Overview

Objectives

• Safely reproduce a simple buffer overflow in a lab

• Observe function frames, input length, and return address behavior

• Demonstrate control redirection with a benign payload

• Recompile with protections and confirm mitigation

Prerequisites

• Virtualization host and a Linux virtual machine

• Familiarity with C and Python

• Comfort with debugging and disassembly fundamentals

Implementation

1. Lab setup

• Provisioned a Linux virtual machine with compiler and debugger tools.

• Snapshotted the virtual machine to allow quick rollback.

2. Vulnerable sample

• Wrote a minimal C program with an unchecked copy into a fixed buffer for teaching purposes.

• Compiled first without hardening to observe the issue in a safe setting.

3. Analysis

• Used debugger and disassembly to inspect the call stack and offsets.

• Calculated input size required to overwrite the saved return address.

4. Proof of concept

• Composed a payload that proved control redirection with a harmless effect in the lab.

• Verified impact only within the virtual machine and documented observations.

5. Mitigation

• Recompiled with stack protection and non-executable stack.

• Re-ran the proof of concept to confirm the mitigation blocked execution.

• Documented secure coding practices and safer library calls.

Outcomes

• Clear, reproducible demonstration of why bounds checking matters

• Practical understanding of compiler and operating system protections

• Evidence that mitigations prevent the attack in this scenario

Skills demonstrated

• Vulnerability research in a contained environment

• Reverse engineering fundamentals and debugging

• Secure coding and mitigation verification