Re: [PATCH v5 4/5] crypto: caam - add in-kernel interface for blob generator

[Jarkko Sakkinen <jarkko@kernel.org>]

On Wed, 2022-02-23 at 17:20 +0100, Ahmad Fatoum wrote:
> On 23.02.22 16:41, Jarkko Sakkinen wrote:
> > On Tue, Feb 22, 2022 at 08:58:18PM +0100, Ahmad Fatoum wrote:
> > > The NXP Cryptographic Acceleration and Assurance Module (CAAM)
> > > can be used to protect user-defined data across system reboot:
> > > 
> > >   - When the system is fused and boots into secure state, the master
> > >     key is a unique never-disclosed device-specific key
> > >   - random key is encrypted by key derived from master key
> > >   - data is encrypted using the random key
> > >   - encrypted data and its encrypted random key are stored alongside
> > >   - This blob can now be safely stored in non-volatile memory
> > > 
> > > On next power-on:
> > >   - blob is loaded into CAAM
> > >   - CAAM writes decrypted data either into memory or key register
> > > 
> > > Add functions to realize encrypting and decrypting into memory alongside
> > > the CAAM driver.
> > > 
> > > They will be used in a later commit as a source for the trusted key
> > > seal/unseal mechanism.
> > > 
> > > Reviewed-by: David Gstir <david@sigma-star.at>
> > > Reviewed-by: Pankaj Gupta <pankaj.gupta@nxp.com>
> > > Tested-By: Tim Harvey <tharvey@gateworks.com>
> > > Tested-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
> > > Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
> > > Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> > > ---
> > > To: "Horia Geantă" <horia.geanta@nxp.com>
> > > To: Aymen Sghaier <aymen.sghaier@nxp.com>
> > > To: Herbert Xu <herbert@gondor.apana.org.au>
> > > To: "David S. Miller" <davem@davemloft.net>
> > > Cc: James Bottomley <jejb@linux.ibm.com>
> > > Cc: Jarkko Sakkinen <jarkko@kernel.org>
> > > Cc: Mimi Zohar <zohar@linux.ibm.com>
> > > Cc: David Howells <dhowells@redhat.com>
> > > Cc: James Morris <jmorris@namei.org>
> > > Cc: Eric Biggers <ebiggers@kernel.org>
> > > Cc: "Serge E. Hallyn" <serge@hallyn.com>
> > > Cc: Jan Luebbe <j.luebbe@pengutronix.de>
> > > Cc: David Gstir <david@sigma-star.at>
> > > Cc: Richard Weinberger <richard@nod.at>
> > > Cc: Franck LENORMAND <franck.lenormand@nxp.com>
> > > Cc: Sumit Garg <sumit.garg@linaro.org>
> > > Cc: Tim Harvey <tharvey@gateworks.com>
> > > Cc: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
> > > Cc: Pankaj Gupta <pankaj.gupta@nxp.com>
> > > 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
> > > ---
> > >  drivers/crypto/caam/Kconfig    |   3 +
> > >  drivers/crypto/caam/Makefile   |   1 +
> > >  drivers/crypto/caam/blob_gen.c | 230 +++++++++++++++++++++++++++++++++
> > >  include/soc/fsl/caam-blob.h    |  56 ++++++++
> > >  4 files changed, 290 insertions(+)
> > >  create mode 100644 drivers/crypto/caam/blob_gen.c
> > >  create mode 100644 include/soc/fsl/caam-blob.h
> > > 
> > > diff --git a/drivers/crypto/caam/Kconfig b/drivers/crypto/caam/Kconfig
> > > index 84ea7cba5ee5..ea9f8b1ae981 100644
> > > --- a/drivers/crypto/caam/Kconfig
> > > +++ b/drivers/crypto/caam/Kconfig
> > > @@ -151,6 +151,9 @@ config CRYPTO_DEV_FSL_CAAM_RNG_API
> > >           Selecting this will register the SEC4 hardware rng to
> > >           the hw_random API for supplying the kernel entropy pool.
> > >  
> > > +config CRYPTO_DEV_FSL_CAAM_BLOB_GEN
> > > +       bool
> > > +
> > >  endif # CRYPTO_DEV_FSL_CAAM_JR
> > >  
> > >  endif # CRYPTO_DEV_FSL_CAAM
> > > diff --git a/drivers/crypto/caam/Makefile b/drivers/crypto/caam/Makefile
> > > index 3570286eb9ce..25f7ae5a4642 100644
> > > --- a/drivers/crypto/caam/Makefile
> > > +++ b/drivers/crypto/caam/Makefile
> > > @@ -21,6 +21,7 @@ caam_jr-$(CONFIG_CRYPTO_DEV_FSL_CAAM_CRYPTO_API_QI) += caamalg_qi.o
> > >  caam_jr-$(CONFIG_CRYPTO_DEV_FSL_CAAM_AHASH_API) += caamhash.o
> > >  caam_jr-$(CONFIG_CRYPTO_DEV_FSL_CAAM_RNG_API) += caamrng.o
> > >  caam_jr-$(CONFIG_CRYPTO_DEV_FSL_CAAM_PKC_API) += caampkc.o pkc_desc.o
> > > +caam_jr-$(CONFIG_CRYPTO_DEV_FSL_CAAM_BLOB_GEN) += blob_gen.o
> > >  
> > >  caam-$(CONFIG_CRYPTO_DEV_FSL_CAAM_CRYPTO_API_QI) += qi.o
> > >  ifneq ($(CONFIG_CRYPTO_DEV_FSL_CAAM_CRYPTO_API_QI),)
> > > diff --git a/drivers/crypto/caam/blob_gen.c b/drivers/crypto/caam/blob_gen.c
> > > new file mode 100644
> > > index 000000000000..513d3f90e438
> > > --- /dev/null
> > > +++ b/drivers/crypto/caam/blob_gen.c
> > > @@ -0,0 +1,230 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Copyright (C) 2015 Pengutronix, Steffen Trumtrar <kernel@pengutronix.de>
> > > + * Copyright (C) 2021 Pengutronix, Ahmad Fatoum <kernel@pengutronix.de>
> > > + */
> > > +
> > > +#include <linux/device.h>
> > > +#include <soc/fsl/caam-blob.h>
> > > +
> > > +#include "compat.h"
> > > +#include "desc_constr.h"
> > > +#include "desc.h"
> > > +#include "error.h"
> > > +#include "intern.h"
> > > +#include "jr.h"
> > > +#include "regs.h"
> > > +
> > > +struct caam_blob_priv {
> > > +       struct device jrdev;
> > > +};
> > > +
> > > +struct caam_blob_job_result {
> > > +       int err;
> > > +       struct completion completion;
> > > +};
> > > +
> > > +static void caam_blob_job_done(struct device *dev, u32 *desc, u32 err, void *context)
> > > +{
> > > +       struct caam_blob_job_result *res = context;
> > > +       int ecode = 0;
> > > +
> > > +       dev_dbg(dev, "%s %d: err 0x%x\n", __func__, __LINE__, err);
> > > +
> > > +       if (err)
> > > +               ecode = caam_jr_strstatus(dev, err);
> > > +
> > > +       res->err = ecode;
> > > +
> > > +       /*
> > > +        * Upon completion, desc points to a buffer containing a CAAM job
> > > +        * descriptor which encapsulates data into an externally-storable
> > > +        * blob.
> > > +        */
> > > +       complete(&res->completion);
> > > +}
> > > +
> > > +static u32 *caam_blob_alloc_desc(size_t keymod_len)
> > > +{
> > > +       size_t len;
> > > +
> > > +       /* header + (key mod immediate) + 2x pointers + op */
> > > +       len = 4 + (4 + ALIGN(keymod_len, 4)) + 2*(4 + 4 + CAAM_PTR_SZ_MAX) + 4;
> > 
> > Nit: the amount of magic numbers is overwhelming here. I neither understand
> > the statement nor how that comment should help me to understand it.
> 
> header              =  4
> (key mod immediate) = (4 + ALIGN(keymod_len, 4))
> 2x pointer          =  2 * (4 + 4 + CAAM_PTR_SZ_MAX)
> op                  =  4

Please create a struct with the associated fields instead and then
it is just sizeof that.

BR, Jarkko