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|
use axum::{
body::Bytes,
extract::{DefaultBodyLimit, State},
http::{HeaderMap, StatusCode},
routing::post,
Router,
};
use subtle::ConstantTimeEq;
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::net::UnixStream;
struct Config {
token: &'static str,
lmtp: &'static str,
rcpt: Option<&'static str>,
bind: &'static str,
}
#[tokio::main]
async fn main() -> anyhow::Result<()> {
tracing_subscriber::fmt::init();
let cfg: &'static Config = Box::leak(Box::new(Config {
token: std::env::var("INGEST_TOKEN")?.leak(),
lmtp: std::env::var("LMTP_SOCK")?.leak(),
bind: std::env::var("LISTEN_ADDR").unwrap_or_else(|_| "127.0.0.1:8080".into()).leak(),
rcpt: match std::env::var("LMTP_RCPT") {
Ok(s) => Some(s.leak()),
Err(_) => None,
},
}));
let app = Router::new()
.route("/inject", post(inject))
.layer(DefaultBodyLimit::max(26 * 1024 * 1024))
.with_state(cfg);
let listener = tokio::net::TcpListener::bind(&cfg.bind).await?;
tracing::info!("listening on {}", listener.local_addr()?);
axum::serve(listener, app).await?;
Ok(())
}
async fn inject(
State(cfg): State<&'static Config>,
headers: HeaderMap,
body: Bytes,
) -> StatusCode {
if !valid_token(&headers, &cfg.token) {
return StatusCode::UNAUTHORIZED;
}
let from = header(&headers, "x-envelope-from");
let to = header(&headers, "x-envelope-to");
match lmtp_deliver(cfg, from, to, &body).await {
Ok(_) => StatusCode::NO_CONTENT,
Err((true, m)) => {
tracing::warn!("permanent: {m}");
StatusCode::UNPROCESSABLE_ENTITY
}
Err((false, m)) => {
tracing::error!("temporary: {m}");
StatusCode::SERVICE_UNAVAILABLE
}
}
}
fn header<'a>(h: &'a HeaderMap, k: &str) -> &'a str {
h.get(k).and_then(|v| v.to_str().ok()).unwrap_or("")
}
fn valid_token(h: &HeaderMap, expected: &str) -> bool {
let Some(v) = h.get("authorization").and_then(|v| v.to_str().ok()) else {
return false;
};
let Some(got) = v.strip_prefix("Bearer ") else { return false };
got.as_bytes().ct_eq(expected.as_bytes()).into()
}
/// Prevent LMTP command executed by the HTTP payload
fn sanitize(v: &str) -> String {
v.chars().filter(|&c| c != '\r' && c != '\n' && c != '>').collect()
}
async fn lmtp_deliver(
cfg: &Config,
from: &str,
to: &str,
msg: &[u8],
) -> Result<(), (bool, String)> {
let stream = UnixStream::connect(cfg.lmtp).await.map_err(|e| (false, e.to_string()))?;
let (rd, mut wr) = stream.into_split();
let mut rd = BufReader::new(rd);
let mut line = String::new();
macro_rules! io {
($e:expr) => {
$e.await.map_err(|e| (false, e.to_string()))?
};
}
macro_rules! expect {
($code:expr) => {{
loop {
line.clear();
if io!(rd.read_line(&mut line)) == 0 {
return Err((false, "connection closed".into()));
}
if line.as_bytes().get(3) != Some(&b'-') {
break;
}
}
if !line.starts_with($code) {
return Err((line.starts_with('5'), line.trim().to_string()));
}
}};
}
let rcpt = cfg.rcpt.unwrap_or(to);
expect!("220");
io!(wr.write_all(b"LHLO localhost\r\n"));
expect!("250");
io!(wr.write_all(format!("MAIL FROM:<{}>\r\n", sanitize(from)).as_bytes()));
expect!("250");
io!(wr.write_all(format!("RCPT TO:<{}>\r\n", sanitize(rcpt)).as_bytes()));
expect!("250");
io!(wr.write_all(b"DATA\r\n"));
expect!("354");
if cfg.rcpt.is_some() {
io!(wr.write_all(format!("X-Original-To: {}\r\n", sanitize(to)).as_bytes()));
}
for chunk in msg.split_inclusive(|&b| b == b'\n') {
if chunk.first() == Some(&b'.') {
io!(wr.write_all(b"."));
}
io!(wr.write_all(chunk));
}
if !msg.ends_with(b"\n") {
io!(wr.write_all(b"\r\n"));
}
io!(wr.write_all(b".\r\n"));
expect!("250");
let _ = wr.write_all(b"QUIT\r\n").await;
Ok(())
}
|
