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[nrf noup] boot: bootutil: Allow configuring number of KMU keys #383

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merged 1 commit into from
Dec 4, 2024
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[nrf noup] boot: bootutil: Allow configuring number of KMU keys #383

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9 changes: 6 additions & 3 deletions boot/bootutil/src/ed25519_psa.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2020 Nordic Semiconductor ASA
* Copyright (c) 2020-2024 Nordic Semiconductor ASA
*
* SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
*/
Expand All @@ -12,6 +12,7 @@

#include <psa/crypto.h>
#include <psa/crypto_types.h>
#include <zephyr/sys/util.h>
#if defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
#include <cracen_psa_kmu.h>
#endif
Expand All @@ -30,7 +31,9 @@ static psa_key_id_t kmu_key_ids[3] = {
MAKE_PSA_KMU_KEY_ID(228),
MAKE_PSA_KMU_KEY_ID(230)
};
#define KMU_KEY_COUNT (sizeof(kmu_key_ids)/sizeof(kmu_key_ids[0]))
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can we have assertion on limit CONFIG_BOOT_SIGNATURE_KMU_SLOTS value to KMU_KEY_COUNT as max?

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The limit is enforced by Kconfig

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Added a build assert


BUILD_ASSERT(CONFIG_BOOT_SIGNATURE_KMU_SLOTS <= ARRAY_SIZE(kmu_key_ids),
"Invalid number of KMU slots, up to 3 are supported on nRF54L15");
#endif

#if !defined(CONFIG_BOOT_SIGNATURE_USING_KMU)
Expand Down Expand Up @@ -103,7 +106,7 @@ int ED25519_verify(const uint8_t *message, size_t message_len,

status = PSA_ERROR_BAD_STATE;

for (int i = 0; i < KMU_KEY_COUNT; ++i) {
for (int i = 0; i < CONFIG_BOOT_SIGNATURE_KMU_SLOTS; ++i) {
psa_key_id_t kid = kmu_key_ids[i];

status = psa_verify_message(kid, PSA_ALG_PURE_EDDSA, message,
Expand Down
12 changes: 12 additions & 0 deletions boot/zephyr/Kconfig
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Expand Up @@ -317,6 +317,18 @@ config BOOT_SIGNATURE_USING_KMU
MCUboot will use keys provisioned to the device key management unit for signature
verification instead of compiling in key data from a file.

if BOOT_SIGNATURE_USING_KMU

config BOOT_SIGNATURE_KMU_SLOTS
int "KMU key slots"
range 1 3
default 1
help
Selects the number of KMU key slots (also known as generations) to use when verifying
an image.

endif

if !BOOT_SIGNATURE_USING_KMU

config BOOT_SIGNATURE_KEY_FILE
Expand Down
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