I don't really see the point in using ips and/or passwords for authentication, when all you really need is a SteamID. If it's available in the forum/CMS database of course, which shouldn't be a problem. Just let users enter theirs in their profiles.
Here's what I'm currently using (with vBulletin 3.7.4):
Code:
select %d,description from vb_usergroup left join vb_user using(usergroupid) left join vb_userfield using(userid) where field5 like '%s'
In my case field5 holds the user's SteamID. This could be changed with a cvar. The query basically reads out the description field for the usergroup that the player/user is a primary member of. This particular field can be editted by any vBulletin admin (not by moderators or so called super moderators) and holds the AMXX userflags that the usergroup is entitled to.
To incorporate statistics that are generated by playing on our servers I installed PsychoStats and whipped up some queries and added that as a vBulletin plugin within the user profiles. This makes additional AMXX plugin code and extra traffic between the gameservers and database unnecessary.
For further inspiration:
Forum mod by Johnny got his gun.
Something else that a lot of people might be looking for is full (user-) integration between their CMS/forum and AXMBans/SourceBans.
I can setup a vBulletin demo combined with phpMyAdmin access in case you need it.
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