Cookie Monster Challenge

A simple web challenge about cookies. Set the right cookie value to get the flag!

Challenge Description

Cookie Monster is looking for his favorite red friend! Set a cookie named Red_Guy's_name with the right value to get the flag.

Building and Running

Using Makefile

The easiest way to deploy and manage this challenge is using the provided Makefile:

# Show available commands
make help

# Deployment with custom flag
make deploy FLAG=flag{custom_flag_here}

# Standard deployment
make deploy

# Full rebuild
make rebuild

# Clean up
make clean

Using Docker

1. Build the Docker image:

docker build -t cookie-monster .

2. Run the container:

docker run -p 80:80 cookie-monster

3. Access the challenge at: http://localhost

Using Custom Flag

To run with a custom flag, set the environment variable:

docker run -p 80:80 -e FLAG="flag{custom_flag_here}" cookie-monster

Using Docker Compose

docker-compose up -d

Solution

The challenge requires setting a cookie with a specific name and value pattern:

Step 1: Understand the Cookie Requirement

• Cookie Name: Red_Guy's_name
• Pattern: The value must match the regex /([Ee])lmo+/

Step 2: Set the Cookie

You can set the cookie using browser developer tools or JavaScript:

Using Browser Developer Tools:

1. Open Developer Tools (F12)
2. Go to Application/Storage tab
3. Find Cookies for localhost
4. Add a new cookie:
   • Name: Red_Guy's_name
   • Value: Elmo (or any value matching the pattern)

Using JavaScript Console:

document.cookie = "Red_Guy's_name=Elmo";

Step 3: Refresh the Page

After setting the cookie, refresh the page to see the flag and Elmo

Valid Cookie Values

Any value that matches the pattern /([Ee])lmo+/ will work:

• Elmo
• elmo
• Elmo123
• elmo_friend
• ELMO
• etc.

File Structure

cookie-monster/
├── challenge.json     # Challenge metadata and configuration
├── Dockerfile        
├── Makefile           
├── docker-compose.yml 
├── build.sh          
├── README.md         
└── web/              # Application source code
    └── index.php     # Main PHP application

Technical Details

• Base Image: PHP 8.2 with Apache
• Port: 80
• Flag Environment Variable: FLAG
• Default Flag: flag{YummyC00k13s}
• Cookie Pattern: /([Ee])lmo+/

Difficulty Level

Beginner - This challenge introduces basic web concepts:

• Understanding HTTP cookies
• Using browser developer tools
• Basic regex pattern matching
• Web application interaction