Issues getting Kerberos to work with realmd and Active Directory

[William MacAllister]

On Thu, Jul 30, 2020 at 10:07 AM Wesley Taylor <wesley.taylor at numerica.us>
wrote:

> Hi All,
>
> I am trying to get HTCondor with Kerberos authentication (
> https://htcondor.readthedocs.io/en/stable/admin-manual/security.html?highlight=Kerberos#kerberos-authentication)
> to work on some linux machines I have which I joined to Windows Active
> Directory with realmd.


Working with AD as a KDC can be challenging. Problems that I frequently
have to deal are caused by the fact that AD does not use the principal name
to identify the LDAP entries that define the principal.  We use Russ
Allbery's wallet to create keytabs which uses msktutil and LDAP to interact
with AD.  Wallet creates a unique 20 character string that is used as the
CN for the distinguished name for the entry holding the principal name
entry.  The actual principal name is stored in the LDAP
attributes userPrincipalName and servicePrincipalName.  When I encounter
problems with the CN-to-principal name mapping I examine the KDC entry
using ldapsearch.  For example:

$ ldapsearch -Q -LLL -h ad-server -b ou=keytabs,dc=domain,dc=com
cn="*keddie*" userPrincipalName servicePrincipalName dNSHostName
dn: CN=keddie.domain.co000,OU=keytabs,OU=DROPBOX,DC=dropbox,DC=internal
dNSHostName: keddie.domain.com
userPrincipalName: host/keddie.domain.com at DROPBOX.INTERNAL
servicePrincipalName: host/keddie.domain.com

If you can access AD with ldapsearch you should be able to determine the
correct principal name to use.

A very common command phrasing we use in bash scripts on linux systems is:

    k5start -f /etc/krb5.keytab host/`hostname -f` -- <some command>

A specific example is:

    k5start -f /etc/krb5.keytab host/`hostname -f` -- ldapwhoami -h
openldap-server

Bill

-- 
Bill MacAllister
Corp SRE, Dropbox