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From: Mimi Zohar <zohar@linux.ibm.com>
To: Matthew Garrett <mjg59@google.com>
Cc: linux-integrity <linux-integrity@vger.kernel.org>,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	miklos@szeredi.hu, linux-fsdevel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	chuck.lever@oracle.com
Subject: Re: Allow FUSE filesystems to provide out-of-band hashes to IMA
Date: Wed, 10 Oct 2018 07:09:15 -0400	[thread overview]
Message-ID: <1539169755.15382.274.camel@linux.ibm.com> (raw)
In-Reply-To: <CACdnJusJ83MH+e7N4qXwS9iMTFLVoQzZrW=zNBHaTwr+LLHL8g@mail.gmail.com>

On Tue, 2018-10-09 at 14:32 -0700, Matthew Garrett wrote:
> On Tue, Oct 9, 2018 at 1:52 PM Mimi Zohar <zohar@linux.ibm.com> wrote:
> >
> > > The performance hit is more noticeable over remote filesystems, but we
> > > have large binaries that take several seconds to hash even on local
> > > filesystems. Would it be helpful to try to define the assumptions that
> > > IMA makes in terms of whether or not it produces trustworthy results?
> > > It feels like it's be easier to talk about this if we have a more
> > > formal set of conditions to take into consideration.
> >
> > [Cc'ing Chuck Lever]
> >
> > Integrity of files on remote filesystems should probably be discussed
> > in the context of fs-verity, not FUSE filesystems.
> 
> Hm. We /could/ fake up fs-verity style behaviour, but we're not
> talking about files that are expected to be immutable so it would seem
> like there might be mismatched semantics there.

If these aren't immutable files, then the file hash needs to be
calculated and re-calculated on file change.  Trust between the kernel
and FUSE isn't bi-directional.  IMA already supports hardware crypto
acceleration.  (Refer to the "ima.ahash_minsize" and
"ima.ahash_bufsize" boot command line options.)  Why is it better that
FUSE calculates the file hash than the kernel?

Mimi

WARNING: multiple messages have this Message-ID (diff)
From: Mimi Zohar <zohar@linux.ibm.com>
To: Matthew Garrett <mjg59@google.com>
Cc: linux-integrity <linux-integrity@vger.kernel.org>,
	Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	miklos@szeredi.hu, linux-fsdevel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	chuck.lever@oracle.com
Subject: Re: Allow FUSE filesystems to provide out-of-band hashes to IMA
Date: Wed, 10 Oct 2018 07:09:15 -0400	[thread overview]
Message-ID: <1539169755.15382.274.camel@linux.ibm.com> (raw)
In-Reply-To: <CACdnJusJ83MH+e7N4qXwS9iMTFLVoQzZrW=zNBHaTwr+LLHL8g@mail.gmail.com>

On Tue, 2018-10-09 at 14:32 -0700, Matthew Garrett wrote:
> On Tue, Oct 9, 2018 at 1:52 PM Mimi Zohar <zohar@linux.ibm.com> wrote:
> >
> > > The performance hit is more noticeable over remote filesystems, but we
> > > have large binaries that take several seconds to hash even on local
> > > filesystems. Would it be helpful to try to define the assumptions that
> > > IMA makes in terms of whether or not it produces trustworthy results?
> > > It feels like it's be easier to talk about this if we have a more
> > > formal set of conditions to take into consideration.
> >
> > [Cc'ing Chuck Lever]
> >
> > Integrity of files on remote filesystems should probably be discussed
> > in the context of fs-verity, not FUSE filesystems.
> 
> Hm. We /could/ fake up fs-verity style behaviour, but we're not
> talking about files that are expected to be immutable so it would seem
> like there might be mismatched semantics there.

If these aren't immutable files, then the file hash needs to be
calculated and re-calculated on file change.  Trust between the kernel
and FUSE isn't bi-directional.  IMA already supports hardware crypto
acceleration.  (Refer to the "ima.ahash_minsize" and
"ima.ahash_bufsize" boot command line options.)  Why is it better that
FUSE calculates the file hash than the kernel?

Mimi

  reply	other threads:[~2018-10-10 18:31 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-04 20:30 Allow FUSE filesystems to provide out-of-band hashes to IMA Matthew Garrett
2018-10-04 20:30 ` [PATCH 1/3] VFS: Add a call to obtain a file's hash Matthew Garrett
2018-10-11 15:22   ` Mimi Zohar
2018-10-11 15:22     ` Mimi Zohar
2018-10-11 18:21     ` Matthew Garrett
2018-10-11 18:24       ` Matthew Garrett
2018-10-11 18:37         ` Mimi Zohar
2018-10-11 18:37           ` Mimi Zohar
2018-10-11 18:43           ` Matthew Garrett
2018-10-04 20:30 ` [PATCH 2/3] IMA: Make use of filesystem-provided hashes Matthew Garrett
2018-10-11 15:23   ` Mimi Zohar
2018-10-11 15:23     ` Mimi Zohar
2018-10-11 20:30     ` Matthew Garrett
2018-10-11 23:03       ` Mimi Zohar
2018-10-12 18:31         ` Matthew Garrett
2018-10-15  1:38           ` Mimi Zohar
2018-10-15  1:38             ` Mimi Zohar
2018-10-15 18:46             ` Matthew Garrett
2018-10-16 13:16               ` Mimi Zohar
2018-10-16 13:16                 ` Mimi Zohar
2018-10-04 20:30 ` [PATCH 3/3] FUSE: Allow filesystems to provide gethash methods Matthew Garrett
2018-10-05 10:49 ` Allow FUSE filesystems to provide out-of-band hashes to IMA Mimi Zohar
2018-10-05 10:49   ` Mimi Zohar
2018-10-05 17:26   ` Matthew Garrett
2018-10-05 18:18     ` Mimi Zohar
2018-10-05 19:25       ` Matthew Garrett
2018-10-08 11:25         ` Mimi Zohar
2018-10-08 11:25           ` Mimi Zohar
2018-10-08 20:19           ` Matthew Garrett
2018-10-08 22:40             ` Mimi Zohar
2018-10-08 22:40               ` Mimi Zohar
2018-10-09 17:21               ` Matthew Garrett
2018-10-09 18:04                 ` Mimi Zohar
2018-10-09 19:29                   ` Matthew Garrett
2018-10-09 20:52                     ` Mimi Zohar
2018-10-09 21:32                       ` Matthew Garrett
2018-10-10 11:09                         ` Mimi Zohar [this message]
2018-10-10 11:09                           ` Mimi Zohar
2018-10-10 16:19                           ` Matthew Garrett

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