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

[Jarkko Sakkinen]

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@xxxxxxxxxxxxx>
> Reviewed-by: Pankaj Gupta <pankaj.gupta@xxxxxxx>
> Tested-By: Tim Harvey <tharvey@xxxxxxxxxxxxx>
> Tested-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx>
> Signed-off-by: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>
> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
> ---
> To: "Horia Geantă" <horia.geanta@xxxxxxx>
> To: Aymen Sghaier <aymen.sghaier@xxxxxxx>
> To: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> To: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: James Bottomley <jejb@xxxxxxxxxxxxx>
> Cc: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
> Cc: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> Cc: David Howells <dhowells@xxxxxxxxxx>
> Cc: James Morris <jmorris@xxxxxxxxx>
> Cc: Eric Biggers <ebiggers@xxxxxxxxxx>
> Cc: "Serge E. Hallyn" <serge@xxxxxxxxxx>
> Cc: Jan Luebbe <j.luebbe@xxxxxxxxxxxxxx>
> Cc: David Gstir <david@xxxxxxxxxxxxx>
> Cc: Richard Weinberger <richard@xxxxxx>
> Cc: Franck LENORMAND <franck.lenormand@xxxxxxx>
> Cc: Sumit Garg <sumit.garg@xxxxxxxxxx>
> Cc: Tim Harvey <tharvey@xxxxxxxxxxxxx>
> Cc: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx>
> Cc: Pankaj Gupta <pankaj.gupta@xxxxxxx>
> Cc: linux-integrity@xxxxxxxxxxxxxxx
> Cc: keyrings@xxxxxxxxxxxxxxx
> Cc: linux-crypto@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-security-module@xxxxxxxxxxxxxxx
> ---
>  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@xxxxxxxxxxxxxx>
> + * Copyright (C) 2021 Pengutronix, Ahmad Fatoum <kernel@xxxxxxxxxxxxxx>
> + */
> +
> +#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.

BR, Jarkko