Messages in this thread | | | Subject | Re: [PATCH v2 00/15] ima: digest list feature | From | Roberto Sassu <> | Date | Fri, 17 Nov 2017 09:55:29 +0100 |
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On 11/17/2017 2:08 AM, Kees Cook wrote: > On Tue, Nov 7, 2017 at 8:45 AM, Roberto Sassu <roberto.sassu@huawei.com> wrote: >> On 11/7/2017 2:37 PM, Mimi Zohar wrote: >>> Normally, the protection of kernel memory is out of scope for IMA. >>> This patch set introduces an in kernel white list, which would be a >>> prime target for attackers looking for ways of by-passing IMA- >>> measurement, IMA-appraisal and IMA-audit. Others might disagree, but >>> from my perspective, this risk is too high. > > BTW, which part of the series does the whitelist? I'd agree generally, > though: we don't want to make things writable if they're normally > read-only.
Patch 5/15 introduces the hash table ima_digests_htable and the functions to add/search file digests
Patches 6-7-8/15 add file digests to ima_digests_htable
Patch 10/15 searches file digests in ima_digests_htable
Original files containing digest lists are discarded after being parsed.
>> It would be much easier for an attacker to just set ima_policy_flag to >> zero. > > That's a fair point. I wonder if ima_policy_flag could be marked > __ro_after_init? Most of the writes are from __init sections, but I > haven't looked closely at when ima_update_policy() gets called.
Unfortunately not. New policies can be loaded by writing to a file in the securityfs filesystem. They could enable different actions (measurement/appraisal/audit).
Roberto
-- HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Bo PENG, Qiuen PENG, Shengli WANG
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