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Date: Tue, 21 Jun 2011 22:28:27 +0400
From: Vasiliy Kulikov <>
To: James Morris <>
Subject: Re: [RFC 2/5 v4] procfs: add hidepid= and gid= mount options

On Mon, Jun 20, 2011 at 20:43 +1000, James Morris wrote:
> On Mon, 20 Jun 2011, Vasiliy Kulikov wrote:
> > > Can you provide evidence that this is a useful feature?  e.g. examples of 
> > > exploits / techniques which would be _usefully_ hampered or blocked.
> > 
> > First, most of these files are usefull in sense of statistics gathering
> > and debugging.  There is no reason to provide this information to the
> > world.
> > 
> > Second, yes, it blocks one source of information used in timing attacks,
> > just use reading the counters as more or less precise time measurement
> > when actual timing measurements are not precise enough.
> Can you provide concrete examples?

This is a PoC of ~user/.ssh/authorized_keys presence infoleak (and
whether it is empty) using taskstats interface:

/proc/PID/io can be used too.

More close interaction with ssh client would gain authorized_keys' size or,
probably, what pam module denied the access.


Vasiliy Kulikov - bringing security into open computing environments

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