linux-kernel - Re: [PATCH v4 4/5] crypto: caam - add in-kernel interface for blob generator

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Date:   Mon, 13 Dec 2021 11:34:39 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Horia Geantă <horia.geanta@....com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>, kernel@...gutronix.de,
        David Gstir <david@...ma-star.at>,
        Tim Harvey <tharvey@...eworks.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jmorris@...ei.org>,
        Eric Biggers <ebiggers@...nel.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Udit Agarwal <udit.agarwal@....com>,
        Jan Luebbe <j.luebbe@...gutronix.de>,
        Richard Weinberger <richard@....at>,
        Franck LENORMAND <franck.lenormand@....com>,
        Sumit Garg <sumit.garg@...aro.org>,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH v4 4/5] crypto: caam - add in-kernel interface for blob
 generator

Hello Jarkko,

On 05.12.21 01:18, Jarkko Sakkinen wrote:
> On Mon, Oct 11, 2021 at 12:02:37PM +0200, Ahmad Fatoum wrote:
>> The CAAM can be used to protect user-defined data across system reboot:
>>
>>   - When the system is fused and boots into secure state, the master
>>     key is a unique never-disclosed device-specific key
>>   - random key is encrypted by key derived from master key
>>   - data is encrypted using the random key
>>   - encrypted data and its encrypted random key are stored alongside
>>   - This blob can now be safely stored in non-volatile memory
>>
>> On next power-on:
>>   - blob is loaded into CAAM
>>   - CAAM writes decrypted data either into memory or key register
>>
>> Add functions to realize encrypting and decrypting into memory alongside
>> the CAAM driver.
>>
>> They will be used in a later commit as a source for the trusted key
>> seal/unseal mechanism.
>>
>> Reviewed-by: David Gstir <david@...ma-star.at>
>> Tested-By: Tim Harvey <tharvey@...eworks.com>
>> Signed-off-by: Steffen Trumtrar <s.trumtrar@...gutronix.de>
>> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
> 
> What is CAAM? This is missing.

That's Crypto Accelerator on NXP SoCs. There is a description in the cover
letter and in the follow-up patch wiring this into the new trusted key
source. I didn't elaborate on this here as this patch touches
drivers/crypto/caam and I assumed familiarity.

For v5, I can add some extra info:

"The NXP Cryptographic Acceleration and Assurance Module (CAAM)
 can be used to protect user-defined data across system reboot..."

Sounds good? Does the last patch in the series look ok to you?

Cheers,
Ahmad

> 
> /Jarkko
> 


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