MIT Kerberos Master principal deletion

[Nico Williams]

On Thu, Jun 11, 2020 at 03:32:35AM +0100, Harshawardhan Kulkarni wrote:
> I basically need an advice on an ongoing issue I am currently stuck on.
> 
> We have a Kerberised Hadoop Cloudera Custer. KDC Admin server is on one of
> the nodes. We don't have a failover node for KDC server yet. On the KDC
> admin server while doing a clean up activity for unwanted kdc principals, I
> deleted the master key principal (K/M at REALM.COM) We never took a kdc dump
> of the master key. So we don't have a backup to restore from.
> 
> Is there any way I can restore the master key principal?

If you have a running KDC you could use a debugger to recover that key.
It won't be easy.  It's not something anyone does on a regular basis, so
I don't have instructions to give you.

> I have tried creating with kdb5_util add_mkey but the error says that KDC
> DB is not able to find a master key credential. I assume this would only
> work when you want to create another master key without deleting the
> primary key.

Adding a new key won't help you: the existing records are encrypted in
the old key.

> Another option for me would be to de-kerberise the cluster and create the
> same REALM and kerberise the cluster again. But there could be serious
> issues if this doesn't fix as this is a live cluster where people are using
> this on a daily basis.

You could rebuild your realm, yes.  That's a flag day.  Users in that
realm will need to be re-enrolled, keytabs will need to be re-created
and distributed...

Nico
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