Re: [PATCH v2 07/10] qcom_scm: scm call for create, prepare and import keys

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Jul 21, 2023 at 08:40:32PM -0700, Bjorn Andersson wrote:
> On Wed, Jul 19, 2023 at 10:04:21AM -0700, Gaurav Kashyap wrote:
> > Storage encryption has two IOCTLs for creating, importing
> > and preparing keys for encryption. For wrapped keys, these
> > IOCTLs need to interface with the secure environment, which
> > require these SCM calls.
> > 
> > generate_key: This is used to generate and return a longterm
> >               wrapped key. Trustzone achieves this by generating
> > 	      a key and then wrapping it using hwkm, returning
> > 	      a wrapped keyblob.
> > import_key:   The functionality is similar to generate, but here,
> >               a raw key is imported into hwkm and a longterm wrapped
> > 	      keyblob is returned.
> > prepare_key:  The longterm wrapped key from import or generate
> >               is made further secure by rewrapping it with a per-boot
> > 	      ephemeral wrapped key before installing it to the linux
> > 	      kernel for programming to ICE.
> > 
> > Signed-off-by: Gaurav Kashyap <quic_gaurkash@quicinc.com>
> > ---
> >  drivers/firmware/qcom_scm.c            | 222 +++++++++++++++++++++++++
> >  drivers/firmware/qcom_scm.h            |   3 +
> >  include/linux/firmware/qcom/qcom_scm.h |  10 ++
> >  3 files changed, 235 insertions(+)
> > 
> > diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> > index 51062d5c7f7b..44dd1857747b 100644
> > --- a/drivers/firmware/qcom_scm.c
> > +++ b/drivers/firmware/qcom_scm.c
> > @@ -1210,6 +1210,228 @@ int qcom_scm_derive_sw_secret(const u8 *wrapped_key, u32 wrapped_key_size,
> >  }
> >  EXPORT_SYMBOL(qcom_scm_derive_sw_secret);
> >  
> > +/**
> > + * qcom_scm_generate_ice_key() - Generate a wrapped key for encryption.
> > + * @longterm_wrapped_key: the wrapped key returned after key generation
> 
> "longterm" was long enough that you didn't feel it made sense in the
> description ;)
> 
> Jokes aside, please follow the convention described in:
> https://www.kernel.org/doc/html/v4.10/process/coding-style.html#naming
> 
> "key" or "wrapped_key" sounds sufficient to me.

The naming I use in my most recent patchset that adds support for
hardware-wrapped inline encryption keys to the block layer and fscrypt
(https://lore.kernel.org/linux-block/20221216203636.81491-1-ebiggers@kernel.org/),
which this patchset is based on, is 'lt_key' for a longterm wrapped key and
'eph_key' for an ephemerally-wrapped key.

> > +int qcom_scm_prepare_ice_key(const u8 *longterm_wrapped_key,
> > +			     u32 longterm_wrapped_key_size,
> > +			     u8 *ephemeral_wrapped_key,
> > +			     u32 ephemeral_wrapped_key_size)
> 
> wrapped, wrapped_size, ephemeral, ephemeral_size perhaps?

lt_key, lt_key_size, eph_key, eph_key_size.

- Eric