linux-kernel - Re: Firmware signing -- Re: [PATCH 00/27] security, efi: Add kernel lockdown

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20171115175246.GN729@wotan.suse.de>
Date:   Wed, 15 Nov 2017 18:52:46 +0100
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Johannes Berg <johannes@...solutions.net>,
        Matthew Garrett <mjg59@...gle.com>,
        David Howells <dhowells@...hat.com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jan Blunck <jblunck@...radead.org>,
        Julia Lawall <julia.lawall@...6.fr>,
        Marcus Meissner <meissner@...e.de>, Gary Lin <GLin@...e.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Firmware signing -- Re: [PATCH 00/27] security, efi: Add kernel
 lockdown

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 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.

  Luis