From: Mimi Zohar <zohar@linux.ibm.com>
To: Roberto Sassu <roberto.sassu@huaweicloud.com>,
corbet@lwn.net, dmitry.kasatkin@gmail.com,
eric.snowberg@oracle.com, paul@paul-moore.com, jmorris@namei.org,
serge@hallyn.com
Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org, wufan@linux.microsoft.com,
pbrobinson@gmail.com, zbyszek@in.waw.pl, hch@lst.de,
mjg59@srcf.ucam.org, pmatilai@redhat.com, jannh@google.com,
dhowells@redhat.com, jikos@kernel.org, mkoutny@suse.com,
ppavlu@suse.com, petr.vorel@gmail.com,
petrtesarik@huaweicloud.com, mzerqung@0pointer.de,
kgold@linux.ibm.com, Roberto Sassu <roberto.sassu@huawei.com>
Subject: Re: [RFC][PATCH 4/8] ima: Add digest_cache_measure and digest_cache_appraise boot-time policies
Date: Thu, 07 Mar 2024 15:17:03 -0500 [thread overview]
Message-ID: <ed5df367582f0c5e212638a12204fd20fd8e46e5.camel@linux.ibm.com> (raw)
In-Reply-To: <20240214143525.2205481-5-roberto.sassu@huaweicloud.com>
On Wed, 2024-02-14 at 15:35 +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Specify the 'digest_cache_measure' boot-time policy with 'ima_policy=' in
> the kernel command line
The 'built-in' policies may be specified on the boot command line. Please
update Subject line, to user the term "built-in" as well as here.
> to add the following rule at the beginning of the
> IMA policy, before other rules:
Comments below...
>
> measure func=DIGEST_LIST_CHECK pcr=12
>
> which will measure digest lists into PCR 12 (or the value in
> CONFIG_IMA_DIGEST_CACHE_MEASURE_PCR_IDX).
>
> 'digest_cache_measure' also adds 'digest_cache=content pcr=12' to the other
> measure rules, if they have a compatible IMA hook. The PCR value still
> comes from CONFIG_IMA_DIGEST_CACHE_MEASURE_PCR_IDX.
>
> Specify 'digest_cache_appraise' to add the following rule at the beginning,
> before other rules:
>
> appraise func=DIGEST_LIST_CHECK appraise_type=imasig|modsig
>
> which will appraise digest lists with IMA signatures or module-style
> appended signatures.
>
> 'digest_cache_appraise' also adds 'digest_cache=content' to the other
> appraise rules, if they have a compatible IMA hook.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
> .../admin-guide/kernel-parameters.txt | 15 ++++++-
> security/integrity/ima/Kconfig | 10 +++++
> security/integrity/ima/ima_policy.c | 45 +++++++++++++++++++
> 3 files changed, 69 insertions(+), 1 deletion(-)
[...]
> @@ -971,6 +1006,16 @@ void __init ima_init_policy(void)
> {
> int build_appraise_entries, arch_entries;
>
> + /*
> + * We need to load digest cache rules at the beginning, to avoid dont_
> + * rules causing ours to not be reached.
> + */
"lockdown" trusts IMA to measure and appraise kernel modules, if the rule
exists. Placing the digest_cache first breaks this trust.
From a trusted and secure boot perspective, the architecture specific policy
rules should not be ignored. Putting the digest_cache before any other rules
will limit others from being able to use digest_cache.
Instead of putting the digest_cache_{measure,appraise} built-in policies first,
skip loading the dont_measure_rules.
Mimi
> + if (ima_digest_cache_measure)
> + add_rules(&measure_digest_cache_rule, 1, IMA_DEFAULT_POLICY);
> +
> + if (ima_digest_cache_appraise)
> + add_rules(&appraise_digest_cache_rule, 1, IMA_DEFAULT_POLICY);
> +
> /* if !ima_policy, we load NO default rules */
> if (ima_policy)
> add_rules(dont_measure_rules, ARRAY_SIZE(dont_measure_rules),
next prev parent reply other threads:[~2024-03-07 20:17 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-14 14:35 [RFC][PATCH 0/8] ima: Integrate with digest_cache LSM Roberto Sassu
2024-02-14 14:35 ` [RFC][PATCH 1/8] ima: Introduce hook DIGEST_LIST_CHECK Roberto Sassu
2024-02-14 14:35 ` [RFC][PATCH 2/8] ima: Nest iint mutex for DIGEST_LIST_CHECK hook Roberto Sassu
2024-03-07 19:42 ` Mimi Zohar
2024-03-08 8:00 ` Roberto Sassu
2024-02-14 14:35 ` [RFC][PATCH 3/8] ima: Add digest_cache policy keyword Roberto Sassu
2024-03-07 19:43 ` Mimi Zohar
2024-03-08 9:05 ` Roberto Sassu
2024-03-08 13:41 ` Mimi Zohar
2024-02-14 14:35 ` [RFC][PATCH 4/8] ima: Add digest_cache_measure and digest_cache_appraise boot-time policies Roberto Sassu
2024-03-07 20:17 ` Mimi Zohar [this message]
2024-03-08 10:36 ` Roberto Sassu
2024-03-08 14:23 ` Mimi Zohar
2024-03-11 13:01 ` Mimi Zohar
2024-02-14 14:35 ` [RFC][PATCH 5/8] ima: Record IMA verification result of digest lists in digest cache Roberto Sassu
2024-03-11 14:00 ` Mimi Zohar
2024-02-14 14:35 ` [RFC][PATCH 6/8] ima: Use digest cache for measurement Roberto Sassu
2024-03-08 16:08 ` Mimi Zohar
2024-03-08 16:27 ` Roberto Sassu
2024-02-14 14:35 ` [RFC][PATCH 7/8] ima: Use digest cache for appraisal Roberto Sassu
2024-02-14 14:35 ` [RFC][PATCH 8/8] ima: Detect if digest cache changed since last measurement/appraisal Roberto Sassu
2024-03-08 17:35 ` Mimi Zohar
2024-03-11 9:11 ` Roberto Sassu
2024-03-11 12:19 ` Mimi Zohar
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