Buffer overflow attacks in Operating Systems - Mini Project: Build & Apply

Understanding Buffer Overflow Attacks

📖 Scenario: You are learning about computer security. One common problem is a buffer overflow attack, where a program writes more data into a memory space than it can hold. This can cause unexpected behavior or let attackers run harmful code.Imagine a simple program that stores a username in a small box (buffer). If someone tries to put a very long name in that box, it might overflow and cause trouble.

🎯 Goal: Build a simple example that shows how a buffer overflow can happen by creating a fixed-size buffer and then trying to add more data than it can hold.

📋 What You'll Learn

Create a fixed-size buffer to hold a username

Set a maximum allowed length for the username

Write code to check if the input username fits in the buffer

Show what happens if the username is too long

💡 Why This Matters

🌍 Real World

Buffer overflow attacks are a common security problem in software. Understanding them helps protect programs from crashes and hacking.

💼 Career

Security analysts, software developers, and system administrators need to know about buffer overflows to write safe code and defend systems.

1

Create a fixed-size buffer

Create a character array called buffer with size 8 to hold a username.

Operating Systems

# Create a character array called buffer with size 8
# Your code here

Need a hint?

Use char buffer[8]; to create a buffer that can hold 7 characters plus a null terminator.

2

Set maximum allowed username length

Create an integer variable called max_length and set it to 7 to limit the username length.

Operating Systems

char buffer[8];
// Define max_length as 7
# Your code here

Need a hint?

This variable will help check if the username fits in the buffer.

3

Check if username fits in buffer

Write an if statement that checks if the length of a username string called input is less than or equal to max_length. Use strlen(input) to get the length.

Operating Systems

char buffer[8];
int max_length = 7;
// Check if input length is within max_length
# Your code here

Need a hint?

This check prevents overflow by ensuring the input fits.

4

Show overflow risk when input is too long

Inside the else block of the if statement, add a comment that says // buffer overflow risk to indicate danger when input is too long.

Operating Systems

char buffer[8];
int max_length = 7;
if (strlen(input) <= max_length) {
    // safe to copy
} else {
    // buffer overflow risk
    # Your code here
}

Need a hint?

This comment helps understand where the problem happens.