From: Roberto Sassu <roberto.sassu@huawei.com>
To: Matthew Garrett <mjg59@google.com>
Cc: linux-integrity <linux-integrity@vger.kernel.org>,
<linux-security-module@vger.kernel.org>,
<linux-fsdevel@vger.kernel.org>, <linux-doc@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <silviu.vlasceanu@huawei.com>
Subject: Re: [PATCH v2 00/15] ima: digest list feature
Date: Wed, 8 Nov 2017 13:00:37 +0100 [thread overview]
Message-ID: <e879759b-d866-e3e3-b070-3025baf3454d@huawei.com> (raw)
In-Reply-To: <CACdnJut-FzG=6DW-Pisx+_Ot5+=62_MabP1SU_RR2d9n-RJvyw@mail.gmail.com>
On 11/7/2017 7:06 PM, Matthew Garrett wrote:
> On Tue, Nov 7, 2017 at 12:53 PM, Roberto Sassu <roberto.sassu@huawei.com> wrote:
>> On 11/7/2017 3:49 PM, Matthew Garrett wrote:
>>> RPM's hardly universal, and distributions are in the process of moving
>>> away from using it for distributing non-core applications (Flatpak and
>>> Snap are becoming increasingly popular here). I think this needs to be
>>> a generic solution rather than having the kernel tied to a specific
>>> package format.
>>
>>
>> Support for new digest list formats can be easily added. Digest list
>> metadata includes the digest list type, so that the appropriate parser
>> is selected.
>
> But we're still left in a state where the kernel has to end up
> supporting a number of very niche formats, and userland agility is
> tied to the kernel. I think it makes significantly more sense to push
> the problem out to userland.
At least for appraisal, digest lists must be parsed by the kernel. If
the parser is moved to userspace, I don't know if we are able to provide
the same guarantee, that the correct set of digests has been uploaded to
IMA. A new measurement can be added, when IMA receives the digests, but
a verifier has to verify the signature of the original file, perform
format conversion, calculate the digest and compare it with that in the
new IMA measurement. If digest lists are parsed directly by the kernel,
then the signature can be verified directly.
>> Digest lists should be parsed directly by the kernel, because processing
>> the lists in userspace would increase the chances that a compromised
>> tool does not upload to the kernel the expected digests. Also, digest
>> lists must be processed before init, otherwise appraisal will deny the
>> execution. Lastly, the mechanism of parsing files from the kernel is
>> already used to parse the IMA policy.
>
> Isn't failing to upload the expected digest list just a DoS? We
> already expect to load keys from initramfs, so it seems fine to parse
> stuff there - what's the problem with extracting information from
> RPMs, translating them to the generic format and pushing that into the
> kernel?
The main problem is that the digest list measurement, performed when the
parser accesses the file containing the RPM header, might not reflect
what IMA uses for digest lookup.
Roberto
--
HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Bo PENG, Qiuen PENG, Shengli WANG
next prev parent reply other threads:[~2017-11-08 12:00 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-07 10:36 [PATCH v2 00/15] ima: digest list feature Roberto Sassu
2017-11-07 10:36 ` [PATCH v2 01/15] ima: generalize ima_read_policy() Roberto Sassu
2017-11-07 10:36 ` [PATCH v2 02/15] ima: generalize ima_write_policy() Roberto Sassu
2017-11-07 10:36 ` [PATCH v2 03/15] ima: generalize policy file operations Roberto Sassu
2017-11-07 10:36 ` [PATCH v2 04/15] ima: use ima_show_htable_value to show hash table data Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 05/15] ima: add functions to manage digest lists Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 06/15] ima: add parser of digest lists metadata Roberto Sassu
2017-11-18 4:20 ` Serge E. Hallyn
2017-11-18 23:23 ` Mimi Zohar
2017-11-20 9:40 ` Roberto Sassu
2017-11-20 13:53 ` Mimi Zohar
2017-11-20 16:52 ` Serge E. Hallyn
2017-11-07 10:37 ` [PATCH v2 07/15] ima: add parser of compact digest list Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 08/15] ima: add parser of RPM package headers Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 09/15] ima: introduce securityfs interfaces for digest lists Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 10/15] ima: disable digest lookup if digest lists are not checked Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 11/15] ima: add policy action digest_list Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 12/15] ima: do not update security.ima if appraisal status is not INTEGRITY_PASS Roberto Sassu
2017-11-18 4:25 ` Serge E. Hallyn
2017-11-07 10:37 ` [PATCH v2 13/15] evm: add kernel command line option to select protected xattrs Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 14/15] ima: add support for appraisal with digest lists Roberto Sassu
2017-11-07 10:37 ` [PATCH v2 15/15] ima: add Documentation/security/IMA-digest-lists.txt Roberto Sassu
2017-11-07 13:37 ` [PATCH v2 00/15] ima: digest list feature Mimi Zohar
2017-11-07 16:45 ` Roberto Sassu
2017-11-17 1:08 ` Kees Cook
2017-11-17 8:55 ` Roberto Sassu
2017-11-17 12:21 ` Mimi Zohar
2017-11-07 14:49 ` Matthew Garrett
2017-11-07 17:53 ` Roberto Sassu
2017-11-07 18:06 ` Matthew Garrett
2017-11-08 12:00 ` Roberto Sassu [this message]
2017-11-08 15:48 ` Matthew Garrett
2017-11-09 9:51 ` Roberto Sassu
2017-11-09 14:47 ` Matthew Garrett
2017-11-09 16:13 ` Roberto Sassu
2017-11-09 16:46 ` Matthew Garrett
2017-11-09 17:23 ` Roberto Sassu
2017-11-09 16:17 ` Mimi Zohar
2017-11-07 18:03 ` Safford, David (GE Global Research, US)
2017-11-08 10:16 ` Roberto Sassu
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