Re: Re: [Security] /proc infoleaks

[Jon Oberheide <jon () oberheide org>]

On Tue, 2010-09-07 at 03:51 -0700, Andrew Morton wrote:
> On Tue, 7 Sep 2010 10:35:46 +0200 Sebastian Krahmer <krahmer () suse de> wrote:
>
> > I have been elected to receive the bashing from all sides,
> > so here we go.
> > It is not about a new vulnerability or even a new discussion
> > but needs to be discussed, at least that we have a clear
> > statement about the status quo.
> >
> > Recent i-CAN-haz-MODHARDEN.c has shown once *again* that
> > certain file permissions make no sense except to exploitation
> > development. There is no reason to have files like
> >
> > /proc/kallsyms
> > /proc/slabinfo
> > /proc/zoneinfo
> >
> > and probably a lot of others world readable. The symbol
> > addresses might be hard-coded for a certain targetlist
> > inside the exploit so you can argue that there
> > wont be any protection benefit from making it unreadable.
> > However this argument aint a reason to also leak it for self-compiled
> > kernels and doesnt even hold for dynamic/runtime content
> > like slabinfos etc.
> > It would be nice to have something like
> >
> > echo 1 > /proc/quiet
> >
> > or something like a umask for kernel-owned proc
> > entries so that you have a polite default and are
> > still able to enable it for certain profiling tools
> > or whereever you need it.
>
> chmod 0440 /proc/slabinfo
>
> What am I missing here?

You're missing the "secure by default" part.

(Obviously hiding slabinfo doesn't prevent exploitation of the vuln, but
not exposing it by default is a positive step.)

Regards,
Jon Oberheide

-- 
Jon Oberheide <jon () oberheide org>
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