Kerberos Authentication and LDAP Authorization In Apache

I’ve been authentcating users of Apache web sites against Active Directory using Kerberos for some time now. Installed krb5-workstation and mod_auth_kerb, configured /etc/krb5.conf for my specific domain, and added some config to the Directory section of the Apache config. Great if you just require valid-user (or require valid-user and then turn around and do some authorization within your web code using something like php_auth_user). Not so great, though, for restricting access to the site outside of web code. And I really didn’t want to code in an authorization function when my web server should be able to do that for me.

I FINALLY got kerberos authentication working in Apache with an LDAP authorization component. Turns out the  mod_auth_kerb version 5.1 that was available from the Yum repository is terribly buggy  – like not usable in this instance buggy. KrbLocalUserMapping did not consistently remove the realm component. I’d hit a site and it would know who I am, click a link and come across as me@REALM.TLD and get access denied errors, click refresh and get in because it knew I was me again. Or not. More than 50% failure rate.I built the 5.4 version from and haven’t had a problem since.

I’m authenticating to Active Directory using the Kerberos module then authorizing against a group housed in an external LDAP directory. You can totally point your LDAP config toward Active Directory & use AD groups instead:

AuthType Kerberos
AuthName “Kerberos AD Test”
KrbAuthoritative off
KrbMethodNegotiate on
KrbMethodK5Passwd on
KrbServiceName HTTP/this.isyour.url.tld@REALM.TLD
KrbAuthRealms REALM.TLD
KrbLocalUserMapping On
Krb5Keytab /path/to/keytabs/keytab.file

AuthBasicAuthoritative On
AuthBasicProvider ldap
AuthLDAPURL “ldaps://*))”

AuthLDAPGroupAttribute uniqueMember
AuthLDAPGroupAttributeIsDN on
require ldap-group cn=Website Test,ou=groups,o=BaseDN


WooHoo! I hit the site from my domain-member computer, it knows I am LisaR. It then turns around and finds an LDAP user matching uid=LisaR and grabs the user’s fully qualified DN (because AuthLDAPGroupAttributesIsDN is ‘on’ here … if you are using just uids in your member list, that would be off). It then verifies that the fully qualified DN is a member of the Website Test group.

Now I’m trying to figure out how to let the user log in without supplying a realm (not everyone’s in the domain … and they need to be able to log in too. Works fine right now, provided they input their username as uid@REALM.TLD).

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