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From: "Luis R. Rodriguez" <mcgrof@kernel.org>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Johannes Berg <johannes@sipsolutions.net>,
	Matthew Garrett <mjg59@google.com>,
	David Howells <dhowells@redhat.com>,
	Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
	"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: Wed, 15 Nov 2017 21:46:51 +0100
Message-ID: <20171115204651.GO729@wotan.suse.de> (raw)
In-Reply-To: <1510775817.3711.315.camel@linux.vnet.ibm.com>

On Wed, Nov 15, 2017 at 02:56:57PM -0500, Mimi Zohar wrote:
> On Wed, 2017-11-15 at 18:52 +0100, Luis R. Rodriguez wrote:
> > On Wed, Nov 15, 2017 at 06:49:57AM -0500, Mimi Zohar wrote:
> > > On Tue, 2017-11-14 at 21:50 +0100, Luis R. Rodriguez wrote:
> > > 
> > > > Johannes made cfg80211 recently just use request_firmware() now via commit on
> > > > linux-next 90a53e4432 ("cfg80211: implement regdb signature checking") [0] as
> > > > he got tired of waiting firmware signing, but note he implemented a signature
> > > > checking on its own so he open codes verify_pkcs7_signature() after the
> > > > request_firmware() call. If we are happy to live with this, then so be it.
> > > > 
> > > > [0] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=90a53e4432b12288316efaa5f308adafb8d304b0
> > > 
> > > Johannes was tired of waiting?  Commit 5a9196d "ima: add support for
> > > measuring and appraising firmware" has been in the kernel since linux-
> > > 3.17.
> > > 
> > > The original firmware hook for verifying firmware signatures were
> > > replaced with the common LSM pre and post kernel_read_file() hooks
> > > in linux-4.6.y.
> > > 
> > > Even if you wanted to support firmware signature verification without
> > > IMA-appraisal, it should be using the LSM hooks.
> > 
> > request_firmware() uses kernel_read_file_from_path() underneath the hood,
> > and so its used for both:
> > 
> > 	/lib/firmware/regulatory.db
> > 	/lib/firmware/regulatory.db.p7s
> 
> The firmware signature validation should occur as part of
> kernel_read_file_from_path(), not as a stand alone verification.
> 
> Why not extend kernel_read_file_from_path() to pass the detached signature?
> Since the signature would only be used for the verification, there's no need
> to return the open file descriptor.

This goes along with the question if there were an other users who wanted it,
or more importantly -- if firmware signing was desirable for any reason, a
modified kernel_read_file_from_path_signed() could in turn be used, *or* an LSM
added to handle READING_FIRMWARE and READING_FIRMWARE_PREALLOC_BUFFER.  The
above use case was one example outside of the typical firmware use.  I've long
pointed out that we no longer use the firmware API for just firmware, and the
above is now a very good example of it. I've been suggesting uses of the
firmware API for non-firmware had already happened and that more uses were on
its way. Trusted boot has nothing to do with these uses as such the gains of
systems pegged with "trusted boot" have nothing to do validation of these files
through hardware.

In this particular case its simply easier to re-use the existing redistribution
mechanisms in place already so that users can get the regulatory.db and
regulatory.db.p7s.

So here is now an example  use of request_firmware() API  with its own key
validation / keyring solution completely open coded.

So, given the wireless regulatory use case *does* benefit from re-using
request_firmware() due to the file redistribution aspects, using a new
kernel_read_file_from_path_signed() for non-firmware with the same
/lib/firmware/ path specified would be rather sloppy and awkward.  The right
way to not open code this is to consider adding firmware signing support
properly.

> > The later only if CONFIG_CFG80211_REQUIRE_SIGNED_REGDB, which defaults
> > to y anyway.
> > 
> > What I meant was that net/wireless/reg.c now open codes firmware signature
> > validation on its own rather than using a helper. IMA appraisal will still
> > be used if enabled given kernel_read_file_from_path() is used.
> > 
> > The open coding of the firmware signature check is what I wanted to highlight.
> 
> How are the keys in the CFG80211_EXTRA_REGDB_KEYDIR verified?  The
> call to key_create_or_update() with the KEY_ALLOC_BYPASS_RESTRICTION
> option by-passes any requirement that the keys in this directory are
> signed.  This by-passes the concept of extending the secure boot
> signature chain of trust.  To safely validate the keys use the
> restrict_link_by_builtin_trusted option.

I'll let Johannes chime in, if he so wishes.

  Luis

  reply index

Thread overview: 151+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-19 14:50 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
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 [this message]
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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