Securing PHP Web Applications

DESCRIPTION

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. Dont 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 youre 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 solutionstechniques 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 softwares performance or your own productivity.

Coverage includes
Designing secure applications from the very beginningand plugging holes in applications you cant rewrite from scratch
Defending against session hijacking, fixation, and poisoning attacks that PHP cant resist on itsown
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 youre 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 elses PHP scripts, you need this bookand 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 SportDon'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 Isnt 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 Validation53

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: Dont 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