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Date: Fri, 24 Jun 2011 16:34:06 +0400
From: Vasiliy Kulikov <>
Subject: CVE request: kernel: taskstats/procfs io infoleak (was: taskstats
 authorized_keys presence infoleak PoC)


On Tue, Jun 21, 2011 at 15:24 -0400, Josh Bressers wrote:
> > /*
> > * This program tries to learn whether ~user/.ssh/authorized_keys exists
> > * and is nonempty for any user on local machine. It uses world-readable
> > * taskstats' nature to get somewhat private io statistics information.  If
> > * implant taskstats or /proc//io polling into ssh client, it would be
> > * possible to learn precise authorized_keys' size (and estimate private
> > * key's(s') size).
> Are you considering this a flaw, or just an interesting security exercise?
> Nothing currently comes to mind, but it's possible there could be other
> data where knowing it exists and the size would be useful.

It can be used to learn ssh and ftp password length.  If privsep is
enabled in openssh and vsftpd, the unprivileged process' activity very
precisely shows password information.

For vsftpd read characters count is strlen("USER username\r\n") +
strlen("PASSWD pass\r\n") + 1, where 1 is one byte read from a pipe
related to a privileged parent.  If measure statistics between user and
passwords commands, actual password length and username length can be

For ssh, vice versa, networking activity is constant in packets length,
but interprocess communications, specifically passwords, depend on
user input.

For ssh pass_len = wchars - CONST, for vsftpd pass_len = rchars - CONST.

Another daemons with more or less constant io activity might be
vulnerable too.  PAM greatly complicates precise measurements.

I think it needs 2 CVE, one for /proc/PID/io and another for taskstats.


Vasiliy Kulikov - bringing security into open computing environments

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