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boot: zephyr: Add ECDSA support using mbedTLS #2537

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boot: zephyr: Add ECDSA support using mbedTLS #2537

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e6d6bd1
boot: zephyr: Add ECDSA support using mbedTLS
prene-se Nov 10, 2025
67140a4
boot: zephyr: Add correct ECDSA kconfig
prene-se Nov 25, 2025
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28 changes: 16 additions & 12 deletions boot/zephyr/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -300,21 +300,25 @@ elseif(CONFIG_BOOT_SIGNATURE_TYPE_ED25519 OR CONFIG_BOOT_ENCRYPT_X25519)
endif()

if(NOT CONFIG_BOOT_ED25519_PSA AND NOT CONFIG_BOOT_ECDSA_PSA)
if(CONFIG_BOOT_ENCRYPT_EC256 OR CONFIG_BOOT_ENCRYPT_X25519)
zephyr_library_sources(
${TINYCRYPT_DIR}/source/aes_encrypt.c
${TINYCRYPT_DIR}/source/aes_decrypt.c
${TINYCRYPT_DIR}/source/ctr_mode.c
${TINYCRYPT_DIR}/source/hmac.c
${TINYCRYPT_DIR}/source/ecc_dh.c
)
if(CONFIG_BOOT_USE_TINYCRYPT)
if(CONFIG_BOOT_ENCRYPT_EC256 OR CONFIG_BOOT_ENCRYPT_X25519)
zephyr_library_sources(
${TINYCRYPT_DIR}/source/aes_encrypt.c
${TINYCRYPT_DIR}/source/aes_decrypt.c
${TINYCRYPT_DIR}/source/ctr_mode.c
${TINYCRYPT_DIR}/source/hmac.c
${TINYCRYPT_DIR}/source/ecc_dh.c
)
endif()
endif()
endif()

if(CONFIG_BOOT_ENCRYPT_EC256 AND NOT CONFIG_BOOT_ECDSA_PSA)
zephyr_library_sources(
${TINYCRYPT_DIR}/source/ecc_dh.c
)
if(CONFIG_BOOT_USE_TINYCRYPT)
if(CONFIG_BOOT_ENCRYPT_EC256 AND NOT CONFIG_BOOT_ECDSA_PSA)
zephyr_library_sources(
${TINYCRYPT_DIR}/source/ecc_dh.c
)
endif()
endif()

if(CONFIG_MCUBOOT_SERIAL)
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14 changes: 14 additions & 0 deletions boot/zephyr/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -283,6 +283,20 @@ config BOOT_ECDSA_TINYCRYPT
bool "Use tinycrypt"
select BOOT_USE_TINYCRYPT

config BOOT_ECDSA_MBEDTLS
bool "Use mbedTLS"
select BOOT_USE_MBEDTLS
select MBEDTLS
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@nordicjm nordicjm Nov 21, 2025

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not really sure how you expect this to work? Given that it doesn't:

/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: app/libapp.a(image_ecdsa.c.obj): in function `bootutil_ecdsa_init':
/tmp/aa/bootloader/mcuboot/boot/bootutil/include/bootutil/crypto/ecdsa.h:490: undefined reference to `mbedtls_ecdsa_init'
/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: app/libapp.a(image_ecdsa.c.obj): in function `bootutil_ecdsa_verify':
/tmp/aa/bootloader/mcuboot/boot/bootutil/include/bootutil/crypto/ecdsa.h:577: undefined reference to `mbedtls_ecp_group_load'
/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: /tmp/aa/bootloader/mcuboot/boot/bootutil/include/bootutil/crypto/ecdsa.h:582: undefined reference to `mbedtls_ecp_point_read_binary'
/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: /tmp/aa/bootloader/mcuboot/boot/bootutil/include/bootutil/crypto/ecdsa.h:587: undefined reference to `mbedtls_ecp_check_pubkey'
/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: /tmp/aa/bootloader/mcuboot/boot/bootutil/include/bootutil/crypto/ecdsa.h:592: undefined reference to `mbedtls_ecdsa_read_signature'
/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: app/libapp.a(image_ecdsa.c.obj): in function `bootutil_ecdsa_drop':
/tmp/aa/bootloader/mcuboot/boot/bootutil/include/bootutil/crypto/ecdsa.h:495: undefined reference to `mbedtls_ecdsa_free'
/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: app/libapp.a(keys.c.obj):/tmp/aa/bootloader/mcuboot/boot/zephyr/keys.c:52: undefined reference to `ecdsa_pub_key'
/opt/zephyr-sdk-0.17.0/arm-zephyr-eabi/bin/../lib/gcc/arm-zephyr-eabi/12.2.0/../../../../arm-zephyr-eabi/bin/ld.bfd: app/libapp.a(keys.c.obj):(.rodata.bootutil_keys+0x4): undefined reference to `ecdsa_pub_key_len'

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@prene-se prene-se Nov 25, 2025

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Previously, I used sysbuild with:

CONFIG_CUSTOM_MBEDTLS_CFG_FILE=y CONFIG_MBEDTLS_CFG_FILE="config-ec.h"

to provide the missing mbedTLS functions.

I have now updated the Kconfig to select all required mbedTLS options directly, without relying on a custom mbedTLS config file. All dependencies are handled via Kconfig, including when BOOT_ENCRYPT_IMAGE is enabled. I am not entirely sure if all requirements are covered, so feedback is welcome.

select MBEDTLS_ECP_C if MBEDTLS_BUILTIN
select MBEDTLS_ECDSA_C if MBEDTLS_BUILTIN
select MBEDTLS_ECP_DP_SECP256R1_ENABLED if MBEDTLS_BUILTIN
select MBEDTLS_ASN1_PARSE_C if MBEDTLS_BUILTIN
select MBEDTLS_ECP_NIST_OPTIM if MBEDTLS_BUILTIN
select MBEDTLS_SHA256 if MBEDTLS_BUILTIN
select MBEDTLS_MD if MBEDTLS_BUILTIN
select MBEDTLS_ECDH_C if MBEDTLS_BUILTIN && BOOT_ENCRYPT_IMAGE
select BOOT_AES_MBEDTLS_DEPENDENCIES if MBEDTLS_BUILTIN && BOOT_ENCRYPT_IMAGE

config BOOT_ECDSA_CC310
bool "Use CC310"
depends on HAS_HW_NRF_CC310
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