n' >&2",
         )
-        .with_target_stdin(slave.try_clone()?)?;
+        .with_target_stdin(slave.try_clone()?)?
+        .with_controlling_terminal();
     let expected_parent = current_process_identity()?;
     let ownership = ProcessOwnershipContext {
         domain_id: DomainId::new([41; 32]),
@@ -193,6 +224,133 @@ fn terminal_child_restores_slave_stdin_and_merges_output() -> std::io::Result<()
     Ok(())
 }
 
+fn terminal_children_isolate_window_signals() -> std::io::Result<()> {
+    let (mut first_master, first) = terminal_child("S1", 51)?;
+    let (mut second_master, second) = terminal_child("S2", 52)?;
+    let mut first_output = Vec::new();
+    let mut second_output = Vec::new();
+    wait_for_terminal_marker(&mut first_master, &mut first_output, b"S1_READY")?;
+    wait_for_terminal_marker(&mut second_master, &mut second_output, b"S2_READY")?;
+    let first_identity = terminal_identity(&first_output, "S1_READY")?;
+    let second_identity = terminal_identity(&second_output, "S2_READY")?;
+    if first_identity
+        .iter()
+        .any(|value| *value != first_identity[0])
+        || second_identity
+            .iter()
+            .any(|value| *value != second_identity[0])
+        || first_identity[0] == second_identity[0]
+    {
+        return Err(std::io::Error::other(
+            "terminal targets did not receive distinct controlling sessions",
+        ));
+    }
+    first.send_signal(Signal::WINCH)?;
+    wait_for_terminal_marker(&mut first_master, &mut first_output, b"S1_WINCH")?;
+    second_master.write_all(b"after\n")?;
+    wait_for_terminal_marker(&mut second_master, &mut second_output, b"S2:after")?;
+    if second_output
+        .windows(b"S2_WINCH".len())
+        .any(|part| part == b"S2_WINCH")
+    {
+        return Err(std::io::Error::other(
+            "window signal crossed terminal process groups",
+        ));
+    }
+    while !first.has_exited()? {
+        std::thread::yield_now();
+    }
+    let first_exit = child_broker().reap_status(first)?;
+    second.send_signal(Signal::KILL)?;
+    let second_exit = child_broker().reap_status(second)?;
+    if first_exit.exit_code != Some(0)
+        || first_exit.terminating_signal.is_some()
+        || second_exit.terminating_signal.is_none()
+    {
+        return Err(std::io::Error::other(
+            "terminal signal isolation produced unexpected exits",
+        ));
+    }
+    Ok(())
+}
+
+fn terminal_child(marker: &str, seed: u8) -> std::io::Result<(File, RetainedProcess)> {
+    let master = openpt(OpenptFlags::RDWR | OpenptFlags::NOCTTY | OpenptFlags::CLOEXEC)?;
+    grantpt(&master)?;
+    unlockpt(&master)?;
+    let slave = File::from(ioctl_tiocgptpeer(
+        &master,
+        OpenptFlags::RDWR | OpenptFlags::NOCTTY | OpenptFlags::CLOEXEC,
+    )?);
+    let target = TargetCommand::new("/usr/bin/python3")
+        .argument("-c")
+        .argument(format!(
+            "import os, signal, sys\nmarker = {marker:?}\ndef winch(*_):\n print(marker + '_WINCH', flush=True)\n sys.exit(0)\nsignal.signal(signal.SIGWINCH, winch)\nprint(f'{{marker}}_READY pid={{os.getpid()}} sid={{os.getsid(0)}} pgrp={{os.getpgrp()}} tty={{os.tcgetpgrp(0)}}', flush=True)\nfor line in sys.stdin:\n print(marker + ':' + line.strip(), flush=True)"
+        ))
+        .with_target_stdin(slave.try_clone()?)?
+        .with_controlling_terminal();
+    let process = child_broker().acquire_with_stdio(
+        current_process_identity()?,
+        ProcessOwnershipContext {
+            domain_id: DomainId::new([seed; 32]),
+            generation_id: GenerationId::new(u64::from(seed)),
+            coordinator_id: CoordinatorId::new([seed.wrapping_add(1); 32]),
+            slot: HostProcessOwnershipSlot::SessionTerminalExecClient(
+                lazaret_core::identity::SessionId::new([seed.wrapping_add(2); 32]),
+            ),
+        },
+        &target,
+        ChildStandardIo::terminal(slave)?,
+        |_| Ok(()),
+        |staged| Ok(ProcessOwnershipCommitAck::v1(staged)),
+    )?;
+    let master = File::from(master);
+    let flags = fcntl_getfl(&master)?;
+    fcntl_setfl(&master, flags | OFlags::NONBLOCK)?;
+    Ok((master, process))
+}
+
+fn terminal_identity(output: &[u8], marker: &str) -> std::io::Result<[u32; 4]> {
+    let text = String::from_utf8_lossy(output);
+    let line = text
+        .lines()
+        .find(|line| line.starts_with(marker))
+        .ok_or_else(|| std::io::Error::other("terminal identity marker is missing"))?;
+    let values = line
+        .split_whitespace()
+        .skip(1)
+        .map(|field| {
+            field
+                .split_once('=')
+                .and_then(|(_, value)| value.parse::<u32>().ok())
+                .ok_or_else(|| std::io::Error::other("terminal identity field is invalid"))
+        })
+        .collect::<std::io::Result<Vec<_>>>()?;
+    values
+        .try_into()
+        .map_err(|_| std::io::Error::other("terminal identity field count is invalid"))
+}
+
+fn wait_for_terminal_marker(
+    master: &mut File,
+    output: &mut Vec<u8>,
+    marker: &[u8],
+) -> std::io::Result<()> {
+    let deadline = Instant::now() + Duration::from_secs(10);
+    while !output.windows(marker.len()).any(|part| part == marker) {
+        read_available(master, output)?;
+        if Instant::now() >= deadline {
+            return Err(std::io::Error::other(format!(
+                "terminal marker {:?} deadline expired with {:?}",
+                String::from_utf8_lossy(marker),
+                String::from_utf8_lossy(output)
+            )));
+        }
+        std::thread::yield_now();
+    }
+    Ok(())
+}
+
 fn transient_captured_child_preserves_streams_and_exit() -> std::io::Result<()> {
     let target = TargetCommand::new("/bin/sh")
         .argument("-c")