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[nrf noup] bootutil: Locking KMU keys #465

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Merged
merged 1 commit into from
Jul 24, 2025
Merged

[nrf noup] bootutil: Locking KMU keys #465

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28 changes: 28 additions & 0 deletions boot/bootutil/src/ed25519_psa.c
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Original file line number Diff line number Diff line change
Expand Up @@ -165,4 +165,32 @@ int exec_revoke(void)
return ret;
}
#endif /* CONFIG_BOOT_KMU_KEYS_REVOCATION */

void nrf_crypto_keys_housekeeping(void)
{
psa_status_t status;

/* We will continue through all keys, even if we have error while
* processing any of it. Only doing BOOT_LOG_DBG, as we do not
* really want to inform on failures to lock.
*/
for (int i = 0; i < CONFIG_BOOT_SIGNATURE_KMU_SLOTS; ++i) {
psa_key_attributes_t attr;

status = psa_get_key_attributes(kmu_key_ids[i], &attr);
BOOT_LOG_DBG("KMU key 0x%x(%d) attr query status == %d",
kmu_key_ids[i], i, status);

if (status == PSA_SUCCESS) {
status = cracen_kmu_block(&attr);
BOOT_LOG_DBG("KMU key lock status == %d", status);
}

status = psa_purge_key(kmu_key_ids[i]);
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Commenting here as we have merged an API that is irrelevant for KMU support
https://arm-software.github.io/psa-api/crypto/1.1/api/keys/management.html#c.psa_purge_key

This type of API is only required when PSA_KEY_USAGE_CACHE is in use, which is not the case for NSIB or MCUboot

There is no key caching functionality forwarded to PSA crypto driver wrappers (psa_crypto_driver_wrapper_purge-key doesn't exists). Likewise there is nothing in the thin PSA core used by bl2

BOOT_LOG_DBG("KMU key 0x%x(%d) purge status == %d",
kmu_key_ids[i], i, status);

}
}

#endif
11 changes: 11 additions & 0 deletions boot/zephyr/include/nrf_cleanup.h
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Expand Up @@ -21,4 +21,15 @@ void nrf_cleanup_peripheral(void);
*/
void nrf_cleanup_ns_ram(void);

/**
* Crypto key storage housekeeping. Intended to clean up key objects from
* crypto backend and apply key policies that should take effect after
* MCUboot no longer needs access to keys.
*/
#if defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
extern void nrf_crypto_keys_housekeeping(void);
#else
#define nrf_crypto_keys_housekeeping() do {} while (0)
#endif

#endif
7 changes: 7 additions & 0 deletions boot/zephyr/main.c
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Expand Up @@ -651,6 +651,13 @@ int main(void)

mcuboot_status_change(MCUBOOT_STATUS_BOOTABLE_IMAGE_FOUND);

/* From this point MCUboot does not need access to crypto keys.
* Clean up backend key objects and apply key access policies that
* will take effect from now through entire boot session and application
* run.
*/
nrf_crypto_keys_housekeeping();

#if USE_PARTITION_MANAGER && CONFIG_FPROTECT

#ifdef PM_S1_ADDRESS
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