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From: Mimi Zohar <zohar@linux.ibm.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Arvind Sankar <niveditas98@gmail.com>,
	Roberto Sassu <roberto.sassu@huawei.com>,
	Rob Landley <rob@landley.net>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org,
	initramfs@vger.kernel.org
Subject: Re: [PATCH v2 0/3] initramfs: add support for xattrs in the initial ram disk
Date: Mon, 13 May 2019 18:09:11 -0400
Message-ID: <1557785351.4969.94.camel@linux.ibm.com> (raw)
In-Reply-To: <20190513184744.GA12386@rani.riverdale.lan>

On Mon, 2019-05-13 at 14:47 -0400, Arvind Sankar wrote:
> On Mon, May 13, 2019 at 02:36:24PM -0400, Mimi Zohar wrote:
> > 
> > > > How does this work today then? Is it actually the case that initramfs
> > > > just cannot be used on an IMA-enabled system, or it can but it leaves
> > > > the initramfs unverified and we're trying to fix that? I had assumed the
> > > > latter.
> > > Oooh, it's done not by starting IMA appraisal later, but by loading a
> > > default policy to ignore initramfs?
> > 
> > Right, when rootfs is a tmpfs filesystem, it supports xattrs, allowing
> > for finer grained policies to be defined.  This patch set would allow
> > a builtin IMA appraise policy to be defined which includes tmpfs.

Clarification: finer grain IMA policy rules are normally defined in
terms of LSM labels.  The LSMs need to enabled, before writing IMA
policy rules in terms of the LSM labels.

> > 
> Ok, but wouldn't my idea still work? Leave the default compiled-in
> policy set to not appraise initramfs. The embedded /init sets all the
> xattrs, changes the policy to appraise tmpfs, and then exec's the real
> init? Then everything except the embedded /init and the file with the
> xattrs will be appraised, and the embedded /init was verified as part of
> the kernel image signature. The only additional kernel change needed
> then is to add a config option to the kernel to disallow overwriting the
> embedded initramfs (or at least the embedded /init).

Yes and no.  The current IMA design allows a builtin policy to be
specified on the boot command line ("ima_policy="), so that it exists
from boot, and allows it to be replaced once with a custom policy.
 After that, assuming that CONFIG_IMA_WRITE_POLICY is configured,
additional rules may be appended.  As your embedded /init solution
already replaces the builtin policy, the IMA policy couldn't currently
be replaced a second time with a custom policy based on LSM labels.

Mimi


  reply index

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-09 11:24 Roberto Sassu
2019-05-09 11:24 ` [PATCH v2 1/3] fs: add ksys_lsetxattr() wrapper Roberto Sassu
2019-05-10 21:28   ` Jann Horn
2019-05-09 11:24 ` [PATCH v2 2/3] initramfs: set extended attributes Roberto Sassu
2019-05-09 11:24 ` [PATCH v2 3/3] initramfs: introduce do_readxattrs() Roberto Sassu
2019-05-10 21:33   ` Jann Horn
2019-05-13 13:03     ` Roberto Sassu
2019-05-09 18:34 ` [PATCH v2 0/3] initramfs: add support for xattrs in the initial ram disk Rob Landley
2019-05-10  6:56   ` Roberto Sassu
2019-05-10 11:49     ` Mimi Zohar
2019-05-10 20:46       ` Rob Landley
2019-05-10 22:38         ` Mimi Zohar
2019-05-11 22:44 ` Andy Lutomirski
2019-05-12  4:04   ` Rob Landley
2019-05-12  4:12     ` Rob Landley
2019-05-12  9:17 ` Dominik Brodowski
2019-05-12 10:18   ` hpa
2019-05-12 15:31     ` Dominik Brodowski
2019-05-13  0:02       ` Mimi Zohar
2019-05-13  0:21         ` hpa
2019-05-13  0:23       ` hpa
2019-05-12 12:52   ` Mimi Zohar
2019-05-12 17:05     ` Rob Landley
2019-05-12 19:43       ` Arvind Sankar
2019-05-13  7:49         ` Roberto Sassu
2019-05-13  9:07           ` Rob Landley
2019-05-13 12:08             ` Mimi Zohar
2019-05-13 12:47             ` Roberto Sassu
2019-05-13 17:20               ` Arvind Sankar
2019-05-13 17:51                 ` Arvind Sankar
2019-05-13 17:52                 ` Arvind Sankar
2019-05-13 18:36                   ` Mimi Zohar
2019-05-13 18:47                     ` Arvind Sankar
2019-05-13 22:09                       ` Mimi Zohar [this message]
2019-05-14  6:06                         ` Rob Landley
2019-05-14 14:44                           ` Arvind Sankar
2019-05-14  6:06               ` Rob Landley
2019-05-14 11:52                 ` Roberto Sassu
2019-05-14 15:12                   ` Rob Landley
2019-05-14 15:27                   ` Arvind Sankar
2019-05-14 15:57                     ` Arvind Sankar
2019-05-14 17:44                       ` Roberto Sassu
2019-05-15  1:00                         ` Arvind Sankar
2019-05-14 15:19               ` Andy Lutomirski
2019-05-14 16:33                 ` Roberto Sassu
2019-05-14 16:58                   ` Greg KH
2019-05-14 17:20                     ` Roberto Sassu
2019-05-15  0:25                       ` Arvind Sankar
2019-05-14 19:18                 ` James Bottomley
2019-05-14 23:39                   ` Rob Landley
2019-05-14 23:54                     ` James Bottomley
2019-05-15  0:52                       ` Arvind Sankar
2019-05-15 11:19                         ` Roberto Sassu
2019-05-15 16:08                           ` Arvind Sankar
2019-05-15 17:06                             ` Roberto Sassu
2019-05-16  5:29                               ` Arvind Sankar
2019-05-16 11:42                                 ` Roberto Sassu
2019-05-16 13:31                                 ` Mimi Zohar

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