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use std::{
io::{BufRead, BufReader, Write},
net::{IpAddr, SocketAddr, TcpListener, TcpStream},
};
use anyhow::Result;
use tokio::spawn;
const SERVER_NAME: &str = "";
pub struct SmtpServer {
listener: TcpListener,
running: bool,
}
impl SmtpServer {
pub fn new(ip: [u8; 4], port: u16) -> Result<Self> {
Ok(Self {
listener: TcpListener::bind((IpAddr::from(ip), port))?,
running: false,
})
}
// TODO: trap SIGINT to stop server?
pub async fn run(&mut self) -> Result<()> {
self.running = true;
while self.running {
let (stream, addr) = self.listener.accept()?;
let session = SessionHandler {
addr,
state: SessionState::default(),
client_host: String::new(),
from: None,
};
spawn(session.run(stream));
}
Ok(())
}
}
struct SessionHandler {
addr: SocketAddr,
state: SessionState,
client_host: String,
from: Option<String>,
}
impl SessionHandler {
async fn run(mut self, stream: TcpStream) -> Result<()> {
let mut writer = stream.try_clone()?;
let mut r = BufReader::new(&stream);
let mut buffer = String::new();
writer.write_all(
Reply::Ready(String::from(SERVER_NAME))
.to_string()
.as_bytes(),
)?;
loop {
if r.read_line(&mut buffer)? == 0 {
break;
}
log::debug!("Received '{}' from '{}'", buffer.trim(), self.addr);
let command = match Command::try_from(buffer.as_str()) {
Err(_) => {
writer.write_all(Reply::InvalidCommand.to_string().as_bytes())?;
continue;
}
Ok(v) => v,
};
let res = self.apply(command).await?;
writer.write_all(res.to_string().as_bytes())?;
buffer.clear();
}
log::info!("Connection closed by {}", self.addr);
Ok(())
}
async fn apply(&mut self, command: Command) -> Result<Reply> {
match &command {
Command::HELO(hostname) => self.helo(hostname).await,
Command::MAIL(from) => self.mail(from).await,
}
}
/// HELO resets buffers
async fn helo(&mut self, hostname: &str) -> Result<Reply> {
self.client_host = String::from(hostname);
self.state = SessionState::Normal;
self.from = None;
Ok(Reply::Completed(String::from(SERVER_NAME)))
}
/// TODO: Validate email address
/// MAIL resets buffers
async fn mail(&mut self, from: &str) -> Result<Reply> {
if from.is_empty() {
return Ok(Reply::InvalidParameter);
}
self.from = Some(String::from(from));
self.state = SessionState::MailTransaction;
Ok(Reply::Completed(String::from("Ok")))
}
}
enum SessionState {
WaitingHelo,
MailTransaction,
Normal,
}
impl Default for SessionState {
fn default() -> Self {
Self::WaitingHelo
}
}
enum Reply {
Ready(String),
Completed(String),
InvalidCommand,
InvalidParameter,
}
impl ToString for Reply {
fn to_string(&self) -> String {
match self {
Reply::Ready(hostname) => format!("220 {}", hostname),
Reply::Completed(hostname) => format!("250 {}", hostname),
Reply::InvalidCommand => format!("500 Command not recognized"),
Reply::InvalidParameter => format!("501 Parameter error"),
}
}
}
enum Command {
HELO(String),
MAIL(String),
}
impl TryFrom<&str> for Command {
type Error = anyhow::Error;
fn try_from(value: &str) -> std::result::Result<Self, Self::Error> {
if value.len() >= 5 && value.to_lowercase().starts_with("helo ") {
return Ok(Command::HELO(String::from(&value[5..])));
}
if value.len() >= 11
&& value.to_lowercase().starts_with("mail from:<")
&& value.contains('>')
{
let from = &value[11..value.find('>').unwrap()];
return Ok(Command::MAIL(String::from(from)));
}
Err(anyhow::format_err!("Invalid command"))
}
}
|
