TL;DR: DomainSleuth is a simple yet powerful Python tool that leverages Server Name Indication (SNI) to uncover hidden domain names associated with your target domain. This information can be invaluable in your bug bounty hunting journey, providing a broader scope for potential vulnerabilities.

Introduction

As a bug bounty hunter, it’s crucial to identify and explore every aspect of your target domain to discover potential vulnerabilities. One aspect often overlooked is the additional domain names that may be associated with the target domain. DomainSleuth, a lightweight Python tool, is designed to make this process easy by leveraging Server Name Indication (SNI) to uncover hidden domain names hosted on the same TLS server.

What is Server Name Indication (SNI)?

Server Name Indication (SNI) is an extension of the TLS protocol that allows a client to specify the desired hostname during the SSL/TLS handshake. This feature enables a single server to host multiple SSL/TLS certificates for multiple domains, making it possible to serve different websites using the same IP address.

How DomainSleuth Works

DomainSleuth connects to the target domain using a TLS connection and extracts the certificate information, specifically the ‘subject’ and ‘subjectAltName’ fields. The ‘subject’ field contains the primary domain for which the certificate was issued, while the ‘subjectAltName’ field lists the alternative domain names associated with the certificate. By examining these fields, DomainSleuth can unveil hidden domain names that might otherwise go unnoticed.

Here’s a brief overview of the DomainSleuth code:

1. Import the required libraries (socket, ssl, and sys).
2. Define the get_sni_info() function that takes a domain as input.
3. Create an SSL context and wrap a socket connection with it.
4. Connect to the domain on port 443 and retrieve the peer certificate.
5. Extract the ‘subject’ and ‘subjectAltName’ fields from the certificate.
6. Print the primary domain (‘commonName’) and the alternative domain names.
7. Close the connection and handle exceptions.

Why DomainSleuth is Valuable for Bug Bounty Hunters

DomainSleuth can provide bug bounty hunters with valuable insights into their target domain’s infrastructure, revealing hidden domain names that could potentially host vulnerabilities. By expanding the scope of your investigation, you increase your chances of discovering security flaws that other hunters might overlook.

Some use cases for DomainSleuth in bug bounty hunting include:

• Identifying additional domains that share the same TLS server as your target domain.
• Uncovering hidden subdomains or domain variations that may contain vulnerabilities.
• Gaining a better understanding of the target domain’s infrastructure and potential attack surface.

How to Use DomainSleuth

DomainSleuth is a command-line tool that requires only a single input — the target domain. To use DomainSleuth, simply run the following command:

python domainsleuth.py <domain>

Replace <domain> with the domain you wish to investigate. DomainSleuth will then return the certificate information, including the primary domain and any alternative domain names.

Accessing DomainSleuth

DomainSleuth is an open-source tool, and you can access it on GitHub by visiting: - https://github.com/Lopseg/DomainSleuth

Feel free to download, explore, and contribute to the project.

I would like to extend my gratitude to Incogbyte for suggesting the idea and inspiring me to develop this useful tool for the bug bounty hunting community.

Future Development and Improvements

As DomainSleuth continues to evolve, we have several plans for future development and enhancements. Some of these ideas include incorporating multi-threading for faster processing, adding support for additional protocols, and developing an interactive user interface to make it even more accessible to users of all skill levels. Additionally, we welcome any suggestions or contributions from the community to help us make DomainSleuth even more powerful and effective for bug bounty hunters.

Conclusion

DomainSleuth is an invaluable tool for bug bounty hunters looking to uncover hidden domains associated with their target domain. By leveraging the power of SNI, DomainSleuth provides a broader scope for discovering potential vulnerabilities and improves your chances of success in your bug bounty hunting journey. Don’t forget to check out the GitHub repository and join us in further enhancing this powerful tool.