From: Matthew Garrett <mjg59@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
"Luis R. Rodriguez" <mcgrof@kernel.org>,
"AKASHI, Takahiro" <takahiro.akashi@linaro.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jan Blunck <jblunck@infradead.org>,
Julia Lawall <julia.lawall@lip6.fr>,
Marcus Meissner <meissner@suse.de>, Gary Lin <GLin@suse.com>,
LSM List <linux-security-module@vger.kernel.org>,
linux-efi <linux-efi@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Firmware signing -- Re: [PATCH 00/27] security, efi: Add kernel lockdown
Date: Tue, 14 Nov 2017 11:58:20 -0800 [thread overview]
Message-ID: <CACdnJuvP=0AHGtfGJ5+cT+kHRy3fU4BLjwkvzP0rLO6q5ejAQQ@mail.gmail.com> (raw)
In-Reply-To: <CA+55aFzvuvqOfsJ9arzcc1QbTGs+U-TsNmsyem9UAVVQC8YkZQ@mail.gmail.com>
On Tue, Nov 14, 2017 at 9:34 AM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> It's this insane "firmware is special" that I disagree with. It's not
> special at all.
Our ability to determine that userland hasn't been tampered with
depends on the kernel being trustworthy. If userland can upload
arbitrary firmware to DMA-capable devices then we can no longer trust
the kernel. So yes, firmware is special.
Here's an example: we have a signed initramfs that's loaded by a
signed bootloader. That initramfs sets up a trustworthy audit chain
and loads an LSM policy that prevents the rest of userland from
interfering with it. From that point on, we don't care about the rest
of userland being signed - we know it can't interfere with us, but we
can reliably inspect what it's doing. Even an offline attack can't do
any damage, since the audit code is still signed. However, the
LSM-imposed boundary depends on the kernel being trustworthy. If an
attacker can replace the firmware that's uploaded to a device that can
do arbitrary DMA then they can tamper with the supposedly trustworthy
audit code and provide false information. Being able to tamper with
the contents of /usr/bin/* doesn't give them that.
next prev parent reply other threads:[~2017-11-14 19:58 UTC|newest]
Thread overview: 151+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-19 14:50 [PATCH 00/27] security, efi: Add kernel lockdown David Howells
2017-10-19 14:50 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image David Howells
2017-10-20 23:19 ` James Morris
2017-10-19 14:50 ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown David Howells
2017-10-19 17:20 ` Randy Dunlap
2017-10-19 22:12 ` David Howells
2017-11-07 17:39 ` Thiago Jung Bauermann
2017-11-07 22:56 ` David Howells
2017-10-19 14:50 ` [PATCH 03/27] Enforce module signatures if the kernel is locked down David Howells
2017-10-20 6:33 ` joeyli
2017-10-20 23:21 ` James Morris
2017-10-27 18:48 ` Mimi Zohar
2017-10-30 17:00 ` David Howells
2017-10-30 17:52 ` Mimi Zohar
2017-11-02 17:22 ` David Howells
2017-11-02 19:13 ` Mimi Zohar
2017-11-02 21:30 ` David Howells
2017-11-02 21:41 ` Mimi Zohar
2017-11-02 22:01 ` David Howells
2017-11-02 22:18 ` Mimi Zohar
2017-10-19 14:51 ` [PATCH 04/27] Restrict /dev/mem and /dev/kmem when " David Howells
2017-10-20 6:37 ` joeyli
2017-10-20 23:21 ` James Morris
2017-10-19 14:51 ` [PATCH 05/27] kexec: Disable at runtime if " David Howells
2017-10-20 6:38 ` joeyli
2017-10-20 23:22 ` James Morris
2017-10-19 14:51 ` [PATCH 06/27] Copy secure_boot flag in boot params across kexec reboot David Howells
2017-10-20 6:40 ` joeyli
2017-10-19 14:51 ` [PATCH 07/27] kexec_file: Disable at runtime if securelevel has been set David Howells
2017-10-20 23:26 ` James Morris
2017-10-23 15:54 ` Mimi Zohar
2017-10-26 7:42 ` joeyli
2017-10-26 14:17 ` Mimi Zohar
2017-10-27 19:30 ` Mimi Zohar
2017-10-27 19:32 ` Mimi Zohar
2017-10-28 8:34 ` joeyli
2017-10-29 22:26 ` Mimi Zohar
2017-10-30 9:00 ` David Howells
2017-10-30 12:01 ` Mimi Zohar
2017-10-26 15:02 ` David Howells
2017-10-26 15:46 ` Mimi Zohar
2017-10-30 15:49 ` David Howells
2017-10-30 16:43 ` Mimi Zohar
2017-11-02 17:00 ` David Howells
2017-10-26 14:51 ` David Howells
2017-11-02 17:29 ` David Howells
2017-10-19 14:51 ` [PATCH 08/27] hibernate: Disable when the kernel is locked down David Howells
2017-10-20 6:40 ` joeyli
2017-10-19 14:51 ` [PATCH 09/27] uswsusp: " David Howells
2017-10-20 6:41 ` joeyli
2017-10-20 23:29 ` James Morris
2017-10-19 14:51 ` [PATCH 10/27] PCI: Lock down BAR access " David Howells
2017-10-20 6:42 ` joeyli
2017-10-19 14:51 ` [PATCH 11/27] x86: Lock down IO port " David Howells
2017-10-20 6:43 ` joeyli
2017-10-19 14:52 ` [PATCH 12/27] x86/msr: Restrict MSR " David Howells
2017-10-20 6:43 ` joeyli
2017-10-20 18:09 ` Alan Cox
2017-10-20 20:48 ` David Howells
2017-10-21 4:39 ` joeyli
2017-10-23 14:49 ` David Howells
2017-10-25 14:03 ` joeyli
2017-10-19 14:52 ` [PATCH 13/27] asus-wmi: Restrict debugfs interface " David Howells
2017-10-20 6:44 ` joeyli
2017-10-19 14:52 ` [PATCH 14/27] ACPI: Limit access to custom_method " David Howells
2017-10-20 6:45 ` joeyli
2017-10-19 14:52 ` [PATCH 15/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been " David Howells
2017-10-20 6:45 ` joeyli
2017-10-19 14:52 ` [PATCH 16/27] acpi: Disable ACPI table override if the kernel is " David Howells
2017-10-20 6:46 ` joeyli
2017-10-19 14:52 ` [PATCH 17/27] acpi: Disable APEI error injection " David Howells
2017-10-20 6:47 ` joeyli
2017-10-19 14:52 ` [PATCH 18/27] bpf: Restrict kernel image access functions when " David Howells
2017-10-19 22:18 ` Alexei Starovoitov
2017-10-20 2:47 ` joeyli
2017-10-20 8:08 ` David Howells
2017-10-20 15:57 ` jlee
2017-10-20 23:00 ` Alexei Starovoitov
2017-10-23 14:51 ` David Howells
2017-10-20 16:03 ` David Howells
2017-10-20 16:43 ` jlee
2017-10-23 14:53 ` David Howells
2017-10-25 7:07 ` joeyli
2017-10-19 22:48 ` David Howells
2017-10-19 23:31 ` Alexei Starovoitov
2017-11-09 17:15 ` David Howells
2017-10-19 14:52 ` [PATCH 19/27] scsi: Lock down the eata driver David Howells
2017-10-19 14:53 ` [PATCH 20/27] Prohibit PCMCIA CIS storage when the kernel is locked down David Howells
2017-10-19 14:53 ` [PATCH 21/27] Lock down TIOCSSERIAL David Howells
2017-10-19 14:53 ` [PATCH 22/27] Lock down module params that specify hardware parameters (eg. ioport) David Howells
2017-10-19 14:53 ` [PATCH 23/27] x86/mmiotrace: Lock down the testmmiotrace module David Howells
2017-10-19 14:53 ` [PATCH 24/27] debugfs: Disallow use of debugfs files when the kernel is locked down David Howells
2017-10-19 14:53 ` [PATCH 25/27] Lock down /proc/kcore David Howells
2017-10-21 2:11 ` James Morris
2017-10-23 14:56 ` David Howells
2017-10-19 14:53 ` [PATCH 26/27] efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode David Howells
2017-10-21 2:19 ` James Morris
2017-10-23 14:58 ` David Howells
2017-10-19 14:53 ` [PATCH 27/27] efi: Lock down the kernel if booted in " David Howells
2017-10-19 22:39 ` [PATCH 00/27] security, efi: Add kernel lockdown David Howells
2017-10-23 14:34 ` [PATCH 04/27] Restrict /dev/mem and /dev/kmem when the kernel is locked down David Howells
2017-10-24 10:48 ` Ethan Zhao
2017-10-24 14:56 ` David Howells
2017-11-02 22:01 ` [PATCH 00/27] security, efi: Add kernel lockdown Mimi Zohar
2017-11-02 22:04 ` Firmware signing -- " David Howells
2017-11-02 22:10 ` Mimi Zohar
2017-11-07 23:07 ` Luis R. Rodriguez
2017-11-08 6:15 ` AKASHI, Takahiro
2017-11-08 19:46 ` Luis R. Rodriguez
2017-11-09 1:48 ` AKASHI, Takahiro
2017-11-09 2:17 ` Mimi Zohar
2017-11-09 4:46 ` AKASHI, Takahiro
2017-11-10 13:37 ` Mimi Zohar
2017-11-11 2:32 ` Alan Cox
2017-11-13 11:49 ` Mimi Zohar
2017-11-13 17:42 ` Luis R. Rodriguez
2017-11-13 21:08 ` Alan Cox
2017-12-04 19:51 ` Luis R. Rodriguez
2017-12-07 15:32 ` Alan Cox
2017-11-13 21:44 ` David Howells
2017-11-13 22:09 ` Linus Torvalds
2017-11-14 0:20 ` Alan Cox
2017-11-14 12:21 ` Mimi Zohar
2017-11-14 12:38 ` Greg Kroah-Hartman
2017-11-14 13:17 ` Mimi Zohar
2017-11-14 17:34 ` Linus Torvalds
2017-11-14 19:58 ` Matthew Garrett [this message]
2017-11-14 20:18 ` Linus Torvalds
2017-11-14 20:31 ` Matthew Garrett
2017-11-14 20:35 ` Linus Torvalds
2017-11-14 20:37 ` Matthew Garrett
2017-11-14 20:50 ` Luis R. Rodriguez
2017-11-14 20:55 ` Matthew Garrett
2017-11-14 22:14 ` James Bottomley
2017-11-14 22:17 ` Matthew Garrett
2017-11-14 22:31 ` James Bottomley
2017-11-14 22:34 ` Matthew Garrett
2017-11-15 11:49 ` Mimi Zohar
2017-11-15 17:52 ` Luis R. Rodriguez
2017-11-15 19:56 ` Mimi Zohar
2017-11-15 20:46 ` Luis R. Rodriguez
2017-11-16 0:05 ` Mimi Zohar
2017-12-05 10:27 ` Pavel Machek
2017-12-07 23:02 ` Luis R. Rodriguez
2017-12-08 17:11 ` Alan Cox
2017-11-10 1:46 ` Luis R. Rodriguez
2017-11-10 13:45 ` Mimi Zohar
2017-11-13 18:50 ` Luis R. Rodriguez
2017-11-13 19:08 ` Luis R. Rodriguez
2017-11-08 20:01 ` Mimi Zohar
2017-11-08 20:09 ` Luis R. Rodriguez
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