Stack-Based Buffer Overflows on Linux x86

Stack-Based Buffer Overflows on Linux x86  Medium

Buffer overflows are common vulnerabilities in software applications that can be exploited to achieve remote code execution (RCE) or perform a Denial-of-Service (DoS) attack. These vulnerabilities are caused by insecure coding, resulting in an attacker being able to overrun a program's buffer and overwrite adjacent memory locations, changing the program's execution path and resulting in unintended actions.

Created by Cry0l1t3

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Summary

This module introduces buffer overflow attacks, principles such as CPU architecture and CPU registers, and walks through the basics of exploit development and shellcode generation. We will also walk through a public exploit proof of concept and cover techniques for preventing these types of attacks.

In this module, we will cover:

  • An introduction to buffer overflows
  • The basics of exploit development
  • Dealing with shellcode length and bad characters
  • Public exploit modification
  • Buffer overflow prevention

This module is broken down into sections with accompanying hands-on exercises to practice each of the tactics and techniques we cover. The module ends with a practical hands-on skills assessment to gauge your understanding of the various topic areas.

As you work through the module, you will see example commands and command output for the various topics introduced. It is worth reproducing as many of these examples as possible to reinforce further the concepts introduced in each section. You can do this in the Pwnbox provided in the interactive sections or your own virtual machine.

You can start and stop the module at any time and pick up where you left off. There is no time limit or "grading," but you must complete all of the exercises and the skills assessment to receive the maximum number of cubes and have this module marked as complete in any paths you have chosen.

The module is classified as "Medium" but assumes a working knowledge of the Linux command line and an understanding of information security fundamentals.

A firm grasp of the following modules can be considered prerequisites for successful completion of this module:

  • Introduction to Networking
  • Linux Fundamentals

Sections

  • Buffer Overflows Overview
  • Exploit Development Introduction
  • CPU Architecture
  • Stack-Based Buffer Overflow
  • CPU Registers
  • Take Control of EIP
  • Determine the Length for Shellcode
  • Identification of Bad Characters
  • Generating Shellcode
  • Identification of the Return Address
  • Public Exploit Modification
  • Prevention Techniques and Mechanisms
  • Skills Assessment - Buffer Overflow

Relevant Paths

This module progresses you towards the following Paths

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Intro to Binary Exploitation

Hard 62 Sections

Cubes Required: 570

Binary exploitation is a core tenet of penetration testing, but learning it can be daunting. This is mainly due to the complexity of binary files and their underlying machine code and how binary files interact with computer memory and the processor. To learn the basics of binary exploitation, we must first have a firm grasp of Computer Architecture and the Assembly Language. To move into more advanced binary exploitation, we must have a firm grasp on basic buffer overflow attacks, principles such as CPU architecture, and CPU registers for 32-bit Windows and Linux systems. Furthermore, a strong foundation in Python scripting is essential for writing and understanding exploit scripts.

 Introduction to Python 3

Easy 14 Sections

Automating tedious or otherwise impossible tasks is highly valued during both penetration testing engagements and everyday life. Introduction to Python 3 aims to introduce the student to the world of scripting with Python 3 and covers the essential building blocks needed for a beginner to understand programming. Some advanced topics are also covered for the more experienced student. In a guided fashion and starting soft, the final goal of this module is to equip the reader with enough know-how to be able to implement simple yet useful pieces of software.

 Intro to Assembly Language

Medium 24 Sections

This module builds the core foundation for Binary Exploitation by teaching Computer Architecture and Assembly language basics.

 Stack-Based Buffer Overflows on Linux x86

Medium 13 Sections

Buffer overflows are common vulnerabilities in software applications that can be exploited to achieve remote code execution (RCE) or perform a Denial-of-Service (DoS) attack. These vulnerabilities are caused by insecure coding, resulting in an attacker being able to overrun a program's buffer and overwrite adjacent memory locations, changing the program's execution path and resulting in unintended actions.

 Stack-Based Buffer Overflows on Windows x86

Medium 11 Sections

This module is your first step into Windows Binary Exploitation, and it will teach you how to exploit local and remote buffer overflow vulnerabilities on Windows machines.

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