use std::net::SocketAddr;
use std::path::PathBuf;
use std::pin::Pin;
use std::process::Command;
use std::str;
use std::sync::Arc;
use clap::Parser;
use color_eyre::eyre::Result;
use eyre::{bail, Context};
use futures::future::{ready, Ready};
use futures::Future;
use metrics_exporter_prometheus::PrometheusBuilder;
use nix::pty::Winsize;
use pty::ChildHandle;
use thrussh::server::{self, Auth, Session};
use thrussh::{ChannelId, CryptoVec};
use thrussh_keys::decode_secret_key;
use thrussh_keys::key::KeyPair;
use tokio::fs::File;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::net::TcpListener;
use tokio::select;
use tokio::time::Instant;
use tracing::{debug, error, info, info_span, trace, warn, Instrument};
use tracing_subscriber::EnvFilter;
use crate::pty::WaitPid;
mod metrics;
mod pty;
use crate::metrics::reported::*;
use crate::metrics::{decrement_gauge, histogram, increment_counter, increment_gauge};
/// SSH-compatible server for playing Xanthous
#[derive(Parser, Debug)]
struct Opts {
/// Address to bind to
#[clap(long, short = 'a', default_value = "0.0.0.0:22")]
address: String,
/// Address to listen to for metrics
#[clap(long, default_value = "0.0.0.0:9000")]
metrics_address: SocketAddr,
/// Format to use when emitting log events
#[clap(
long,
env = "LOG_FORMAT",
default_value = "full",
possible_values = &["compact", "full", "pretty", "json"]
)]
log_format: String,
/// Full path to the xanthous binary
#[clap(long, env = "XANTHOUS_BINARY_PATH")]
xanthous_binary_path: String,
/// Path to a file containing the ed25519 secret key for the server
#[clap(long, env = "SECRET_KEY_FILE")]
secret_key_file: PathBuf,
/// Level to log at
#[clap(long, env = "LOG_LEVEL", default_value = "info")]
log_level: String,
}
impl Opts {
async fn read_secret_key(&self) -> Result<KeyPair> {
let mut file = File::open(&self.secret_key_file)
.await
.context("Reading secret key file")?;
let mut secret_key = Vec::with_capacity(464);
file.read_to_end(&mut secret_key).await?;
Ok(decode_secret_key(str::from_utf8(&secret_key)?, None)?)
}
async fn ssh_server_config(&self) -> Result<server::Config> {
let key_pair = self.read_secret_key().await?;
Ok(server::Config {
server_id: "SSH-2.0-xanthous".to_owned(),
keys: vec![key_pair],
..Default::default()
})
}
fn init_logging(&self) -> Result<()> {
let filter = EnvFilter::try_new(&self.log_level)?;
let s = tracing_subscriber::fmt().with_env_filter(filter);
match self.log_format.as_str() {
"compact" => s.compact().init(),
"full" => s.init(),
"pretty" => s.pretty().init(),
"json" => s.json().with_current_span(true).init(),
f => bail!("Invalid log format `{}`", f),
}
Ok(())
}
}
struct Handler {
address: SocketAddr,
xanthous_binary_path: &'static str,
username: Option<String>,
child: Option<ChildHandle>,
}
async fn run_child(
mut child: pty::Child,
mut server_handle: server::Handle,
channel_id: ChannelId,
) -> Result<()> {
let mut buf = [0; 2048];
loop {
select! {
r = child.tty.read(&mut buf) => {
let read_bytes = r?;
if read_bytes == 0 {
info!("EOF received from process");
let _ = server_handle.close(channel_id).await;
return Ok(())
} else {
trace!(?read_bytes, "read bytes from child");
let _ = server_handle.data(channel_id, CryptoVec::from_slice(&buf[..read_bytes])).await;
}
}
status = WaitPid::new(child.pid) => {
match status {
Ok(_status) => info!("Child exited"),
Err(error) => error!(%error, "Child failed"),
}
let _ = server_handle.close(channel_id).await;
return Ok(())
}
}
}
}
impl Handler {
async fn spawn_shell(
&mut self,
mut handle: server::Handle,
channel_id: ChannelId,
term: String,
winsize: Winsize,
) -> Result<()> {
let mut cmd = Command::new(self.xanthous_binary_path);
cmd.env("TERM", term);
if let Some(username) = &self.username {
cmd.args(["--name", username]);
}
cmd.arg("--disable-saving");
let child = pty::spawn(cmd, Some(winsize), None).await?;
info!(pid = %child.pid, "Spawned child");
increment_gauge!(RUNNING_PROCESSES, 1.0);
self.child = Some(child.handle().await?);
tokio::spawn(
async move {
let span = info_span!("child", pid = %child.pid);
if let Err(error) = run_child(child, handle.clone(), channel_id)
.instrument(span.clone())
.await
{
span.in_scope(|| error!(%error, "Error running child"));
let _ = handle.close(channel_id).await;
}
decrement_gauge!(RUNNING_PROCESSES, 1.0);
}
.in_current_span(),
);
Ok(())
}
}
#[allow(clippy::type_complexity)]
impl server::Handler for Handler {
type Error = eyre::Error;
type FutureAuth = Ready<Result<(Self, Auth)>>;
type FutureUnit = Pin<Box<dyn Future<Output = Result<(Self, Session)>> + Send + 'static>>;
type FutureBool = Ready<Result<(Self, Session, bool)>>;
fn finished_auth(self, auth: Auth) -> Self::FutureAuth {
ready(Ok((self, auth)))
}
fn finished_bool(self, b: bool, session: Session) -> Self::FutureBool {
ready(Ok((self, session, b)))
}
fn finished(self, session: Session) -> Self::FutureUnit {
Box::pin(ready(Ok((self, session))))
}
fn auth_none(mut self, username: &str) -> Self::FutureAuth {
info!(%username, "Accepted new connection");
self.username = Some(username.to_owned());
self.finished_auth(Auth::Accept)
}
fn auth_password(mut self, username: &str, _password: &str) -> Self::FutureAuth {
info!(%username, "Accepted new connection");
self.username = Some(username.to_owned());
self.finished_auth(Auth::Accept)
}
fn auth_publickey(
mut self,
username: &str,
_: &thrussh_keys::key::PublicKey,
) -> Self::FutureAuth {
info!(%username, "Accepted new connection");
self.username = Some(username.to_owned());
self.finished_auth(Auth::Accept)
}
fn pty_request(
mut self,
channel: thrussh::ChannelId,
term: &str,
col_width: u32,
row_height: u32,
pix_width: u32,
pix_height: u32,
modes: &[(thrussh::Pty, u32)],
session: Session,
) -> Self::FutureUnit {
let term = term.to_owned();
let modes = modes.to_vec();
Box::pin(async move {
debug!(
%term,
%col_width,
%row_height,
%pix_width,
%pix_height,
?modes,
"PTY Requested"
);
self.spawn_shell(
session.handle(),
channel,
term,
Winsize {
ws_row: row_height as _,
ws_col: col_width as _,
ws_xpixel: pix_width as _,
ws_ypixel: pix_height as _,
},
)
.await?;
Ok((self, session))
})
}
fn window_change_request(
mut self,
_channel: ChannelId,
col_width: u32,
row_height: u32,
pix_width: u32,
pix_height: u32,
session: Session,
) -> Self::FutureUnit {
Box::pin(async move {
if let Some(child) = self.child.as_mut() {
trace!(%row_height, %col_width, "Window resize request received");
child
.resize_window(Winsize {
ws_row: row_height as _,
ws_col: col_width as _,
ws_xpixel: pix_width as _,
ws_ypixel: pix_height as _,
})
.await?;
} else {
warn!("Resize request received without child process; ignoring");
}
Ok((self, session))
})
}
fn data(
mut self,
_channel: thrussh::ChannelId,
data: &[u8],
session: Session,
) -> Self::FutureUnit {
trace!(data = %String::from_utf8_lossy(data), raw_data = ?data);
let data = data.to_owned();
Box::pin(async move {
if let Some(child) = self.child.as_mut() {
child.write_all(&data).await?;
} else {
warn!("Data received without child process; ignoring");
}
Ok((self, session))
})
}
}
#[tokio::main]
async fn main() -> Result<()> {
color_eyre::install()?;
let opts = Box::leak::<'static>(Box::new(Opts::parse()));
opts.init_logging()?;
PrometheusBuilder::new()
.listen_address(opts.metrics_address)
.install()?;
metrics::register();
let config = Arc::new(opts.ssh_server_config().await?);
info!(address = %opts.address, "Listening for new SSH connections");
let listener = TcpListener::bind(&opts.address).await?;
loop {
let (stream, address) = listener.accept().await?;
increment_counter!(CONNECTIONS_ACCEPTED);
increment_gauge!(ACTIVE_CONNECTIONS, 1.0);
let config = config.clone();
let handler = Handler {
xanthous_binary_path: &opts.xanthous_binary_path,
address,
username: None,
child: None,
};
tokio::spawn(async move {
let span = info_span!("client", address = %handler.address);
let start = Instant::now();
if let Err(error) = server::run_stream(config, stream, handler)
.instrument(span.clone())
.await
{
span.in_scope(|| error!(%error));
}
let duration = start.elapsed();
span.in_scope(|| info!(duration_ms = %duration.as_millis(), "Client disconnected"));
histogram!(CONNECTION_DURATION, duration);
decrement_gauge!(ACTIVE_CONNECTIONS, 1.0);
});
}
}
#[cfg(test)]
mod tests {
use tempfile::NamedTempFile;
use super::*;
#[tokio::test]
async fn read_secret_key() {
use std::io::Write;
let mut file = NamedTempFile::new().unwrap();
file.write_all(
b"
-----BEGIN OPENSSH PRIVATE KEY-----
b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
QyNTUxOQAAACAYz80xcK7jYxZMAl6apIHKRtB0Z2U78gG39c1QaIhgMwAAAJB9vxK9fb8S
vQAAAAtzc2gtZWQyNTUxOQAAACAYz80xcK7jYxZMAl6apIHKRtB0Z2U78gG39c1QaIhgMw
AAAEDNZ0d3lLNBGU6Im4JOpr490TOjm+cB7kMVXjVg3iCowBjPzTFwruNjFkwCXpqkgcpG
0HRnZTvyAbf1zVBoiGAzAAAACHRlc3Qta2V5AQIDBAU=
-----END OPENSSH PRIVATE KEY-----
",
)
.unwrap();
let opts: Opts = Opts::parse_from(&[
"xanthous-server".as_ref(),
"--xanthous-binary-path".as_ref(),
"/bin/xanthous".as_ref(),
"--secret-key-file".as_ref(),
file.path().as_os_str(),
]);
opts.read_secret_key().await.unwrap();
}
}
