linux-kernel - Re: [PATCH] integrity: Allow ima_appraise bootparam to be set when SB is enabled

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Message-ID: <48467663-5CD6-49C5-B43F-9FA0887D0575@oracle.com>
Date:   Wed, 27 Apr 2022 16:12:41 +0000
From:   Eric Snowberg <eric.snowberg@...cle.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>
CC:     "dmitry.kasatkin@...il.com" <dmitry.kasatkin@...il.com>,
        "jmorris@...ei.org" <jmorris@...ei.org>,
        "serge@...lyn.com" <serge@...lyn.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] integrity: Allow ima_appraise bootparam to be set when SB
 is enabled



> On Apr 26, 2022, at 12:18 PM, Mimi Zohar <zohar@...ux.ibm.com> wrote:
> 
> On Mon, 2022-04-25 at 18:21 -0400, Eric Snowberg wrote:
>> The IMA_APPRAISE_BOOTPARM config allows enabling different "ima_appraise="
>> modes (log, fix, enforce) to be configured at boot time.  When booting
>> with Secure Boot enabled, all modes are ignored except enforce.  To use
>> log or fix, Secure Boot must be disabled.
>> 
>> With a policy such as:
>> 
>> appraise func=BPRM_CHECK appraise_type=imasig
>> 
>> A user may just want to audit signature validation. Not all users
>> are interested in full enforcement and find the audit log appropriate
>> for their use case.
>> 
>> Add a new IMA_APPRAISE_SB_BOOTPARAM config allowing "ima_appraise="
>> to work when Secure Boot is enabled.
>> 
>> Signed-off-by: Eric Snowberg <eric.snowberg@...cle.com>
> 
> Since the IMA architecture specific policy rules were first
> upstreamed, either enabling IMA_APPRAISE_BOOTPARAM or IMA_ARCH_POLICY
> was permitted, but not both.  

I don’t see code preventing this and just created a config with both of them
enabled.  Is this an assumption everyone is supposed to understand?

> This Kconfig negates the assumptions on
> which the CONFIG_IMA_ARCH_POLICY and the ima_appraise_signature() are
> based without any indication of the ramifications.   This impacts the
> kexec file syscall lockdown LSM assumptions as well.

I will fix this in the next round

> A fuller, more complete explanation for needing "log" mode when secure
> boot is enabled is required.

and add a more thorough explanation.  Thanks.