From: Mimi Zohar <zohar@kernel.org>
To: Scott Branden <scott.branden@broadcom.com>,
Luis Chamberlain <mcgrof@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
David Brown <david.brown@linaro.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Shuah Khan <shuah@kernel.org>,
bjorn.andersson@linaro.org,
Shuah Khan <skhan@linuxfoundation.org>,
Arnd Bergmann <arnd@arndb.de>,
"Rafael J . Wysocki" <rafael@kernel.org>,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
Olof Johansson <olof@lixom.net>,
Andrew Morton <akpm@linux-foundation.org>,
Dan Carpenter <dan.carpenter@oracle.com>,
Colin Ian King <colin.king@canonical.com>,
Kees Cook <keescook@chromium.org>, Takashi Iwai <tiwai@suse.de>,
linux-kselftest@vger.kernel.org, Andy Gross <agross@kernel.org>,
linux-security-module <linux-security-module@vger.kernel.org>,
linux-integrity <linux-integrity@vger.kernel.org>
Subject: Re: [PATCH v5 1/7] fs: introduce kernel_pread_file* support
Date: Wed, 13 May 2020 19:00:43 -0400 [thread overview]
Message-ID: <1589410843.5098.220.camel@kernel.org> (raw)
In-Reply-To: <f8de785c-60df-3fec-c2c6-b1dd2c77db17@broadcom.com>
On Wed, 2020-05-13 at 15:48 -0700, Scott Branden wrote:
>
> On 2020-05-13 3:12 p.m., Mimi Zohar wrote:
> > On Wed, 2020-05-13 at 21:28 +0000, Luis Chamberlain wrote:
> >> On Wed, May 13, 2020 at 05:20:14PM -0400, Mimi Zohar wrote:
> >>> On Wed, 2020-05-13 at 12:41 -0700, Scott Branden wrote:
> >>>> On 2020-05-13 12:39 p.m., Mimi Zohar wrote:
> >>>>> On Wed, 2020-05-13 at 12:18 -0700, Scott Branden wrote:
> >>>>>> On 2020-05-13 12:03 p.m., Mimi Zohar wrote:
> >>>>>>> On Wed, 2020-05-13 at 11:53 -0700, Scott Branden wrote:
> >>>>>> Even if the kernel successfully verified the firmware file signature it
> >>>>>> would just be wasting its time. The kernel in these use cases is not always
> >>>>>> trusted. The device needs to authenticate the firmware image itself.
> >>>>> There are also environments where the kernel is trusted and limits the
> >>>>> firmware being provided to the device to one which they signed.
> >>>>>
> >>>>>>> The device firmware is being downloaded piecemeal from somewhere and
> >>>>>>> won't be measured?
> >>>>>> It doesn't need to be measured for current driver needs.
> >>>>> Sure the device doesn't need the kernel measuring the firmware, but
> >>>>> hardened environments do measure firmware.
> >>>>>
> >>>>>> If someone has such need the infrastructure could be added to the kernel
> >>>>>> at a later date. Existing functionality is not broken in any way by
> >>>>>> this patch series.
> >>>>> Wow! You're saying that your patch set takes precedence over the
> >>>>> existing expectations and can break them.
> >>>> Huh? I said existing functionality is NOT broken by this patch series.
> >>> Assuming a system is configured to measure and appraise firmware
> >>> (rules below), with this change the firmware file will not be properly
> >>> measured and will fail signature verification.
> So no existing functionality has been broken.
> >>>
> >>> Sample IMA policy rules:
> >>> measure func=FIRMWARE_CHECK
> >>> appraise func=FIRMWARE_CHECK appraise_type=imasig
> >> Would a pre and post lsm hook for pread do it?
> > IMA currently measures and verifies the firmware file signature on the
> > post hook. The file is read once into a buffer. With this change,
> > IMA would need to be on the pre hook, to read the entire file,
> > calculating the file hash and verifying the file signature. Basically
> > the firmware would be read once for IMA and again for the device.
> The entire file may not fit into available memory to measure and
> verify. Hence the reason for a partial read.
Previously, IMA pre-read the file in page size chunks in order to
calculate the file hash. To avoid reading the file twice, the file is
now read into a buffer.
>
> Is there some way we could add a flag when calling the
> request_firmware_into_buf to indicate it is ok that the data requested
> does not need to be measured?
The decision as to what needs to be measured is a policy decision left
up to the system owner, which they express by loading an IMA policy.
Mimi
next prev parent reply other threads:[~2020-05-13 23:00 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-08 0:27 [PATCH v5 0/7] firmware: add partial read support in request_firmware_into_buf Scott Branden
2020-05-08 0:27 ` [PATCH v5 1/7] fs: introduce kernel_pread_file* support Scott Branden
2020-05-13 0:27 ` Luis Chamberlain
2020-05-13 6:23 ` Scott Branden
2020-05-13 6:51 ` Greg Kroah-Hartman
2020-05-13 8:16 ` Scott Branden
2020-05-13 18:39 ` Mimi Zohar
2020-05-13 18:53 ` Scott Branden
2020-05-13 18:57 ` Scott Branden
2020-05-13 19:03 ` Mimi Zohar
2020-05-13 19:18 ` Scott Branden
2020-05-13 19:39 ` Mimi Zohar
2020-05-13 19:41 ` Scott Branden
2020-05-13 21:20 ` Mimi Zohar
2020-05-13 21:28 ` Luis Chamberlain
2020-05-13 22:12 ` Mimi Zohar
2020-05-13 22:48 ` Scott Branden
2020-05-13 23:00 ` Mimi Zohar [this message]
2020-05-13 23:34 ` Kees Cook
2020-05-13 23:58 ` Mimi Zohar
2020-05-08 0:27 ` [PATCH v5 2/7] firmware: add offset to request_firmware_into_buf Scott Branden
2020-05-13 0:33 ` Luis Chamberlain
2020-05-13 18:35 ` Scott Branden
2020-05-15 20:44 ` Luis Chamberlain
2020-05-08 0:27 ` [PATCH v5 3/7] test_firmware: add partial read support for request_firmware_into_buf Scott Branden
2020-05-13 0:35 ` Luis Chamberlain
2020-05-08 0:27 ` [PATCH v5 4/7] firmware: test partial file reads of request_firmware_into_buf Scott Branden
2020-05-08 0:27 ` [PATCH v5 5/7] bcm-vk: add bcm_vk UAPI Scott Branden
2020-05-08 0:27 ` [PATCH v5 7/7] MAINTAINERS: bcm-vk: add maintainer for Broadcom VK Driver Scott Branden
[not found] ` <20200508002739.19360-7-scott.branden@broadcom.com>
2020-05-13 0:38 ` [PATCH v5 6/7] misc: bcm-vk: add Broadcom VK driver Luis Chamberlain
2020-05-13 6:31 ` Scott Branden
2020-05-13 6:50 ` Greg Kroah-Hartman
2020-05-13 12:30 ` Luis Chamberlain
2020-05-13 18:39 ` Scott Branden
2020-05-13 16:23 ` [PATCH v5 0/7] firmware: add partial read support in request_firmware_into_buf Mimi Zohar
2020-05-15 20:47 ` Luis Chamberlain
2020-05-15 23:28 ` Scott Branden
2020-05-16 1:05 ` Luis Chamberlain
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