Lap Around Web Application Vulnerabilities

Walter WongMVP – Visual Developer (Security)walter_wws@hotmail.comhttp://spaces.live.com/walterwws

Top 10 Web Application vulnerabilities in 2007

•Cross-site Scripting (XSS)

1

•Injection Flaws

2

•Malicious File Execution

3

•Insecure Direct Object Reference

4

•Cross Site Request Forgery

5

•Information Leakage and Improper Error Handling

6

•Broken Authentication and Session Management

7

•Insecure Cryptographic Storage

8

•Insecure Communications

9

•Failure to Restrict URL Access

10

Source: http://www.owasp.org/index.php/top_10_2007

Agenda

The foundation of attackAdvance attack techniquesObfuscationAutomated Testing

Foundation of attack

Application attack also known as “layer 7 attack”Program is just a set of instruction.Developer is the key protectorAll input is evil (Writing Secure Code by Michael Howard and David LeBlanc)

3 basic techniques

Path Traversal

Cross-site Scripting

SQL Injection

SQL Injection

Build SQL statement using string concatenationAttacker change the semantics of SQL queryDeveloper prefer string concatenation because is easy but they also known the safer method but requires more thought

Scenario #1

Attacker submit specially crafted input when performing search

SQL Injection

Date : 12 June 2008

http://www.lowyat.net

3 basic techniques

Path Traversal

Cross-site Scripting

SQL Injection

Cross-site Scripting (XSS)

How it works?1. Take input from user2. Fails to validate input3. Echoes input directly to web page4. Done!

Scenario #2

When developer using

<%# DataBinder.Eval(Container.DataItem, “Column1”) %>

to bind data in Datalist.

Cross-Site Scripting (XSS)

3 basic techniques

Path Travers

al

Cross-site

Scripting

SQL Injectio

n

Path Traversal

Access files that application not intend to accessTo read any files in the systemUsing “dot-dot-slash” to backtrack the folder

Example:http://app.com/GetImage.aspx?file=..\..\windows\repair\sam

Scenario #3

To prevent “Resource cannot be found”, developer create a page to check whether the picture file it exist or not. If doesn’t exist it will show the generic image.

Path Traversal

Advance Technique

Utilizing the basic attack techniquesAble to unveil a lot of privacy information of serversExample:

WMI AttackHost File Hijacking

WMI Attack

WMI = Windows Management InstrumentationWMI is a essential tools for IT Administrator to manage the servers and workstationsDamages:

Retrieve server’s information Remotely uninstall application

Scenario #4

Attack retrieve the software installed in web server and uninstall the software.

WMI Attack

Host File Hijacking

Windows rely on DNS and Host file to resolve the target IP addressHost file location : %windir%\system32\drivers\etc\hostsDamages:

Corrupt the host file so it can redirect the data to malicious server

Scenario #5

Attacker redirect the traffic for www.abc.com to different IP address. Imagine a antivirus application refer the wrong IP address to download the latest signature file.

Host File Hijacking

Obfuscation

The default .Net assembly format allow developer to disassemble and decompile.Obfuscate is a process to rebuilds the .Net assembly into a new format that is impossible to dissemble, decompile and difficult to understand.Prevent competitors and hackers from getting your source code.

Scenario #6

Attacker download the .Net assembly through Path Traversal attack. He successfully dissemble and decompile the assembly. Attacker now able to view all the logic behind the source code.

Obfuscator

Automated Testing

Develop your own testing tools Automate your testing processVisual Studio Tester Edition have a capability to do automated testing

The Dark Side……

Brutal Force attack are using the same techniqueIt is a common attack to “try” out passwordTo prevent such attack, identify the source.

MAC AddressIP AddressLogin username

Scenario #7

Develop a simple application to automate the brutal force attack on wireless router.

Automate the task

Steps to Defense Against Attackers

Validate both client-side and server-side inputDuplicated the validation functions in both client-side and server sideNO SQL Injection – use Parameter class in .NetNO XSS – Validate Input, Validate Output (VIVO)Obfuscate your code TODAY!Be innovative and creative in testing

Walter_wws@hotmail.com

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