Script for generating STIR/SHAKEN certificates (including self-signed)

While working on my company’s implemenation of STIR/SHAKEN, I ran into a very basic issue – how do I easily create test self-signed SHAKEN certificates?

While I did find a couple of posts on how to do this, I wanted a nice script that would accomplish the following:

1. Generate either a self-signed certificate or a key/CSR pair for use with an official certificate authority
2. Allow easy passing of the certificate subject information (Country, State, Locality, etc.)
3. Create certificate filenames with a unique identifier, to prevent name collisions (by default, the identifier is a UNIX timestamp)

Below is the script I came up with:

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Credit to the original source posts, here and here.