Intro to Web Application Security

Information Assurance Club Information Assurance Club 20072007

Understanding Web Application Security

What is Application Security?What is Application Security?

Application Security Application Security encompasses measures taken to prevent exceptions in the security policy of an application or the underlying system vulnerabilities through flaws in the design, development, or deployment of the application. [Wikipedia]

Make sure codeMake sure code• Properly uses security mechanisms

• Has no design or implementation flaws

Application Layer VS Network Application Layer VS Network LayerLayer Application Layer

Attackers send attacks inside valid HTTP requests

Custom code is manipulated to do something it shouldn’t

Security requires software development expertise, not signatures

Network Layer Firewall, hardening,

patches, IDS, IPS SSL cannot detect or

prevent attacks inside HTTP requests

Security based on signature database

Test Your Hacking KnowledgeTest Your Hacking Knowledge

What might happen in an application if an attacker… Adds “; rm –rf /” to a menu selection passed to a

system call Replaces the unitprice hidden field with -500 Sends 1000000 ‘A’ characters to a login script Figures out the encoding used for cookies Disables all client side Javascript for form validation Adds to the end of an account ID parameter

“%27%20OR%201%3d1” Sends 1,000 HTTP requests per second to the search

field for an hour

Why Should I Care?Why Should I Care? How likely is a successful web application attack?

Anyone in the world, including insiders, can send an HTTP request to your server

Vulnerabilities are highly prevalent Easy to exploit without special tools or knowledge Little chance of being detected Hundreds of thousands of developers with no security background

or training

Consequences? Corruption or disclosure of database contents Root access to web and application servers Loss of authentication and access control for users Defacement Loss of use / availability Secondary attacks from your site

Application security is just as important as Network Security

Attacks Shift Towards Attacks Shift Towards Application LayerApplication Layer 75% of All Attacks on Information

Security Are Directed to the Web Application Layer

2/3 of All Web Applications Are Vulnerable

-Gartner

How Do Attackers Do It?How Do Attackers Do It?

Proxies Browser plugins Vulnerability scanning tools Many attacks can be launched using

only a browser and text editor

HyperText Transfer Protocol HyperText Transfer Protocol (HTTP)(HTTP)

GET /index.html HTTP/1.1GET /index.html HTTP/1.1Host: www.example.comHost: www.example.com

HTTP/1.1 200 OKHTTP/1.1 200 OKDate: Mon, 23 April 2007 22:38:34 GMTDate: Mon, 23 April 2007 22:38:34 GMTServer: Apache/1.3.27 (Unix) (Red-Hat/Linux)Server: Apache/1.3.27 (Unix) (Red-Hat/Linux)Last-Modified: Wed, 08 Jan 2003 23:11:55 GMTLast-Modified: Wed, 08 Jan 2003 23:11:55 GMTEtag: "3f80f-1b6-3e1cb03b"Etag: "3f80f-1b6-3e1cb03b"Accept-Ranges: bytesAccept-Ranges: bytesContent-Length: 438Content-Length: 438Connection: closeConnection: closeContent-Type: text/html; charset=UTF-8Content-Type: text/html; charset=UTF-8

HTTPS

Just encryption Eavesdropping

Protect Passwords Gmail

Bypass IPS Doesn't prevent hacking

Transparent Proxy

http://fiddler2.com/sandbox/ Fiddler is a HTTP Debugging Proxy which logs all

HTTP traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP Traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.

Fiddler is freeware and can debug traffic from virtually any application, including Internet Explorer, Mozilla Firefox, Opera, and thousands more.

Others: Paros, Web Scarab, etc

Authentication Common Problems Never expire (facebook) Not protected by SSL Easy to forge (cookies) Replay attacks

Re-using cookies Preventable with encrypted date/time stamp

Authentication Best Practices

Ensure HTTPS is being used Login failures should NOT indicate

whether username or password failed Strong password policy (don’t store in

clear text) Use brute force countermeasures

CAPTCHA Time delay

State Problems HTTP is a stateless protocol Session ID tells client browser who you are Server maintains a map of session objects Hijacking techniques

Guessing XSS Not using HTTPS Session ID exposed using URL-rewriting

Session Best Practices Single sign on/off Seemingly random and at least 20 bytes Timeout Use SSL Avoid URL-rewriting (disclosure risk)

Access Control

Restricting access Who? What can they see? What can they do?

Should exist in UI, BLL, and DAL

Broken Access Control Attacker notices URL indicating role

/guest/getAccountInfo They modify it to another directory (role)

/admin/getAccountInfo /auth/getAccountInfo

Attacker views more accounts than just their own

Cross-Site Scripting (XSS) Web application vulnerability that allows an attacker to

execute a malicious script in a victim's web browser How it works

Web browsers support scripting languages like Javascript that allow web pages to perform logic

If an attacker can get a web server to send their malicious script to a victim, the script executes as if it came from that web site

Consequences Steal session cookies Deface websites Information disclosure

XSS Vulnerability Pattern

Web app vulnerable to XSS if Attacker can provide malicious user input Site puts user input into a response

Search, form field, message board, etc Site doesn't properly validate or sanitize

that user input Unless developer is familiar with XSS, it's

very likely that proper input validation is not being done

Two Types of XSS Stored XSS

Dangerous user input is stored on the site and displayed at some later time

Typically found in message boards, guest books, surveys

Like leaving a land mine for a victim to trip across on a vulnerable site

Reflected XSS Dangerous user input is immediately sent back to the

user that submitted it Possibly a malicious link with an embedded script Typically found in search fields, error pages, etc

Cross-site Scripting - Tricks Scripts can only access data from their own site

Enforced by the browser “sandbox” SOP Trick: Use an anonymous proxy

Scripts can't access the OS or file system Trick: Wscript http://my.3c.ist.psu.edu/rrr174/email.js

The browser isn't doing anything abnormal Cheat Sheet: http://ha.ckers.org/xss.html Demos: http://www.attacklabs.com

XSS Real World Example MySpace XSS Worm – Oct 2005

AKA Samy worm Introduced an XSS attack into his own profile When anyone viewed his profile, the attack:

added Samy as a 'friend' to that user's profile and infected them with the same XSS attack in their own

profile Then, when anyone views the infected profile, starts all

over... The exploit:

Used 'java\nscript' since 'javascript' was filtered out, String.fromCharCode(34) to generate a double quote, etc.

Used XmlHttpRequest (AJAX), so does Yamanner worm 10 hrs – 560 friends, 13 hrs – 6400 friends, 18 hrs - 1,000,000

friends, 19 hrs - entire site down, 22 hrs – site back up again

XSS– Input Filters Many applications attempt XSS protection with filters

Convert < and > to &lt and &gt Strip out HTML tags Eliminate <script> tags Strip out Javascript

.NET provides XSS protection by default <%@ Page ValidateRequest=”true” %> Anti-Cross Site Scripting Library

http://msdn2.microsoft.com/en-us/security/aa973814.aspx

Better to white list input instead of black list VALIDATE USER INPUT!!! TRUST NOTHING FROM THE

CLIENT!!!

PSU Webmail XSSPSU Webmail XSS

https://webmaillite.psu.edu/webmail/inbox.cgi?mailbox=

https://my.3c.ist.psu.edu/rrr174/xss.js

popMessage param (cookie)

Now what? Hijack web access session ID Steal email Go phishing Do anything the user can do

View Passwords

javascript:(function(){var s,F,j,f,i; s = %22%22; F = document.forms; for(j=0; j<F.length; ++j) { f = F[j]; for (i=0; i<f.length; ++i) { if (f[i].type.toLowerCase() == %22password%22) s += f[i].value + %22\n%22; } } if (s) alert(%22Passwords in forms on this page:\n\n%22 + s); else alert(%22There are no passwords in forms on this page.%22);})();

CSRF (Sea-Surf)

Cross-site request forgery, also known as one click attack or session riding

Digg and Amazon have been targets Prevention

Include a secret, user-specific token in forms that is verified in addition to the cookie

Users can help protect their accounts at poorly designed sites by logging off the site before visiting another, or clearing their browser's cookies at the end of each browser session

Injection Overview Many applications invoke interpreters

SQL OS command shell (cmd.exe, perl) Sendmail, LDAP, XPath, XSLT

Interpreters take commands and data and execute the instructions Attacker can send malicious data or

commands into your application tricking it into behaving differently

Frequently interpreters run as root or administrator

SQL Injection – Example Get rows from table based on user provided

parameter SELECT * FROM users WHERE SSN='” + ssn + “'”

SSN goes from user to web application to database Never validated Attacker sends 123456789' OR '1'='1

Application builds a query SELECT * FROM users WHERE SSN='123456789'

OR '1'='1' Returns every user in the database

Blind SQL Injection: http://www.0x90.org/releases/absinthe

Prevent SQL Injection

Validate user input Stored procedures Parameterized queries Connection strings (Access Control)

Prevent DELETE and DROP queries

Injection DemoInjection Demo

SQL Injection:

Almost every IST student’s web application is vulnerable

https://my.3c.ist.psu.edu/jeb5010/customer.php?Name

='%20OR%201=1--

Remote Code Execution:

http://scripts.cac.psu.edu/pxn126/finger.cgi

Conclusion Be aware of security threats

Train yourself Assess security at every step of the SDLC Define unacceptable risks

Then implement policy Ensure accountability

Consider commercial solutions (Get help)

Where can I learn more? http://www.owasp.org/index.php/OWASP_Top_Ten_Project http://en.wikipedia.org/wiki/Category:Web_security_exploits http://www.spidynamics.com/spilabs/index.html http://ha.ckers.org http://johnny.ihackstuff.com/ghdb.php http://www.foundstone.com/resources/freetools.htm http://www.owasp.org/index.php/

Category:OWASP_WebGoat_Project http://blogged-on.de/xss http://leastprivilege.com

Download this presentation http://my.3c.ist.psu.edu/rrr174/webappsec.ppt

Questions?

Ask questions and I'll try to answer them