Ajax Security

This is the eBook version of the printed book. If the print book includes a CD-ROM, this content is not included within the eBook version. The Hands-On, Practical Guide to Preventing Ajax-Related Security Vulnerabilities   More and more Web sites are being rewritten as Ajax applications; even traditional desktop software is rapidly moving to the Web via Ajax. But, all too often, this transition is being made with reckless disregard for security. If Ajax applications aren’t designed and coded properly, they can be susceptible to far more dangerous security vulnerabilities than conventional Web or desktop software. Ajax developers desperately need guidance on securing their applications: knowledge that’s been virtually impossible to find, until now.             Ajax Security systematically debunks today’s most dangerous myths about Ajax security, illustrating key points with detailed case studies of actual exploited Ajax vulnerabilities, ranging from MySpace’s Samy worm to MacWorld’s conference code validator. Even more important, it delivers specific, up-to-the-minute recommendations for securing Ajax applications in each major Web programming language and environment, including .NET, Java, PHP, and even Ruby on Rails. You’ll learn how to:   ·        Mitigate unique risks associated with Ajax, including overly granular Web services, application control flow tampering, and manipulation of program logic ·        Write new Ajax code more safely—and identify and fix flaws in existing code ·        Prevent emerging Ajax-specific attacks, including JavaScript hijacking and persistent storage theft ·        Avoid attacks based on XSS and SQL Injection—including a dangerous SQL Injection variant that can extract an entire backend database with just two requests ·        Leverage security built into Ajax frameworks like Prototype, Dojo, and ASP.NET AJAX Extensions—and recognize what you still must implement on your own ·        Create more secure “mashup” applications   Ajax Security will be an indispensable resource for developers coding or maintaining Ajax applications; architects and development managers planning or designing new Ajax software, and all software security professionals, from QA specialists to penetration testers.

Table of Contents:
    Preface xvii     Preface (The Real One) xvix Chapter 1 Introduction to Ajax Security 1     An Ajax Primer 2         What Is Ajax? 2         Asynchronous 3         JavaScript 6         XML 11         Dynamic HTML (DHTML) 11     The Ajax Architecture Shift 11         Thick-Client Architecture 12         Thin-Client Architecture 13         Ajax: The Goldilocks of Architecture 15         A Security Perspective: Thick-Client Applications 16         A Security Perspective: Thin-Client Applications 17         A Security Perspective: Ajax Applications 18     A Perfect Storm of Vulnerabilities 19         Increased Complexity, Transparency, and Size 19         Sociological Issues 22         Ajax Applications: Attractive and Strategic Targets 23     Conclusions 24 Chapter 2 The Heist 25     Eve 25         Hacking HighTechVacations.net 26         Hacking the Coupon System 26         Attacking Client-Side Data Binding 32         Attacking the Ajax API 36     A Theft in the Night 42 Chapter 3 Web Attacks 45     The Basic Attack Categories 45         Resource Enumeration 46         Parameter Manipulation 50     Other Attacks 75         Cross-Site Request Forgery (CSRF) 75         Phishing 76         Denial-of-Service (DoS) 77     Protecting Web Applications from Resource Enumeration and Parameter         Manipulation 77         Secure Sockets Layer 78     Conclusions 78 Chapter 4  Ajax Attack Surface 81     Understanding the Attack Surface 81     Traditional Web Application Attack Surface 83         Form Inputs 83         Cookies 84         Headers 85         Hidden Form Inputs 86         Query Parameters 86         Uploaded Files 89     Traditional Web Application Attacks: A Report Card 90     Web Service Attack Surface 92         Web Service Methods 92         Web Service Definitions 94     Ajax Application Attack Surface 94         The Origin of the Ajax Application Attack Surface 96         Best of Both Worlds–for the Hacker 98     Proper Input Validation 98         The Problem with Blacklisting and Other Specific Fixes 99         Treating the Symptoms Instead of the Disease 102         Whitelist Input Validation 105         Regular Expressions 109         Additional Thoughts on Input Validation 109     Validating Rich User Input 111         Validating Markup Languages 111         Validating Binary Files 113         Validating JavaScript Source Code 114         Validating Serialized Data 120     The Myth of User-Supplied Content 122     Conclusion 123 Chapter 5 Ajax Code Complexity 125     Multiple Languages and Architectures 125         Array Indexing 126         String Operations 128         Code Comments 129         Someone Else’s Problem 130     JavaScript Quirks 132         Interpreted, Not Compiled 132         Weakly Typed 133     Asynchronicity 135         Race Conditions 135         Deadlocks and the Dining Philosophers Problem 139         Client-Side Synchronization 144     Be Careful Whose Advice You Take 144     Conclusions 145 Chapter 6 Transparency in Ajax Applications 147     Black Boxes Versus White Boxes 147         Example: MyLocalWeatherForecast.com 150         Example: MyLocalWeatherForecast.com “Ajaxified” 152         Comparison Conclusions 156     The Web Application as an API 156         Data Types and Method Signatures 158     Specific Security Mistakes 158         Improper Authorization 159         Overly Granular Server API 161         Session State Stored in JavaScript 164         Sensitive Data Revealed to Users 165         Comments and Documentation Included in Client-Side Code 166         Data Transformation Performed on the Client 167     Security through Obscurity 172         Obfuscation 173     Conclusions 174 Chapter 7 Hijacking Ajax Applications 175     Hijacking Ajax Frameworks 176         Accidental Function Clobbering 176         Function Clobbering for Fun and Profit 178     Hijacking On-Demand Ajax 184     Hijacking JSON APIs 190         Hijacking Object Literals 195         Root of JSON Hijacking 195         Defending Against JSON Hijacking 196     Conclusions 199 Chapter 8 Attacking Client-Side Storage 201     Overview of Client-Side Storage Systems 201         General Client-Side Storage Security 202     HTTP Cookies 204         Cookie Access Control Rules 206         Storage Capacity of HTTP Cookies 211         Lifetime of Cookies 215         Additional Cookie Storage Security Notes 216         Cookie Storage Summary 216     Flash Local Shared Objects 218         Flash Local Shared Objects Summary 225     DOM Storage 226         Session Storage 227         Global Storage 229         The Devilish Details of DOM Storage 231         DOM Storage Security 233         DOM Storage Summary 234     Internet Explorer userData 235         Security Summary 240     General Client-Side Storage Attacks and Defenses 240         Cross-Domain Attacks 241         Cross-Directory Attacks 242         Cross-Port Attacks 243     Conclusions 243 Chapter 9 Offline Ajax Applications 245     Offline Ajax Applications 245     Google Gears 247         Native Security Features and Shortcomings of Google Gears 248         Exploiting WorkerPool 251         LocalServer Data Disclosure and Poisoning 253         Directly Accessing the Google Gears Database 257         SQL Injection and Google Gears 258         How Dangerous Is Client-Side SQL Injection? 262     Dojo.Offline 264         Keeping the Key Safe 265         Keeping the Data Safe 266         Good Passwords Make for Good Keys 267     Client-Side Input Validation Becomes Relevant 268     Other Approaches to Offline Applications 270     Conclusions 270 Chapter 10 Request Origin Issues 273     Robots, Spiders, Browsers, and Other Creepy Crawlers 273         “Hello! My Name Is Firefox. I Enjoy Chunked Encoding, PDFs, and         Long Walks on the Beach.” 275     Request Origin Uncertainty and JavaScript 276         Ajax Requests from the Web Server’s Point of View 276         Yourself, or Someone Like You 280         Sending HTTP Requests with JavaScript 282         JavaScript HTTP Attacks in a Pre-Ajax World 284         Hunting Content with XMLHttpRequest 286         Combination XSS/XHR Attacks in Action 290     Defenses 292     Conclusions 294 Chapter 11 Web Mashups and Aggregators 295     Machine-Consumable Data on the Internet 296         Early 90’s: Dawn of the Human Web 296         Mid 90s: The Birth of the Machine Web 297         2000s: The Machine Web Matures 298         Publicly Available Web Services 299     Mashups: Frankenstein on the Web 301         ChicagoCrime.org 302         HousingMaps.com 303         Other Mashups 304     Constructing Mashups 304         Mashups and Ajax 306     Bridges, Proxies, and Gateways–Oh My! 308         Ajax Proxy Alternatives 309     Attacking Ajax Proxies 310         Et Tu, HousingMaps.com? 312     Input Validation in Mashups 314     Aggregate Sites 317     Degraded Security and Trust 324     Conclusions 327 Chapter 12 Attacking the Presentation Layer 329     A Pinch of Presentation Makes the Content Go Down 329     Attacking the Presentation Layer 333     Data Mining Cascading Style Sheets 334     Look and Feel Hacks 337         Advanced Look and Feel Hacks 341     Embedded Program Logic 345     Cascading Style Sheets Vectors 347         Modifying the Browser Cache 348     Preventing Presentation Layer Attacks 352     Conclusion 353 Chapter 13 JavaScript Worms 355     Overview of JavaScript Worms 355         Traditional Computer Viruses 356     JavaScript Worms 359         JavaScript Worm Construction 361         JavaScript Limitations 363         Propagating JavaScript Worms 364         JavaScript Worm Payloads 364         Putting It All Together 372     Case Study: Samy Worm 373         How It Worked 374         The Virus’ Payload 377         Conclusions About the Samy Worm 379     Case Study: Yamanner Worm (JS/Yamanner-A) 380         How It Worked 380         The Virus’ Payload 383         Conclusions About the Yamanner Worm 384     Lessons Learned from Real JavaScript Worms 387     Conclusions 389 Chapter 14 Testing Ajax Applications 391     Black Magic 391     Not Everyone Uses a Web Browser to Browse the Web 396         Catch-22 398     Security Testing Tools–or Why Real Life Is Not Like Hollywood 399         Site Cataloging 400         Vulnerability Detection 401         Analysis Tool: Sprajax 403         Analysis Tool: Paros Proxy 406         Analysis Tool: LAPSE (Lightweight Analysis for Program Security in Eclipse) 408         Analysis Tool:WebInspect™ 409     Additional Thoughts on Security Testing 411 Chapter 15 Analysis of Ajax Frameworks 413     ASP.NET 413         ASP.NET AJAX (formerly Atlas) 414         ScriptService 417         Security Showdown: UpdatePanel Versus ScriptService 419         ASP.NET AJAX and WSDL 420         ValidateRequest 424         ViewStateUserKey 425         ASP.NET Configuration and Debugging 426     PHP 427         Sajax 427         Sajax and Cross-Site Request Forgery 430     Java EE 431         Direct Web Remoting (DWR) 432     JavaScript Frameworks 434         A Warning About Client-Side Code 435         Prototype 435     Conclusions 437 Appendix A Samy Source Code 439 Appendix B Source Code for Yamanner Worm 447 Index 453

About the Author :
Billy Hoffman is the lead researcher for HP Security Labs of HP Software. At HP, Billy focuses on JavaScript source code analysis, automated discovery of Web application vulnerabilities, and Web crawling technologies. He has worked in the security space since 2001 after he wrote an article on cracking software for 2600, “The Hacker Quarterly,” and learned that people would pay him to be curious. Over the years Billy has worked a variety of projects including reverse engineering file formats, micro-controllers, JavaScript malware, and magstripes. He is the creator of Stripe Snoop, a suite of research tools that captures, modifies, validates, generates, analyzes, and shares data from magstripes. Billy’s work has been featured in Wired, Make magazine, Slashdot, G4TechTV, and in various other journals and Web sites. Billy is a regular presenter at hacker conferences including Toorcon, Shmoocon, Phreaknic, Summercon, and Outerz0ne and is active in the South East hacking scene. Occasionally the suits make him take off the black t-shirt and he speaks at more mainstream security events including RSA, Infosec, AJAXWorld, and Black Hat. Billy graduated from the Georgia Institute of Technology in 2005 with a BS in Computer Science with specializations in networking and embedded systems. He lives in Atlanta with his wife and two tubby and very spoiled cats.   Bryan Sullivan is a software development manager for the Application Security Center division of HP Software. He has been a professional software developer and development manager for over 12 years, with the last five years focused on the Internet security software industry. Prior to HP, Bryan was a security researcher for SPI Dynamics, a leading Web application security company acquired by HP in August 2007.While at SPI, he created the DevInspect product, which analyzes Web applications for security vulnerabilities during development. Bryan is a frequent speaker at industry events, most recently AjaxWorld, Black Hat, and RSA. He was involved in the creation of the Application Vulnerability Description Language (AVDL) and has three patents on security assessment and remediation methodologies pending review. He is a graduate of the Georgia Institute of Technology with a BS in Applied Mathematics. When he’s not trying to break the Internet, Bryan spends as much time as he can on the golf links. If any Augusta National members are reading this, Bryan would be exceedingly happy to tell you everything he knows about Ajax security over a round or two.