Re: [PATCH 0/4] KEYS: trusted: Introduce support for NXP CAAM-based trusted keys

[Tim Harvey <tharvey@gateworks.com>]

On Fri, Aug 20, 2021 at 9:20 AM Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
>
> Hello Tim,
>
> On 20.08.21 17:39, Tim Harvey wrote:
> > On Wed, Jul 21, 2021 at 9:49 AM Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
> >>
> >> Series applies on top of
> >> https://lore.kernel.org/linux-integrity/20210721160258.7024-1-a.fatoum@pengutronix.de/T/#u
> >>
> >> v2 -> v3:
> >>  - Split off first Kconfig preparation patch. It fixes a regression,
> >>    so sent that out, so it can be applied separately (Sumit)
> >>  - Split off second key import patch. I'll send that out separately
> >>    as it's a development aid and not required within the CAAM series
> >>  - add MAINTAINERS entry
> >>
> >> v1 -> v2:
> >>  - Added new commit to make trusted key Kconfig option independent
> >>    of TPM and added new Kconfig file for trusted keys
> >>  - Add new commit for importing existing key material
> >>  - Allow users to force use of kernel RNG (Jarkko)
> >>  - Enforce maximum keymod size (Horia)
> >>  - Use append_seq_(in|out)_ptr_intlen instead of append_seq_(in|out)_ptr
> >>    (Horia)
> >>  - Make blobifier handle private to CAAM glue code file (Horia)
> >>  - Extend trusted keys documentation for CAAM
> >>  - Rebased and updated original cover letter:
> >>
> >> The Cryptographic Acceleration and Assurance Module (CAAM) is an IP core
> >> built into many newer i.MX and QorIQ SoCs by NXP.
> >>
> >> Its blob mechanism can AES encrypt/decrypt user data using a unique
> >> never-disclosed device-specific key.
> >>
> >> There has been multiple discussions on how to represent this within the kernel:
> >>
> >> The Cryptographic Acceleration and Assurance Module (CAAM) is an IP core
> >> built into many newer i.MX and QorIQ SoCs by NXP.
> >>
> >> Its blob mechanism can AES encrypt/decrypt user data using a unique
> >> never-disclosed device-specific key. There has been multiple
> >> discussions on how to represent this within the kernel:
> >>
> >>  - [RFC] crypto: caam - add red blobifier
> >>    Steffen implemented[1] a PoC sysfs driver to start a discussion on how to
> >>    best integrate the blob mechanism.
> >>    Mimi suggested that it could be used to implement trusted keys.
> >>    Trusted keys back then were a TPM-only feature.
> >>
> >>  - security/keys/secure_key: Adds the secure key support based on CAAM.
> >>    Udit added[2] a new "secure" key type with the CAAM as backend. The key
> >>    material stays within the kernel only.
> >>    Mimi and James agreed that this needs a generic interface, not specific
> >>    to CAAM. Mimi suggested trusted keys. Jan noted that this could serve as
> >>    basis for TEE-backed keys.
> >>
> >>  - [RFC] drivers: crypto: caam: key: Add caam_tk key type
> >>    Franck added[3] a new "caam_tk" key type based on Udit's work. This time
> >>    it uses CAAM "black blobs" instead of "red blobs", so key material stays
> >>    within the CAAM and isn't exposed to kernel in plaintext.
> >>    James voiced the opinion that there should be just one user-facing generic
> >>    wrap/unwrap key type with multiple possible handlers.
> >>    David suggested trusted keys.
> >>
> >>  - Introduce TEE based Trusted Keys support
> >>    Sumit reworked[4] trusted keys to support multiple possible backends with
> >>    one chosen at boot time and added a new TEE backend along with TPM.
> >>    This now sits in Jarkko's master branch to be sent out for v5.13
> >>
> >> This patch series builds on top of Sumit's rework to have the CAAM as yet another
> >> trusted key backend.
> >>
> >> The CAAM bits are based on Steffen's initial patch from 2015. His work had been
> >> used in the field for some years now, so I preferred not to deviate too much from it.
> >>
> >> This series has been tested with dmcrypt[5] on an i.MX6DL.
> >>
> >> Looking forward to your feedback.
> >>
> >> Cheers,
> >> Ahmad
> >>
> >>  [1]: https://lore.kernel.org/linux-crypto/1447082306-19946-2-git-send-email-s.trumtrar@pengutronix.de/
> >>  [2]: https://lore.kernel.org/linux-integrity/20180723111432.26830-1-udit.agarwal@nxp.com/
> >>  [3]: https://lore.kernel.org/lkml/1551456599-10603-2-git-send-email-franck.lenormand@nxp.com/
> >>  [4]: https://lore.kernel.org/lkml/1604419306-26105-1-git-send-email-sumit.garg@linaro.org/
> >>  [5]: https://lore.kernel.org/linux-integrity/20210122084321.24012-2-a.fatoum@pengutronix.de/
> >>
> >> ---
> >> To: Jarkko Sakkinen <jarkko@kernel.org>
> >> To: "Horia Geantă" <horia.geanta@nxp.com>
> >> To: Mimi Zohar <zohar@linux.ibm.com>
> >> To: Aymen Sghaier <aymen.sghaier@nxp.com>
> >> To: Herbert Xu <herbert@gondor.apana.org.au>
> >> To: "David S. Miller" <davem@davemloft.net>
> >> To: James Bottomley <jejb@linux.ibm.com>
> >> Cc: David Howells <dhowells@redhat.com>
> >> Cc: James Morris <jmorris@namei.org>
> >> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> >> Cc: Steffen Trumtrar <s.trumtrar@pengutronix.de>
> >> Cc: Udit Agarwal <udit.agarwal@nxp.com>
> >> Cc: Jan Luebbe <j.luebbe@pengutronix.de>
> >> Cc: David Gstir <david@sigma-star.at>
> >> Cc: Eric Biggers <ebiggers@kernel.org>
> >> Cc: Richard Weinberger <richard@nod.at>
> >> Cc: Franck LENORMAND <franck.lenormand@nxp.com>
> >> Cc: Sumit Garg <sumit.garg@linaro.org>
> >> Cc: linux-integrity@vger.kernel.org
> >> Cc: keyrings@vger.kernel.org
> >> Cc: linux-crypto@vger.kernel.org
> >> Cc: linux-kernel@vger.kernel.org
> >> Cc: linux-security-module@vger.kernel.org
> >>
> >> Ahmad Fatoum (4):
> >>   KEYS: trusted: allow users to use kernel RNG for key material
> >>   KEYS: trusted: allow trust sources to use kernel RNG for key material
> >>   crypto: caam - add in-kernel interface for blob generator
> >>   KEYS: trusted: Introduce support for NXP CAAM-based trusted keys
> >>
> >>  Documentation/admin-guide/kernel-parameters.txt   |   8 +-
> >>  Documentation/security/keys/trusted-encrypted.rst |  60 +++-
> >>  MAINTAINERS                                       |   9 +-
> >>  drivers/crypto/caam/Kconfig                       |   3 +-
> >>  drivers/crypto/caam/Makefile                      |   1 +-
> >>  drivers/crypto/caam/blob_gen.c                    | 230 +++++++++++++++-
> >>  include/keys/trusted-type.h                       |   2 +-
> >>  include/keys/trusted_caam.h                       |  11 +-
> >>  include/soc/fsl/caam-blob.h                       |  56 ++++-
> >>  security/keys/trusted-keys/Kconfig                |  11 +-
> >>  security/keys/trusted-keys/Makefile               |   2 +-
> >>  security/keys/trusted-keys/trusted_caam.c         |  74 +++++-
> >>  security/keys/trusted-keys/trusted_core.c         |  23 +-
> >>  13 files changed, 477 insertions(+), 13 deletions(-)
> >>  create mode 100644 drivers/crypto/caam/blob_gen.c
> >>  create mode 100644 include/keys/trusted_caam.h
> >>  create mode 100644 include/soc/fsl/caam-blob.h
> >>  create mode 100644 security/keys/trusted-keys/trusted_caam.c
> >>
> >> base-commit: 97408d81ed533b953326c580ff2c3f1948b3fcee
> >> --
> >> git-series 0.9.1
> >
> > Ahmad,
> >
> > Thanks for your work!
> >
> > I've been asked to integrate the capability of using CAAM to
> > blob/deblob data to an older 5.4 kernel such as NXP's downstream
> > vendor kernel does [1] and I'm trying to understand how your series
> > works. I'm not at all familiar with the Linux Key Management API's or
> > trusted keys. Can you provide an example of how this can be used for
> > such a thing?
>
> Here's an example with dm-crypt:
>
>   https://lore.kernel.org/linux-integrity/5d44e50e-4309-830b-79f6-f5d888b1ef69@pengutronix.de/
>
> dm-crypt is a bit special at the moment, because it has direct support for
> trusted keys. For interfacing with other parts of the kernel like ecryptfs
> or EVM, you have to create encrypted keys rooted to the trusted keys and use
> those. The kernel documentation has an example:
>
>   https://www.kernel.org/doc/html/v5.13/security/keys/trusted-encrypted.html
>
> If you backport this series, you can include the typo fix spotted by David.
>
> I'll send out a revised series, but given that a regression fix I want to
> rebase on hasn't been picked up for 3 weeks now, I am not in a hurry.
>

Ahmad,

Thanks for the reference.

I'm still trying to understand the keyctl integration with caam. For
the 'data' param to keyctl you are using tings like 'new <len>' and
'load <data>'. Where are these 'commands' identified?

I may still be missing something. I'm using 4.14-rc6 with your series
and seeing the following:
# cat /proc/cmdline
trusted.source=caam
# keyctl add trusted mykey 'new 32' @s)# create new trusted key named
'mykey' of 32 bytes in the session keyring
480104283
# keyctl print 480104283 # dump the key
keyctl_read_alloc: Unknown error 126
^^^ not clear what this is

Best regards,

Tim