tfm: Move TF-M attestation data to provisioned OTP region

Optional fields to TF-M attestation were previously stored in
tfm_otp_nv_counters region, which we were not able to provision.
This moves the psa_certification_reference to the provisioned
OTP-region and adds support for accessing the variable data in
bl_storage.h.

Verification service URL and profile may change with device
upgrades, for this reason they are added as Kconfigs.

Note that we still need to keep the tfm_otp_nv_counters region
when TFM_PARTITION_PROTECTED_STORAGE and
TFM_PS_ROLLBACK_PROTECTION are enabled. TF-M will increase
monotonic counters every time new data is written and given the
limited size of our OTP-region it would not support many updates.

NCSDK-17932

Signed-off-by: Markus Lassila <[email protected]>

cmake/sysbuild/provision_hex.cmake

@@ -87,6 +87,10 @@ function(provision application prefix_name)
     set(mcuboot_counters_slots --mcuboot-counters-slots ${SB_CONFIG_MCUBOOT_HW_DOWNGRADE_PREVENTION_COUNTER_SLOTS})
   endif()
 
+  if(SB_CONFIG_TFM_OTP_PSA_CERTIFICATE_REFERENCE AND SB_CONFIG_TFM_PSA_CERTIFICATE_REFERENCE_VALUE)
+    set(psa_certificate_reference --psa-certificate-reference ${SB_CONFIG_TFM_PSA_CERTIFICATE_REFERENCE_VALUE})
+  endif()
+
   if(CONFIG_SECURE_BOOT)
     add_custom_command(
       OUTPUT
@@ -103,6 +107,7 @@ function(provision application prefix_name)
       ${monotonic_counter_arg}
       ${no_verify_hashes_arg}
       ${mcuboot_counters_slots}
+      ${psa_certificate_reference}
       --lcs-state-size ${lcs_state_struct_size}
       DEPENDS
       ${PROVISION_KEY_DEPENDS}
@@ -126,6 +131,7 @@ function(provision application prefix_name)
       --max-size ${CONFIG_PM_PARTITION_SIZE_PROVISION}
       ${mcuboot_counters_num}
       ${mcuboot_counters_slots}
+      ${psa_certificate_reference}
       --lcs-state-size ${lcs_state_struct_size}
       DEPENDS
       ${PROVISION_KEY_DEPENDS}

include/bl_storage.h

@@ -44,6 +44,12 @@ typedef uint32_t lcs_reserved_t;
 /* We truncate the 32 byte sha256 down to 16 bytes before storing it */
 #define SB_PUBLIC_KEY_HASH_LEN 16
 
+/* Supported collection types. */
+enum collection_type {
+	BL_COLLECTION_TYPE_MONOTONIC_COUNTERS = 1,
+	BL_COLLECTION_TYPE_VARIABLE_DATA = 0x9312,
+};
+
 /* Counter used by NSIB to check the firmware version */
 #define BL_MONOTONIC_COUNTERS_DESC_NSIB 0x1
 
@@ -91,20 +97,47 @@ struct monotonic_counter {
 	counter_t counter_slots[1];
 };
 
+/** Common part for all collections. */
+struct collection {
+	uint16_t type;
+	uint16_t count;
+};
+
 /** The second data structure in the provision page. It has unknown length since
  *  'counters' is repeated. Note that each entry in counters also has unknown
  *  length, and each entry can have different length from the others, so the
  *  entries beyond the first cannot be accessed via array indices.
  */
 struct counter_collection {
-	uint16_t type; /* Must be "monotonic counter". */
-	uint16_t num_counters; /* Number of entries in 'counters' list. */
+	struct collection collection;  /* Type must be BL_COLLECTION_TYPE_MONOTONIC_COUNTERS */
 	struct monotonic_counter counters[1];
 };
 
+/* Variable data types. */
+enum variable_data_type {
+	BL_VARIABLE_DATA_TYPE_PSA_CERTIFICATION_REFERENCE = 0x1
+};
+struct variable_data {
+	uint8_t type;
+	uint8_t length;
+	uint8_t data[1];
+};
+
+/* The third data structure in the provision page. It has unknown length since
+ * 'variable_data' is repeated. The collection starts immediately after the
+ * counter collection. As the counter collection has unknown length, the start
+ * of the variable data collection must be calculated dynamically. Similarly,
+ * the entries in the variable data collection have unknown length, so they
+ * cannot be accessed via array indices.
+ */
+struct variable_data_collection {
+	struct collection collection; /* Type must be BL_COLLECTION_TYPE_VARIABLE_DATA */
+	struct variable_data variable_data[1];
+};
+
 /** The first data structure in the bootloader storage. It has unknown length
  *  since 'key_data' is repeated. This data structure is immediately followed by
- *  struct counter_collection.
+ *  struct counter_collection, which is then followed by struct variable_data_collection.
  */
 struct bl_storage_data {
 	/* NB: When placed in OTP, reads must be 4 bytes and 4 byte aligned */
@@ -117,6 +150,27 @@ struct bl_storage_data {
 		uint32_t valid;
 		uint8_t hash[SB_PUBLIC_KEY_HASH_LEN];
 	} key_data[1];
+
+	/* Monotonic counter collection:
+	 * uint16_t type;
+	 * uint16_t count;
+	 * struct {
+	 *	uint16_t description;
+	 *	uint16_t num_counter_slots;
+	 *	uint16_t counter_slots[1];
+	 * } counters[1];
+	 */
+
+	/* Variable data collection:
+	 * uint16_t type;
+	 * uint16_t count;
+	 * struct {
+	 *	uint8_t type;
+	 *	uint8_t length;
+	 *	uint8_t data[1];
+	 * } variable_data[1];
+	 * uint8_t padding[1];  // Padding to align to 4 bytes
+	 */
 };
 
 #define BL_STORAGE ((const volatile struct bl_storage_data *)(PM_PROVISION_ADDRESS))
@@ -150,7 +204,7 @@ uint32_t s1_address_read(void);
 uint32_t num_public_keys_read(void);
 
 /**
- * @brief Function for reading number of public key data slots.
+ * @brief Function for verifying public keys.
  *
  * @retval 0         if all keys are ok.
  * @retval -EHASHFF  if one or more keys contains an aligned 0xFFFF.
@@ -265,6 +319,26 @@ int update_life_cycle_state(enum lcs next_lcs);
  */
 void read_implementation_id_from_otp(uint8_t *buf);
 
+/**
+ * @brief Read variable data from OTP.
+ *
+ * Variable data starts with variable data collection ID, followed by amount of variable data
+ * entries and the variable data entries themselves.
+ * [Collection ID][Variable count][Type][Variable data length][Variable data][Type]...
+ *  2 bytes        2 bytes         1 byte 1 byte                0-255 bytes
+ *
+ * @note If data is not found, function does not fail. Instead, 0 length is returned.
+ *
+ * @param[in] data_type Type of the variable data to read.
+ * @param[out] buf      Buffer to store the variable data.
+ * @param[in,out] buf_len  On input, the size of the buffer. On output, the length of the data.
+ *
+ * @retval 0            Variable data read successfully, or not found.
+ * @retval -EINVAL      No buffer provided.
+ * @retval -ENOMEM      Buffer too small.
+ */
+int read_variable_data(enum variable_data_type data_type, uint8_t *buf, uint32_t *buf_len);
+
 #endif
 
   /** @} */

modules/trusted-firmware-m/CMakeLists.txt

@@ -168,6 +168,10 @@ set_property(TARGET zephyr_property_target
   -DCRYPTO_HW_ACCELERATOR=True
 )
 
+set_property(TARGET zephyr_property_target
+  APPEND PROPERTY TFM_CMAKE_OPTIONS -DPLATFORM_DEFAULT_NV_SEED=OFF
+  )
+
 if(CONFIG_TFM_ALLOW_NON_SECURE_FAULT_HANDLING)
   set_property(TARGET zephyr_property_target
     APPEND PROPERTY TFM_CMAKE_OPTIONS
@@ -187,13 +191,21 @@ if(CONFIG_TFM_PROFILE_TYPE_MINIMAL)
     APPEND PROPERTY TFM_CMAKE_OPTIONS
     -DPLATFORM_DEFAULT_ROTPK=OFF
     -DPLATFORM_DEFAULT_IAK=OFF
-    -DPLATFORM_DEFAULT_NV_SEED=OFF
     -DPLATFORM_DEFAULT_OTP=OFF
     -DPLATFORM_DEFAULT_OTP_WRITEABLE=OFF
     -DPLATFORM_DEFAULT_NV_COUNTERS=OFF
   )
 endif()
 
+if(CONFIG_TFM_PLATFORM_NV_COUNTER_MODULE_DISABLED)
+  set_property(TARGET zephyr_property_target
+    APPEND PROPERTY TFM_CMAKE_OPTIONS
+    -DPLATFORM_DEFAULT_OTP=OFF
+    -DPLATFORM_DEFAULT_OTP_WRITEABLE=OFF
+    -DPLATFORM_DEFAULT_NV_COUNTERS=OFF
+    )
+endif()
+
 if(NOT CONFIG_MBEDTLS_PSA_CRYPTO_STORAGE_C)
   # Workaround: NCSDK-13530
   # Allow TF-M crypto to not depend on ITS when PSA crypto storage is disabled.
@@ -307,7 +319,7 @@ set(CRYPTO_ASYM_ENCRYPT_MODULE_ENABLED     ${CONFIG_TFM_CRYPTO_ASYM_ENCRYPT_MODU
 set(CRYPTO_KEY_DERIVATION_MODULE_ENABLED   ${CONFIG_TFM_CRYPTO_KEY_DERIVATION_MODULE_ENABLED})
 set(CRYPTO_PAKE_MODULE_ENABLED             ${CONFIG_TFM_CRYPTO_PAKE_MODULE_ENABLED})
 set(CRYPTO_IOVEC_BUFFER_SIZE               ${CONFIG_TFM_CRYPTO_IOVEC_BUFFER_SIZE})
-set(CRYPTO_NV_SEED                         ${CONFIG_TFM_CRYPTO_NV_SEED})
+set(CRYPTO_NV_SEED                         0)
 set(CRYPTO_SINGLE_PART_FUNCS_DISABLED      ${CONFIG_TFM_CRYPTO_SINGLE_PART_FUNCS_DISABLED})
 set(CRYPTO_STACK_SIZE                      ${CONFIG_TFM_CRYPTO_PARTITION_STACK_SIZE})
 set(CRYPTO_LIBRARY_ABI_COMPAT              ON)

modules/trusted-firmware-m/Kconfig

@@ -43,8 +43,9 @@ config TFM_PLATFORM_SP_STACK_SIZE
 
 config TFM_PLATFORM_NV_COUNTER_MODULE_DISABLED
 	bool "Disable Non-volatile counter module"
-	default y if TFM_PROFILE_TYPE_MINIMAL
-
+	default n if SOC_NRF54L15_ENGA_CPUAPP
+	default n if TFM_PARTITION_PROTECTED_STORAGE && TFM_PS_ROLLBACK_PROTECTION
+	default y
 endmenu
 
 # Copied from secure_fw/partitions/crypto/Kconfig, appended the TFM prefix
@@ -130,6 +131,13 @@ config TFM_ATTEST_INCLUDE_OPTIONAL_CLAIMS
 	bool "Include optional claims in initial attestation token"
 	default y
 
+config TFM_ATTEST_VERIFICATION_SERVICE_URL
+	string "TF-M attestation verification service URL"
+	default ""
+	depends on TFM_ATTEST_INCLUDE_OPTIONAL_CLAIMS
+	help
+	  Optional claim of URL of the verification service in the TF-M attestation token.
+
 config TFM_ATTEST_INCLUDE_COSE_KEY_ID
 	bool "Include COSE key-id in initial attestation token"
 	default n

modules/trusted-firmware-m/tfm_boards/common/attest_hal.c

@@ -11,7 +11,6 @@
 #include "tfm_attest_hal.h"
 #include "tfm_plat_boot_seed.h"
 #include "tfm_plat_device_id.h"
-#include "tfm_plat_otp.h"
 #include <nrf_cc3xx_platform.h>
 #include "tfm_strnlen.h"
 #include "nrf_provisioning.h"
@@ -72,50 +71,30 @@ int tfm_attest_update_security_lifecycle_otp(enum tfm_security_lifecycle_t slc)
 	return update_life_cycle_state(next_lcs);
 }
 
-enum tfm_plat_err_t tfm_attest_hal_get_verification_service(uint32_t *size, uint8_t *buf)
+static const char *get_attestation_profile(void)
 {
-	enum tfm_plat_err_t err;
-	size_t otp_size;
-	size_t copy_size;
-
-	err = tfm_plat_otp_read(PLAT_OTP_ID_VERIFICATION_SERVICE_URL, *size, buf);
-	if (err != TFM_PLAT_ERR_SUCCESS) {
-		return err;
-	}
-
-	err = tfm_plat_otp_get_size(PLAT_OTP_ID_VERIFICATION_SERVICE_URL, &otp_size);
-	if (err != TFM_PLAT_ERR_SUCCESS) {
-		return err;
-	}
-
-	/* Actually copied data is always the smaller */
-	copy_size = *size < otp_size ? *size : otp_size;
-	/* String content */
-	*size = tfm_strnlen((char *)buf, copy_size);
-
-	return TFM_PLAT_ERR_SUCCESS;
+#if defined(CONFIG_TFM_ATTEST_TOKEN_PROFILE_PSA_IOT_1)
+	return "PSA_IOT_PROFILE_1";
+#elif defined(CONFIG_TFM_ATTEST_TOKEN_PROFILE_PSA_2_0_0)
+	return "http://arm.com/psa/2.0.0";
+#elif defined(CONFIG_TFM_ATTEST_TOKEN_PROFILE_ARM_CCA)
+	return "http://arm.com/CCA-SSD/1.0.0";
+#else
+#error "Attestation token profile not defined"
+#endif
 }
 
 enum tfm_plat_err_t tfm_attest_hal_get_profile_definition(uint32_t *size, uint8_t *buf)
 {
-	enum tfm_plat_err_t err;
-	size_t otp_size;
-	size_t copy_size;
-
-	err = tfm_plat_otp_read(PLAT_OTP_ID_PROFILE_DEFINITION, *size, buf);
-	if (err != TFM_PLAT_ERR_SUCCESS) {
-		return err;
-	}
+	const char *profile = get_attestation_profile();
+	uint32_t profile_len = strlen(profile);
 
-	err = tfm_plat_otp_get_size(PLAT_OTP_ID_PROFILE_DEFINITION, &otp_size);
-	if (err != TFM_PLAT_ERR_SUCCESS) {
-		return err;
+	if (*size < profile_len) {
+		return TFM_PLAT_ERR_SYSTEM_ERR;
 	}
 
-	/* Actually copied data is always the smaller */
-	copy_size = *size < otp_size ? *size : otp_size;
-	/* String content */
-	*size = tfm_strnlen((char *)buf, copy_size);
+	memcpy(buf, profile, profile_len);
+	*size = profile_len;
 
 	return TFM_PLAT_ERR_SUCCESS;
 }
@@ -144,27 +123,30 @@ enum tfm_plat_err_t tfm_plat_get_implementation_id(uint32_t *size, uint8_t *buf)
 	return TFM_PLAT_ERR_SUCCESS;
 }
 
-enum tfm_plat_err_t tfm_plat_get_cert_ref(uint32_t *size, uint8_t *buf)
+#if CONFIG_TFM_ATTEST_INCLUDE_OPTIONAL_CLAIMS
 
+enum tfm_plat_err_t tfm_plat_get_cert_ref(uint32_t *size, uint8_t *buf)
 {
-	enum tfm_plat_err_t err;
-	size_t otp_size;
-	size_t copy_size;
-
-	err = tfm_plat_otp_read(PLAT_OTP_ID_CERT_REF, *size, buf);
-	if (err != TFM_PLAT_ERR_SUCCESS) {
-		return err;
+	if (read_variable_data(BL_VARIABLE_DATA_TYPE_PSA_CERTIFICATION_REFERENCE, buf, size)) {
+		return TFM_PLAT_ERR_SYSTEM_ERR;
 	}
 
-	err = tfm_plat_otp_get_size(PLAT_OTP_ID_CERT_REF, &otp_size);
-	if (err != TFM_PLAT_ERR_SUCCESS) {
-		return err;
+	return TFM_PLAT_ERR_SUCCESS;
+}
+
+enum tfm_plat_err_t tfm_attest_hal_get_verification_service(uint32_t *size, uint8_t *buf)
+{
+	const char *url = CONFIG_TFM_ATTEST_VERIFICATION_SERVICE_URL;
+	uint32_t url_len = strlen(url);
+
+	if (*size < url_len) {
+		return TFM_PLAT_ERR_SYSTEM_ERR;
 	}
 
-	/* Actually copied data is always the smaller */
-	copy_size = *size < otp_size ? *size : otp_size;
-	/* String content */
-	*size = tfm_strnlen((char *)buf, copy_size);
+	memcpy(buf, url, url_len);
+	*size = url_len;
 
 	return TFM_PLAT_ERR_SUCCESS;
 }
+
+#endif /* CONFIG_TFM_ATTEST_INCLUDE_OPTIONAL_CLAIMS */

modules/trusted-firmware-m/tfm_boards/partition/flash_layout.h

@@ -148,11 +148,13 @@
 #define TFM_HAL_ITS_PROGRAM_UNIT      (0x4)
 
 /* OTP / NV counter definitions */
+#ifdef PM_TFM_OTP_NV_COUNTERS_ADDRESS
 #define TFM_OTP_NV_COUNTERS_AREA_SIZE	(FLASH_OTP_NV_COUNTERS_AREA_SIZE / 2)
 #define TFM_OTP_NV_COUNTERS_AREA_ADDR	FLASH_OTP_NV_COUNTERS_AREA_OFFSET
 #define TFM_OTP_NV_COUNTERS_SECTOR_SIZE FLASH_OTP_NV_COUNTERS_SECTOR_SIZE
 #define TFM_OTP_NV_COUNTERS_BACKUP_AREA_ADDR                                                       \
 	(TFM_OTP_NV_COUNTERS_AREA_ADDR + TFM_OTP_NV_COUNTERS_AREA_SIZE)
+#endif
 
 /* Use Flash memory to store Code data */
 #define FLASH_BASE_ADDRESS (0x00000000)

samples/tfm/tfm_psa_template/prj.conf

@@ -67,3 +67,6 @@ CONFIG_TFM_ISOLATION_LEVEL=2
 
 # Initial Attestation requires RNG
 CONFIG_PSA_WANT_GENERATE_RANDOM=y
+
+# Optional attestation token fields
+CONFIG_TFM_ATTEST_VERIFICATION_SERVICE_URL="verification_url"

samples/tfm/tfm_psa_template/sysbuild.conf

@@ -10,3 +10,4 @@ SB_CONFIG_BOOT_SIGNATURE_TYPE_ECDSA_P256=y
 SB_CONFIG_MCUBOOT_MODE_OVERWRITE_ONLY=y
 SB_CONFIG_APPROTECT_LOCK=y
 SB_CONFIG_SECURE_APPROTECT_LOCK=y
+SB_CONFIG_TFM_OTP_PSA_CERTIFICATE_REFERENCE=y