linux-kernel - Re: [PATCH v2] sanitize task->comm to avoid leaking escape codes

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Date:	Wed, 30 Jun 2010 09:16:08 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Steve Grubb <sgrubb@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Stefani Seibold <stefani@...bold.net>,
	Kees Cook <kees.cook@...onical.com>,
	linux-kernel@...r.kernel.org,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>,
	Veaceslav Falico <vfalico@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Roland McGrath <roland@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Eric Paris <eparis@...hat.com>,
	James Morris <jmorris@...ei.org>,
	"Andrew G. Morgan" <morgan@...nel.org>,
	Dhaval Giani <dhaval.giani@...il.com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Christoph Hellwig <hch@....de>, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] sanitize task->comm to avoid leaking escape codes

> On Monday, June 28, 2010 11:05:56 pm KOSAKI Motohiro wrote:
> > > Am Freitag, den 25.06.2010, 08:56 +0900 schrieb KOSAKI Motohiro:
> > > > > Through get_task_comm() and many direct uses of task->comm in the
> > > > > kernel, it is possible for escape codes and other non-printables to
> > > > > leak into dmesg, syslog, etc.  In the worst case, these strings
> > > > > could be used to attack administrators using vulnerable terminal
> > > > > emulators, and at least cause confusion through the injection of \r
> > > > > characters.
> > > > > 
> > > > > This patch sanitizes task->comm to only contain printable characters
> > > > > when it is set.  Additionally, it redefines get_task_comm so that it
> > > > > is more obvious when misused by callers (presently nothing was
> > > > > incorrectly calling get_task_comm's unsafe use of strncpy).
> 
> For the audit system, we want the real, unsanitized task->comm. We record it 
> in a special format to the audit logs such that unprintable characters are 
> included. We want it exactly this way for certification purposes as well as 
> forensic evidence if someone was playing games. If you do sanitize it for 
> other areas of the kernel, please give us a way to get the unsanitized text.

Probably this mail is offtopic. I think audit is unrelated with this discusstion. because when 
forensic, admins shouldn't believe task->comm at all. because 1) no path information, 
perhaps "ls" might mean "/home/attackers-dir/evil-script/ls" 2) easily obscured by 
prctl(PR_SET_NAME).

That said, audit have to logged following two point if task name is necessary.
1) exec
2) prctl(PRT_SET_NAME)

Thought ?



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