Awesome

SAN Scanner is a Burp Suite extension for enumerating associated domains & services via the Subject Alt Names section of SSL certificates.

What is a SAN cert

Some webmasters use a single SSL certificate to secure multiple domain names. This is accomplished via the Subject Alternative Name field. For example, the cert for StackOverflow.com contains dozens of other domain names covered by the same cert:

SAN certs convenience admins because they only have to worry about updating a single certificate for the various domains under their stewardship.

Use for security professionals

Examining Subject Alt Names is a routine part of enumeration and OSINT. Given a domain, SANs help you find associated domains and services, often hosted in the same network or server. Recreationally, SAN enumeration is often useful for CTF security games (the Mango machine on HackTheBox famously hid a needed domain name in an otherwise inocuous SSL cert).

Aside from the offensive component, SANs often point to out-of-date or no longer extant domains that can be or have been picked up by others. This extension is useful for reminding webmasters to update such certs.

Building the extension

You can build the directory using the following commands (on Linux):

git clone git@github.com:seisvelas/SAN-Scanner.git
cd SAN-Scanner/
gradle build

That's it! The .jar will be created in build/libs/SAN\ Scanner.jar, which you can load into Burp Extender.