Admin panel single sign on

[Agentpoint]

Our company is rolling out a internal single sign on system as we use quite a few different systems and most of them support SSO via SAML although the specific technology doesn't matter in this instance.

I've been trying to implement this in WHMCS but I can't figure out the hashes to make this work.

I see two ways of accomplishing this.

1. Injecting $_SESSION. This involves three variables:
tkval - Random token, I believe it's purely random alpha numeric but could be wrong.
adminid - Easy enough, the ID of the user in tbladmins.
adminpw - A SHA1 hash which clearly depends on the password, but it also includes something else I can't figure out. I've tried many permuations.

2. Calculating the Remember Me cookie. Slightly less ideal but would still achieve the desired result.
This is simply "<adminid>:<hash>" but same problem again, what the hash is actually of is unknown and I can't figure it out.

I actually wrote a script to try various permutations of variables and separators and got zero results.

Does anyone else have any insight? I can't figure out why this would be so opaque as having the exact formula of those hashes public doesn't decrease security at all.