linux-kernel - Re: [PATCH v1 0/3] KEYS: trusted: Introduce support for NXP CAAM-based trusted keys

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Message-ID: <a07e5544-1e62-a8da-485e-6fcafd16bab9@pengutronix.de>
Date:   Tue, 23 Mar 2021 17:37:17 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Horia Geantă <horia.geanta@....com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        James Bottomley <jejb@...ux.ibm.com>
Cc:     "kernel@...gutronix.de" <kernel@...gutronix.de>,
        David Howells <dhowells@...hat.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        Udit Agarwal <udit.agarwal@....com>,
        Jan Luebbe <j.luebbe@...gutronix.de>,
        David Gstir <david@...ma-star.at>,
        Franck Lenormand <franck.lenormand@....com>,
        Sumit Garg <sumit.garg@...aro.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v1 0/3] KEYS: trusted: Introduce support for NXP
 CAAM-based trusted keys

Hello Horia,

On 21.03.21 21:01, Horia Geantă wrote:
>>  - [RFC] drivers: crypto: caam: key: Add caam_tk key type
>>    Franck added[3] a new "caam_tk" key type based on Udit's work. The key
>>    material stays within the kernel only, but can optionally be user-set
>>    instead of coming from RNG. James voiced the opinion that there should
>>    be just one user-facing generic wrap/unwrap key type with multiple
>>    possible handlers. David suggested trusted keys.
>>
> The whole point was to use caam "black blobs", with the main advantage of
> keys being kept encrypted in memory after "unsealing" the blobs.
> (Keys in blobs are encrypted with a persistent BKEK - blob KEK, derived from
> fuse-based OTPMK. OTOH black keys are keys encrypted with an ephemeral, random
> KEK that is stored in an internal caam register. When a black blob is unsealed,
> the key is practically rekeyed, the random key replacing the BKEK; key is never
> exposed in plaintext, rekeying happens in caam).
> 
> Current implementation uses "red blobs", which means keys are left unprotected
> in memory after blobs are unsealed.

Oh. I will reread the series when sending the v2 cover letter. Thanks for spotting.

(Sorry for the noise, missed this question first time)

>>  - Introduce TEE based Trusted Keys support
>>    Sumit reworked[4] trusted keys to support multiple possible backends with
>>    one chosen at boot time and added a new TEE backend along with TPM.
>>    This now sits in Jarkko's master branch to be sent out for v5.13
>>
>> This patch series builds on top of Sumit's rework to have the CAAM as yet another
>> trusted key backend.
>>
> Shouldn't the description under TRUSTED_KEYS (in security/keys/Kconfig)
> be updated to reflect the availability of multiple backends?
> 
> Thanks,
> Horia
> 

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