From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:47046 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725892AbeJIFyi (ORCPT ); Tue, 9 Oct 2018 01:54:38 -0400 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w98MYBJ2039691 for ; Mon, 8 Oct 2018 18:40:39 -0400 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0b-001b2d01.pphosted.com with ESMTP id 2n0fa9hp2b-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 08 Oct 2018 18:40:39 -0400 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 8 Oct 2018 23:40:37 +0100 Subject: Re: Allow FUSE filesystems to provide out-of-band hashes to IMA From: Mimi Zohar To: Matthew Garrett Cc: linux-integrity , Dmitry Kasatkin , miklos@szeredi.hu, linux-fsdevel@vger.kernel.org, Alexander Viro Date: Mon, 08 Oct 2018 18:40:32 -0400 In-Reply-To: References: <20181004203007.217320-1-mjg59@google.com> <1538736566.3702.436.camel@linux.ibm.com> <1538763521.3541.31.camel@linux.ibm.com> <1538997900.15382.90.camel@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <1539038432.15382.181.camel@linux.ibm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 2018-10-08 at 13:19 -0700, Matthew Garrett wrote: > On Mon, Oct 8, 2018 at 4:25 AM Mimi Zohar wrote: > > On Fri, 2018-10-05 at 12:25 -0700, Matthew Garrett wrote: > > > I agree that using FUSE in general is incompatible with IMA's goals, > > > but it's possible to configure systems where you can ensure that only > > > trustworthy code is involved. In that scenario this patch improves > > > performance without compromising security. > > > > If you trust a FUSE filesystem to not only behave properly, but also > > to return file hashes, what is the value of measuring/appraising the > > files? Define a custom policy that doesn't measure/appraise files on > > FUSE filesystems. > > We trust that the filesystem will return us accurate binaries and > hashes, but we don't the binaries themselves may not be trustworthy - > we want the same level of audit trail associated with their execution > that we'd have for something run off local disk. We could certainly > rearchitect our filesystems to generate audit events themselves, but > we'd be duplicating functionality that already exists in the kernel. I'm really not comfortable with the FUSE filesystem calculating the file hash being used by IMA.  Adding FUSE i_version support would have been better, instead of returning the actual file hash.  Based on a mount option and the i_version, the kernel could then decide whether or not to limit re-calculating the file hash. Mimi