Re: dhclient: avoiding hostname disclosure via DHCP request

[Dan Williams <dcbw redhat com>]

On Sat, 2013-12-28 at 14:08 +0100, Geert Stappers wrote:
> Op 2013-12-23 om 20:33 schreef Robert Horovitz:
> > > Mark in /etc/dhcp/dhclient.conf 'send host-name' as comment.
> >
> > Since the resulting file is created by merging /etc/dhcp/dhclient.conf
> > into /var/lib/NetworkManager/dhclient-em1.conf that does not do the trick.
> >
> > The final file looks like:
> >
> > -----
> > # Created by NetworkManager
> > # Merged from /etc/dhcp/dhclient.conf
> >
> > # send host-name "foobar";
> > [...]
> > send host-name "foobar"; # added by NetworkManager
> > [...]
> > -----
>
> That does surprise me. But, hey, I'm also new to the inner working of NM.
>
>
> The (graphical) user interface of Network Manager
> has an option named 'DHCP client ID'
>
> Providing there a string like 'anon' should hide "foobar".
> That is the place where I would expect the program code that does add
> 'send host-name "foobar"; # added by NetworkManager' to /var/lib/NetworkManager/dhclient-em1.conf
>
> When that place in the source code is found,
> it is easy to remove it.  ( easier as adding code to the right place )

If you're using 'keyfile' configuration files, you can add the line
"dhcp-send-hostname=false" to the [ipv4] block to prevent sending the
hostname to the DHCP server.  I don't believe it's exposed anywhere in
the nm-connection-editor UI at least.  Note that setting that option
does not prevent a custom dhclient.conf with "send host-name" from
working, so make sure it's not their either.

Dan