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use crate::{
error::Error,
imsg::{Handler, Message},
};
use arrayvec::ArrayVec;
use close_fds::close_open_fds;
use derive_more::{AsRef, Deref, Display, From};
use nix::{
fcntl::{fcntl, open, FcntlArg, FdFlag, OFlag},
sys::{
signal::{signal, SigHandler, Signal},
stat::Mode,
},
unistd::{
self, chdir, chroot, close, dup2, execve, fork, geteuid, setsid, ForkResult, Pid, User,
},
};
use std::{
borrow::Cow,
collections::HashSet,
env,
ffi::CString,
ops,
os::unix::{
ffi::OsStrExt,
io::{AsRawFd, RawFd},
},
path::Path,
};
pub const PRIVSEP_FD: RawFd = libc::STDERR_FILENO + 1;
pub const PARENT: &str = "parent";
#[derive(Clone, Debug, Default)]
pub struct Config {
pub foreground: bool,
pub log_level: Option<String>,
}
#[cfg(feature = "log")]
impl From<&Config> for privsep_log::Config {
fn from(config: &Config) -> Self {
Self {
foreground: config.foreground,
filter: config.log_level.clone(),
}
}
}
#[derive(Debug, Default, From)]
pub struct Options {
pub disable_privdrop: bool,
pub username: Cow<'static, str>,
pub config: Config,
}
#[derive(AsRef, Debug, From)]
pub struct Process {
#[as_ref]
pub name: &'static str,
pub connect: bool,
}
pub type Processes<const N: usize> = [Process; N];
#[derive(Debug, AsRef)]
pub struct Peer {
#[as_ref]
pub name: &'static str,
pub handler: Option<Handler>,
pub pid: Pid,
}
impl Default for Peer {
fn default() -> Self {
Self {
name: "",
handler: None,
pid: Pid::parent(),
}
}
}
impl ops::Deref for Peer {
type Target = Handler;
#[inline]
fn deref(&self) -> &Self::Target {
self.handler
.as_ref()
.unwrap_or_else(|| panic!("unconfigured privsep channel: {}", self.name))
}
}
pub type Peers<const N: usize> = ArrayVec<Peer, N>;
#[derive(Debug, Display, Deref)]
#[display(fmt = "{}({})", "crate::process::PARENT", "pid")]
pub struct Parent<const N: usize> {
pub pid: Pid,
#[deref]
pub children: Peers<N>,
}
impl<const N: usize> Parent<N> {
pub async fn new(processes: Processes<N>, options: &Options) -> Result<Parent<N>, Error> {
if !options.disable_privdrop && !geteuid().is_root() {
return Err(Error::PermissionDenied);
}
if processes.first().map(|process| process.name) != Some(PARENT) {
return Err(Error::MissingParent);
}
let program = env::current_exe()?;
let mut children = Peers::default();
for proc in &processes {
if !proc.connect {
children.push(Peer {
name: proc.name,
handler: None,
pid: Pid::this(),
});
continue;
}
let (handler, remote) = Handler::pair()?;
let pid = match unsafe { fork() }? {
ForkResult::Parent { child, .. } => child,
ForkResult::Child => {
new_session(options.config.foreground, true)?;
let fd = dup2(remote.as_raw_fd(), PRIVSEP_FD)?;
set_cloexec(fd, false)?;
unsafe {
close_open_fds(PRIVSEP_FD + 1, &[]);
}
let name = path_to_cstr(&program);
let args = [
&CString::new(proc.name).unwrap(),
&CString::new(if options.config.foreground { "-d" } else { "" }).unwrap(),
];
let env = [&CString::new(format!(
"RUST_LOG={}",
env::var("RUST_LOG")
.ok()
.as_deref()
.or_else(|| options.config.log_level.as_deref())
.unwrap_or_default()
))
.unwrap()];
execve(&name, &args, &env)?;
return Err(Error::PermissionDenied);
}
};
children.push(Peer {
name: proc.name,
handler: Some(handler),
pid,
})
}
assert_eq!(children.len(), N, "child processes");
unsafe { signal(Signal::SIGPIPE, SigHandler::SigIgn) }?;
Ok(Self {
pid: Pid::this(),
children,
})
}
pub async fn connect(self, processes: [Processes<N>; N]) -> Result<Self, Error> {
let pairs = processes
.iter()
.enumerate()
.skip(1)
.flat_map(|(a, outer)| {
outer
.iter()
.enumerate()
.skip(1)
.filter_map(move |(b, inner)| {
if !inner.connect || a == b {
None
} else if a < b {
Some((a, b))
} else {
Some((b, a))
}
})
})
.collect::<HashSet<_>>();
for (a, b) in pairs {
let (left, right) = Handler::socketpair()?;
self[a]
.send_message_internal(Message::connect(b), Some(&left), &())
.await?;
self[b]
.send_message_internal(Message::connect(a), Some(&right), &())
.await?;
}
Ok(self)
}
}
#[derive(AsRef, Debug, Deref, Display)]
#[display(fmt = "{}({})", "name, pid")]
pub struct Child<const N: usize> {
#[as_ref]
pub name: &'static str,
pub pid: Pid,
#[deref]
pub peers: Peers<N>,
}
impl<const N: usize> Child<N> {
pub async fn new<const M: usize>(
processes: Processes<M>,
name: &'static str,
options: &Options,
) -> Result<Self, Error> {
assert!(M <= N);
set_cloexec(PRIVSEP_FD, true)?;
let mut peers = Peers::default();
peers.push(Peer {
name: processes[0].name,
handler: Some(Handler::from_raw_fd(PRIVSEP_FD)?),
..Peer::default()
});
for process in processes.iter().skip(1) {
peers.push(Peer {
name: process.name,
..Peer::default()
});
}
if !options.disable_privdrop {
let user = User::from_name(&options.username)?
.ok_or_else(|| Error::UserNotFound(options.username.clone()))?;
let dir = if user.dir.is_dir() {
user.dir.as_path()
} else {
Path::new("/var/empty")
};
chroot(dir).map_err(|err| Error::Privdrop("chroot", err.into()))?;
chdir("/").map_err(|err| Error::Privdrop("chdir", err.into()))?;
#[cfg(not(any(target_os = "ios", target_os = "macos", target_os = "redox")))]
unistd::setgroups(&[user.gid])
.map_err(|err| Error::Privdrop("setgroups", err.into()))?;
cfg_if::cfg_if! {
if #[cfg(any(target_os = "android", target_os = "freebsd",
target_os = "linux", target_os = "openbsd"))] {
unistd::setresgid(user.gid, user.gid, user.gid)
.map_err(|err| Error::Privdrop("setresgid", err.into()))?;
unistd::setresuid(user.uid, user.uid, user.uid)
.map_err(|err| Error::Privdrop("setresuid", err.into()))?;
} else {
unistd::setegid(user.gid).map_err(|err| Error::Privdrop("setegid", err.into()))?;
unistd::setgid(user.gid).map_err(|err| Error::Privdrop("setgid", err.into()))?;
#[cfg(not(any(target_os = "ios", target_os = "macos")))]
unistd::seteuid(user.uid).map_err(|err| Error::Privdrop("seteuid", err.into()))?;
unistd::setuid(user.uid).map_err(|err| Error::Privdrop("setuid", err.into()))?;
}
}
}
unsafe { signal(Signal::SIGPIPE, SigHandler::SigIgn) }?;
let mut wait_connections = processes
.iter()
.enumerate()
.skip(1)
.filter_map(|(id, proc)| proc.connect.then(|| id))
.collect::<HashSet<_>>();
while !wait_connections.is_empty() {
match peers[0].recv_message().await? {
Some((Message { id: 1, peer_id, .. }, Some(fd), ())) => {
let peer_id = peer_id as usize;
if !wait_connections.remove(&peer_id) {
panic!("Received invalid peer message, terminating");
}
fd.is_open()?;
println!("{} connect {}", name, peers[peer_id].name);
peers[peer_id].handler = Some(Handler::from_raw_fd(fd)?);
}
_ => panic!("Failed to get peer message, terminating"),
}
}
Ok(Self {
name,
pid: Pid::this(),
peers,
})
}
pub fn shutdown(&self) {
self.peers
.iter()
.map(ops::Deref::deref)
.for_each(Handler::shutdown);
}
}
fn set_cloexec(fd: RawFd, add: bool) -> Result<(), Error> {
let mut flags = FdFlag::from_bits_truncate(fcntl(fd, FcntlArg::F_GETFD)?);
flags.set(FdFlag::FD_CLOEXEC, add);
fcntl(fd, FcntlArg::F_SETFD(flags))?;
Ok(())
}
fn path_to_cstr(path: &Path) -> CString {
let ospath = path.as_os_str().as_bytes().to_vec();
unsafe { CString::from_vec_unchecked(ospath) }
}
pub fn daemon(no_close: bool, no_chdir: bool) -> Result<(), Error> {
cfg_if::cfg_if! {
if #[cfg(target_os = "macos")] {
match unsafe { fork() }? {
ForkResult::Parent { .. } => unsafe { libc::_exit(0) },
ForkResult::Child => new_session(no_close, no_chdir),
}
} else {
unistd::daemon(no_close, no_chdir).map_err(Into::into)
}
}
}
fn new_session(no_close: bool, no_chdir: bool) -> Result<(), Error> {
if setsid()? != Pid::this() {
return Err("Failed to create new session".into());
}
if !no_chdir {
let _ = chdir("/");
}
if !no_close {
if let Ok(fd) = open("/dev/null", OFlag::O_RDWR, Mode::empty()) {
let _ = dup2(fd, libc::STDIN_FILENO);
let _ = dup2(fd, libc::STDOUT_FILENO);
let _ = dup2(fd, libc::STDERR_FILENO);
if fd > libc::STDERR_FILENO {
let _ = close(fd);
}
}
}
Ok(())
}