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import config from "./config.ts";
import log from "./log.ts";
import { MailDeliverer } from "./mail.ts";
const CRLF = "\r\n";
const SERVER_NAME = `[${config.SMTP_HOST}]:${config.SMTP_PORT}`;
const RESPONSES = {
"READY": `220 ${SERVER_NAME} SMTP Ready`,
"EHLO": `250 ${SERVER_NAME}`,
"MAIL": "250 2.1.0 Sender OK",
"RCPT": "250 2.1.5 Recipient OK",
"DATA": "354 Start mail input; end with <CRLF>.<CRLF>",
"QUIT": `211 2.0.0 ${SERVER_NAME} closing connection`,
"INVALID": "500 5.5.1 Error: command not recognized",
} as const;
export class DumbSmtpServer {
#deliverer: MailDeliverer;
constructor(deliverer: MailDeliverer) {
this.#deliverer = deliverer;
}
async #handleConnection(conn: Deno.Conn) {
using disposeStack = new DisposableStack();
disposeStack.defer(() => {
log.info("Close smtp session tcp connection.");
conn.close();
});
const writer = conn.writable.getWriter();
disposeStack.defer(() => writer.releaseLock());
const reader = conn.readable.getReader();
disposeStack.defer(() => reader.releaseLock());
const [decoder, encoder] = [new TextDecoder(), new TextEncoder()];
const decode = (data: Uint8Array) => decoder.decode(data);
const send = async (s: string) =>
await writer.write(encoder.encode(s + CRLF));
let buffer: string = "";
let rawMail: string | null = null;
await send(RESPONSES["READY"]);
while (true) {
const { value, done } = await reader.read();
if (done) break;
buffer += decode(value);
while (true) {
const eolPos = buffer.indexOf(CRLF);
if (eolPos === -1) break;
const line = buffer.slice(0, eolPos);
buffer = buffer.slice(eolPos + CRLF.length);
if (rawMail == null) {
log.info("Smtp server received line:", line);
const upperLine = line.toUpperCase();
if (upperLine.startsWith("EHLO") || upperLine.startsWith("HELO")) {
await send(RESPONSES["EHLO"]);
} else if (upperLine.startsWith("MAIL FROM:")) {
await send(RESPONSES["MAIL"]);
} else if (upperLine.startsWith("RCPT TO:")) {
await send(RESPONSES["RCPT"]);
} else if (upperLine === "DATA") {
await send(RESPONSES["DATA"]);
log.info("Begin to receive mail data...");
rawMail = "";
} else if (upperLine === "QUIT") {
await send(RESPONSES["QUIT"]);
return;
} else {
log.warn("Smtp server command unrecognized:", line);
await send(RESPONSES["INVALID"]);
return;
}
} else {
if (line === ".") {
try {
log.info("Done receiving mail data, begin to relay...");
const { message } = await this.#deliverer.deliverRaw(rawMail);
await send(`250 2.6.0 ${message}`);
rawMail = null;
log.info("Done SMTP mail session.");
} catch (err) {
log.info(err);
await send("554 5.3.0 Error: check server log");
return;
}
} else {
const dataLine = line.startsWith("..") ? line.slice(1) : line;
rawMail += dataLine + CRLF;
}
}
}
}
}
async serve() {
const listener = Deno.listen({
hostname: config.SMTP_HOST,
port: config.SMTP_PORT,
});
listener.unref();
log.info(`Dumb SMTP server starts running on port ${config.SMTP_PORT}.`);
for await (const conn of listener) {
try {
await this.#handleConnection(conn);
} catch (cause) {
log.error("One smtp connection session throws an error " + cause);
}
}
}
}
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