[PATCH v3 1/3] crypto: mxs-dcp: Add support for hardware provided keys

David Gstir david at sigma-star.at
Wed Sep 27 16:25:24 AEST 2023


> On 25.09.2023, at 17:22, Jarkko Sakkinen <jarkko at kernel.org> wrote:
> On Mon Sep 18, 2023 at 5:18 PM EEST, David Gstir wrote:
>> DCP is capable to performing AES with hardware-bound keys.
>> These keys are not stored in main memory and are therefore not directly
>> accessible by the operating system.
>> So instead of feeding the key into DCP, we need to place a
>> reference to such a key before initiating the crypto operation.
>> Keys are referenced by a one byte identifiers.
> Not sure what the action of feeding key into DCP even means if such
> action does not exists.
> What you probably would want to describe here is how keys get created
> and how they are referenced by the kernel.
> For the "use" part please try to avoid academic paper style long
> expression starting with "we" pronomine.
> So the above paragraph would normalize into "The keys inside DCP
> are referenced by one byte identifier". Here of course would be
> for the context nice to know what is this set of DCP keys. E.g.
> are total 256 keys or some subset?
> When using too much prose there can be surprsingly little digestable
> information, thus this nitpicking.

Thanks for reviewing that in detail! I’ll rephrase the commit
messages on all patches to get rid of the academic paper style.

>> DCP supports 6 different keys: 4 slots in the secure memory area,
>> a one time programmable key which can be burnt via on-chip fuses
>> and an unique device key.
>> Using these keys is restricted to in-kernel users that use them as building
>> block for other crypto tools such as trusted keys. Allowing userspace
>> (e.g. via AF_ALG) to use these keys to crypt or decrypt data is a security
>> risk, because there is no access control mechanism.
> Unless this patch has anything else than trusted keys this should not
> be an open-ended sentence. You want to say roughly that DCP hardware
> keys are implemented for the sake to implement trusted keys support,
> and exactly and only that.
> This description also lacks actions taken by the code changes below,
> which is really the beef of any commit description.

You’re right. I’ll add that.

- David

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