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Re: Sounds of silence--I want volume!

On Mon, 2002-12-09 at 16:51, Pigeon wrote:
> On Mon, Dec 09, 2002 at 04:13:50AM +0100, Carel Fellinger wrote:
> > On Mon, Dec 09, 2002 at 12:20:38AM +0000, Chris Owen wrote:
> > > Haralambos Geortgilakis wrote:
> > ...
> > > Try running (as root)
> > > chmod ugo+rwx /dev/cdrom
> > 
> > I think it's ill advice, not worthy of this list --sory for the rant,
> > it's not personally, it's just that you're not the first to give such
> > nonsensical advice, it seems that it's even a favourite one lately:(--
> > , to advice people to mess with those flags where the proper way is to
> > add users to specific groups.  In this case the cdrom group.  And
> > whilst the OP is add it, he might as well check he's in the audio group
> > too.
> Re groups: he did...
> Why is this advice nonsensical, though? As you say, several people
> have given it recently. Rather fewer people have responded, as you did,
> saying it's a bad idea. Nobody has explained WHY it's a bad idea. What
> harm does it do if the world and his dog can read my CD-ROM?
> Pigeon

I remember a couple decades ago how there were more than a few
*backdoors* in the Unix code to allow system configuration and access
for programmers/administrators that knew about them and needed to make
special tweaks. They were holes that were acknowledge early on as the
first target if Unix were to be firmed up to be commercially viable,
particularly for business and government environments. Part of that
firming was putting everything under group and user security, and only
advancing security access when absolutely necessary.

This is the theory involving switching ownership/access to devices. If
you need access to something for justifiable reasons, you get added to
the group that uses it. If not, you aren't in that group. I allow
outside access to a few people for my system - a couple use it for
email, and one for a personal website for her relatives a third of the
way around the world to see pictures of her kids and for those relatives
to log in and leave messages for the kids. None of these users have a
need to muddle around on my cdrom or cd-burner, or send audio to my
sound card. Moreover, they don't need to access my spare hard drive that
I'm currently using to reduce space pressure while organising what I can
move offline of some reports. Moreover, if someone does hack my system
as an account other than root, I can have substantive areas inaccessible
through hardened permissions.

Mind you, I would love to have ACLs with an eye on tools and
configurations such as disallowing access to /sbin and /usr/sbin from
locations outside my server site, and not permit any other than selected
users (eg. myself) to see what is under /dev, given I use devfs, which
indicates *just what* is installed. Those with permissions to use this
or that device could still do that, but the risk of them getting through
to say, overwrite a floppy that might be sitting in a drive (shouldn't
happen, unless the permissions for the device got buggered about) would
be substantively reduced.

Permissions are there for a reason, and weakening something so that you
can get around a protection in the security system to use something
because you don't know the way to reasonably access that item securely
opens you up to the sort of damage that Windows users come to expect
when they are infected with a virus.
ML Kahnt New Markets Consulting
Tel: (613) 531-8684 / (613) 539-0935
Email: kahnt@hosehead.dyndns.org

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