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import { Logger } from "@crupest/base/log";
import { MailDeliverer } from "./mail.ts";
const CRLF = "\r\n";
function createResponses(host: string, port: number | string) {
const serverName = `[${host}]:${port}`;
return {
serverName,
READY: `220 ${serverName} SMTP Ready`,
EHLO: `250 ${serverName}`,
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 ${serverName} closing connection`,
INVALID: "500 5.5.1 Error: command not recognized",
} as const;
}
const LOG_TAG = "[dumb-smtp]";
export class DumbSmtpServer {
#logger;
#deliverer;
#responses: ReturnType<typeof createResponses> = createResponses(
"invalid",
"invalid",
);
constructor(logger: Logger, deliverer: MailDeliverer) {
this.#logger = logger;
this.#deliverer = deliverer;
}
async #handleConnection(conn: Deno.Conn) {
using disposeStack = new DisposableStack();
disposeStack.defer(() => {
this.#logger.tagInfo(LOG_TAG, "Close session's tcp connection.");
conn.close();
});
this.#logger.tagInfo(LOG_TAG, "New session's tcp connection established.");
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) => {
this.#logger.tagInfo(LOG_TAG, "Send line: " + s);
await writer.write(encoder.encode(s + CRLF));
};
let buffer: string = "";
let rawMail: string | null = null;
await send(this.#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) {
this.#logger.tagInfo(LOG_TAG, "Received line: " + line);
const upperLine = line.toUpperCase();
if (upperLine.startsWith("EHLO") || upperLine.startsWith("HELO")) {
await send(this.#responses["EHLO"]);
} else if (upperLine.startsWith("MAIL FROM:")) {
await send(this.#responses["MAIL"]);
} else if (upperLine.startsWith("RCPT TO:")) {
await send(this.#responses["RCPT"]);
} else if (upperLine === "DATA") {
await send(this.#responses["DATA"]);
this.#logger.tagInfo(LOG_TAG, "Begin to receive mail data...");
rawMail = "";
} else if (upperLine === "QUIT") {
await send(this.#responses["QUIT"]);
return;
} else {
this.#logger.tagWarn(
LOG_TAG,
"Unrecognized command from client: " + line,
);
await send(this.#responses["INVALID"]);
return;
}
} else {
if (line === ".") {
try {
this.#logger.tagInfo(
LOG_TAG,
"Mail data Received, begin to relay...",
);
const { message } = await this.#deliverer.deliverRaw(rawMail);
await send(`250 2.6.0 ${message}`);
rawMail = null;
this.#logger.tagInfo(LOG_TAG, "Relay succeeded.");
} catch (err) {
this.#logger.tagError(LOG_TAG, "Relay failed.", 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(options: { hostname: string; port: number }) {
const listener = Deno.listen(options);
this.#responses = createResponses(options.hostname, options.port);
this.#logger.tagInfo(
LOG_TAG,
`Dumb SMTP server starts to listen on ${this.#responses.serverName}.`,
);
for await (const conn of listener) {
try {
await this.#handleConnection(conn);
} catch (cause) {
this.#logger.tagError(
LOG_TAG,
"Tcp connection throws an error.",
cause,
);
}
}
}
}
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