Hacker techniques introduction to buffer overflows

buffer overflow: a hacker's primer

buffer overflows are a classic vulnerability in software that allows attackers to overwrite memory, potentially gaining control of a program's execution. they're a fundamental concept in security and understanding them is crucial for both defensive and offensive security practitioners. this tutorial will provide a detailed introduction, covering the theory, practical examples, and mitigation techniques.

**disclaimer:** this tutorial is for educational purposes only. attempting to exploit vulnerabilities on systems you do not own or have permission to access is illegal and unethical. use this knowledge to learn about security and protect systems.

**1. what is a buffer overflow?**

imagine a container (a buffer) designed to hold a specific amount of data. a buffer overflow occurs when you try to put *more* data into that container than it can hold. the excess data spills over into adjacent memory locations, potentially overwriting important information, like other variables, function return addresses, or even executable code.

**why does this happen?**

* **lack of bounds checking:** many older programming languages (like c and c++) do not automatically check if data being written into a buffer exceeds its allocated size. it's the programmer's responsibility to ensure this doesn't happen, and mistakes can occur.
* **unsafe functions:** some functions are inherently vulnerable to buffer overflows because they don't perform adequate size checks. examples include `strcpy`, `gets`, and `sprintf` in c.

**2. the stack and function calls (crucial background)**

to understand how buffer overflows can be exploited, you need a basic understanding of how programs store data and execute functions on the stack.

* **the stack:** the stack is a region of memory used to store temporary data during function calls. it operates on a lifo (last-in, first-out) principle. think of it like a stack of plates – you add (push) plates to the to ...

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