Description Arvid Requate 2019-10-17 17:15:43 CEST

Created attachment 10210 [details]
Screenshot

I saw two cases, one in-house and one customer where an Administrator created a host record named @ in some forward_zone, triggering a chain of actions that finally led to a full DNS blackout for that forward_zone. Here is how:

The Admin opens the DNS module in UMC, clicks on the zone and add a host record with name @. The attached screenshot shows the result in the UMC DNS treeview: It lokks as if the zone has been duplicated as a child of itself.

In named/bind9 terms, the Admin has just written a second resource record named @ into his zone file. The UMC should not allow this.

Since UMC/UDM currenlty allow this, the Admin is now in a very dangerous situation:

With a high probability, the Admin right-clicks the unwanted object and deletes it. If Samba/AD is installed in the domain, then the S4-Connector interprets this as the removal of an SOA record and removes the SOA record of that zone in Samba/AD. That's silent and nobody notices until the nameserver services (bind9) gets restarted at some point in the future and the nameserver doesn't recognize the zone as valid any longer and the customer experiences severe DNS issues for the entire domain.