linux-kernel - Re: [GIT PULL] kdbus for 4.1-rc1

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Date:	Tue, 21 Apr 2015 15:55:17 -0400
From:	Austin S Hemmelgarn <ahferroin7@...il.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Tom Gundersen <teg@...m.no>, Jiri Kosina <jkosina@...e.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Daniel Mack <daniel@...que.org>,
	David Herrmann <dh.herrmann@...il.com>,
	Djalal Harouni <tixxdz@...ndz.org>
Subject: Re: [GIT PULL] kdbus for 4.1-rc1

On 2015-04-21 15:38, Matthew Garrett wrote:
> On Tue, Apr 21, 2015 at 11:36:54AM -0500, Eric W. Biederman wrote:
>>
>> HeHeHe.  You mean all I need to do to get around all of the logging servers is
>> capture CAP_SYS_BOOT?  Say like just capture this crazy watchdog program
>> that doesn't run as root so that it can only reboot the system? HeHeHe
>> So I can just trigger a clean reboot wait for journald, auditd, and
>> syslog all to shut down and then do evil things to the machine without
>> having to worry about erasing forensic evidence?
>
> CAP_SYS_BOOT gives you kexec, and kexec with init=/bin/sh lets you do
> anything. You added that in dc009d92435f99498cbc579ce76bf28e837e2c14 and
> now the horse is long gone. Don't give CAP_SYS_BOOT to anything you
> don't trust with full privileges.
>
The point is that Eric's suggestion works even on kernels without 
kexec(), which is significant because a significant number of security 
minded people (myself included) explicitly disable kexec in their kernel 
configuration.


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