TIBCO API Exchange (APIX) authenticates users based on the resource/properties file configured.

Check this document for the details on the properties file used to configure LDAP Authentication for ConfigUI:
https://docs.tibco.com/pub/api-exchange-gateway/2.3.3/doc/html/GUID-29C988E8-950D-4EF0-ADBE-2F77D61506B1.html?scroll=GUID-29C988E8-950D-4EF0-ADBE-2F77D61506B1

Check this document for the details on the properties file used for LDAP Authentication Security Policy:
https://docs.tibco.com/pub/api-exchange-gateway/2.3.3/doc/html/GUID-47708465-316D-46FC-B464-4B52B28EB964.html
 

All Supported Platforms

To limit the number of authenticated users that can access ConfigUI, you can use these suggestions.

1) Enhance the UserSearchExpression to include certain attributes as well
for e.g.:
userSearchExpression=(&(sAMAccountName={0})(ismemberof=<role/group>))

2) Have all allowed users under the same directory and restrict using userSearchBaseDN
for e.g.:
userSearchBaseDN=DC=ConfigUIUsers,DC=MyCompany,DC=COM

These should be tuned based on the LDAP server in use and tested thoroughly.
Please work with your LDAP Administrator / team to restrict users that are authenticated.

This article provides inputs on limiting the number of authenticated users when using an LDAP server in TIBCO API Exchange (APIX)