ntpd v4.2 problem

[Harlan Stenn]

> The problem in the manual is different. You do not have any access 
> control in your server, your server is worldwide open to other people 
> changing your runtime configuration etc. (as it seems from your conf file)

Wrong - ntpd will never allow changes to itself without explicitly allowing
it (via a private key file, and mutually-agreed key numbersi and passwords).

>  From ntp handbook page!
> ----
> If you only want to allow machines within your own network to 
> synchronize their clocks with your server, but ensure they are not 
> allowed to configure the server or used as peers to synchronize against, add

That line may be technically true, but it is alarmist and wrong.

> restrict 192.168.1.0 mask 255.255.255.0 notrust nomodify notrap

See http://ntp.isc.org/Support/ConfRestrict for info about notrust.
Dave Mimlls changed the behavior of notrust between the 4.1 and 4.2
releases of ntp.

In 4.1, notrust means "do not trust this host/subnet for time".

In 4.2, notrust means "require crypto auth before believing this
host/subnet for time".

nomodify will block changes even with the correct key/password.  But you
have to have the correct key and password first.

> But if you use notrust in this line no clients are able to connect. I am 
> not sure why. That is why I asked about an ntpd pro having a look.

We'd appreciate more folks adding more info to ntp.isc.org.

H