Preface

CERT was formed by the Defense Advanced Research Projects Agency (DARPA) in November 1988 in response to the Morris worm incident, which brought 10 percent of Internet systems to a halt in November 1988. CERT is located in Pittsburgh, Pennsylvania, at the Software Engineering Institute (SEI), a federally funded research and development center sponsored by the U.S. Department of Defense.

The initial focus of CERT was incident response and analysis. Incidents include successful attacks such as compromises and denials of service, as well as attack attempts, probes, and scans. Since 1988, CERT has received more than 22,665 hotline calls reporting computer security incidents or requesting information and has handled more than 319,992 computer security incidents. The number of incidents reported each year continues to grow.

Responding to incidents, while necessary, is insufficient to secure the Internet and interconnected information systems. Analysis indicates that the majority of incidents is caused by trojans, social engineering, and the exploitation of software vulnerabilities, including software defects, design decisions, configuration decisions, and unexpected interactions among systems. CERT monitors public sources of vulnerability information and regularly receives reports of vulnerabilities. Since 1995, more than 16,726 vulnerabilities have been reported. When a report is received, CERT analyzes the potential vulnerability and works with technology producers to inform them of security deficiencies in their products and to facilitate and track their responses to those problems.¹

1. CERT interacts with more than 1,900 hardware and software developers.

Similar to incident reports, vulnerability reports continue to grow at an alarming rate.² While managing vulnerabilities pushes the process upstream, it is again insufficient to address the issues of Internet and information system security. To address the growing number of both vulnerabilities and incidents, it is increasingly apparent that the problem must be attacked at the source by working to prevent the introduction of software vulnerabilities during software development and ongoing maintenance. Analysis of existing vulnerabilities indicates that a relatively small number of root causes accounts for the majority of vulnerabilities. The goal of this book is to educate developers about these root causes and the steps that can be taken so that vulnerabilities are not introduced.

2. See www.cert.org/stats/cert_stats.html for current statistics.

• If you are a C/C++ programmer, this book will teach you how to identify common programming errors that result in software vulnerabilities, understand how these errors are exploited, and implement a solution in a secure fashion.

• If you are a software project manager, this book identifies the risks and consequences of software vulnerabilities to guide investments in developing secure software.

• If you are a computer science student, this book will teach you programming practices that will help you to avoid developing bad habits and enable you to develop secure programs during your professional career.

• If you are a security analyst, this book provides a detailed description of common vulnerabilities, identifies ways to detect these vulnerabilities, and offers practical avoidance strategies.

Secure Coding in C and C++ is organized around functional capabilities commonly implemented by software engineers that have potential security consequences, such as formatted output and arithmetic operations. Each chapter describes insecure programming practices and common errors that can lead to vulnerabilities, how these programming flaws can be exploited, the potential consequences of exploitation, and secure alternatives. Root causes of software vulnerabilities, such as buffer overflows, integer type range errors, and invalid format strings, are identified and explained where applicable. Strategies for securely implementing functional capabilities are described in each chapter, as well as techniques for discovering vulnerabilities in existing code.

This book contains the following chapters:

• Chapter 1 provides an overview of the problem, introduces security terms and concepts, and provides insight into why so many vulnerabilities are found in C and C++ programs.

• Chapter 2 describes string manipulation in C and C++, common security flaws, and resulting vulnerabilities, including buffer overflow and stack smashing. Both code and arc injection exploits are examined.

• Chapter 3 introduces arbitrary memory write exploits that allow an attacker to write a single address to any location in memory. This chapter describes how these exploits can be used to execute arbitrary code on a compromised machine. Vulnerabilities resulting from arbitrary memory writes are discussed in later chapters.

• Chapter 4 describes dynamic memory management. Dynamically allocated buffer overflows, writing to freed memory, and double-free vulnerabilities are described.

• Chapter 5 covers integral security issues (security issues dealing with integers), including integer overflows, sign errors, and truncation errors.

• Chapter 6 describes the correct and incorrect use of formatted output functions. Both format string and buffer overflow vulnerabilities resulting from the incorrect use of these functions are described.

• Chapter 7 focuses on concurrency and vulnerabilities that can result from deadlock, race conditions, and invalid memory access sequences.

• Chapter 8 describes common vulnerabilities associated with file I/O, including race conditions and time of check, time of use (TOCTOU) vulnerabilities.

• Chapter 9 recommends specific development practices for improving the overall security of your C / C++ application. These recommendations are in addition to the recommendations included in each chapter for addressing specific vulnerability classes.

Secure Coding in C and C++ contains hundreds of examples of secure and insecure code as well as sample exploits. Almost all of these examples are in C and C++, although comparisons are drawn with other languages. The examples are implemented for Windows and Linux operating systems. While the specific examples typically have been compiled and tested in one or more specific environments, vulnerabilities are evaluated to determine whether they are specific to or generalizable across compiler version, operating system, microprocessor, applicable C or C++ standards, little or big endian architectures, and execution stack architecture.

This book, as well as the online course based on it, focuses on common programming errors using C and C++ that frequently result in software vulnerabilities. However, because of size and space constraints, not every potential source of vulnerabilities is covered. Additional and updated information, event schedules, and news related to Secure Coding in C and C++ are available at www.cert.org/books/secure-coding/. Vulnerabilities discussed in the book are also cross-referenced with real-world examples from the US-CERT Vulnerability Notes Database at www.kb.cert.org/vuls/.

Access to the online secure coding course that accompanies this book is available through Carnegie Mellon’s Open Learning Initiative (OLI) at https://oli.cmu.edu/. Enter the course key: 0321822137.