[EXT] Re: [RFC PATCH HBK: 0/8] HW BOUND KEY as TRUSTED KEY

[Pankaj Gupta]

> -----Original Message-----
> From: Michael Walle <michael at walle.cc>
> Sent: Tuesday, September 6, 2022 12:43 PM
> To: Pankaj Gupta <pankaj.gupta at nxp.com>
> Cc: jarkko at kernel.org; a.fatoum at pengutronix.de; Jason at zx2c4.com;
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> Subject: [EXT] Re: [RFC PATCH HBK: 0/8] HW BOUND KEY as TRUSTED KEY
> 
> Caution: EXT Email
> 
> Hi,
> 
> Am 2022-09-06 08:51, schrieb Pankaj Gupta:
> > Hardware Bound key(HBK), is never acessible as plain key outside of
> > the hardware boundary. Thus, it is un-usable, even if somehow fetched
> > from kernel memory. It ensures run-time security.
> >
> > This patchset adds generic support for classing the Hardware Bound
> > Key, based on:
> >
> > - Newly added flag-'is_hbk', added to the tfm.
> >
> >   Consumer of the kernel crypto api, after allocating
> >   the transformation, sets this flag based on the basis
> >   of the type of key consumer has.
> >
> > - This helps to influence the core processing logic
> >   for the encapsulated algorithm.
> >
> > - This flag is set by the consumer after allocating
> >   the tfm and before calling the function crypto_xxx_setkey().
> >
> > First implementation is based on CAAM.
> >
> > NXP built CAAM IP is the Cryptographic Acceleration and Assurance
> > Module.
> > This is contain by the i.MX and QorIQ SoCs by NXP.
> >
> > CAAM is a suitable backend (source) for kernel trusted keys.
> > This backend source can be used for run-time security as well by
> > generating the hardware bound key.
> >
> > Along with plain key, the CAAM generates black key. A black key is an
> > encrypted key, which can only be decrypted inside CAAM. Hence, CAAM's
> > black key can only be used by CAAM. Thus it is declared as a hardware
> > bound key.
> 
> What is the difference to the current trusted keys with CAAM?
> When I tested the patch series back then, I wasn't able to import a sealed
> key on another board with the same SoC.
> 

Currently, keys that are part of trusted key-ring, contains plain key.

With this patch-set, these key will become Hw Bound Key, which is not a plain key anymore.
After this patch-set, if somehow the HB-key is retrieved from the keyring, the retrieved key  would be un-usable without hw.
 

> -michael