dcrouter/test/suite/smtpserver_edge-cases/test.edge-06.extremely-long-headers.ts

import { tap, expect } from '@git.zone/tstest/tapbundle';
import * as net from 'net';
import { startTestServer, stopTestServer, type ITestServer } from '../../helpers/server.loader.js';

const TEST_PORT = 2525;
const TEST_TIMEOUT = 30000;

let testServer: ITestServer;

tap.test('setup - start test server', async () => {
  testServer = await startTestServer({ port: TEST_PORT });
  await new Promise(resolve => setTimeout(resolve, 1000));
  expect(testServer).toBeDefined();
});

tap.test('Extremely Long Headers - should handle single extremely long header', async (tools) => {
  const done = tools.defer();
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Get banner
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send EHLO
    socket.write('EHLO testclient\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Send MAIL FROM
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    const mailResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(mailResponse).toInclude('250');
    
    // Send RCPT TO
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    const rcptResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(rcptResponse).toInclude('250');
    
    // Send DATA
    socket.write('DATA\r\n');
    const dataResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(dataResponse).toInclude('354');
    
    // Send email with extremely long header (3000 characters)
    const longValue = 'X'.repeat(3000);
    const emailContent = [
      `Subject: Test Email`,
      `From: sender@example.com`,
      `To: recipient@example.com`,
      `X-Long-Header: ${longValue}`,
      '',
      'This email has an extremely long header.',
      '.',
      ''
    ].join('\r\n');
    
    socket.write(emailContent);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Server might accept or reject - both are valid for extremely long headers
    const accepted = finalResponse.includes('250');
    const rejected = finalResponse.includes('552') || finalResponse.includes('554') || finalResponse.includes('500');
    
    console.log(`Long header test ${accepted ? 'accepted' : 'rejected'}: ${finalResponse.trim()}`);
    expect(accepted || rejected).toEqual(true);
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    done.resolve();
  }
});

tap.test('Extremely Long Headers - should handle multi-line header with many segments', async (tools) => {
  const done = tools.defer();
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Get banner
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send EHLO
    socket.write('EHLO testclient\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Send MAIL FROM
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    const mailResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(mailResponse).toInclude('250');
    
    // Send RCPT TO
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    const rcptResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(rcptResponse).toInclude('250');
    
    // Send DATA
    socket.write('DATA\r\n');
    const dataResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(dataResponse).toInclude('354');
    
    // Create multi-line header with 50 segments (RFC 5322 folding)
    const segments = [];
    for (let i = 0; i < 50; i++) {
      segments.push(`  Segment ${i}: ${' '.repeat(60)}value`);
    }
    
    const emailContent = [
      `Subject: Test Email`,
      `From: sender@example.com`,
      `To: recipient@example.com`,
      `X-Multi-Line: Initial value`,
      ...segments,
      '',
      'This email has a multi-line header with many segments.',
      '.',
      ''
    ].join('\r\n');
    
    socket.write(emailContent);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    const accepted = finalResponse.includes('250');
    const rejected = finalResponse.includes('552') || finalResponse.includes('554') || finalResponse.includes('500');
    
    console.log(`Multi-line header test ${accepted ? 'accepted' : 'rejected'}: ${finalResponse.trim()}`);
    expect(accepted || rejected).toEqual(true);
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    done.resolve();
  }
});

tap.test('Extremely Long Headers - should handle multiple long headers in one email', async (tools) => {
  const done = tools.defer();
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Get banner
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send EHLO
    socket.write('EHLO testclient\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Send MAIL FROM
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    const mailResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(mailResponse).toInclude('250');
    
    // Send RCPT TO
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    const rcptResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(rcptResponse).toInclude('250');
    
    // Send DATA
    socket.write('DATA\r\n');
    const dataResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(dataResponse).toInclude('354');
    
    // Create multiple long headers
    const header1 = 'A'.repeat(1000);
    const header2 = 'B'.repeat(1500);
    const header3 = 'C'.repeat(2000);
    
    const emailContent = [
      `Subject: Test Email with Multiple Long Headers`,
      `From: sender@example.com`,
      `To: recipient@example.com`,
      `X-Long-Header-1: ${header1}`,
      `X-Long-Header-2: ${header2}`,
      `X-Long-Header-3: ${header3}`,
      '',
      'This email has multiple long headers.',
      '.',
      ''
    ].join('\r\n');
    
    const totalHeaderSize = header1.length + header2.length + header3.length;
    console.log(`Total header size: ${totalHeaderSize} bytes`);
    
    socket.write(emailContent);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    const accepted = finalResponse.includes('250');
    const rejected = finalResponse.includes('552') || finalResponse.includes('554') || finalResponse.includes('500');
    
    console.log(`Multiple long headers test ${accepted ? 'accepted' : 'rejected'}: ${finalResponse.trim()}`);
    expect(accepted || rejected).toEqual(true);
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    done.resolve();
  }
});

tap.test('Extremely Long Headers - should handle header with exactly RFC limit', async (tools) => {
  const done = tools.defer();
  
  try {
    const socket = net.createConnection({
      host: 'localhost',
      port: TEST_PORT,
      timeout: TEST_TIMEOUT
    });
    
    await new Promise<void>((resolve, reject) => {
      socket.once('connect', () => resolve());
      socket.once('error', reject);
    });
    
    // Get banner
    await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // Send EHLO
    socket.write('EHLO testclient\r\n');
    await new Promise<string>((resolve) => {
      let data = '';
      const handler = (chunk: Buffer) => {
        data += chunk.toString();
        if (data.includes('\r\n') && (data.match(/^250 /m) || data.match(/^250-.*\r\n250 /ms))) {
          socket.removeListener('data', handler);
          resolve(data);
        }
      };
      socket.on('data', handler);
    });
    
    // Send MAIL FROM
    socket.write('MAIL FROM:<sender@example.com>\r\n');
    const mailResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(mailResponse).toInclude('250');
    
    // Send RCPT TO
    socket.write('RCPT TO:<recipient@example.com>\r\n');
    const rcptResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(rcptResponse).toInclude('250');
    
    // Send DATA
    socket.write('DATA\r\n');
    const dataResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    expect(dataResponse).toInclude('354');
    
    // Create header line exactly at RFC 5322 limit (998 chars excluding CRLF)
    // Header name and colon take some space
    const headerName = 'X-RFC-Limit';
    const colonSpace = ': ';
    const remainingSpace = 998 - headerName.length - colonSpace.length;
    const headerValue = 'X'.repeat(remainingSpace);
    
    const emailContent = [
      `Subject: Test Email`,
      `From: sender@example.com`,
      `To: recipient@example.com`,
      `${headerName}${colonSpace}${headerValue}`,
      '',
      'This email has a header at exactly the RFC limit.',
      '.',
      ''
    ].join('\r\n');
    
    socket.write(emailContent);
    
    const finalResponse = await new Promise<string>((resolve) => {
      socket.once('data', (chunk) => resolve(chunk.toString()));
    });
    
    // This should be accepted since it's exactly at the limit
    const accepted = finalResponse.includes('250');
    const rejected = finalResponse.includes('552') || finalResponse.includes('554') || finalResponse.includes('500');
    
    console.log(`RFC limit header test ${accepted ? 'accepted' : 'rejected'}: ${finalResponse.trim()}`);
    expect(accepted || rejected).toEqual(true);
    
    // RFC compliant servers should accept headers exactly at the limit
    if (accepted) {
      console.log('✓ Server correctly accepts headers at RFC limit');
    } else {
      console.log('⚠ Server rejected header at RFC limit (may be overly strict)');
    }
    
    // Clean up
    socket.write('QUIT\r\n');
    socket.end();
    
  } finally {
    done.resolve();
  }
});

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

tap.start();