nrf_security: Add key policy for the Cracen builtin keys

subsys/nrf_security/src/drivers/cracen/cracenpsa/cracenpsa.cmake

@@ -23,6 +23,12 @@ list(APPEND cracen_driver_sources
   ${CMAKE_CURRENT_LIST_DIR}/src/prng_pool.c
 )
 
+if(BUILD_INSIDE_TFM)
+  list(APPEND cracen_driver_sources
+    ${CMAKE_CURRENT_LIST_DIR}/src/cracen_builtin_key_policy.c
+  )
+endif()
+
 # Include hardware cipher implementation for all devices except nRF54LM20A
 # nRF54LM20A uses only cracen_sw
 if(NOT CONFIG_CRACEN_NEED_MULTIPART_WORKAROUNDS)

subsys/nrf_security/src/drivers/cracen/cracenpsa/include/cracen_psa.h

@@ -18,10 +18,6 @@
 #include "cracen_psa_key_ids.h"
 #include "sxsymcrypt/keyref.h"
 
-#ifdef __NRF_TFM__
-#include <tfm_builtin_key_loader.h>
-#endif
-
 /**
  * See "PSA Cryptography API" for documentation.
  */

subsys/nrf_security/src/drivers/cracen/cracenpsa/include/cracen_psa_builtin_key_policy.h

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#ifndef CRACEN_BUILTIN_KEY_POLICY_H
+#define CRACEN_BUILTIN_KEY_POLICY_H
+
+#include "common.h"
+#include <psa/crypto.h>
+#include <psa/crypto_values.h>
+
+#if defined(__NRF_TFM__)
+
+typedef struct {
+	mbedtls_key_owner_id_t user;
+	psa_drv_slot_number_t key_slot;
+} cracen_builtin_ikg_key_policy_t;
+
+typedef enum {
+	KMU_ENTRY_SLOT_SINGLE,
+	KMU_ENTRY_SLOT_RANGE,
+} cracen_kmu_entry_type_t;
+
+/* When defining a range of KMU slots both the start and end slot numbers are inclusive. */
+typedef struct {
+	mbedtls_key_owner_id_t user;
+	psa_drv_slot_number_t key_slot_start;
+	psa_drv_slot_number_t key_slot_end;
+	cracen_kmu_entry_type_t kmu_entry_type;
+} cracen_builtin_kmu_key_policy_t;
+
+bool cracen_builtin_key_user_allowed(const psa_key_attributes_t *attributes);
+
+#else
+
+static inline bool cracen_builtin_key_user_allowed(const psa_key_attributes_t *attributes)
+{
+	(void)attributes;
+	return true;
+}
+
+#endif /* __NRF_TFM__ */
+
+#endif /* CRACEN_BUILTIN_KEY_POLICY_H */

subsys/nrf_security/src/drivers/cracen/cracenpsa/src/cracen_builtin_key_policy.c

@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+#include "common.h"
+
+#include <psa/crypto.h>
+#include <psa/crypto_values.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "psa_manifest/pid.h"
+#include "tfm_builtin_key_ids.h"
+#include <cracen_psa_builtin_key_policy.h>
+
+#define NUMBER_OF_ELEMENTS_OF(x) (sizeof(x) / sizeof(*(x)))
+
+#define MAPPED_TZ_NS_AGENT_DEFAULT_CLIENT_ID (-0x3c000000)
+
+const cracen_builtin_ikg_key_policy_t g_builtin_ikg_policy[] = {
+#ifdef TFM_SP_ITS
+	{.user = TFM_SP_ITS, .key_slot = TFM_BUILTIN_KEY_ID_HUK},
+#endif /* TFM_SP_ITS */
+#ifdef TFM_SP_PS
+	{.user = TFM_SP_PS, .key_slot = TFM_BUILTIN_KEY_ID_HUK},
+#endif /* TFM_SP_PS */
+#ifdef TFM_SP_INITIAL_ATTESTATION
+	{.user = TFM_SP_INITIAL_ATTESTATION, .key_slot = TFM_BUILTIN_KEY_ID_IAK}
+#endif /* TFM_SP_INITIAL_ATTESTATION */
+};
+
+#ifdef PSA_NEED_CRACEN_KMU_DRIVER
+
+const cracen_builtin_kmu_key_policy_t g_builtin_kmu_policy[] = {
+	/* 0x0 is used by libraries like the hw_unique_key library when manually generating psa
+	 * key_ids. Allow access to all slots for these libraries since they don't have the logic to
+	 * have an owner id and reside inside TF-M.
+	 */
+	{.user = 0x0,
+	 .key_slot_start = 0,
+	 .key_slot_end = 255,
+	 .kmu_entry_type = KMU_ENTRY_SLOT_RANGE},
+#ifdef TFM_SP_ITS
+	{.user = TFM_SP_ITS,
+	 .key_slot_start = 0,
+	 .key_slot_end = 255,
+	 .kmu_entry_type = KMU_ENTRY_SLOT_RANGE},
+#endif /* TFM_SP_ITS */
+#ifdef TFM_SP_CRYPTO
+	{.user = TFM_SP_CRYPTO,
+	 .key_slot_start = 0,
+	 .key_slot_end = 255,
+	 .kmu_entry_type = KMU_ENTRY_SLOT_RANGE},
+#endif /* TFM_SP_CRYPTO */
+	/* The docs have KMU slots >= 180 reserved so don't allow NS users to access them */
+	{.user = MAPPED_TZ_NS_AGENT_DEFAULT_CLIENT_ID,
+	 .key_slot_start = 0,
+	 .key_slot_end = 179,
+	 .kmu_entry_type = KMU_ENTRY_SLOT_RANGE}};
+
+static bool cracen_builtin_kmu_user_allowed(mbedtls_key_owner_id_t owner,
+					    psa_drv_slot_number_t slot_number,
+					    const psa_key_attributes_t *attributes)
+{
+	for (uint32_t i = 0; i < NUMBER_OF_ELEMENTS_OF(g_builtin_kmu_policy); i++) {
+
+		switch (g_builtin_kmu_policy[i].kmu_entry_type) {
+		case KMU_ENTRY_SLOT_SINGLE:
+			if (g_builtin_kmu_policy[i].user == owner &&
+			    g_builtin_kmu_policy[i].key_slot_start == slot_number) {
+				return true;
+			}
+			break;
+
+		case KMU_ENTRY_SLOT_RANGE:
+			if (g_builtin_kmu_policy[i].user == owner &&
+			    (slot_number >= g_builtin_kmu_policy[i].key_slot_start &&
+			     slot_number <= g_builtin_kmu_policy[i].key_slot_end)) {
+				return true;
+			}
+			break;
+		default:
+			break;
+		}
+	}
+
+	return false;
+}
+#endif /* PSA_NEED_CRACEN_KMU_DRIVER */
+
+static bool cracen_builtin_ikg_user_allowed(mbedtls_key_owner_id_t owner,
+					    psa_drv_slot_number_t slot_number,
+					    const psa_key_attributes_t *attributes)
+{
+	for (uint32_t i = 0; i < NUMBER_OF_ELEMENTS_OF(g_builtin_ikg_policy); i++) {
+		if (g_builtin_ikg_policy[i].user == owner &&
+		    g_builtin_ikg_policy[i].key_slot == slot_number) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+bool cracen_builtin_key_user_allowed(const psa_key_attributes_t *attributes)
+{
+	mbedtls_key_owner_id_t owner = MBEDTLS_SVC_KEY_ID_GET_OWNER_ID(psa_get_key_id(attributes));
+	psa_drv_slot_number_t slot_id;
+
+	if (PSA_KEY_LIFETIME_GET_LOCATION(psa_get_key_lifetime(attributes)) ==
+	    PSA_KEY_LOCATION_CRACEN) {
+
+		slot_id = MBEDTLS_SVC_KEY_ID_GET_KEY_ID(psa_get_key_id(attributes));
+		if (!cracen_builtin_ikg_user_allowed(owner, slot_id, attributes)) {
+			return false;
+		}
+	}
+
+#ifdef PSA_NEED_CRACEN_KMU_DRIVER
+	if (PSA_KEY_LIFETIME_GET_LOCATION(psa_get_key_lifetime(attributes)) ==
+	    PSA_KEY_LOCATION_CRACEN_KMU) {
+
+		slot_id = CRACEN_PSA_GET_KMU_SLOT(
+			MBEDTLS_SVC_KEY_ID_GET_KEY_ID(psa_get_key_id(attributes)));
+		if (!cracen_builtin_kmu_user_allowed(owner, slot_id, attributes)) {
+			return false;
+		}
+	}
+#endif /* PSA_NEED_CRACEN_KMU_DRIVER */
+
+	return true;
+}

subsys/nrf_security/src/drivers/cracen/cracenpsa/src/key_management.c

@@ -14,6 +14,7 @@
 #include <cracen_psa_montgomery.h>
 #include <cracen_psa_ikg.h>
 #include <cracen_psa_rsa_keygen.h>
+#include <cracen_psa_builtin_key_policy.h>
 #include <nrf_security_mutexes.h>
 #include "ecc.h"
 #include <silexpk/sxops/rsa.h>
@@ -894,6 +895,10 @@ psa_status_t cracen_export_public_key(const psa_key_attributes_t *attributes,
 		return PSA_ERROR_INVALID_ARGUMENT;
 	}
 
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 	if (IS_ENABLED(PSA_NEED_CRACEN_KEY_TYPE_ECC_KEY_PAIR_EXPORT)) {
 		if (PSA_KEY_TYPE_IS_ECC_KEY_PAIR(key_type)) {
 			return export_ecc_public_key_from_keypair(attributes, key_buffer,
@@ -945,6 +950,10 @@ psa_status_t cracen_import_key(const psa_key_attributes_t *attributes, const uin
 		return PSA_ERROR_INVALID_ARGUMENT;
 	}
 
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 	psa_key_location_t location =
 		PSA_KEY_LIFETIME_GET_LOCATION(psa_get_key_lifetime(attributes));
 #ifdef PSA_NEED_CRACEN_KMU_DRIVER
@@ -1198,6 +1207,10 @@ psa_status_t cracen_generate_key(const psa_key_attributes_t *attributes, uint8_t
 	psa_key_location_t location =
 		PSA_KEY_LIFETIME_GET_LOCATION(psa_get_key_lifetime(attributes));
 
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 #ifdef PSA_NEED_CRACEN_KMU_DRIVER
 	if (location == PSA_KEY_LOCATION_CRACEN_KMU) {
 		return generate_key_for_kmu(attributes, key_buffer, key_buffer_size,
@@ -1330,6 +1343,11 @@ psa_status_t cracen_get_builtin_key(psa_drv_slot_number_t slot_number,
 	 * and the `lifetime` field of the attribute struct. We will fill all the other
 	 * attributes, and update the `lifetime` field to be more specific.
 	 */
+
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 	switch (slot_number) {
 	case CRACEN_BUILTIN_IDENTITY_KEY_ID:
 	case CRACEN_BUILTIN_MKEK_ID:
@@ -1387,6 +1405,10 @@ psa_status_t cracen_export_key(const psa_key_attributes_t *attributes, const uin
 	psa_key_location_t location =
 		PSA_KEY_LIFETIME_GET_LOCATION(psa_get_key_lifetime(attributes));
 
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 	if (location == PSA_KEY_LOCATION_CRACEN_KMU) {
 		/* The keys will already be in the key buffer as they got loaded their by a previous
 		 * call to cracen_get_builtin_key or cached in the memory.
@@ -1435,6 +1457,10 @@ psa_status_t cracen_copy_key(psa_key_attributes_t *attributes, const uint8_t *so
 			     size_t target_key_buffer_size, size_t *target_key_buffer_length)
 {
 #ifdef PSA_NEED_CRACEN_KMU_DRIVER
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 	psa_key_location_t location =
 		PSA_KEY_LIFETIME_GET_LOCATION(psa_get_key_lifetime(attributes));
 
@@ -1489,6 +1515,10 @@ psa_status_t cracen_copy_key(psa_key_attributes_t *attributes, const uint8_t *so
 psa_status_t cracen_destroy_key(const psa_key_attributes_t *attributes)
 {
 #ifdef PSA_NEED_CRACEN_KMU_DRIVER
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 	return cracen_kmu_destroy_key(attributes);
 #endif
 
@@ -1501,6 +1531,10 @@ psa_status_t cracen_derive_key(const psa_key_attributes_t *attributes, const uin
 {
 	psa_key_type_t key_type = psa_get_key_type(attributes);
 
+	if (!cracen_builtin_key_user_allowed(attributes)) {
+		return PSA_ERROR_NOT_PERMITTED;
+	}
+
 	if (PSA_KEY_TYPE_IS_SPAKE2P_KEY_PAIR(key_type) && IS_ENABLED(PSA_NEED_CRACEN_SPAKE2P)) {
 		return cracen_derive_spake2p_key(attributes, input, input_length, key, key_size,
 						 key_length);