Securing PHP Web Applications

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. Easy, Powerful Code Security Techniques for Every PHP Developer   Hackers specifically target PHP Web applications. Why? Because they know many of these apps are written by programmers with little or no experience or training in software security. Don’t be victimized. Securing PHP Web Applications will help you master the specific techniques, skills, and best practices you need to write rock-solid PHP code and harden the PHP software you’re already using.   Drawing on more than fifteen years of experience in Web development, security, and training, Tricia and William Ballad show how security flaws can find their way into PHP code, and they identify the most common security mistakes made by PHP developers. The authors present practical, specific solutions–techniques that are surprisingly easy to understand and use, no matter what level of PHP programming expertise you have.   Securing PHP Web Applications covers the most important aspects of PHP code security, from error handling and buffer overflows to input validation and filesystem access. The authors explode the myths that discourage PHP programmers from attempting to secure their code and teach you how to instinctively write more secure code without compromising your software’s performance or your own productivity.   Coverage includes Designing secure applications from the very beginning–and plugging holes in applications you can’t rewrite from scratch Defending against session hijacking, fixation, and poisoning attacks that PHP can’t resist on its own Securing the servers your PHP code runs on, including specific guidance for Apache, MySQL, IIS/SQL Server, and more Enforcing strict authentication and making the most of encryption Preventing dangerous cross-site scripting (XSS) attacks Systematically testing yourapplications for security, including detailed discussions of exploit testing and PHP test automation Addressing known vulnerabilities in the third-party applications you’re already running Tricia and William Ballad demystify PHP security by presenting realistic scenarios and code examples, practical checklists, detailed visuals, and more. Whether you write Web applications professionally or casually, or simply use someone else’s PHP scripts, you need this book–and you need it now, before the hackers find you!

Table of Contents:
Acknowledgments xiii About the Authors xv   Part I: Web Development Is a Blood Sport–Don't Wander onto the Field Without a Helmet 1   Chapter 1: Security Is a Server Issue and Other Myths 3 Reality Check 3 Security Is a Server Issue 5 Security Through Obscurity 7 Native Session Management Provides Plenty of Security 9 “My Application Isn’t Major Enough to Get Hacked” 9 The “Barbarians at the Gate” Syndrome 10 Wrapping It Up 10   Part II: Is That Hole Really Big Enough to Drive a Truck Through? 11   Chapter 2: Error Handling 13 The Guestbook Application 13 Users Do the Darnedest Things . . . 15 Building an Error-Handling Mechanism 19 Wrapping It Up 26   Chapter 3: System Calls 27 Navigating the Dangerous Waters of exec(), system(), and Backticks 27 Using escapeshellcmd() and escapeshellarg() to Secure System Calls 30 Create an API to Handle All System Calls 31 Patch the Guestbook Application 32 Wrapping It Up 34   Part III: What's In a Name? More Than You Expect 35   Chapter 4: Buffer Overflows and Variable Sanitation 37 What Is a Buffer, How Does It Overflow, and Why Should You Care? 37 Prevent Buffer Overflows by Sanitizing Variables 46 Patch the Application 49 Wrapping It Up 52   Chapter 5: Input Validation 53 New Feature: Allow Users to Sign Their Guestbook Comments 53 The Problem: Users Who Give You More Than You Asked For 54 Assumptions: You Know What Your Data Looks Like 55 The Solution: Regular Expressions to Validate Input 57 Wrapping It Up 67   Chapter 6: Filesystem Access: Accessing the Filesystem for Fun and Profit 69 Opening Files 69 Creating and Storing Files 73 Changing File Properties Safely 76 Patching the Application to Allow User-Uploaded Image Files 88 Wrapping It Up 90   Part IV: “Aw come on man, you can trust me” 93   Chapter 7: Authentication 95 What Is User Authentication? 95 Privileges 100 How to Authenticate Users 101 Storing Usernames and Passwords 115 Patching the Application to Authenticate Users 117 Wrapping It Up 120   Chapter 8: Encryption 121 What Is Encryption? 121 Choosing an Encryption Type 123 Password Security 125 Patching the Application to Encrypt Passwords 125 Wrapping It Up 128   Chapter 9: Session Security 129 What Is a Session Variable? 129 Major Types of Session Attacks 129 Patching the Application to Secure the Session 133 Wrapping It Up 136   Chapter 10: Cross-Site Scripting 137 What Is XSS? 137 Reflected XSS 137 Stored XSS 138 Patching the Application to Prevent XSS Attacks 138 Wrapping It Up 139   Part V: Locking Up for the Night 141   Chapter 11: Securing Apache and MySQL 143 Programming Languages, Web Servers, and Operating Systems Are Inherently Insecure 143 Securing a UNIX, Linux, or Mac OS X Environment 144 Securing Apache 147 Securing MySQL 159 Wrapping It Up 166   Chapter 12: Securing IIS and SQL Server 167 Securing a Windows Server Environment 167 Securing IIS 177 Securing SQL Server 187 Wrapping It Up 205   Chapter 13: Securing PHP on the Server 207 Using the Latest Version of PHP 207 Using the Security Features Built into PHP and Apache 213 Using ModSecurity 215 Hardening php.ini 216 Wrapping It Up 218   Chapter 14: Introduction to Automated Testing 219 Why Are We Talking About Testing in a Security Book? 219 Testing Framework 220 Types of Tests 222 Choosing Solid Test Data 223 Wrapping It Up 224   Chapter 15: Introduction to Exploit Testing 225 What Is Exploit Testing? 225 Fuzzing 226 Testing Toolkits 233 Proprietary Test Suites 246 Wrapping It Up 254   Part VI: “Don’t Get Hacked” Is Not a Viable Security Policy 255   Chapter 16: Plan A: Designing a Secure Application from the Beginning 257 Before You Sit Down at the Keyboard . . . 257 Identifying Points of Failure 269 Wrapping It Up 271   Chapter 17: Plan B: Plugging the Holes in Your Existing Application 273 Set Up Your Environment 273 Application Hardening Checklist 276 Wrapping It Up 278   Epilogue: Security Is a Lifestyle Choice: Becoming a Better Programmer 279 Avoid Feature Creep 279 Write Self-Documenting Code 280 Use the Right Tools for the Job 282 Have Your Code Peer-Reviewed 283 Wrapping It Up 284   Appendix: Additional Resources 285 PEAR 285 Books 286 Web Sites 287 Tools 288   Glossary 289 Index 293