dcrouter/test/suite/security/test.bounce-management.ts

import { tap, expect } from '@git.zone/tstest/tapbundle';
import * as plugins from '../plugins.js';
import * as net from 'net';
import { startTestServer, stopTestServer, TEST_PORT, sendEmailWithRawSocket } from '../server.loader.js';
import type { SmtpServer } from '../../../ts/mail/delivery/smtpserver/index.js';

let testServer: SmtpServer;

tap.test('setup - start test server', async () => {
  testServer = await startTestServer();
  await plugins.smartdelay.delayFor(1000);
});

tap.test('Bounce Management - Invalid recipient domain', async (tools) => {
  const done = tools.defer();
  
  const socket = net.createConnection({
    host: 'localhost',
    port: TEST_PORT,
    timeout: 30000
  });
  
  let dataBuffer = '';
  let step = 'greeting';
  
  socket.on('data', (data) => {
    dataBuffer += data.toString();
    console.log('Server response:', data.toString());
    
    if (step === 'greeting' && dataBuffer.includes('220 ')) {
      step = 'ehlo';
      socket.write('EHLO testclient\r\n');
      dataBuffer = '';
    } else if (step === 'ehlo' && dataBuffer.includes('250')) {
      step = 'mail';
      socket.write('MAIL FROM:<sender@example.com>\r\n');
      dataBuffer = '';
    } else if (step === 'mail' && dataBuffer.includes('250')) {
      step = 'rcpt';
      // Send to non-existent domain
      socket.write('RCPT TO:<nonexistent@invalid-domain-that-does-not-exist.com>\r\n');
      dataBuffer = '';
    } else if (step === 'rcpt') {
      if (dataBuffer.includes('550') || dataBuffer.includes('551') || dataBuffer.includes('553')) {
        console.log('Bounce management active - invalid recipient properly rejected');
        expect(true).toBeTrue();
        
        socket.write('QUIT\r\n');
        socket.end();
        done.resolve();
      } else if (dataBuffer.includes('250')) {
        // Server accepted, may generate bounce later
        console.log('Invalid recipient accepted - bounce may be generated later');
        step = 'data';
        socket.write('DATA\r\n');
        dataBuffer = '';
      }
    } else if (step === 'data' && dataBuffer.includes('354')) {
      const email = [
        `From: sender@example.com`,
        `To: nonexistent@invalid-domain-that-does-not-exist.com`,
        `Subject: Bounce Management Test`,
        `Return-Path: <bounce@example.com>`,
        `Date: ${new Date().toUTCString()}`,
        `Message-ID: <bounce-test-${Date.now()}@example.com>`,
        '',
        'This email is designed to test bounce management functionality.',
        '.',
        ''
      ].join('\r\n');
      
      socket.write(email);
      dataBuffer = '';
    } else if (dataBuffer.includes('250 ') && dataBuffer.includes('Message accepted')) {
      console.log('Email accepted for processing - bounce will be generated');
      expect(true).toBeTrue();
      
      socket.write('QUIT\r\n');
      socket.end();
      done.resolve();
    }
  });
  
  socket.on('error', (err) => {
    console.error('Socket error:', err);
    done.reject(err);
  });
  
  await done.promise;
});

tap.test('Bounce Management - Empty return path (null sender)', async (tools) => {
  const done = tools.defer();
  
  const socket = net.createConnection({
    host: 'localhost',
    port: TEST_PORT,
    timeout: 30000
  });
  
  let dataBuffer = '';
  let step = 'greeting';
  
  socket.on('data', (data) => {
    dataBuffer += data.toString();
    console.log('Server response:', data.toString());
    
    if (step === 'greeting' && dataBuffer.includes('220 ')) {
      step = 'ehlo';
      socket.write('EHLO testclient\r\n');
      dataBuffer = '';
    } else if (step === 'ehlo' && dataBuffer.includes('250')) {
      step = 'mail';
      // Empty return path (null sender) - used for bounce messages
      socket.write('MAIL FROM:<>\r\n');
      dataBuffer = '';
    } else if (step === 'mail') {
      if (dataBuffer.includes('250')) {
        console.log('Null sender accepted (for bounce messages)');
        step = 'rcpt';
        socket.write('RCPT TO:<recipient@example.com>\r\n');
        dataBuffer = '';
      } else {
        console.log('Null sender rejected');
        expect(true).toBeTrue();
        
        socket.write('QUIT\r\n');
        socket.end();
        done.resolve();
      }
    } else if (step === 'rcpt' && dataBuffer.includes('250')) {
      step = 'data';
      socket.write('DATA\r\n');
      dataBuffer = '';
    } else if (step === 'data' && dataBuffer.includes('354')) {
      // Bounce message format
      const email = [
        `From: MAILER-DAEMON@example.com`,
        `To: recipient@example.com`,
        `Subject: Mail delivery failed: returning message to sender`,
        `Date: ${new Date().toUTCString()}`,
        `Message-ID: <bounce-${Date.now()}@example.com>`,
        `Auto-Submitted: auto-replied`,
        '',
        'This message was created automatically by mail delivery software.',
        '',
        'A message that you sent could not be delivered to one or more recipients.',
        '.',
        ''
      ].join('\r\n');
      
      socket.write(email);
      dataBuffer = '';
    } else if (dataBuffer.includes('250 ') && dataBuffer.includes('Message accepted')) {
      console.log('Bounce message with null sender accepted');
      expect(true).toBeTrue();
      
      socket.write('QUIT\r\n');
      socket.end();
      done.resolve();
    }
  });
  
  socket.on('error', (err) => {
    console.error('Socket error:', err);
    done.reject(err);
  });
  
  await done.promise;
});

tap.test('Bounce Management - DSN headers', async (tools) => {
  const done = tools.defer();
  
  const socket = net.createConnection({
    host: 'localhost',
    port: TEST_PORT,
    timeout: 30000
  });
  
  let dataBuffer = '';
  let step = 'greeting';
  
  socket.on('data', (data) => {
    dataBuffer += data.toString();
    console.log('Server response:', data.toString());
    
    if (step === 'greeting' && dataBuffer.includes('220 ')) {
      step = 'ehlo';
      socket.write('EHLO testclient\r\n');
      dataBuffer = '';
    } else if (step === 'ehlo' && dataBuffer.includes('250')) {
      step = 'mail';
      socket.write('MAIL FROM:<sender@example.com>\r\n');
      dataBuffer = '';
    } else if (step === 'mail' && dataBuffer.includes('250')) {
      step = 'rcpt';
      socket.write('RCPT TO:<recipient@example.com>\r\n');
      dataBuffer = '';
    } else if (step === 'rcpt' && dataBuffer.includes('250')) {
      step = 'data';
      socket.write('DATA\r\n');
      dataBuffer = '';
    } else if (step === 'data' && dataBuffer.includes('354')) {
      // Email with DSN request headers
      const email = [
        `From: sender@example.com`,
        `To: recipient@example.com`,
        `Subject: DSN Test`,
        `Return-Path: <bounce-handler@example.com>`,
        `Disposition-Notification-To: sender@example.com`,
        `Return-Receipt-To: sender@example.com`,
        `Date: ${new Date().toUTCString()}`,
        `Message-ID: <dsn-test-${Date.now()}@example.com>`,
        '',
        'This email requests delivery status notifications.',
        '.',
        ''
      ].join('\r\n');
      
      socket.write(email);
      dataBuffer = '';
    } else if (dataBuffer.includes('250 ') && dataBuffer.includes('Message accepted')) {
      console.log('Email with DSN headers accepted');
      expect(true).toBeTrue();
      
      socket.write('QUIT\r\n');
      socket.end();
      done.resolve();
    }
  });
  
  socket.on('error', (err) => {
    console.error('Socket error:', err);
    done.reject(err);
  });
  
  await done.promise;
});

tap.test('Bounce Management - Bounce loop prevention', async (tools) => {
  const done = tools.defer();
  
  const socket = net.createConnection({
    host: 'localhost',
    port: TEST_PORT,
    timeout: 30000
  });
  
  let dataBuffer = '';
  let step = 'greeting';
  
  socket.on('data', (data) => {
    dataBuffer += data.toString();
    console.log('Server response:', data.toString());
    
    if (step === 'greeting' && dataBuffer.includes('220 ')) {
      step = 'ehlo';
      socket.write('EHLO testclient\r\n');
      dataBuffer = '';
    } else if (step === 'ehlo' && dataBuffer.includes('250')) {
      step = 'mail';
      // Null sender (bounce message)
      socket.write('MAIL FROM:<>\r\n');
      dataBuffer = '';
    } else if (step === 'mail' && dataBuffer.includes('250')) {
      step = 'rcpt';
      // To another mailer-daemon (potential loop)
      socket.write('RCPT TO:<mailer-daemon@another-server.com>\r\n');
      dataBuffer = '';
    } else if (step === 'rcpt') {
      if (dataBuffer.includes('550') || dataBuffer.includes('553')) {
        console.log('Bounce loop prevented - mailer-daemon recipient rejected');
        expect(true).toBeTrue();
        
        socket.write('QUIT\r\n');
        socket.end();
        done.resolve();
      } else if (dataBuffer.includes('250')) {
        console.log('Mailer-daemon recipient accepted - check for loop prevention');
        step = 'data';
        socket.write('DATA\r\n');
        dataBuffer = '';
      }
    } else if (step === 'data' && dataBuffer.includes('354')) {
      const email = [
        `From: MAILER-DAEMON@example.com`,
        `To: mailer-daemon@another-server.com`,
        `Subject: Delivery Status Notification (Failure)`,
        `Date: ${new Date().toUTCString()}`,
        `Message-ID: <bounce-loop-${Date.now()}@example.com>`,
        `Auto-Submitted: auto-replied`,
        `X-Loop: example.com`,
        '',
        'This is a bounce of a bounce - potential loop.',
        '.',
        ''
      ].join('\r\n');
      
      socket.write(email);
      dataBuffer = '';
    } else if (dataBuffer.includes('250 ') || dataBuffer.includes('550 ')) {
      const result = dataBuffer.includes('250') ? 'accepted' : 'rejected';
      console.log(`Bounce loop test: ${result}`);
      expect(true).toBeTrue();
      
      socket.write('QUIT\r\n');
      socket.end();
      done.resolve();
    }
  });
  
  socket.on('error', (err) => {
    console.error('Socket error:', err);
    done.reject(err);
  });
  
  await done.promise;
});

tap.test('Bounce Management - Valid email (control test)', async (tools) => {
  const done = tools.defer();
  
  const socket = net.createConnection({
    host: 'localhost',
    port: TEST_PORT,
    timeout: 30000
  });
  
  let dataBuffer = '';
  let step = 'greeting';
  
  socket.on('data', (data) => {
    dataBuffer += data.toString();
    console.log('Server response:', data.toString());
    
    if (step === 'greeting' && dataBuffer.includes('220 ')) {
      step = 'ehlo';
      socket.write('EHLO testclient\r\n');
      dataBuffer = '';
    } else if (step === 'ehlo' && dataBuffer.includes('250')) {
      step = 'mail';
      socket.write('MAIL FROM:<sender@example.com>\r\n');
      dataBuffer = '';
    } else if (step === 'mail' && dataBuffer.includes('250')) {
      step = 'rcpt';
      socket.write('RCPT TO:<valid@example.com>\r\n');
      dataBuffer = '';
    } else if (step === 'rcpt' && dataBuffer.includes('250')) {
      step = 'data';
      socket.write('DATA\r\n');
      dataBuffer = '';
    } else if (step === 'data' && dataBuffer.includes('354')) {
      const email = [
        `From: sender@example.com`,
        `To: valid@example.com`,
        `Subject: Valid Email Test`,
        `Return-Path: <sender@example.com>`,
        `Date: ${new Date().toUTCString()}`,
        `Message-ID: <valid-email-${Date.now()}@example.com>`,
        '',
        'This is a valid email that should not trigger bounce.',
        '.',
        ''
      ].join('\r\n');
      
      socket.write(email);
      dataBuffer = '';
    } else if (dataBuffer.includes('250 ') && dataBuffer.includes('Message accepted')) {
      console.log('Valid email accepted - no bounce expected');
      expect(true).toBeTrue();
      
      socket.write('QUIT\r\n');
      socket.end();
      done.resolve();
    }
  });
  
  socket.on('error', (err) => {
    console.error('Socket error:', err);
    done.reject(err);
  });
  
  await done.promise;
});

tap.test('cleanup - stop test server', async () => {
  await stopTestServer(testServer);
});

tap.start();