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From: Matthew Garrett <mjg59@google.com>
To: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>,
	linux-integrity <linux-integrity@vger.kernel.org>,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	linux-fsdevel@vger.kernel.org, miklos@szeredi.hu
Subject: Re: [PATCH V2 3/4] IMA: Optionally make use of filesystem-provided hashes
Date: Fri, 5 Apr 2019 13:55:22 -0700	[thread overview]
Message-ID: <CACdnJut_vN9pJXq-j9fEO1CFZ-Aq83cO2LiFmep=Fn9_NOKhWQ@mail.gmail.com> (raw)
In-Reply-To: <1554431217.24612.37.camel@HansenPartnership.com>

On Thu, Apr 4, 2019 at 7:27 PM James Bottomley
<James.Bottomley@hansenpartnership.com> wrote:
>
> On Thu, 2019-04-04 at 18:50 -0700, Matthew Garrett wrote:
> > On Thu, Apr 4, 2019 at 3:35 PM James Bottomley
> > <James.Bottomley@hansenpartnership.com> wrote:
> > > Redundant information is always possible, but it can become
> > > inconsistent and, because the hashes can't be derived from each
> > > other, it's hard to tell if it is inconsistent without redoing the
> > > whole hash with each method.
> >
> > Part of the problem here is that IMA is effectively used for two
> > related but different purposes - measurement and appraisal. You
> > generally want measurements to be comparable across filesystems,
> > whereas appraisal doesn't need to be.
>
> Sure, but I think the only requirement for measurement is knowing how
> to reproduce them.  As long as you know the algorithm the filesystem is
> using ... i.e. it's recorded in the IMA log, you should be able to
> verify them.

Mm. I think this is use-case dependent, but there are certainly use
cases where this would be sufficient. I think this would work on the
VFS side, but we'd need to extend IMA to allow you to write a policy
that specified the use of the fs-verity data on the appropriate
filesystems (right now IMA uses one hash type globally) - if anyone's
interested in deploying that, I'm happy to add support for it.

  reply	other threads:[~2019-04-05 20:55 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-26 21:50 Allow trusted filesystems to provide IMA hashes directly Matthew Garrett
2019-02-26 21:50 ` [PATCH V2 1/4] VFS: Add a call to obtain a file's hash Matthew Garrett
2019-02-26 21:50 ` [PATCH V2 2/4] IMA: Allow rule matching on filesystem subtype Matthew Garrett
2019-02-26 21:50 ` [PATCH V2 3/4] IMA: Optionally make use of filesystem-provided hashes Matthew Garrett
2019-02-28 16:03   ` Mimi Zohar
2019-02-28 18:05     ` Mimi Zohar
2019-02-28 21:41       ` Matthew Garrett
2019-02-28 21:59         ` Mimi Zohar
2019-02-28 22:38           ` Matthew Garrett
2019-03-04 19:52             ` Matthew Garrett
2019-03-04 20:32               ` Mimi Zohar
2019-03-04 22:10                 ` Matthew Garrett
2019-03-05 13:18                   ` Mimi Zohar
2019-03-05 18:39                     ` Matthew Garrett
2019-03-05 19:51                       ` Mimi Zohar
2019-03-05 20:27                         ` Matthew Garrett
2019-03-06 12:30                           ` Mimi Zohar
2019-03-06 18:31                             ` Matthew Garrett
2019-03-06 22:38                               ` Mimi Zohar
2019-03-06 23:36                                 ` Matthew Garrett
2019-03-07  1:54                                   ` Mimi Zohar
2019-03-07  4:19                                     ` Matthew Garrett
2019-03-07 20:48                                       ` Mimi Zohar
2019-03-07 22:41                                         ` Matthew Garrett
2019-04-04 21:46                                           ` Matthew Garrett
2019-04-04 22:18                                             ` James Bottomley
2019-04-04 22:26                                               ` Matthew Garrett
2019-04-04 22:35                                                 ` James Bottomley
2019-04-05  1:50                                                   ` Matthew Garrett
2019-04-05  2:26                                                     ` James Bottomley
2019-04-05 20:55                                                       ` Matthew Garrett [this message]
2019-04-29 22:51                                                         ` Matthew Garrett
2019-05-02 20:25                                                           ` Mimi Zohar
2019-05-02 22:37                                                             ` Matthew Garrett
2019-05-02 23:02                                                               ` Mimi Zohar
2019-05-03  6:51                                                                 ` Roberto Sassu
2019-05-03  8:17                                                                   ` Roberto Sassu
2019-05-03 12:47                                                                     ` Mimi Zohar
2019-05-03 13:20                                                                       ` Roberto Sassu
2019-02-26 21:50 ` [PATCH V2 4/4] FUSE: Allow filesystems to provide gethash methods Matthew Garrett
2019-02-27 14:26   ` Jann Horn

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