From: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
Russell King - ARM Linux <linux@armlinux.org.uk>,
Balbir Singh <bsingharora@gmail.com>,
Stewart Smith <stewart@linux.vnet.ibm.com>,
bhe@redhat.com, kexec@lists.infradead.org, dyoung@redhat.com,
Petr Tesarik <ptesarik@suse.cz>,
linux-kernel@vger.kernel.org,
AKASHI Takahiro <takahiro.akashi@linaro.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
linuxppc-dev@lists.ozlabs.org, Vivek Goyal <vgoyal@redhat.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC 0/3] extend kexec_file_load system call
Date: Wed, 20 Jul 2016 12:50:11 -0300 [thread overview]
Message-ID: <2545578.SWp0m9VQX8@hactar> (raw)
In-Reply-To: <34243612.Gid3QHG1hd@wuerfel>
Am Mittwoch, 20 Juli 2016, 13:12:20 schrieb Arnd Bergmann:
> On Wednesday, July 20, 2016 8:47:45 PM CEST Michael Ellerman wrote:
> > At least for stdout-path, I can't really see how that would
> > significantly help an attacker, but I'm all ears if anyone has ideas.
>
> That's actually an easy one that came up before: If an attacker controls
> a tty device (e.g. network console) that can be used to enter a debugger
> (kdb, kgdb, xmon, ...), enabling that to be the console device
> gives you a direct attack vector. The same thing will happen if you
> have a piece of software that intentially gives extra rights to the
> owner of the console device by treating it as "physical presence".
I think people are talking past each other a bit in these arguments about
what is relevant to security or not.
For the kexec maintainers, kexec_file_load has one very specific and narrow
purpose: enable Secure Boot as defined by UEFI.
And from what I understand of their arguments so far, there is one and only
one security concern: when in Secure Boot mode, a system must not allow
execution of unsigned code with kernel privileges. So even if one can
specify a different root filesystem and do a lot of nasty things to the
system with a rogue userspace in that root filesystem, as long as the kernel
won't load unsigned modules that's not a problem as far as they're
concerned.
Also, AFAIK attacks requiring "physical presence" are out of scope for the
UEFI Secure Boot security model. Thus an attack that involves control of a
console of plugging an USB device is also not a concern.
One thing I don't know is whether an attack involving a networked IPMI
console or a USB device that can be "plugged" virtually by a managing system
(BMC) is considered a physical attack or a remote attack in the context of
UEFI Secure Boot.
--
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center
next prev parent reply other threads:[~2016-07-20 15:50 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-12 1:41 [RFC 0/3] extend kexec_file_load system call AKASHI Takahiro
2016-07-12 1:41 ` [RFC 1/3] syscall: add kexec_file_load to generic unistd.h AKASHI Takahiro
2016-07-12 1:42 ` [RFC 2/3] kexec: add dtb info to struct kimage AKASHI Takahiro
2016-07-12 1:42 ` [RFC 3/3] kexec: extend kexec_file_load system call AKASHI Takahiro
2016-07-15 13:09 ` Vivek Goyal
2016-07-15 13:19 ` Mark Rutland
2016-07-18 2:30 ` Dave Young
2016-07-18 10:07 ` Mark Rutland
2016-07-19 0:55 ` Dave Young
2016-07-19 10:52 ` Mark Rutland
2016-07-19 12:24 ` Vivek Goyal
2016-07-19 12:47 ` Mark Rutland
2016-07-19 13:26 ` Vivek Goyal
2016-07-20 11:41 ` David Laight
2016-07-21 9:21 ` Russell King - ARM Linux
2016-07-18 2:33 ` Dave Young
2016-07-27 0:24 ` [PATCH v2 " Thiago Jung Bauermann
2016-08-05 20:46 ` Thiago Jung Bauermann
2016-07-12 13:25 ` [RFC 0/3] " Eric W. Biederman
2016-07-12 13:58 ` Thiago Jung Bauermann
2016-07-12 14:02 ` Vivek Goyal
2016-07-12 23:45 ` Stewart Smith
2016-07-13 13:27 ` Vivek Goyal
2016-07-12 14:02 ` Arnd Bergmann
2016-07-12 14:18 ` Vivek Goyal
2016-07-12 14:24 ` Arnd Bergmann
2016-07-12 14:50 ` Mark Rutland
2016-07-13 2:36 ` Dave Young
2016-07-13 8:01 ` Arnd Bergmann
2016-07-13 8:23 ` Stewart Smith
2016-07-13 9:41 ` Mark Rutland
2016-07-13 13:13 ` Arnd Bergmann
2016-07-13 18:45 ` Thiago Jung Bauermann
2016-07-13 19:59 ` Arnd Bergmann
2016-07-14 2:18 ` Thiago Jung Bauermann
2016-07-14 8:29 ` Arnd Bergmann
2016-07-15 1:44 ` Thiago Jung Bauermann
2016-07-15 7:31 ` Arnd Bergmann
2016-07-15 13:26 ` Vivek Goyal
2016-07-15 13:33 ` Mark Rutland
2016-07-15 15:29 ` Thiago Jung Bauermann
2016-07-15 15:47 ` Mark Rutland
2016-07-15 13:42 ` Russell King - ARM Linux
2016-07-15 20:26 ` Arnd Bergmann
2016-07-15 21:03 ` Thiago Jung Bauermann
2016-07-22 0:09 ` Thiago Jung Bauermann
2016-07-22 0:53 ` Jeremy Kerr
2016-07-22 2:54 ` Michael Ellerman
2016-07-22 20:41 ` Thiago Jung Bauermann
2016-07-15 8:49 ` Russell King - ARM Linux
2016-07-15 13:03 ` Vivek Goyal
2016-07-13 9:34 ` Mark Rutland
2016-07-13 17:38 ` AKASHI Takahiro
2016-07-13 17:58 ` Mark Rutland
2016-07-13 19:57 ` Arnd Bergmann
2016-07-14 12:42 ` Mark Rutland
2016-07-14 1:54 ` Dave Young
2016-07-14 1:50 ` Dave Young
2016-07-12 16:25 ` Thiago Jung Bauermann
2016-07-12 20:58 ` Petr Tesarik
2016-07-12 21:22 ` Eric W. Biederman
2016-07-12 21:36 ` Eric W. Biederman
2016-07-12 21:53 ` Petr Tesarik
2016-07-12 22:18 ` Russell King - ARM Linux
2016-07-13 4:59 ` Stewart Smith
2016-07-13 7:36 ` Russell King - ARM Linux
2016-07-13 7:47 ` Ard Biesheuvel
2016-07-13 8:09 ` Russell King - ARM Linux
2016-07-13 8:20 ` Stewart Smith
2016-07-13 7:55 ` Stewart Smith
2016-07-13 8:26 ` Russell King - ARM Linux
2016-07-13 8:36 ` Dave Young
2016-07-13 8:57 ` Petr Tesarik
2016-07-13 13:03 ` Vivek Goyal
2016-07-13 17:40 ` Russell King - ARM Linux
2016-07-13 18:22 ` Vivek Goyal
2016-07-18 12:46 ` Balbir Singh
2016-07-18 13:26 ` Vivek Goyal
2016-07-18 13:38 ` Vivek Goyal
2016-07-20 3:45 ` Balbir Singh
2016-07-20 8:35 ` Russell King - ARM Linux
2016-07-20 11:12 ` Arnd Bergmann
2016-07-20 15:50 ` Thiago Jung Bauermann [this message]
2016-07-20 12:46 ` Vivek Goyal
2016-07-20 12:27 ` Vivek Goyal
2016-07-12 23:41 ` Stewart Smith
2016-07-13 13:25 ` Vivek Goyal
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