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 <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>
Tested-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Tested-by: Michael Walle <michael@walle.cc> # on ls1028a (non-E and E)
Tested-by: John Ernberg <john.ernberg@actia.se> # iMX8QXP
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

1 files changed, 103 insertions, 0 deletions

diff --git a/include/soc/fsl/caam-blob.h b/include/soc/fsl/caam-blob.h
new file mode 100644
index 000000000000..937cac52f36d
--- /dev/null
+++ b/include/soc/fsl/caam-blob.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Pengutronix, Ahmad Fatoum <kernel@pengutronix.de>
+ */
+
+#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