Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v5 1/4] IMA: Add func to measure LSM state and policy
To:     Casey Schaufler <casey@schaufler-ca.com>,
        Tyler Hicks <tyhicks@linux.microsoft.com>
Cc:     zohar@linux.ibm.com, stephen.smalley.work@gmail.com,
        sashal@kernel.org, jmorris@namei.org,
        linux-integrity@vger.kernel.org, selinux@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200730034724.3298-1-nramas@linux.microsoft.com>
 <20200730034724.3298-2-nramas@linux.microsoft.com>
 <20200730150228.GV4181@sequoia>
 <b4428195-7a68-365d-a792-2855609c2221@schaufler-ca.com>
From:   Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Message-ID: <1819121c-bc76-2414-a8e1-8bfd1c014d6b@linux.microsoft.com>
Date:   Thu, 30 Jul 2020 09:33:03 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <b4428195-7a68-365d-a792-2855609c2221@schaufler-ca.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 7/30/20 9:19 AM, Casey Schaufler wrote:

>>> Critical data structures of security modules need to be measured to
>>> enable an attestation service to verify if the configuration and
>>> policies for the security modules have been setup correctly and
>>> that they haven't been tampered with at runtime. A new IMA policy is
>>> required for handling this measurement.
>>>
>>> Define two new IMA policy func namely LSM_STATE and LSM_POLICY to
>>> measure the state and the policy provided by the security modules.
> 
> If, as you suggest below, this is SELinux specific,
> these should be SELINUX_STATE and SELINUX_POLICY.
> It makes me very uncomfortable when I see LSM used
> in cases where SELinux is required. The LSM is supposed
> to be an agnostic interface, so if you need to throw
> 
> 	if (IS_ENABLED(CONFIG_SECURITY_SELINUX) &&
> 
> into the IMA code you're clearly not thinking in terms
> of the LSM layer. I have no problem with seeing SELinux
> oriented and/or specific code in IMA if that's what you want.
> Just don't call it LSM.

The hook defined in IMA is not SELinux specific - it is generic enough 
to be used by any security module to measure their STATE and POLICY.

I have implemented the measurement for SELinux to illustrate the usage.

Tyler's suggestion was to allow this IMA policy only when component(s) 
that are using it are also enabled.

  -lakshmi