crypto: caam - add in-kernel interface for blob generator

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 <[e-mail]>
Reviewed-by: Pankaj Gupta <[e-mail]>
Tested-by: Tim Harvey <[e-mail]>
Tested-by: Matthias Schiffer <[e-mail]>
Tested-by: Pankaj Gupta <[e-mail]>
Tested-by: Michael Walle <[e-mail]> # on ls1028a (non-E and E)
Tested-by: John Ernberg <[e-mail]> # iMX8QXP
Signed-off-by: Steffen Trumtrar <[e-mail]>
Signed-off-by: Ahmad Fatoum <[e-mail]>
Signed-off-by: Jarkko Sakkinen <[e-mail]>

drivers/crypto/caam/Kconfig

···
 	  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

drivers/crypto/caam/Makefile

···
 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),)

drivers/crypto/caam/blob_gen.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2015 Pengutronix, Steffen Trumtrar <[e-mail]>
+ * Copyright (C) 2021 Pengutronix, Ahmad Fatoum <[e-mail]>
+ */
+
+#define pr_fmt(fmt) "caam blob_gen: " fmt
+
+#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"
+
+#define CAAM_BLOB_DESC_BYTES_MAX					\
+	/* Command to initialize & stating length of descriptor */	\
+	(CAAM_CMD_SZ +							\
+	/* Command to append the key-modifier + key-modifier data */	\
+	 CAAM_CMD_SZ + CAAM_BLOB_KEYMOD_LENGTH +			\
+	/* Command to include input key + pointer to the input key */	\
+	 CAAM_CMD_SZ + CAAM_PTR_SZ_MAX +				\
+	/* Command to include output key + pointer to the output key */	\
+	 CAAM_CMD_SZ + CAAM_PTR_SZ_MAX +				\
+	/* Command describing the operation to perform */		\
+	 CAAM_CMD_SZ)
+
+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);
+}
+
+int caam_process_blob(struct caam_blob_priv *priv,
+		      struct caam_blob_info *info, bool encap)
+{
+	struct caam_blob_job_result testres;
+	struct device *jrdev = &priv->jrdev;
+	dma_addr_t dma_in, dma_out;
+	int op = OP_PCLID_BLOB;
+	size_t output_len;
+	u32 *desc;
+	int ret;
+
+	if (info->key_mod_len > CAAM_BLOB_KEYMOD_LENGTH)
+		return -EINVAL;
+
+	if (encap) {
+		op |= OP_TYPE_ENCAP_PROTOCOL;
+		output_len = info->input_len + CAAM_BLOB_OVERHEAD;
+	} else {
+		op |= OP_TYPE_DECAP_PROTOCOL;
+		output_len = info->input_len - CAAM_BLOB_OVERHEAD;
+	}
+
+	desc = kzalloc(CAAM_BLOB_DESC_BYTES_MAX, GFP_KERNEL | GFP_DMA);
+	if (!desc)
+		return -ENOMEM;
+
+	dma_in = dma_map_single(jrdev, info->input, info->input_len,
+				DMA_TO_DEVICE);
+	if (dma_mapping_error(jrdev, dma_in)) {
+		dev_err(jrdev, "unable to map input DMA buffer\n");
+		ret = -ENOMEM;
+		goto out_free;
+	}
+
+	dma_out = dma_map_single(jrdev, info->output, output_len,
+				 DMA_FROM_DEVICE);
+	if (dma_mapping_error(jrdev, dma_out)) {
+		dev_err(jrdev, "unable to map output DMA buffer\n");
+		ret = -ENOMEM;
+		goto out_unmap_in;
+	}
+
+	/*
+	 * A data blob is encrypted using a blob key (BK); a random number.
+	 * The BK is used as an AES-CCM key. The initial block (B0) and the
+	 * initial counter (Ctr0) are generated automatically and stored in
+	 * Class 1 Context DWords 0+1+2+3. The random BK is stored in the
+	 * Class 1 Key Register. Operation Mode is set to AES-CCM.
+	 */
+
+	init_job_desc(desc, 0);
+	append_key_as_imm(desc, info->key_mod, info->key_mod_len,
+			  info->key_mod_len, CLASS_2 | KEY_DEST_CLASS_REG);
+	append_seq_in_ptr_intlen(desc, dma_in, info->input_len, 0);
+	append_seq_out_ptr_intlen(desc, dma_out, output_len, 0);
+	append_operation(desc, op);
+
+	print_hex_dump_debug("data@"__stringify(__LINE__)": ",
+			     DUMP_PREFIX_ADDRESS, 16, 1, info->input,
+			     info->input_len, false);
+	print_hex_dump_debug("jobdesc@"__stringify(__LINE__)": ",
+			     DUMP_PREFIX_ADDRESS, 16, 1, desc,
+			     desc_bytes(desc), false);
+
+	testres.err = 0;
+	init_completion(&testres.completion);
+
+	ret = caam_jr_enqueue(jrdev, desc, caam_blob_job_done, &testres);
+	if (ret == -EINPROGRESS) {
+		wait_for_completion(&testres.completion);
+		ret = testres.err;
+		print_hex_dump_debug("output@"__stringify(__LINE__)": ",
+				     DUMP_PREFIX_ADDRESS, 16, 1, info->output,
+				     output_len, false);
+	}
+
+	if (ret == 0)
+		info->output_len = output_len;
+
+	dma_unmap_single(jrdev, dma_out, output_len, DMA_FROM_DEVICE);
+out_unmap_in:
+	dma_unmap_single(jrdev, dma_in, info->input_len, DMA_TO_DEVICE);
+out_free:
+	kfree(desc);
+
+	return ret;
+}
+EXPORT_SYMBOL(caam_process_blob);
+
+struct caam_blob_priv *caam_blob_gen_init(void)
+{
+	struct caam_drv_private *ctrlpriv;
+	struct device *jrdev;
+
+	/*
+	 * caam_blob_gen_init() may expectedly fail with -ENODEV, e.g. when
+	 * CAAM driver didn't probe or when SoC lacks BLOB support. An
+	 * error would be harsh in this case, so we stick to info level.
+	 */
+
+	jrdev = caam_jr_alloc();
+	if (IS_ERR(jrdev)) {
+		pr_info("job ring requested, but none currently available\n");
+		return ERR_PTR(-ENODEV);
+	}
+
+	ctrlpriv = dev_get_drvdata(jrdev->parent);
+	if (!ctrlpriv->blob_present) {
+		dev_info(jrdev, "no hardware blob generation support\n");
+		caam_jr_free(jrdev);
+		return ERR_PTR(-ENODEV);
+	}
+
+	return container_of(jrdev, struct caam_blob_priv, jrdev);
+}
+EXPORT_SYMBOL(caam_blob_gen_init);
+
+void caam_blob_gen_exit(struct caam_blob_priv *priv)
+{
+	caam_jr_free(&priv->jrdev);
+}
+EXPORT_SYMBOL(caam_blob_gen_exit);

include/soc/fsl/caam-blob.h

···
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Pengutronix, Ahmad Fatoum <[e-mail]>
+ */
+
+#ifndef __CAAM_BLOB_GEN
+#define __CAAM_BLOB_GEN
+
+#include <linux/types.h>
+#include <linux/errno.h>
+
+#define CAAM_BLOB_KEYMOD_LENGTH		16
+#define CAAM_BLOB_OVERHEAD		(32 + 16)
+#define CAAM_BLOB_MAX_LEN		4096
+
+struct caam_blob_priv;
+
+/**
+ * struct caam_blob_info - information for CAAM blobbing
+ * @input:       pointer to input buffer (must be DMAable)
+ * @input_len:   length of @input buffer in bytes.
+ * @output:      pointer to output buffer (must be DMAable)
+ * @output_len:  length of @output buffer in bytes.
+ * @key_mod:     key modifier
+ * @key_mod_len: length of @key_mod in bytes.
+ *	         May not exceed %CAAM_BLOB_KEYMOD_LENGTH
+ */
+struct caam_blob_info {
+	void *input;
+	size_t input_len;
+
+	void *output;
+	size_t output_len;
+
+	const void *key_mod;
+	size_t key_mod_len;
+};
+
+/**
+ * caam_blob_gen_init - initialize blob generation
+ * Return: pointer to new &struct caam_blob_priv instance on success
+ * and ``ERR_PTR(-ENODEV)`` if CAAM has no hardware blobbing support
+ * or no job ring could be allocated.
+ */
+struct caam_blob_priv *caam_blob_gen_init(void);
+
+/**
+ * caam_blob_gen_exit - free blob generation resources
+ * @priv: instance returned by caam_blob_gen_init()
+ */
+void caam_blob_gen_exit(struct caam_blob_priv *priv);
+
+/**
+ * caam_process_blob - encapsulate or decapsulate blob
+ * @priv:   instance returned by caam_blob_gen_init()
+ * @info:   pointer to blobbing info describing key, blob and
+ *          key modifier buffers.
+ * @encap:  true for encapsulation, false for decapsulation
+ *
+ * Return: %0 and sets ``info->output_len`` on success and a negative
+ * error code otherwise.
+ */
+int caam_process_blob(struct caam_blob_priv *priv,
+		      struct caam_blob_info *info, bool encap);
+
+/**
+ * caam_encap_blob - encapsulate blob
+ * @priv:   instance returned by caam_blob_gen_init()
+ * @info:   pointer to blobbing info describing input key,
+ *          output blob and key modifier buffers.
+ *
+ * Return: %0 and sets ``info->output_len`` on success and
+ * a negative error code otherwise.
+ */
+static inline int caam_encap_blob(struct caam_blob_priv *priv,
+				  struct caam_blob_info *info)
+{
+	if (info->output_len < info->input_len + CAAM_BLOB_OVERHEAD)
+		return -EINVAL;
+
+	return caam_process_blob(priv, info, true);
+}
+
+/**
+ * caam_decap_blob - decapsulate blob
+ * @priv:   instance returned by caam_blob_gen_init()
+ * @info:   pointer to blobbing info describing output key,
+ *          input blob and key modifier buffers.
+ *
+ * Return: %0 and sets ``info->output_len`` on success and
+ * a negative error code otherwise.
+ */
+static inline int caam_decap_blob(struct caam_blob_priv *priv,
+				  struct caam_blob_info *info)
+{
+	if (info->input_len < CAAM_BLOB_OVERHEAD ||
+	    info->output_len < info->input_len - CAAM_BLOB_OVERHEAD)
+		return -EINVAL;
+
+	return caam_process_blob(priv, info, false);
+}
+
+#endif