Day 2: Data Types and Integer Overflows

Data Types in Detail

Each data type in C has a specific size (e.g., int is typically 4 bytes) and a range of values it can represent (e.g., int can range from -2,147,483,648 to 2,147,483,647 in a 32-bit system). Understanding these limitations is crucial for finding vulnerabilities like integer overflows, where operations exceed these boundaries.

Integer Overflows

An integer overflow occurs when an arithmetic operation results in a value that exceeds the maximum (or minimum) value a data type can hold. This can lead to unexpected behavior, such as wrapping around to negative values, which can be exploited to manipulate program logic or bypass security checks.

Theory

Data Type Deep Dive

Objective: Understand the limitations of different data types.

Data Types in C: Read Here

Knowing the exact size and behavior of data types is essential when writing or analyzing code, especially in low-level contexts like systems programming or embedded development. Misunderstanding these can lead to critical security vulnerabilities.

Integer Overflows Explained

Objective: Learn how integer overflows occur and how they can be exploited.

Integer Overflow Vulnerabilities: Read Here

Integer overflows can be a gateway to larger exploits, allowing attackers to bypass checks, cause crashes, or execute arbitrary code. They are common in C programs due to the language’s lack of built-in overflow protection.

Practice

Hands-On Exercise

Experiment with integer overflows: Write a C program that intentionally causes an integer overflow. For example, add 1 to INT_MAX and observe the results. Research real-world examples: Find examples of vulnerabilities caused by integer overflows, such as the infamous Heartbleed bug, and understand the impact they had on security. Simulate an Attack: Create a scenario where an integer overflow could be exploited to bypass a security check (e.g., an array bounds check).