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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

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

I haven't heard back from the CAAM maintainers yet since v1. Perhaps now
is a good occasion to chime in? :-)

@Jarkko, could you take a look at patch 5? That's the gist of the series
and I have yet to get maintainer feedback on that one.

Cheers,
Ahmad


> 
> BR, Jarkko
> 


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