C and C++ vulnerabilities, exploits and countermeasures

Learning objectives

Understand

• the risks associated with the use of unsafe programming languages such as C and C++
• common vulnerabilities such as buffer overflows, use after free vulnerabilities and integer errors
• common attack techniques such as return address clobbering and indirect pointer overwriting
• common defense techniques such as stack canaries, address space layout randomization and other techniques

Overview

The C and C++ programming languages have some serious shortcomings from the point of view of security. Certain kinds of bugs in these languages can have disastrous consequences. Stack- or heap-based buffer overruns, double frees, dangling pointers, race conditions and format-string related vulnerabilities are typical examples of bugs that can make a C/C++ application vulnerable to extremely powerful attacks such as code injection.

In a code injection attack, an attacker succeeds in running code of his choosing on the target machine. This module will discuss the most important types of vulnerabilities, and will demonstrate, by example, how they can be exploited.

Programmers must avoid these vulnerabilities by observing strict coding disciplines to compensate for the freedom offered by the language and execution environment. Recently, improvements to the compiler and run-time environment have aided in mitigating the risk. An overview of such recent infrastructural improvements such as address space randomization and stack canaries is presented. The module also looks at how attackers have developed ways around some of these techniques.

The following papers are useful for the module:

• Y. Younan, W. Joosen and F. Piessens. Code injection in C and C++: A survey of vulnerabilities and Countermeasures
• Y. Younan. Efficient countermeasures for software vulnerabilities due to memory management errors
• Ú. Erlingsson, Y. Younan, F. Piessens, Low-level software security by example