Re: [RESEND][RFC][PATCH 2/7] implementation of LSM hooks

Karl MacMillan
2006-04-18T17:29:03Z

On Tue, 2006-04-18 at 09:50 -0700, Gerrit Huizenga wrote:
> On Tue, 18 Apr 2006 12:58:19 BST, Christoph Hellwig wrote:
> > On Mon, Apr 17, 2006 at 06:44:51PM -0700, Gerrit Huizenga wrote:
> > >
> > > On Mon, 17 Apr 2006 23:55:25 BST, Christoph Hellwig wrote:
> > > > On Mon, Apr 17, 2006 at 03:15:29PM -0700, Gerrit Huizenga wrote:
> > > > > configure correctly that most of them disable it. In theory, LSM +
> > > > > something like AppArmour provides a much simpler security model for
> > > >
> > > > apparmor falls into the findamentally broken category above, so it's
> > > > totally uninteresting except as marketing candy for the big red company.
> > >
> > > Is there a pointer to why it is fundamentally broken? I haven't seen
> > > such comments before but it may be that I've been hanging out on the
> > > wrong lists or spending too much time inhaling air at 30,000 feet.
> >
> > It's doing access control on pathnames, which can't work in unix enviroments.
> > It's following the default permit behaviour which causes pain in anything
> > security-related (compare [1]).
> >
> >
> > [1] http://www.ranum.com/security/computer_security/editorials/dumb/
>
> Interesting but I'm not impressed by the article. I think Stephen's
> reference has a bit more meat to it. According to this article my
> laptop should set so I have a white list of apps (which would be
> really really long, ergo why make a list? I run much more than
> 5 apps on a day to day basis). Even on a general purpose machine
> that is shared by many users will have a large number of apps. When
> your white list is a large percentage of the apps that are on the
> machine, these two approaches start to converge.

Which is one reason why SELinux has types (equivalence classes) - it
makes it possible to group large numbers of applications or resources
into the same security category. The targeted policy that ships with
RHEL / Fedora shows how this works in practice.

Karl

--
Karl MacMillan
Tresys Technology
www.tresys.com

> In the end it always
> comes down to "how much security are you prepared to endure, given
> that security almost always limits user capability".
>
> Based on what this article says, it sounds like MACs and ACLs would be
> required because without them they permit you to share data with people
> that may not need that data, people should only have access to the
> limited set of applications and data that they need, and the machine
> should be tightened down to the point where the security approaches
> absolute security.
>
> While that might fit in with "perfect" security, most people aren't
> interested in that level of perfection. "Default permit" was so popular
> because it caught the obvious exploits without overly limiting people's
> ability to use a machine. It is still pretty commonly used today.
> Also, any security protection has a whole range of protections, from
> firewalls, limiting which packages are installed, accounts/passwords,
> validation of users, etc. Does everyone have to have "perfect" security
> or are there places where a "less than perfect, easy to use, good enough"
> security policy? I believe there is room for both based on the end
> users' needs and desires. But that is just my opinion.
>
> gerrit
> -
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