linux-kernel - Re: [PATCH v3] ima: Access decompressed kernel module to verify appended signature

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Message-ID: <fc1d67e411ef53460517db4c03bdcf1b9d9f8a8f.camel@linux.ibm.com>
Date: Wed, 19 Nov 2025 08:29:22 -0500
From: Mimi Zohar <zohar@...ux.ibm.com>
To: Coiby Xu <coxu@...hat.com>, linux-integrity@...r.kernel.org
Cc: Karel Srot <ksrot@...hat.com>, Paul Moore <paul@...l-moore.com>,
        Luis
 Chamberlain <mcgrof@...nel.org>,
        Petr Pavlu <petr.pavlu@...e.com>, Daniel
 Gomez <da.gomez@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Roberto Sassu <roberto.sassu@...wei.com>,
        Dmitry Kasatkin	
 <dmitry.kasatkin@...il.com>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
        Fan
 Wu <wufan@...nel.org>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        open list	
 <linux-kernel@...r.kernel.org>,
        "open list:MODULE SUPPORT"	
 <linux-modules@...r.kernel.org>,
        "open list:SECURITY SUBSYSTEM"	
 <linux-security-module@...r.kernel.org>,
        "open list:SELINUX SECURITY
 MODULE"	 <selinux@...r.kernel.org>
Subject: Re: [PATCH v3] ima: Access decompressed kernel module to verify
 appended signature

Hi Coiby,

On Wed, 2025-11-19 at 11:47 +0800, Coiby Xu wrote:
> Currently, when in-kernel module decompression (CONFIG_MODULE_DECOMPRESS)
> is enabled, IMA has no way to verify the appended module signature as it
> can't decompress the module.
> 
> Define a new kernel_read_file_id enumerate READING_MODULE_COMPRESSED so
> IMA can know only to collect original module data hash on
> READING_MODULE_COMPRESSED and defer appraising/measuring it until on
> READING_MODULE when the module has been decompressed.

This paragraph is a bit awkward.  Perhaps something like:

-> so IMA can calculate the compressed kernel module data hash and defer
measuring/appraising ...

> 
> Before enabling in-kernel module decompression, a kernel module in
> initramfs can still be loaded with ima_policy=secure_boot. So adjust the
> kernel module rule in secure_boot policy to allow either an IMA
> signature OR an appended signature i.e. to use
> "appraise func=MODULE_CHECK appraise_type=imasig|modsig".
> 
> Reported-by: Karel Srot <ksrot@...hat.com>
> Suggested-by: Mimi Zohar <zohar@...ux.ibm.com>
> Suggested-by: Paul Moore <paul@...l-moore.com>
> Signed-off-by: Coiby Xu <coxu@...hat.com>

Thanks, Coiby!

The patch applies cleanly to linus' tree, but needs to be applied to next-
integrity.  Please re-base.

-- 

thanks,

Mimi