Re: [PATCH v5 1/7] fs: introduce kernel_pread_file* support

[Luis Chamberlain]

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.
> 
> 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?

  Luis