Initial commit

.gitignore

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+/target
+Cargo.lock

Cargo.toml

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+[package]
+name = "eatmail"
+version = "0.1.0"
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+tokio = { version = "1.25.0", features = ["full"] }

src/main.rs

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+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio::net::TcpListener;
+
+use std::env;
+use std::error::Error;
+
+// FIXME: wrap in a struct implementing a state machine
+async fn handle_smtp(msg: &str) -> &'static [u8] {
+    println!("Received {msg}");
+    let mut msg = msg.split_whitespace();
+    let command = msg.next().expect("empty message").to_lowercase();
+    match command.as_str() {
+        "ehlo" | "helo" => b"250\n",
+        "mail" => {
+            println!(
+                "{}",
+                msg.map(|s| s.to_string())
+                    .collect::<Vec<String>>()
+                    .join(" ")
+            );
+            b"250\n"
+        }
+        "rcpt" => {
+            println!(
+                "{}",
+                msg.map(|s| s.to_string())
+                    .collect::<Vec<String>>()
+                    .join(" ")
+            );
+            b"250\n"
+        }
+        "data" => b"354\n",
+        "quit" => b"221\n",
+        _ => b"250\n",
+    }
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    let addr = env::args()
+        .nth(1)
+        .unwrap_or_else(|| "127.0.0.1:8080".to_string());
+
+    let listener = TcpListener::bind(&addr).await?;
+    println!("Listening on: {}", addr);
+
+    loop {
+        // Asynchronously wait for an inbound socket.
+        let (mut socket, _) = listener.accept().await?;
+
+        tokio::spawn(async move {
+            println!("Accepted");
+            socket
+                .write_all(b"220 eatmail\n")
+                .await
+                .expect("failed to introduce myself");
+            let mut buf = vec![0; 65536];
+
+            // In a loop, read data from the socket and write the data back.
+            loop {
+                let n = socket
+                    .read(&mut buf)
+                    .await
+                    .expect("failed to read data from socket");
+
+                if n == 0 {
+                    println!("Received \\0");
+                    return;
+                }
+                let msg = match std::str::from_utf8(&buf) {
+                    Ok(msg) => msg,
+                    Err(e) => {
+                        println!("Unexpected response: {e}");
+                        break;
+                    }
+                };
+                let response = handle_smtp(msg).await;
+                socket
+                    .write_all(response)
+                    .await
+                    .expect("failed to write the response");
+                if response == b"221\n" {
+                    // fixme with enum
+                    break;
+                }
+            }
+        });
+    }
+}

test/payload.py

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+import smtplib
+
+fromaddr = "[email protected]"
+toaddr  = "[email protected]"
+
+# Add the From: and To: headers at the start!
+msg = f"From: {fromaddr}\r\nTo: {toaddr}\r\n\r\n"
+msg += "test \nmail\n goodbye\n"
+
+server = smtplib.SMTP('localhost', port=8080)
+server.set_debuglevel(1)
+server.sendmail(fromaddr, toaddr, msg)
+server.quit()