jwtcat

A CPU-based JSON Web Token (JWT) cracker and - to some extent - scanner

jwtcat is a Python script designed to detect and exploit well-known cryptographic flaws present in JSON Web Token (JWT).

These vulnerabilities, if successfully exploited by an adversary could allow authentication bypass, information disclosure and could ultimately lead to the compromise of an entire information system.

More information about JWT vulnerabilities can be found at:

• https://auth0.com/blog/critical-vulnerabilities-in-json-web-token-libraries/

Features

• Test against the following vulnerabilitie(s):
  • CVE-2018-1000531: JWT signature bypass due to the use of None hashing algorithm (alg=none)
• Guessing attacks against JWT private keys signed with the HS256 hashing algorithm:
  • Brute-force attacks
  • Wordlist attacks

Requirements

jwtcat is fully written in Python 3 and requires a minimum of Python 3.6 in addition to the following libraries:

• coloredlogs
• PyJWT
• tqdm

Installation

1. Clone the repository:

   git clone https://github.com/AresS31/jwtcat
   cd jwtcat

2. (Optional but recommended) Create and activate a new Python virtual environment:

   1. Create the virtual environment:

      python -m venv env

   2. Activate the newly created environment:

      • On POSIX:

        source ./env/bin/activate

      • On Windows:

        ./env/Scripts/Activate.ps1

3. Install dependencies:

   python -m pip install -r requirements.txt

Usage

• To list the available options:

  python jwtcat.py -h

• To list available options specific to brute force attacks:

  python jwtcat.py brute-force -h

  

• To list available options specific to wordlist attacks:

  python jwtcat.py wordlist -h

  

• To test a JWT against CVE-2018-1000531 and HS256 brute-force attacks:

  python jwtcat.py vulnerable -h

  

Roadmap

• Implement additional attack vectors.
• Implement support for multithreading or multiprocessing.
• Implement support for the -tF, --token-file swicth.
• Improve the code logic for:
  • TQDM integration with the logger.
• Improve the script performances.

Changelog

v1.1 - May 2020:

• Added checks to see if JWT is signed with HS256.
• Added checks to see if JWT is vulnerable to CVE-2018-1000531.
• Added potfile options.
• Added support for brute-force attacks.
• Code refactoring.
• Improved the standard output formatting.
• Switched from python-colorlog to coloredlogs.

Sponsor 💖

If you want to support this project and appreciate the time invested in developping, maintening and extending it; consider donating toward my next cup of coffee. ☕

It is easy, all you got to do is press the Sponsor button at the top of this page or alternatively click this link. 💸

Reporting Issues

Found a bug? I would love to squash it! 🐛

Please report all issues on the GitHub issues tracker.

Contributing

You would like to contribute to better this project? 🤩

Please submit all PRs on the GitHub pull requests tracker.

License

See LICENSE.