linux-kernel - Re: [PATCH v10 0/8] IMA: support for measuring kernel integrity critical data

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Message-ID: <e3deb1a0-a624-f85f-e2d2-3206fa609b64@linux.microsoft.com>
Date:   Fri, 15 Jan 2021 09:26:58 -0800
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, stephen.smalley.work@...il.com,
        casey@...aufler-ca.com, agk@...hat.com, snitzer@...hat.com,
        gmazyland@...il.com, paul@...l-moore.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: Re: [PATCH v10 0/8] IMA: support for measuring kernel integrity
 critical data



On 2021-01-15 4:54 a.m., Mimi Zohar wrote:
> On Thu, 2021-01-07 at 20:07 -0800, Tushar Sugandhi wrote:
>> IMA measures files and buffer data such as keys, command-line arguments
>> passed to the kernel on kexec system call, etc.  While these measurements
>> are necessary for monitoring and validating the integrity of the system,
>> they are not sufficient.  Various data structures, policies, and states
>> stored in kernel memory also impact the integrity of the system.
>> Several kernel subsystems contain such integrity critical data -
>> e.g.  LSMs like SELinux, AppArmor etc.  or device-mapper targets like
>> dm-crypt, dm-verity, dm-integrity etc.  These kernel subsystems help
>> protect the integrity of a system.  Their integrity critical data is not
>> expected to change frequently during run-time.  Some of these structures
>> cannot be defined as __ro_after_init, because they are initialized later.
>>
>> For a given system, various external services/infrastructure tools
>> (including the attestation service) interact with it - both during the
>> setup and during rest of the system run-time.  They share sensitive data
>> and/or execute critical workload on that system.  The external services
>> may want to verify the current run-time state of the relevant kernel
>> subsystems before fully trusting the system with business critical
>> data/workload.  For instance, verifying that SELinux is in "enforce" mode
>> along with the expected policy, disks are encrypted with a certain
>> configuration, secure boot is enabled etc.
>>
>> This series provides the necessary IMA functionality for kernel
>> subsystems to ensure their configuration can be measured:
>>    - by kernel subsystems themselves,
>>    - in a tamper resistant way,
>>    - and re-measured - triggered on state/configuration change.
>>
>> This patch set:
>>    - defines a new IMA hook ima_measure_critical_data() to measure
>>      integrity critical data,
>>    - limits the critical data being measured based on a label,
>>    - defines a builtin critical data measurement policy,
>>    - and includes an SELinux consumer of the new IMA critical data hook.
> 
> Thanks Tushar, Lakshmi.  This patch set is queued in the next-
> integrity-testing branch.
> 
> Mimi
> 
Hello Mimi, Paul, Stephen, Tyler,
Thanks a lot for reviewing this series and providing all the valuable 
feedback over the last few months.

We really really appreciate it.

Thanks,
Tushar