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From: "AKASHI, Takahiro" <takahiro.akashi@linaro.org>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Jan Blunck <jblunck@infradead.org>,
	Julia Lawall <julia.lawall@lip6.fr>,
	David Howells <dhowells@redhat.com>,
	Marcus Meissner <meissner@suse.de>, Gary Lin <GLin@suse.com>,
	linux-security-module@vger.kernel.org,
	gnomes@lxorguk.ukuu.org.uk, linux-efi <linux-efi@vger.kernel.org>,
	linux-kernel@vger.kernel.org, Matthew Garrett <mjg59@google.com>
Subject: Re: Firmware signing -- Re: [PATCH 00/27] security, efi: Add kernel lockdown
Date: Thu, 9 Nov 2017 13:46:21 +0900
Message-ID: <20171109044619.GG7859@linaro.org> (raw)
In-Reply-To: <1510193857.4484.95.camel@linux.vnet.ibm.com>

Mimi,

On Wed, Nov 08, 2017 at 09:17:37PM -0500, Mimi Zohar wrote:
> > > IMHO that should just fail then, ie, a "locked down" kernel should not want to
> > > *pass* a firmware signature if such thing could not be done.
> > > 
> > > Its no different than trying to verify a signed module on a "locked down" for
> > > which it has no signature.
> > > 
> > > But perhaps I'm not understanding the issue well, let me know.
> > 
> > My point is quite simple:
> > my_deviceA_init() {
> >         err = request_firmware(&fw, "deviceA"); <--- (a)
> >         if (err)
> >                 goto err_request;
> > 
> >         err = verify_firmware(fw);  <--- (b)
> >         if (err)
> >                 goto err_verify;
> > 
> >         load_fw_to_deviceA(fw);     <--- (c)
> >         ...
> > }
> > 
> > As legacy device drivers does not have (b), there is no chance to
> > prevent loading a firmware at (c) for locked-down kernel.
> > 
> > If you allow me to bring in yet another function, say
> > request_firmware_signable(), which should be used in place of (a)
> > for all verification-aware drivers, that would be fine.
> 
> I really don't understand why you need a new function.  The
> request_firmware() eventually calls kernel_read_file_from_path(),
> which already calls the pre and post LSM hooks.

My assumption here is:
1) there are some less important and so security-insensitive firmwares,
   by which I mean that such firmwares won't be expected to be signed in
   terms of vulnerability or integrity.
   (I can't give you examples though.)
2) firmware's signature will be presented separately from the firmware
   blob itself. Say, "firmware.bin.p7s" for "firmware.bin"

I don't think that the current security_kernel(_post)_read_file() scheme
fit with this assumption very well.

Thanks,
-Takahiro AKASHI


> IMA-appraisal is already on these hooks verifying the requested
> firmware's signature.  For systems with "lockdown" enabled, but
> without IMA-appraisal enabled, define a small, builtin LSM that sits
> on these LSM hooks and denies the unsigned firmware requests.
> 
> Mimi
> 
> > In this case, all the invocation of request_firmware() in legacy code
> > could be forced to fail in locked-down kernel.
> > 
> > But I think that "signable" should be allowed to be combined with other
> > features of request_firmware variants like _(no)wait or _direct.
> > 
> > -Takahiro AKASHI
> 

  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 [this message]
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
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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