Jawab/services/smtp/actions.js

const auth = require("./authenticate")
const storage = require("../storage")
const security = require("../security")

const codes = {
    220: "Service ready",
    221: "Closing transmission channel",
    235: "2.7.0 Authentication successful",
    250: "Requested mail action okay, completed",
    354: "Start mail input; end with <CR><LF>.<CR><LF>",
    421: "Service not available, closing transmission channel",
    451: "Requested action aborted: local error in processing",
    500: "Syntax error, command unrecognized",
    501: "Syntax error in parameters or arguments",
    503: "Bad sequence of commands",
    530: "5.7.0 Authentication required",
    535: "5.7.8 Authentication credentials invalid",
    550: "Requested action not taken: mailbox unavailable",
    552: "Requested mail action aborted: exceeded storage allocation"
}

const features = ["Jawab Mail Server", "AUTH PLAIN", "SIZE 10485760", "HELP"]

function reply(socket, code, extra = null) {
    const message = codes[code]

    if (Array.isArray(extra)) {
        for (let i = 0; i < extra.length - 1; i++) {
            socket.write(`${code}-${extra[i]}\r\n`);
        }
        return socket.write(`${code} ${extra[extra.length - 1]}\r\n`)
    }

    const responseText = extra ? `${message} ${extra}` : message
    return socket.write(`${code} ${responseText}\r\n`)
}

function handleCommand(socket, session, line) {
    if (!security.isLineSafe(line)) {
        return reply(socket, 500, "Line too long")
    }

    const parts = line.split(" ")
    const command = parts[0].toUpperCase()
    const args = parts.slice(1).join(" ")

    if (session.isCollectingData) {
        return handleDataStreaming(socket, session, line)
    }

    switch (command) {
        case "EHLO":
        case "HELO":
            handleHelo(socket, session, args)
            break
        case "AUTH":
            handleAuth(socket, session, args)
            break
        case "MAIL":
            handleMailFrom(socket, session, args)
            break
        case "RCPT":
            handleRcptTo(socket, session, args)
            break
        case "DATA":
            handleDataStart(socket, session)
            break
        case "RSET":
            handleReset(socket, session)
            break
        case "QUIT":
            handleQuit(socket)
            break
        case "NOOP":
            reply(socket, 250)
            break
        default:
            reply(socket, 500)
    }
}

function handleAuth(socket, session, args) {
    const [mechanism, payload] = args.split(" ")
    
    if (mechanism !== "PLAIN" || !payload) {
        return reply(socket, 501)
    }

    const { identity, secret } = auth.decodeSASL(payload)
    
    if (auth.authenticate(identity, secret)) {
        session.authenticated = true
        session.user = identity
        return reply(socket, 235)
    } else {
        return reply(socket, 535)
    }
}

function handleMailFrom(socket, session, args) {
    if (!session.authenticated) {
        return reply(socket, 530)
    }

    const emailMatch = args.match(/FROM:\s*<(.+?)>/i)
    if (!emailMatch) {
        return reply(socket, 501)
    }

    const email = emailMatch[1]

    if (!security.validateEmail(email)) {
        return reply(socket, 501)
    }

    session.from = email
    session.sizeChecker = security.createSizeChecker()
    return reply(socket, "250")
}

function handleRcptTo(socket, session, args) {
    if (!session.from) {
        return reply(socket, 503)
    }
    
    const emailMatch = args.match(/TO:\s*<(.+?)>/i)
    if (!emailMatch) {
        return reply(socket, 501)
    }

    const email = emailMatch[1]

    if (!security.validateEmail(email)) {
        return reply(socket, 501)
    }

    session.to = email
    return reply(socket, "250")
}

function handleDataStart(socket, session) {
    if (!session.from || !session.to) return reply(socket, 503)
    
    const { writeStream } = storage.createMailWriteStream()
    
    session.isCollectingData = true
    session.currentWriteStream = writeStream
    
    return reply(socket, 354)
}

function handleDataStart(socket, session) {
    if (!session.from || !session.to) return reply(socket, 503)
    
    const { writeStream } = storage.createMailWriteStream()
    session.currentWriteStream = writeStream
    session.sizeChecker = security.createSizeChecker()
    session.isCollectingData = true

    return reply(socket, 354)
}

function handleDataStreaming(socket, session, line) {
    if (line.trim() === ".") {
        session.isCollectingData = false
        session.currentWriteStream.end()
        session.currentWriteStream = null
        return reply(socket, 250)
    }

    if (session.sizeChecker && !session.sizeChecker(line.length)) {
        session.isCollectingData = false
        session.currentWriteStream.destroy()
        return reply(socket, 552)
    }

    return session.currentWriteStream.write(line + "\n")
}

function handleReset(socket, session) {
    if (session.currentWriteStream) {
        session.currentWriteStream.destroy()
    }
    session.from = null
    session.to = null
    session.isCollectingData = false
    return reply(socket, 250)
}

function handleQuit(socket) {
    reply(socket, 221)
    return socket.end()
}

function handleHelo(socket, session, args) {
    if (!args) {
        return reply(socket, 501)
    }
    
    session.helo = args
    session.hasHelo = true
    
    return reply(socket, 250, features)
}

module.exports = {
    handleCommand
}