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// Copyright 2018-2019 Peter Williams <peter@newton.cx> // Licensed under both the MIT License and the Apache-2.0 license. #![deny(missing_docs)] #![doc(html_root_url = "https://docs.rs/tokio-pty-process/0.4.0")] //! Spawn a child process under a pseudo-TTY, interacting with it //! asynchronously using Tokio. //! //! A [pseudo-terminal](https://en.wikipedia.org/wiki/Pseudoterminal) (or //! “pseudo-TTY” or “PTY”) is a special Unix file handle that models the kind //! of text terminal through which users used to interact with computers. A //! PTY enables a specialized form of bidirectional interprocess communication //! that a variety of user-facing Unix programs take advantage of. //! //! The basic way to use this crate is: //! //! 1. Create a Tokio [Reactor](https://docs.rs/tokio/*/tokio/reactor/struct.Reactor.html) //! that will handle all of your asynchronous I/O. //! 2. Create an `AsyncPtyMaster` that represents your ownership of //! an OS pseudo-terminal. //! 3. Use your master and the `spawn_pty_async` or `spawn_pty_async_raw` //! functions of the `CommandExt` extension trait, which extends //! `std::process::Command`, to launch a child process that is connected to //! your master. //! 4. Optionally control the child process (e.g. send it signals) through the //! `Child` value returned by that function. //! //! This crate only works on Unix since pseudo-terminals are a Unix-specific //! concept. //! //! The `Child` type is largely copied from Alex Crichton’s //! [tokio-process](https://github.com/alexcrichton/tokio-process) crate. extern crate bytes; #[macro_use] extern crate futures; extern crate libc; extern crate mio; extern crate tokio; extern crate tokio_io; extern crate tokio_signal; use futures::future::FlattenStream; use futures::{Async, Future, Poll, Stream}; use libc::{c_int, c_ushort}; use mio::event::Evented; use mio::unix::{EventedFd, UnixReady}; use mio::{PollOpt, Ready, Token}; use std::ffi::{CStr, OsStr, OsString}; use std::fmt; use std::fs::{File, OpenOptions}; use std::io::{self, Read, Write}; use std::mem; use std::os::unix::prelude::*; use std::os::unix::process::CommandExt as StdUnixCommandExt; use std::process::{self, ExitStatus}; use tokio::io::{AsyncRead, AsyncWrite}; use tokio::reactor::PollEvented2; use tokio_signal::unix::Signal; use tokio_signal::IoFuture; mod split; pub use split::{AsyncPtyMasterReadHalf, AsyncPtyMasterWriteHalf}; // First set of hoops to jump through: a read-write pseudo-terminal master // with full async support. As far as I can tell, we need to create an inner // wrapper type to implement Evented on a type that we can then wrap in a // PollEvented. Lame. #[derive(Debug)] struct AsyncPtyFile(File); impl AsyncPtyFile { pub fn new(inner: File) -> Self { AsyncPtyFile(inner) } } impl Read for AsyncPtyFile { fn read(&mut self, bytes: &mut [u8]) -> io::Result<usize> { self.0.read(bytes) } } impl Write for AsyncPtyFile { fn write(&mut self, bytes: &[u8]) -> io::Result<usize> { self.0.write(bytes) } fn flush(&mut self) -> io::Result<()> { self.0.flush() } } impl Evented for AsyncPtyFile { fn register( &self, poll: &mio::Poll, token: Token, interest: Ready, opts: PollOpt, ) -> io::Result<()> { EventedFd(&self.0.as_raw_fd()).register(poll, token, interest | UnixReady::hup(), opts) } fn reregister( &self, poll: &mio::Poll, token: Token, interest: Ready, opts: PollOpt, ) -> io::Result<()> { EventedFd(&self.0.as_raw_fd()).reregister(poll, token, interest | UnixReady::hup(), opts) } fn deregister(&self, poll: &mio::Poll) -> io::Result<()> { EventedFd(&self.0.as_raw_fd()).deregister(poll) } } /// A handle to a pseudo-TTY master that can be interacted with /// asynchronously. /// /// This type implements both `AsyncRead` and `AsyncWrite`. pub struct AsyncPtyMaster(PollEvented2<AsyncPtyFile>); impl AsyncPtyMaster { /// Open a pseudo-TTY master. /// /// This function performs the C library calls `posix_openpt()`, /// `grantpt()`, and `unlockpt()`. It also sets the resulting pseudo-TTY /// master handle to nonblocking mode. pub fn open() -> Result<Self, io::Error> { let inner = unsafe { // On MacOS, O_NONBLOCK is not documented as an allowed option to // posix_openpt(), but it is in fact allowed and functional, and // trying to add it later with fcntl() is forbidden. Meanwhile, on // FreeBSD, O_NONBLOCK is *not* an allowed option to // posix_openpt(), and the only way to get a nonblocking PTY // master is to add the nonblocking flag with fcntl() later. So, // we have to jump through some #[cfg()] hoops. const APPLY_NONBLOCK_AFTER_OPEN: bool = cfg!(target_os = "freebsd"); let fd = if APPLY_NONBLOCK_AFTER_OPEN { libc::posix_openpt(libc::O_RDWR | libc::O_NOCTTY) } else { libc::posix_openpt(libc::O_RDWR | libc::O_NOCTTY | libc::O_NONBLOCK) }; if fd < 0 { return Err(io::Error::last_os_error()); } if libc::grantpt(fd) != 0 { return Err(io::Error::last_os_error()); } if libc::unlockpt(fd) != 0 { return Err(io::Error::last_os_error()); } if APPLY_NONBLOCK_AFTER_OPEN { let flags = libc::fcntl(fd, libc::F_GETFL, 0); if flags < 0 { return Err(io::Error::last_os_error()); } if libc::fcntl(fd, libc::F_SETFL, flags | libc::O_NONBLOCK) == -1 { return Err(io::Error::last_os_error()); } } File::from_raw_fd(fd) }; Ok(AsyncPtyMaster(PollEvented2::new(AsyncPtyFile::new(inner)))) } /// Split the AsyncPtyMaster into an AsyncPtyReadHalf implementing `Read` and /// and `AsyncRead` as well as an `AsyncPtyWriteHalf` implementing /// `AsyncPtyWrite`. pub fn split(self) -> (AsyncPtyMasterReadHalf, AsyncPtyMasterWriteHalf) { split::split(self) } /// Open a pseudo-TTY slave that is connected to this master. /// /// The resulting file handle is *not* set to non-blocking mode. fn open_sync_pty_slave(&self) -> Result<File, io::Error> { let mut buf: [libc::c_char; 512] = [0; 512]; let fd = self.as_raw_fd(); #[cfg(not(any(target_os = "macos", target_os = "freebsd")))] { if unsafe { libc::ptsname_r(fd, buf.as_mut_ptr(), buf.len()) } != 0 { return Err(io::Error::last_os_error()); } } #[cfg(any(target_os = "macos", target_os = "freebsd"))] unsafe { let st = libc::ptsname(fd); if st.is_null() { return Err(io::Error::last_os_error()); } libc::strncpy(buf.as_mut_ptr(), st, buf.len()); } let ptsname = OsStr::from_bytes(unsafe { CStr::from_ptr(&buf as _) }.to_bytes()); OpenOptions::new().read(true).write(true).open(ptsname) } } impl AsRawFd for AsyncPtyMaster { fn as_raw_fd(&self) -> RawFd { self.0.get_ref().0.as_raw_fd() } } impl Read for AsyncPtyMaster { fn read(&mut self, bytes: &mut [u8]) -> io::Result<usize> { self.0.read(bytes) } } impl AsyncRead for AsyncPtyMaster {} impl Write for AsyncPtyMaster { fn write(&mut self, bytes: &[u8]) -> io::Result<usize> { self.0.write(bytes) } fn flush(&mut self) -> io::Result<()> { self.0.flush() } } impl AsyncWrite for AsyncPtyMaster { fn shutdown(&mut self) -> Poll<(), io::Error> { self.0.shutdown() } } // Now, the async-ified child process framework. /// A child process that can be interacted with through a pseudo-TTY. #[must_use = "futures do nothing unless polled"] pub struct Child { inner: process::Child, kill_on_drop: bool, reaped: bool, sigchld: FlattenStream<IoFuture<Signal>>, } impl fmt::Debug for Child { fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result { fmt.debug_struct("Child") .field("pid", &self.inner.id()) .field("inner", &self.inner) .field("kill_on_drop", &self.kill_on_drop) .field("reaped", &self.reaped) .field("sigchld", &"..") .finish() } } impl Child { fn new(inner: process::Child) -> Child { Child { inner: inner, kill_on_drop: true, reaped: false, sigchld: Signal::new(libc::SIGCHLD).flatten_stream(), } } /// Returns the OS-assigned process identifier associated with this child. pub fn id(&self) -> u32 { self.inner.id() } /// Forces the child to exit. /// /// This is equivalent to sending a SIGKILL on unix platforms. pub fn kill(&mut self) -> io::Result<()> { if self.reaped { Ok(()) } else { self.inner.kill() } } /// Drop this `Child` without killing the underlying process. /// /// Normally a `Child` is killed if it's still alive when dropped, but this /// method will ensure that the child may continue running once the `Child` /// instance is dropped. pub fn forget(mut self) { self.kill_on_drop = false; } /// Check whether this `Child` has exited yet. pub fn poll_exit(&mut self) -> Poll<ExitStatus, io::Error> { assert!(!self.reaped); loop { if let Some(e) = self.try_wait()? { self.reaped = true; return Ok(e.into()); } // If the child hasn't exited yet, then it's our responsibility to // ensure the current task gets notified when it might be able to // make progress. // // As described in `spawn` above, we just indicate that we can // next make progress once a SIGCHLD is received. if self.sigchld.poll()?.is_not_ready() { return Ok(Async::NotReady); } } } fn try_wait(&self) -> io::Result<Option<ExitStatus>> { let id = self.id() as c_int; let mut status = 0; loop { match unsafe { libc::waitpid(id, &mut status, libc::WNOHANG) } { 0 => return Ok(None), n if n < 0 => { let err = io::Error::last_os_error(); if err.kind() == io::ErrorKind::Interrupted { continue; } return Err(err); } n => { assert_eq!(n, id); return Ok(Some(ExitStatus::from_raw(status))); } } } } } impl Future for Child { type Item = ExitStatus; type Error = io::Error; fn poll(&mut self) -> Poll<ExitStatus, io::Error> { self.poll_exit() } } impl Drop for Child { fn drop(&mut self) { if self.kill_on_drop { drop(self.kill()); } } } /// A Future for getting the Pty file descriptor. /// /// # Example /// /// ``` /// extern crate tokio; /// extern crate tokio_pty_process; /// /// use tokio_pty_process::{AsyncPtyMaster, AsyncPtyFd}; /// use tokio::prelude::*; /// /// fn main() { /// let master = AsyncPtyMaster::open() /// .expect("Could not open the PTY"); /// /// let fd = AsyncPtyFd::from(master).wait() /// .expect("Could not get the File descriptor"); /// } /// ``` pub struct AsyncPtyFd<T: AsAsyncPtyFd>(T); impl<T: AsAsyncPtyFd> AsyncPtyFd<T> { /// Construct a new AsyncPtyFd future pub fn from(inner: T) -> Self { AsyncPtyFd(inner) } } impl<T: AsAsyncPtyFd> Future for AsyncPtyFd<T> { type Item = RawFd; type Error = io::Error; fn poll(&mut self) -> Poll<RawFd, io::Error> { self.0.as_async_pty_fd() } } /// Trait to asynchronously get the `RawFd` of the master side of the PTY pub trait AsAsyncPtyFd { /// Return a `Poll` containing the RawFd fn as_async_pty_fd(&self) -> Poll<RawFd, io::Error>; } impl AsAsyncPtyFd for AsyncPtyMaster { fn as_async_pty_fd(&self) -> Poll<RawFd, io::Error> { Ok(Async::Ready(self.as_raw_fd())) } } /// Trait containing generalized methods for PTYs pub trait PtyMaster { /// Return the full pathname of the slave device counterpart /// /// # Example /// /// ``` /// extern crate tokio; /// extern crate tokio_pty_process; /// /// use std::ffi::OsString; /// use tokio::prelude::*; /// use tokio_pty_process::{AsyncPtyMaster, PtyMaster}; /// /// struct PtsName<T: PtyMaster>(T); /// /// impl<T: PtyMaster> Future for PtsName<T> { /// type Item = OsString; /// type Error = std::io::Error; /// /// fn poll(&mut self) -> Poll<Self::Item, Self::Error> { /// self.0.ptsname() /// } /// } /// /// fn main() { /// let master = AsyncPtyMaster::open().expect("Could not open the PTY"); /// /// let ptsname = PtsName(master).wait().expect("Could not get the ptsname"); /// /// println!("PTS name: {}", ptsname.to_string_lossy()); /// } /// ``` fn ptsname(&self) -> Poll<OsString, io::Error>; /// Resize the PTY /// /// # Example /// /// ``` /// extern crate tokio; /// extern crate tokio_pty_process; /// extern crate libc; /// /// use tokio_pty_process::{AsyncPtyMaster, PtyMaster, CommandExt}; /// use tokio::prelude::*; /// use std::ffi::OsString; /// use libc::c_ushort; /// struct Resize<T: PtyMaster> { /// pty: T, /// rows: c_ushort, /// cols: c_ushort, /// } /// /// impl<T: PtyMaster> Future for Resize<T> { /// type Item = (); /// type Error = std::io::Error; /// /// fn poll(&mut self) -> Poll<Self::Item, Self::Error> { /// self.pty.resize(self.rows, self.cols) /// } /// } /// /// fn main() { /// let master = AsyncPtyMaster::open().expect("Could not open the PTY"); /// /// // On macos, it's only possible to resize a PTY with a child spawned /// // On it, so let's just do that: /// #[cfg(target_os="macos")] /// let mut child = std::process::Command::new("cat") /// .spawn_pty_async(&master) /// .expect("Could not spawn child"); /// /// Resize { /// pty: master, /// cols: 80, /// rows: 50, /// } /// .wait() /// .expect("Could not resize the PTY"); /// /// #[cfg(target_os="macos")] /// child.kill().expect("Could not kill child"); /// } /// ``` fn resize(&self, rows: c_ushort, cols: c_ushort) -> Poll<(), io::Error>; /// Get the PTY size /// /// # Example /// /// ``` /// extern crate tokio; /// extern crate tokio_pty_process; /// extern crate libc; /// /// use tokio_pty_process::{AsyncPtyMaster, PtyMaster, CommandExt}; /// use tokio::prelude::*; /// use std::ffi::OsString; /// use libc::c_ushort; /// /// struct GetSize<'a, T: PtyMaster> (&'a T); /// impl<'a, T: PtyMaster> Future for GetSize<'a, T> { /// type Item = (c_ushort, c_ushort); /// type Error = std::io::Error; /// fn poll(&mut self) -> Poll<Self::Item, Self::Error> { /// self.0.winsize() /// } /// } /// /// fn main() { /// let master = AsyncPtyMaster::open().expect("Could not open the PTY"); /// /// // On macos, it's only possible to resize a PTY with a child spawned /// // On it, so let's just do that: /// #[cfg(target_os="macos")] /// let mut child = std::process::Command::new("cat") /// .spawn_pty_async(&master) /// .expect("Could not spawn child"); /// /// let (rows, cols) = GetSize(&master) /// .wait() /// .expect("Could not get PTY size"); /// /// #[cfg(target_os="macos")] /// child.kill().expect("Could not kill child"); /// } /// ``` fn winsize(&self) -> Poll<(c_ushort, c_ushort), io::Error>; } impl<T: AsAsyncPtyFd> PtyMaster for T { fn ptsname(&self) -> Poll<OsString, io::Error> { let mut buf: [libc::c_char; 512] = [0; 512]; let fd = try_ready!(self.as_async_pty_fd()); #[cfg(not(any(target_os = "macos", target_os = "freebsd")))] { if unsafe { libc::ptsname_r(fd, buf.as_mut_ptr(), buf.len()) } != 0 { return Err(io::Error::last_os_error()); } } #[cfg(any(target_os = "macos", target_os = "freebsd"))] unsafe { let st = libc::ptsname(fd); if st.is_null() { return Err(io::Error::last_os_error()); } libc::strncpy(buf.as_mut_ptr(), st, buf.len()); } let ptsname = OsStr::from_bytes(unsafe { CStr::from_ptr(&buf as _) }.to_bytes()); Ok(Async::Ready(ptsname.to_os_string())) } fn winsize(&self) -> Poll<(c_ushort, c_ushort), io::Error> { let fd = try_ready!(self.as_async_pty_fd()); let mut winsz: libc::winsize = unsafe { std::mem::zeroed() }; if unsafe { libc::ioctl(fd, libc::TIOCGWINSZ.into(), &mut winsz) } != 0 { return Err(io::Error::last_os_error()); } Ok(Async::Ready((winsz.ws_row, winsz.ws_col))) } fn resize(&self, rows: c_ushort, cols: c_ushort) -> Poll<(), io::Error> { let fd = try_ready!(self.as_async_pty_fd()); let winsz = libc::winsize { ws_row: rows, ws_col: cols, ws_xpixel: 0, ws_ypixel: 0, }; if unsafe { libc::ioctl(fd, libc::TIOCSWINSZ.into(), &winsz) } != 0 { return Err(io::Error::last_os_error()); } Ok(Async::Ready(())) } } /// A private trait for the extending `std::process::Command`. trait CommandExtInternal { fn spawn_pty_async_full(&mut self, ptymaster: &AsyncPtyMaster, raw: bool) -> io::Result<Child>; } impl CommandExtInternal for process::Command { fn spawn_pty_async_full(&mut self, ptymaster: &AsyncPtyMaster, raw: bool) -> io::Result<Child> { let master_fd = ptymaster.as_raw_fd(); let slave = ptymaster.open_sync_pty_slave()?; let slave_fd = slave.as_raw_fd(); self.stdin(slave.try_clone()?); self.stdout(slave.try_clone()?); self.stderr(slave); // XXX any need to close slave handles in the parent process beyond // what's done here? self.before_exec(move || { unsafe { if raw { let mut attrs: libc::termios = mem::zeroed(); if libc::tcgetattr(slave_fd, &mut attrs as _) != 0 { return Err(io::Error::last_os_error()); } libc::cfmakeraw(&mut attrs as _); if libc::tcsetattr(slave_fd, libc::TCSANOW, &attrs as _) != 0 { return Err(io::Error::last_os_error()); } } // This is OK even though we don't own master since this process is // about to become something totally different anyway. if libc::close(master_fd) != 0 { return Err(io::Error::last_os_error()); } if libc::setsid() < 0 { return Err(io::Error::last_os_error()); } if libc::ioctl(0, libc::TIOCSCTTY.into(), 1) != 0 { return Err(io::Error::last_os_error()); } } Ok(()) }); Ok(Child::new(self.spawn()?)) } } /// An extension trait for the `std::process::Command` type. /// /// This trait provides new `spawn_pty_async` and `spawn_pty_async_raw` /// methods that allow one to spawn a new process that is connected to the /// current process through a pseudo-TTY. pub trait CommandExt { /// Spawn a subprocess that connects to the current one through a /// pseudo-TTY in canonical (“cooked“, not “raw”) mode. /// /// This function creates the necessary PTY slave and uses /// `std::process::Command::before_exec` to do the neccessary setup before /// the child process is spawned. In particular, it calls `setsid()` to /// launch a new TTY sesson. /// /// The child process’s standard input, standard output, and standard /// error are all connected to the pseudo-TTY slave. fn spawn_pty_async(&mut self, ptymaster: &AsyncPtyMaster) -> io::Result<Child>; /// Spawn a subprocess that connects to the current one through a /// pseudo-TTY in raw (“non-canonical”, not “cooked”) mode. /// /// This function creates the necessary PTY slave and uses /// `std::process::Command::before_exec` to do the neccessary setup before /// the child process is spawned. In particular, it sets the slave PTY /// handle to raw mode and calls `setsid()` to launch a new TTY sesson. /// /// The child process’s standard input, standard output, and standard /// error are all connected to the pseudo-TTY slave. fn spawn_pty_async_raw(&mut self, ptymaster: &AsyncPtyMaster) -> io::Result<Child>; } impl CommandExt for process::Command { fn spawn_pty_async(&mut self, ptymaster: &AsyncPtyMaster) -> io::Result<Child> { self.spawn_pty_async_full(ptymaster, false) } fn spawn_pty_async_raw(&mut self, ptymaster: &AsyncPtyMaster) -> io::Result<Child> { self.spawn_pty_async_full(ptymaster, true) } } #[cfg(test)] mod tests { extern crate errno; extern crate libc; use super::*; /// Test that the PTY master file descriptor is in nonblocking mode. We do /// this in a pretty hacky and dumb way, by creating the AsyncPtyMaster /// and then just snarfing its FD and seeing whether a Unix `read(2)` call /// errors out with EWOULDBLOCK (instead of blocking forever). In /// principle it would be nice to actually spawn a subprogram and test /// reading through the whole Tokio I/O subsystem, but that's annoying to /// implement and can actually muddy the picture. Namely: if you try to /// `master.read()` inside a Tokio event loop here, on Linux you'll get an /// ErrorKind::WouldBlock I/O error from Tokio without it even attempting /// the underlying `read(2)` system call, because Tokio uses epoll to test /// the FD's readiness in a way that works orthogonal to whether it's set /// to non-blocking mode. #[test] fn basic_nonblocking() { let master = AsyncPtyMaster::open().unwrap(); let fd = master.as_raw_fd(); let mut buf = [0u8; 128]; let rval = unsafe { libc::read(fd, buf.as_mut_ptr() as *mut libc::c_void, 128) }; let errno: i32 = errno::errno().into(); assert_eq!(rval, -1); assert_eq!(errno, libc::EWOULDBLOCK as i32); } struct GetSize<'a, T: PtyMaster>(&'a T); impl<'a, T: PtyMaster> Future for GetSize<'a, T> { type Item = (c_ushort, c_ushort); type Error = std::io::Error; fn poll(&mut self) -> Poll<Self::Item, Self::Error> { self.0.winsize() } } struct Resize<'a, T: PtyMaster> { pty: &'a T, rows: c_ushort, cols: c_ushort, } impl<'a, T: PtyMaster> Future for Resize<'a, T> { type Item = (); type Error = std::io::Error; fn poll(&mut self) -> Poll<Self::Item, Self::Error> { self.pty.resize(self.rows, self.cols) } } #[test] fn test_winsize() { let master = AsyncPtyMaster::open().expect("Could not open the PTY"); // On macos, it's only possible to resize a PTY with a child spawned // On it, so let's just do that: #[cfg(target_os = "macos")] let mut child = std::process::Command::new("cat") .spawn_pty_async(&master) .expect("Could not spawn child"); // Set the size Resize { pty: &master, cols: 80, rows: 50, } .wait() .expect("Could not resize the PTY"); let (rows, cols) = GetSize(&master).wait().expect("Could not get PTY size"); assert_eq!(cols, 80); assert_eq!(rows, 50); #[cfg(target_os = "macos")] child.kill().expect("Could not kill child"); } }