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Open Source Web Entry Server. Ivan Bütler: „This talk is about web-application firewalls with pre-authentication, session hiding, content rewriting and filtering capabilities with open-source software.“. Ivan Bütler About me. Ivan Bütler ¦ E1.

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Open Source Web Entry Server

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Open source web entry server

Open Source Web Entry Server

  • Ivan Bütler: „This talk is about web-application firewalls with pre-authentication, session hiding, content rewriting and filtering capabilities with open-source software.“

Ivan Bütler

About me

About me

Ivan Bütler ¦ E1

  • Founder & Security Researcher for Compass SecuritySince 1999, Switzerland –

  • Speaker @ BlackHat Las Vegas 2008SmartCard (In) Security – APDU Analysis

  • Speaker @ IT Underground Warsaw 2009Advanced Web Hacking

  • Speaker @ Swiss IT Leadership ForumNice2009Cyber Underground

  • Lead Swiss Cyber Storm2011Security Conference12-15. May 2011, Switzerland –

  • Board member of Information SecuritySociety Switzerland (ISSS)

  • Lecturing Activities: HSR & HSLU & FHSG

Open source web entry server

  • Win a Car! – Wargame!USD 30‘000 main prize


  • May 12-15, 2011

  • Switzerland, near Zürich

  • OWASP Trainings planned!

Goal of this talk

Goal of this Talk

  • Learn how to turn the Apache web server into a front-end web-application firewall with pre-authentication, session hiding and URL authorization

  • We will play with Facebook as our backend application

  • The LiveCD includes all demos



Pci dss requirement

PCI DSS Requirement

Without a web application firewall

Without a Web Application Firewall

Multiple connections into DMZ

Applications directly accessible

Web app firewall waf

Web App Firewall (WAF)

Demo with FB

Web Application Firewall

  • Reverse Proxy to FB

  • Security Checks

  • Content Rewriting

TOOL TIPmod_proxy

Demo 1 2

DEMO 1 + 2

demo movies shown here availablein Hacking-Lab – OWASP

Content rewriting

Content Rewriting

  • Relative URL‘s are not a problem!

  • Content rewriting is not required

<link href="/css/mystyle.css" rel="stylesheet" type="text/css">

Content rewriting1

Content Rewriting

  • Absolute URLs must be rewritten

  • Cookie domain must be rewritten

  • Cookie values must be rewritten (in some cases)

<a href="" type="text/css">

TOOL TIPmod_replace

Demo 4

Demo 4

Request Header PatchingCookie Value Patching

Web app firewall

Web App Firewall

  • @inspectFile operator is simply a type of API that will allow you to inspect file attachments

< requestfiltering | e.g. sql injection >

< responsefiltering | e.g. stacktraces >

< inspectfiles | e.g. pdfexploitanalysis >

TOOL TIPmod_security

Demo 5 6

Demo 5 + 6


Web entry server

Web Entry Server

  • Pre-Authentication

  • Delegated Login Service (DLS)

  • Session Hiding

  • URL Access Control

  • Principal Delegation to Backend App

TOOL TIPmod_but

Web entry server swiss blueprint

Web Entry Server- Swiss Blueprint -

Web Entry Server

  • Backend requests are always authenticated!

  • Strong forensic and logging capabilities

Central Login Service

Pre authentication principal delegation

Pre-AuthenticationPrincipal Delegation


GET /app HTTP/1.0UserID=1234


Login=OKSet-Cookie: UserID=1234;

Pre authentication single sign on

Pre-AuthenticationSingle Sign On


Server gets initial request with UserID=1234 from WES

Server extracts UserID

Server creates a new, authenticated session

Server authorizes only


User must authenticated twice (SSO disabled)

Delegated Login Service (DLS)


Principal ticket should be an encrypted/signed, timestampted value (against replay attacks) instead of plain-text UserID=1234!

Pre authetication dls d elegated l ogin s ervice

Pre-Authetication - DLSDelegated Login Service


DLS authenticates on behalf (knowsthecredentials out oftheuserrepository)

-> Non origin cookies are then set to


Demo 7 sso

Demo 7 - SSO

Web forensics ntp is not enough

Web ForensicsNTP is not enough!

TOOL TIPmod_unique-id


Demo 7 uniqueid

Demo 7 - UniqueID

Url access control

URL Access Control


Login=OKSet-Cookie: AUTHORIZATION=(^/app1|^/app2);

Demo 8

Demo 8

Service Level ACL

Session management without session store

Session Managementwithout session store

Reverse Proxy

Without Session Cache

Session management with session hiding

Session Managementwith session hiding

Reverse Proxy

Session Cache (SHM)

Entry server toolkit

Entry Server ToolKit



Remember i

Remember (I)

  • Pre-Authentication reduces the attack surface of unauthenticated users

  • Unique-ID enables proper forensics

  • Cookie store hides insecure cookies

  • Service ACL is a second line of defence for the application authorization scheme

Remember ii

Remember (II)

  • Hacking-Lab LiveCD includes all tools you need to replay

  • Win a car! Qualification wargames have started at

  • All movies of this talk are available online at

Thank you ivan b tler e1

Thank youIvan Bütler, E1

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