Pentest HTTP Smuggling

Purpose

Detect and exploit discrepancies between front-end proxies and back-end servers in HTTP request parsing. These attacks bypass security controls, poison caches, and hijack requests — entirely absent from standard taint analysis pipelines.

Prerequisites

Authorization Requirements

• Written authorization with explicit scope for protocol-level testing
• Infrastructure awareness — identify all reverse proxies, CDNs, load balancers in path
• Rollback plan for cache poisoning tests (CDN purge access)
• Emergency contacts for infrastructure team (smuggling can affect other users)

Environment Setup

• Python 3.x with raw socket capability for crafted HTTP requests
• Burp Suite Professional with HTTP Request Smuggler extension
• curl compiled with HTTP/2 support (--http2-prior-knowledge)
• Turbo Intruder for timing-sensitive attacks
• Network capture tool (Wireshark/tcpdump) for response analysis

Core Workflow

1. Stack Fingerprinting: Identify reverse proxies (nginx, HAProxy, Cloudflare, AWS ALB), CDNs, load balancers. Determine HTTP version support (HTTP/1.1, HTTP/2) and parsing behavior.
2. CL.TE Smuggling: Craft requests where front-end uses Content-Length and back-end uses Transfer-Encoding. Observe differential parsing and request boundary confusion.
3. TE.CL Smuggling: Reverse scenario — front-end uses Transfer-Encoding, back-end uses Content-Length. Test with obfuscated TE headers.
4. TE.TE Smuggling: Both sides use Transfer-Encoding but one can be confused with header obfuscation (capitalization, whitespace, duplicate headers).
5. HTTP/2 Downgrade: Exploit H2-to-H1 translation at reverse proxies. Header injection via pseudo-headers, CRLF injection in H2 headers, request splitting through H2 CONTINUATION frames.
6. Cache Poisoning: Poison cached responses with attacker-controlled content. Test cache key vs cache content discrepancies. Verify with different client sessions.
7. Host Header Attacks: Host header injection, password reset poisoning, routing-based SSRF, web cache poisoning via ambiguous Host headers (WSTG-INPV-17).
8. Impact Validation: Demonstrate cache poisoning, credential theft, request hijacking, or security control bypass as PoC.

WSTG Coverage

WSTG ID	Test Name	Status
WSTG-INPV-15	HTTP Request Smuggling	✅
WSTG-INPV-17	Host Header Injection	✅

Tool Categories

Category	Tools	Purpose
Smuggling Detection	smuggler.py, HTTP Request Smuggler (Burp)	Automated CL.TE/TE.CL detection
HTTP/2 Testing	h2csmuggler, curl --http2, nghttp	H2 downgrade and desync attacks
Timing Attacks	Turbo Intruder	Microsecond-precision request timing
Raw Requests	Python sockets, netcat	Crafted malformed HTTP requests
Cache Analysis	curl, custom scripts	Cache behavior verification
Traffic Capture	Wireshark, tcpdump	Response boundary analysis

References

• references/tools.md - Tool function signatures and parameters
• references/workflows.md - Attack pattern definitions and test vectors