platformservice/ts/mta/mta.classes.smtpserver.ts

import * as plugins from '../plugins.js';
import * as paths from '../paths.js';
import { Email } from './mta.classes.email.js';
import type { MTA } from './mta.classes.mta.js';

export interface ISmtpServerOptions {
  port: number;
  key: string;
  cert: string;
}

export class SMTPServer {
  public mtaRef: MTA;
  private smtpServerOptions: ISmtpServerOptions;
  private server: plugins.net.Server;
  private emailBufferStringMap: Map<plugins.net.Socket, string>;

  constructor(mtaRefArg: MTA, optionsArg: ISmtpServerOptions) {
    console.log('SMTPServer instance is being created...');

    this.mtaRef = mtaRefArg;
    this.smtpServerOptions = optionsArg;
    this.emailBufferStringMap = new Map();

    this.server = plugins.net.createServer((socket) => {
      console.log('New connection established...');

      socket.write('220 mta.lossless.one ESMTP Postfix\r\n');

      socket.on('data', (data) => {
        this.processData(socket, data);
      });

      socket.on('end', () => {
        console.log('Socket closed. Deleting related emailBuffer...');
        socket.destroy();
        this.emailBufferStringMap.delete(socket);
      });

      socket.on('error', () => {
        console.error('Socket error occurred. Deleting related emailBuffer...');
        socket.destroy();
        this.emailBufferStringMap.delete(socket);
      });

      socket.on('close', () => {
        console.log('Connection was closed by the client');
        socket.destroy();
        this.emailBufferStringMap.delete(socket);
      });
    });
  }

  private startTLS(socket: plugins.net.Socket) {
    const secureContext = plugins.tls.createSecureContext({
      key: this.smtpServerOptions.key,
      cert: this.smtpServerOptions.cert,
    });

    const tlsSocket = new plugins.tls.TLSSocket(socket, {
      secureContext: secureContext,
      isServer: true,
    });

    tlsSocket.on('secure', () => {
      console.log('Connection secured.');
      this.emailBufferStringMap.set(tlsSocket, this.emailBufferStringMap.get(socket) || '');
      this.emailBufferStringMap.delete(socket);
    });

    // Use the same handler for the 'data' event as for the unsecured socket.
    tlsSocket.on('data', (data: Buffer) => {
      this.processData(tlsSocket, Buffer.from(data));
    });

    tlsSocket.on('end', () => {
      console.log('TLS socket closed. Deleting related emailBuffer...');
      this.emailBufferStringMap.delete(tlsSocket);
    });

    tlsSocket.on('error', (err) => {
      console.error('TLS socket error occurred. Deleting related emailBuffer...');
      this.emailBufferStringMap.delete(tlsSocket);
    });
  }

  private processData(socket: plugins.net.Socket | plugins.tls.TLSSocket, data: Buffer) {
    const dataString = data.toString();
    console.log(`Received data:`);
    console.log(`${dataString}`)

    if (dataString.startsWith('EHLO')) {
      socket.write('250-mta.lossless.one Hello\r\n250 STARTTLS\r\n');
    } else if (dataString.startsWith('MAIL FROM')) {
      socket.write('250 Ok\r\n');
    } else if (dataString.startsWith('RCPT TO')) {
      socket.write('250 Ok\r\n');
    } else if (dataString.startsWith('STARTTLS')) {
      socket.write('220 Ready to start TLS\r\n');
      this.startTLS(socket);
    } else if (dataString.startsWith('DATA')) {
      socket.write('354 End data with <CR><LF>.<CR><LF>\r\n');
      let emailBuffer = this.emailBufferStringMap.get(socket);
      if (!emailBuffer) {
        this.emailBufferStringMap.set(socket, '');
      }
    } else if (dataString.startsWith('QUIT')) {
      socket.write('221 Bye\r\n');
      console.log('Received QUIT command, closing the socket...');
      socket.destroy();
      this.parseEmail(socket);
    } else {
      let emailBuffer = this.emailBufferStringMap.get(socket);
      if (typeof emailBuffer === 'string') {
        emailBuffer += dataString;
        this.emailBufferStringMap.set(socket, emailBuffer);
      }
      socket.write('250 Ok\r\n');
    }
    
    if (dataString.endsWith('\r\n.\r\n')  ) { // End of data
      console.log('Received end of data.');
    }
  }

  private async parseEmail(socket: plugins.net.Socket | plugins.tls.TLSSocket) {
    let emailData = this.emailBufferStringMap.get(socket);
    // lets strip the end sequence
    emailData = emailData?.replace(/\r\n\.\r\n$/, '');

    plugins.smartfile.fs.ensureDirSync(paths.receivedEmailsDir);
    plugins.smartfile.memory.toFsSync(emailData, plugins.path.join(paths.receivedEmailsDir, `${Date.now()}.eml`));


    if (!emailData) {
      console.error('No email data found for socket.');
      return;
    }

    let mightBeSpam = false;

    // Verifying the email with DKIM
    try {
      const isVerified = await this.mtaRef.dkimVerifier.verify(emailData);
      mightBeSpam = !isVerified;
    } catch (error) {
      console.error('Failed to verify DKIM signature:', error);
      mightBeSpam = true;
    }

    const parsedEmail = await plugins.mailparser.simpleParser(emailData);
    console.log(parsedEmail)
    const email = new Email({
      from: parsedEmail.from?.value[0].address || '',
      to:
        parsedEmail.to instanceof Array
          ? parsedEmail.to[0].value[0].address
          : parsedEmail.to?.value[0].address,
      subject: parsedEmail.subject || '',
      text: parsedEmail.html || parsedEmail.text,
      attachments:
        parsedEmail.attachments?.map((attachment) => ({
          filename: attachment.filename || '',
          content: attachment.content,
          contentType: attachment.contentType,
        })) || [],
      mightBeSpam: mightBeSpam,
    });

    console.log('mail received!');
    console.log(email);

    this.emailBufferStringMap.delete(socket);
  }

  public start() {
    this.server.listen(this.smtpServerOptions.port, () => {
      console.log(`SMTP Server is now running on port ${this.smtpServerOptions.port}`);
    });
  }

  public stop() {
    this.server.getConnections((err, count) => {
      if (err) throw err;
      console.log('Number of active connections: ', count);
    });
    this.server.close(() => {
      console.log('SMTP Server is now stopped');
    });
  }
}