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-rw-r--r--src/lmtp.rs263
1 files changed, 263 insertions, 0 deletions
diff --git a/src/lmtp.rs b/src/lmtp.rs
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+++ b/src/lmtp.rs
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+use std::collections::HashMap;
+use std::net::SocketAddr;
+use std::{pin::Pin, sync::Arc};
+
+use anyhow::{bail, Result};
+use async_trait::async_trait;
+use duplexify::Duplex;
+use futures::{io, AsyncRead, AsyncReadExt, AsyncWrite};
+use futures::{stream, stream::FuturesUnordered, StreamExt};
+use log::*;
+use rusoto_s3::{PutObjectRequest, S3Client, S3};
+use tokio::net::{TcpListener, TcpStream};
+use tokio::select;
+use tokio::sync::watch;
+use tokio_util::compat::*;
+
+use smtp_message::{Email, EscapedDataReader, Reply, ReplyCode};
+use smtp_server::{reply, Config, ConnectionMetadata, Decision, MailMetadata, Protocol};
+
+use crate::config::*;
+use crate::cryptoblob::*;
+use crate::login::*;
+use crate::mail_uuid::*;
+
+pub struct LmtpServer {
+ bind_addr: SocketAddr,
+ hostname: String,
+ login_provider: Arc<dyn LoginProvider + Send + Sync>,
+}
+
+impl LmtpServer {
+ pub fn new(
+ config: LmtpConfig,
+ login_provider: Arc<dyn LoginProvider + Send + Sync>,
+ ) -> Arc<Self> {
+ Arc::new(Self {
+ bind_addr: config.bind_addr,
+ hostname: config.hostname,
+ login_provider,
+ })
+ }
+
+ pub async fn run(self: &Arc<Self>, mut must_exit: watch::Receiver<bool>) -> Result<()> {
+ let tcp = TcpListener::bind(self.bind_addr).await?;
+ let mut connections = FuturesUnordered::new();
+
+ while !*must_exit.borrow() {
+ let wait_conn_finished = async {
+ if connections.is_empty() {
+ futures::future::pending().await
+ } else {
+ connections.next().await
+ }
+ };
+ let (socket, remote_addr) = select! {
+ a = tcp.accept() => a?,
+ _ = wait_conn_finished => continue,
+ _ = must_exit.changed() => continue,
+ };
+
+ let conn = tokio::spawn(smtp_server::interact(
+ socket.compat(),
+ smtp_server::IsAlreadyTls::No,
+ Conn { remote_addr },
+ self.clone(),
+ ));
+
+ connections.push(conn);
+ }
+ drop(tcp);
+
+ info!("LMTP server shutting down, draining remaining connections...");
+ while connections.next().await.is_some() {}
+
+ Ok(())
+ }
+}
+
+// ----
+
+pub struct Conn {
+ remote_addr: SocketAddr,
+}
+
+pub struct Message {
+ to: Vec<PublicCredentials>,
+}
+
+#[async_trait]
+impl Config for LmtpServer {
+ const PROTOCOL: Protocol = Protocol::Lmtp;
+
+ type ConnectionUserMeta = Conn;
+ type MailUserMeta = Message;
+
+ fn hostname(&self, _conn_meta: &ConnectionMetadata<Conn>) -> &str {
+ &self.hostname
+ }
+
+ async fn new_mail(&self, _conn_meta: &mut ConnectionMetadata<Conn>) -> Message {
+ Message { to: vec![] }
+ }
+
+ async fn tls_accept<IO>(
+ &self,
+ _io: IO,
+ _conn_meta: &mut ConnectionMetadata<Conn>,
+ ) -> io::Result<Duplex<Pin<Box<dyn Send + AsyncRead>>, Pin<Box<dyn Send + AsyncWrite>>>>
+ where
+ IO: Send + AsyncRead + AsyncWrite,
+ {
+ Err(io::Error::new(
+ io::ErrorKind::InvalidInput,
+ "TLS not implemented for LMTP server",
+ ))
+ }
+
+ async fn filter_from(
+ &self,
+ from: Option<Email>,
+ meta: &mut MailMetadata<Message>,
+ _conn_meta: &mut ConnectionMetadata<Conn>,
+ ) -> Decision<Option<Email>> {
+ Decision::Accept {
+ reply: reply::okay_from().convert(),
+ res: from,
+ }
+ }
+
+ async fn filter_to(
+ &self,
+ to: Email,
+ meta: &mut MailMetadata<Message>,
+ _conn_meta: &mut ConnectionMetadata<Conn>,
+ ) -> Decision<Email> {
+ let to_str = match to.hostname.as_ref() {
+ Some(h) => format!("{}@{}", to.localpart, h),
+ None => to.localpart.to_string(),
+ };
+ match self.login_provider.public_login(&to_str).await {
+ Ok(creds) => {
+ meta.user.to.push(creds);
+ Decision::Accept {
+ reply: reply::okay_to().convert(),
+ res: to,
+ }
+ }
+ Err(e) => Decision::Reject {
+ reply: Reply {
+ code: ReplyCode::POLICY_REASON,
+ ecode: None,
+ text: vec![smtp_message::MaybeUtf8::Utf8(e.to_string())],
+ },
+ },
+ }
+ }
+
+ async fn handle_mail<'a, R>(
+ &self,
+ reader: &mut EscapedDataReader<'a, R>,
+ _mail: MailMetadata<Message>,
+ _conn_meta: &mut ConnectionMetadata<Conn>,
+ ) -> Decision<()>
+ where
+ R: Send + Unpin + AsyncRead,
+ {
+ unreachable!();
+ }
+
+ async fn handle_mail_multi<'a, 'slife0, 'slife1, 'stream, R>(
+ &'slife0 self,
+ reader: &mut EscapedDataReader<'a, R>,
+ meta: MailMetadata<Message>,
+ conn_meta: &'slife1 mut ConnectionMetadata<Conn>,
+ ) -> Pin<Box<dyn futures::Stream<Item = Decision<()>> + Send + 'stream>>
+ where
+ R: Send + Unpin + AsyncRead,
+ 'slife0: 'stream,
+ 'slife1: 'stream,
+ Self: 'stream,
+ {
+ let err_response_stream = |meta: MailMetadata<Message>, msg: String| {
+ Box::pin(
+ stream::iter(meta.user.to.into_iter()).map(move |_| Decision::Reject {
+ reply: Reply {
+ code: ReplyCode::POLICY_REASON,
+ ecode: None,
+ text: vec![smtp_message::MaybeUtf8::Utf8(msg.clone())],
+ },
+ }),
+ )
+ };
+
+ let mut text = Vec::new();
+ if reader.read_to_end(&mut text).await.is_err() {
+ return err_response_stream(meta, "io error".into());
+ }
+ reader.complete();
+
+ let encrypted_message = match EncryptedMessage::new(text) {
+ Ok(x) => Arc::new(x),
+ Err(e) => return err_response_stream(meta, e.to_string()),
+ };
+
+ Box::pin(stream::iter(meta.user.to.into_iter()).then(move |creds| {
+ let encrypted_message = encrypted_message.clone();
+ async move {
+ match encrypted_message.deliver_to(creds).await {
+ Ok(()) => Decision::Accept {
+ reply: reply::okay_mail().convert(),
+ res: (),
+ },
+ Err(e) => Decision::Reject {
+ reply: Reply {
+ code: ReplyCode::POLICY_REASON,
+ ecode: None,
+ text: vec![smtp_message::MaybeUtf8::Utf8(e.to_string())],
+ },
+ },
+ }
+ }
+ }))
+ }
+}
+
+// ----
+
+struct EncryptedMessage {
+ key: Key,
+ encrypted_body: Vec<u8>,
+}
+
+impl EncryptedMessage {
+ fn new(body: Vec<u8>) -> Result<Self> {
+ let key = gen_key();
+ let encrypted_body = seal(&body, &key)?;
+ Ok(Self {
+ key,
+ encrypted_body,
+ })
+ }
+
+ async fn deliver_to(self: Arc<Self>, creds: PublicCredentials) -> Result<()> {
+ let s3_client = creds.storage.s3_client()?;
+
+ let encrypted_key =
+ sodiumoxide::crypto::sealedbox::seal(self.key.as_ref(), &creds.public_key);
+ let key_header = base64::encode(&encrypted_key);
+
+ let mut por = PutObjectRequest::default();
+ por.bucket = creds.storage.bucket.clone();
+ por.key = format!("incoming/{}", gen_uuid().to_string());
+ por.metadata = Some(
+ [("Message-Key".to_string(), key_header)]
+ .into_iter()
+ .collect::<HashMap<_, _>>(),
+ );
+ por.body = Some(self.encrypted_body.clone().into());
+ s3_client.put_object(por).await?;
+
+ Ok(())
+ }
+}