In a Microsoft Active Directory (AD) environment user IDs are case-sensitive.

For example, we have a user that resolves as 'JohnD' and other DBs and the Linux OS recognize it as such. However, when that user attempts to authenticate to MariaDB as 'JohnD' via PAM, the authentication fails, even though I've created the user as 'JohnD' IDENTIFIED VIA pam.

If I create the user in MariaDB as 'johnd' (all lower case) and have the user specify it that way, it does properly authenticate via PAM, so MariaDB is casting the PAM account to lowercase and failing to recognize the username with correct capitalization.