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Ajax Security

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  • Copyright 2008
  • Edition: 1st
  • eBook (Watermarked)
  • ISBN-10: 0-13-280024-1
  • ISBN-13: 978-0-13-280024-2

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.

Sample Content

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


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