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Date: Thu, 9 Oct 2014 01:05:23 +0200
From: Jann Horn <>
Subject: Re: openssh on linux rce in sftp-only mode

On Wed, Oct 08, 2014 at 06:44:32PM -0400, Josh Bressers wrote:
> > > 
> > > I think one has to assume if a user has unrestricted sftp access, they can
> > > figure out how to do most anything. Even with the upstream hardening patch,
> > > it really only protects the sftpd process. Any other processes the user may
> > > own could be modified.
> > 
> > Not that easily - /proc/$pid/mem requires you to either be the same process
> > or be attached to it via ptrace, I think.
> > 
> I can't speak for other systems (I don't understand the details), but I can
> read arbitrary process memory for processes I own in Fedora 20.

Hmm, just tried it on Debian Testing, I can reproduce that.

> Does someone know what the typical default is?

I looked through the git history of fs/proc/base.c now, looks like commit
e268337dfe26dfc7efd422a804dbb27977a3cccc ("proc: clean up and fix
/proc/<pid>/mem handling") changed the behavior to be more permissive. That commit
is between kernel 3.2 and 3.3. Meh. :(

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