KEYS: trusted: Introduce support for NXP CAAM-based trusted keys

The Cryptographic Acceleration and Assurance Module (CAAM) is an IP core
built into many newer i.MX and QorIQ SoCs by NXP.

The CAAM does crypto acceleration, hardware number generation and
has a blob mechanism for encapsulation/decapsulation of sensitive material.

This blob mechanism depends on a device specific random 256-bit One Time
Programmable Master Key that is fused in each SoC at manufacturing
time. This key is unreadable and can only be used by the CAAM for AES
encryption/decryption of user data.

This makes it a suitable backend (source) for kernel trusted keys.

Previous commits generalized trusted keys to support multiple backends
and added an API to access the CAAM blob mechanism. Based on these,
provide the necessary glue to use the CAAM for trusted keys.

Reviewed-by: David Gstir <david@sigma-star.at>
Reviewed-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
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: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

4 files changed, 97 insertions, 2 deletions

diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-keys/Kconfig
index fc4abd581abb..dbfdd8536468 100644
--- a/security/keys/trusted-keys/Kconfig
+++ b/security/keys/trusted-keys/Kconfig
@@ -24,6 +24,15 @@ config TRUSTED_KEYS_TEE
 	  Enable use of the Trusted Execution Environment (TEE) as trusted
 	  key backend.
 
-if !TRUSTED_KEYS_TPM && !TRUSTED_KEYS_TEE
+config TRUSTED_KEYS_CAAM
+	bool "CAAM-based trusted keys"
+	depends on CRYPTO_DEV_FSL_CAAM_JR >= TRUSTED_KEYS
+	select CRYPTO_DEV_FSL_CAAM_BLOB_GEN
+	default y
+	help
+	  Enable use of NXP's Cryptographic Accelerator and Assurance Module
+	  (CAAM) as trusted key backend.
+
+if !TRUSTED_KEYS_TPM && !TRUSTED_KEYS_TEE && !TRUSTED_KEYS_CAAM
 comment "No trust source selected!"
 endif
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index 2e2371eae4d5..735aa0bc08ef 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -12,3 +12,5 @@ trusted-$(CONFIG_TRUSTED_KEYS_TPM) += trusted_tpm2.o
 trusted-$(CONFIG_TRUSTED_KEYS_TPM) += tpm2key.asn1.o
 
 trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
+
+trusted-$(CONFIG_TRUSTED_KEYS_CAAM) += trusted_caam.o
diff --git a/security/keys/trusted-keys/trusted_caam.c b/security/keys/trusted-keys/trusted_caam.c
new file mode 100644
index 000000000000..e3415c520c0a
--- /dev/null
+++ b/security/keys/trusted-keys/trusted_caam.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Pengutronix, Ahmad Fatoum <kernel@pengutronix.de>
+ */
+
+#include <keys/trusted_caam.h>
+#include <keys/trusted-type.h>
+#include <linux/build_bug.h>
+#include <linux/key-type.h>
+#include <soc/fsl/caam-blob.h>
+
+static struct caam_blob_priv *blobifier;
+
+#define KEYMOD "SECURE_KEY"
+
+static_assert(MAX_KEY_SIZE + CAAM_BLOB_OVERHEAD <= CAAM_BLOB_MAX_LEN);
+static_assert(MAX_BLOB_SIZE <= CAAM_BLOB_MAX_LEN);
+
+static int trusted_caam_seal(struct trusted_key_payload *p, char *datablob)
+{
+	int ret;
+	struct caam_blob_info info = {
+		.input  = p->key,  .input_len   = p->key_len,
+		.output = p->blob, .output_len  = MAX_BLOB_SIZE,
+		.key_mod = KEYMOD, .key_mod_len = sizeof(KEYMOD) - 1,
+	};
+
+	ret = caam_encap_blob(blobifier, &info);
+	if (ret)
+		return ret;
+
+	p->blob_len = info.output_len;
+	return 0;
+}
+
+static int trusted_caam_unseal(struct trusted_key_payload *p, char *datablob)
+{
+	int ret;
+	struct caam_blob_info info = {
+		.input   = p->blob,  .input_len  = p->blob_len,
+		.output  = p->key,   .output_len = MAX_KEY_SIZE,
+		.key_mod = KEYMOD,  .key_mod_len = sizeof(KEYMOD) - 1,
+	};
+
+	ret = caam_decap_blob(blobifier, &info);
+	if (ret)
+		return ret;
+
+	p->key_len = info.output_len;
+	return 0;
+}
+
+static int trusted_caam_init(void)
+{
+	int ret;
+
+	blobifier = caam_blob_gen_init();
+	if (IS_ERR(blobifier))
+		return PTR_ERR(blobifier);
+
+	ret = register_key_type(&key_type_trusted);
+	if (ret)
+		caam_blob_gen_exit(blobifier);
+
+	return ret;
+}
+
+static void trusted_caam_exit(void)
+{
+	unregister_key_type(&key_type_trusted);
+	caam_blob_gen_exit(blobifier);
+}
+
+struct trusted_key_ops trusted_key_caam_ops = {
+	.migratable = 0, /* non-migratable */
+	.init = trusted_caam_init,
+	.seal = trusted_caam_seal,
+	.unseal = trusted_caam_unseal,
+	.exit = trusted_caam_exit,
+};
diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index 9235fb7d0ec9..c6fc50d67214 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c
@@ -9,6 +9,7 @@
 #include <keys/user-type.h>
 #include <keys/trusted-type.h>
 #include <keys/trusted_tee.h>
+#include <keys/trusted_caam.h>
 #include <keys/trusted_tpm.h>
 #include <linux/capability.h>
 #include <linux/err.h>
@@ -29,7 +30,7 @@ MODULE_PARM_DESC(rng, "Select trusted key RNG");
 
 static char *trusted_key_source;
 module_param_named(source, trusted_key_source, charp, 0);
-MODULE_PARM_DESC(source, "Select trusted keys source (tpm or tee)");
+MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee or caam)");
 
 static const struct trusted_key_source trusted_key_sources[] = {
 #if defined(CONFIG_TRUSTED_KEYS_TPM)
@@ -38,6 +39,9 @@ static const struct trusted_key_source trusted_key_sources[] = {
 #if defined(CONFIG_TRUSTED_KEYS_TEE)
 	{ "tee", &trusted_key_tee_ops },
 #endif
+#if defined(CONFIG_TRUSTED_KEYS_CAAM)
+	{ "caam", &trusted_key_caam_ops },
+#endif
 };
 
 DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);