Re: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)

From: James Morris
Date: Sun Jan 10 2010 - 18:00:47 EST

On Sun, 10 Jan 2010, Michael Stone wrote:

> Pavel's position is that disablenetwork is likely to permit some attacker
> somewhere to deny network access to some setuid app some day in a way that
> violates some security policy.
> He has mentioned specific concern over scenarios like:
> Alice configures PAM auth to 'fail open' by checking login credentials
> against a restrictive LDAP server and, if the server is unavailable, against
> a very permissive files database.
> Alice updates her kernel to a version with disablenetwork.
> Mallory calls disablenetwork, calls su -, and vanquishes all.
> My position is that better isolation facilities like disablenetwork will
> prevent far more grievous security faults than they (theoretically) cause.
> What is your perspective on the matter?

Unexpected failure modes for privileged apps using security interfaces has
already proven to be a problem (e.g. the sendmail capabilities bug), so it
seems prudent to try and mitigate that as well. I don't think we need to
look at this as an either-or situation -- it seems we can do both, and get
something useful in its own right from the mitigation.

James Morris
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