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For apache2, you need the authnz_ldap module installed, and the config looks something like this:
<directory /data/web/some/secret/place> AuthType Basic AuthBasicProvider ldap AuthName "Secret Place for Opers Only" AuthLDAPGroupAttribute memberUid AuthLDAPGroupAttributeIsDN off AuthLDAPURL ldaps://your.ldapserver.com/ou=Users,dc=afternet,dc=org?uid?sub?(objectclass=*) require ldap-group cn=Opers,ou=Groups,dc=afternet,dc=org </directory>