[PATCH v2 6/6] KEYS: trusted: Introduce support for NXP CAAM-based trusted keys

Ahmad Fatoum a.fatoum at pengutronix.de
Fri Jul 2 12:33:52 UTC 2021

On 02.07.21 12:53, Richard Weinberger wrote:
> Ahmad,
> ----- Ursprüngliche Mail -----
>> Von: "Ahmad Fatoum" <a.fatoum at pengutronix.de>
>>> I'm still think that hard coding the key modifier is not wise.
>>> As I said[0], there are folks out there that want to provide their own modifier,
>>> so it is not only about being binary compatible with other CAAM blob patches in
>>> the wild.
>> I don't think the characterization as a salt is accurate. AFAIU it's more
>> of a namespace, so blobs being loaded are "type-checked" against the modifier.
> Well, the CAAM programmer's reference manual states that the blob key is a 128 bit modifier
> and has two purposes:
> 1. It can be used as tag to provide separation between blobs to detect accidental replacement of blobs.
> 2. But it can also be treated as secret to provide additional protection. Because the blob encryption
> key derivation includes the key modifier.
> While you have case 1 in mind, I care about case 2. :-)

Ah, using the key modifier as a passphrase didn't occur to me.

>>> I'll happily implement that feature after your patches got merged but IMHO we
>>> should first agree on an interface.
>>> How about allowing another optional parameter to Opt_new and Opt_load
>> Sound good to me. pcrlock for TPM trusted keys has the same interface.
>> I'd prefer the new option to accept strings, not hex though.
> Both is possible. If the string starts with "0x" it needs to be decoded to a
> 128 bit key. Otherwise it has to be a up to 16 byte string.

Fine by me. Looking forward to your patches. :-)


> Thanks,
> //richard

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