Censys Subdomain Finder – Perform Subdomain Enumeration Using The Certificate Transparency Logs From Censys

This is a tool to enumerate subdomains using the Certificate Transparency logs stored by Censys. It should return any subdomain who has ever been issued a SSL certificate by a public CA.

$ python censys_subdomain_finder.py github.com

[*] Searching Censys for subdomains of github.com
[*] Found 42 unique subdomains of github.com in ~1.7 seconds

- hq.github.com
- talks.github.com
- cla.github.com
- github.com
- cloud.github.com
- enterprise.github.com
- help.github.com
- collector-cdn.github.com
- central.github.com
- smtp.github.com
- cas.octodemo.github.com
- schrauger.github.com
- jobs.github.com
- classroom.github.com
- dodgeball.github.com
- visualstudio.github.com
- branch.github.com
- www.github.com
- edu.github.com
- education.github.com
- import.github.com
- styleguide.github.com
- community.github.com
- server.github.com
- mac-installer.github.com
- registry.github.com
- f.cloud.github.com
- offer.github.com
- helpnext.github.com
- foo.github.com
- porter.github.com
- id.github.com
- atom-installer.github.com
- review-lab.github.com
- vpn-ca.iad.github.com
- maintainers.github.com
- raw.github.com
- status.github.com
- camo.github.com
- support.enterprise.github.com
- stg.github.com
- rs.github.com

Setup

1. Register an account (free) on https://censys.io/register
2. Browse to https://censys.io/account, and set two environment variables with your API ID and API secret

$ export CENSYS_API_ID=...
$ export CENSYS_API_SECRET=...

3. Clone the repository

$ git clone https://github.com/christophetd/censys-subdomain-finder.git

4. Install the dependencies

$ cd censys-subdomain-finder
$ pip install -r requirements.txt

5. Run the script on example.com to make sure everything works as expected.

$ python censys_subdomain_finder.py example.com
[*] Searching Censys for subdomains of example.com
[*] Found 5 unique subdomains of example.com

- products.example.com
- www.example.com
- dev.example.com
- example.com
- support.example.com

Usage

usage: censys_subdomain_finder.py [-h] [-o OUTPUT_FILE]
                                  [--censys-api-id CENSYS_API_ID]
                                  [--censys-api-secret CENSYS_API_SECRET]
                                  domain

positional arguments:
domain The domain to scan

optional arguments:
-h, --help show this help message and exit
-o OUTPUT_FILE, --output OUTPUT_FILE
A file to output the list of subdomains to (default:
None)
--censys-api-id CENSYS_API_ID
Censys API ID. Can also be defined using the
CENSYS_API_ID environment variable (default: None)
--censys-api-secret CENSYS_API_SECRET
Censys API secret. Can also be defined using the
CENSYS_API_SECRET environment variable (default: None)

Compatibility
Should run on Python 2.7 and 3.5.

Notes
The Censys API has a limit rate of 120 queries per 5 minutes window. Each invocation of this tool makes exactly one API call to Censys.
Feel free to open an issue or to tweet @christophetd for suggestions or remarks.