linux-kernel - Re: [PATCH v4 00/12] Enroll kernel keys thru MOK

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Date:   Fri, 27 Aug 2021 16:44:53 -0400
From:   Nayna <nayna@...ux.vnet.ibm.com>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        David Howells <dhowells@...hat.com>
Cc:     keyrings@...r.kernel.org,
        linux-integrity <linux-integrity@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>, keescook@...omium.org,
        gregkh@...uxfoundation.org, torvalds@...ux-foundation.org,
        scott.branden@...adcom.com, weiyongjun1@...wei.com,
        nayna@...ux.ibm.com, ebiggers@...gle.com, ardb@...nel.org,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        lszubowi@...hat.com, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org,
        linux-security-module@...r.kernel.org, pjones@...hat.com,
        "konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
        Patrick Uiterwijk <patrick@...terwijk.org>
Subject: Re: [PATCH v4 00/12] Enroll kernel keys thru MOK


On 8/25/21 6:27 PM, James Bottomley wrote:
> On Thu, 2021-08-26 at 01:21 +0300, Jarkko Sakkinen wrote:
>> On Tue, 2021-08-24 at 10:34 -0400, Mimi Zohar wrote:
>>>>>> Jarkko, I think the emphasis should not be on "machine" from
>>>>>> Machine Owner Key (MOK), but on "owner".  Whereas Nayna is
>>>>>> focusing more on the "_ca" aspect of the name.   Perhaps
>>>>>> consider naming it "system_owner_ca" or something along those
>>>>>> lines.
>>>>> What do you gain such overly long identifier? Makes no sense.
>>>>> What is "ca aspect of the name" anyway?
>>>> As I mentioned previously, the main usage of this new keyring is
>>>> that it should contain only CA keys which can be later used to
>>>> vouch for user keys loaded onto secondary or IMA keyring at
>>>> runtime. Having ca in the  name like .xxxx_ca, would make the
>>>> keyring name self-describing. Since you preferred .system, we can
>>>> call it .system_ca.
>>> Sounds good to me.  Jarkko?
>>>
>>> thanks,
>>>
>>> Mimi
>> I just wonder what you exactly gain with "_ca"?
> Remember, a CA cert is a self signed cert with the CA:TRUE basic
> constraint.  Pretty much no secure boot key satisfies this (secure boot
> chose deliberately NOT to use CA certificates, so they're all some type
> of intermediate or leaf), so the design seems to be only to pick out
> the CA certificates you put in the MOK keyring.  Adding the _ca suffix
> may deflect some of the "why aren't all my MOK certificates in the
> keyring" emails ...


My understanding is the .system_ca keyring should not be restricted only 
to self-signed CAs (Root CA). Any cert that can qualify as Root or 
Intermediate CA with Basic Constraints CA:TRUE should be allowed. In 
fact, the intermediate CA certificates closest to the leaf nodes would 
be best.

Thanks for bringing up that adding the _ca suffix may deflect some of 
the "why aren't all my MOK certificates in the keyring" emails.

Thanks & Regards,

     - Nayna