Skip to content

Extract Sink::set_stdioe and exec_with_creds_and_err_pipe #135

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
bjorn3 wants to merge 1 commit into from
Open

Extract Sink::set_stdioe and exec_with_creds_and_err_pipe #135

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
177 changes: 100 additions & 77 deletions beam-init/src/services.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use std::collections::BTreeMap;
use std::collections::btree_map::Entry;
use std::ffi::{CString, NulError, c_int, c_uint};
use std::io::{self, Read, Write};
use std::ffi::{CStr, CString, NulError, c_char, c_int, c_uint};
use std::io::{self, PipeWriter, Read, Write};
use std::os::fd::{AsRawFd, OwnedFd};
use std::pin::pin;
use std::process::ExitStatus;
Expand Down Expand Up @@ -658,6 +658,16 @@ enum Sink<'a> {
PTY(PtyClient<'a, StoredFd>),
}

fn expect_no_panic<T>(res: io::Result<T>, msg: &'static str) -> T {
match res {
Ok(x) => x,
Err(err) => {
eprintln!("{msg}: {err}");
_exit(101);
}
}
}

fn spawn_service(old_sigmask: OldSigmask, config: &ServiceConfig, sink: Sink) -> io::Result<pid_t> {
let cmd = CString::new(config.cmd.clone())?;

Expand All @@ -672,16 +682,7 @@ fn spawn_service(old_sigmask: OldSigmask, config: &ServiceConfig, sink: Sink) ->
.chain(Some(ptr::null()))
.collect::<Vec<_>>();

let (mut err_rx, mut err_tx) = io::pipe()?;
fn expect_no_panic<T>(res: io::Result<T>, msg: &'static str) -> T {
match res {
Ok(x) => x,
Err(err) => {
eprintln!("{msg}: {err}");
_exit(101);
}
}
}
let (mut err_rx, err_tx) = io::pipe()?;
// SAFETY: We only run async-signal-safe functions inside the child process.
let child_pid = unsafe {
unsafe_fork!({
Expand All @@ -695,72 +696,10 @@ fn spawn_service(old_sigmask: OldSigmask, config: &ServiceConfig, sink: Sink) ->
// SAFETY: setsid is safe to call.
expect_no_panic(cerr(libc::setsid()), "failed to setsid");

match sink {
Sink::PTY(pty) => {
let pty_fd = expect_no_panic(
pty.make_tty(),
"could not make the pty the controlling terminal",
);

// Set the pseudoterminal as stdin, stdout and stderr
// SAFETY: dup2 is memory safe to call. This technically violates IO-safety, but nothing
// accessed after this point depends on stdout/stderr pointing to a particular fd.
expect_no_panic(
[libc::STDIN_FILENO, libc::STDOUT_FILENO, libc::STDERR_FILENO]
.into_iter()
.try_for_each(|fd| {
cerr(libc::dup2(pty_fd.as_raw_fd(), fd))?;
Ok(())
}),
"failed to attach pty",
);
}
Sink::Log(log_writer) => {
// Set the log pipe as stdout and stderr
// SAFETY: as above
expect_no_panic(
cerr(libc::dup2(log_writer.as_raw_fd(), libc::STDOUT_FILENO)),
"failed to set stdout",
);
expect_no_panic(
cerr(libc::dup2(log_writer.as_raw_fd(), libc::STDERR_FILENO)),
"failed to set stderr",
);
}
}

// Using raw syscall as musl doesn't have a close_range() wrapper.
// SAFETY: SYS_close_range with CLOSE_RANGE_CLOEXEC doesn't violate IO safety.
expect_no_panic(
cerr(libc::syscall(
libc::SYS_close_range,
3,
c_uint::MAX,
libc::CLOSE_RANGE_CLOEXEC.cast_signed(),
) as c_int),
"failed to `close_range",
);

// Set the group and user ID (derived from socket) as well as an empty supplementary
// group list.
expect_no_panic(
config.credentials.set_creds(),
"failed to set process credentials",
);
sink.set_stdioe();

libc::execvp(cmd.as_ptr(), args.as_ptr());

// If we reach this point, the exec failed.
let Some(err) = io::Error::last_os_error().raw_os_error() else {
eprintln!("last_os_error didn't return OS error");
_exit(101);
};

expect_no_panic(
err_tx.write_all(&i32::to_ne_bytes(err)),
"failed to write error code",
);
_exit(1);
// SAFETY: args is a NULL terminated list of C strings.
exec_with_creds_and_err_pipe(&cmd, &args, &config.credentials, err_tx)
})
}?;
drop(err_tx);
Expand All @@ -772,3 +711,87 @@ fn spawn_service(old_sigmask: OldSigmask, config: &ServiceConfig, sink: Sink) ->
Err(err) => Err(err),
}
}

impl Sink<'_> {
fn set_stdioe(self) {
match self {
Sink::PTY(pty) => {
let pty_fd = expect_no_panic(
pty.make_tty(),
"could not make the pty the controlling terminal",
);

// Set the pseudoterminal as stdin, stdout and stderr
expect_no_panic(
[libc::STDIN_FILENO, libc::STDOUT_FILENO, libc::STDERR_FILENO]
.into_iter()
.try_for_each(|fd| {
// SAFETY: dup2 is memory safe to call. This technically violates
// IO-safety, but nothing accessed after this point depends on
// stdout/stderr pointing to a particular fd.
cerr(unsafe { libc::dup2(pty_fd.as_raw_fd(), fd) })?;
Ok(())
}),
"failed to attach pty",
);
}
Sink::Log(log_writer) => {
// Set the log pipe as stdout and stderr
expect_no_panic(
// SAFETY: as above
cerr(unsafe { libc::dup2(log_writer.as_raw_fd(), libc::STDOUT_FILENO) }),
"failed to set stdout",
);
expect_no_panic(
// SAFETY: as above
cerr(unsafe { libc::dup2(log_writer.as_raw_fd(), libc::STDERR_FILENO) }),
"failed to set stderr",
);
}
}
}
}

/// # Safety
///
/// `args` must be a NULL terminated list of C strings.
unsafe fn exec_with_creds_and_err_pipe(
cmd: &CStr,
args: &[*const c_char],
credentials: &Credentials,
mut err_tx: PipeWriter,
) -> ! {
// Using raw syscall as musl doesn't have a close_range() wrapper.
// SAFETY: SYS_close_range with CLOSE_RANGE_CLOEXEC doesn't violate IO safety.
expect_no_panic(
cerr(unsafe {
libc::syscall(
libc::SYS_close_range,
3,
c_uint::MAX,
libc::CLOSE_RANGE_CLOEXEC.cast_signed(),
) as c_int
}),
"failed to `close_range",
);

// Set the group and user ID (derived from socket) as well as an empty
// supplementary group list.
expect_no_panic(credentials.set_creds(), "failed to set process credentials");

// SAFETY: Per the safety requirements of this function, args is a NULL
// terminated list of C strings.
unsafe { libc::execvp(cmd.as_ptr(), args.as_ptr()) };

// If we reach this point, the exec failed.
let Some(err) = io::Error::last_os_error().raw_os_error() else {
eprintln!("last_os_error didn't return OS error");
_exit(101);
};

expect_no_panic(
err_tx.write_all(&i32::to_ne_bytes(err)),
"failed to write error code",
);
_exit(1);
}