modules: openthread: use PSA Crypto API as default choice for crypto #98088

valeriosetti · 2025-10-22T14:23:26Z

Modify OpenThread's Kconfig options in order to always use PSA Crypto API by default instead of legacy Mbed TLS crypto.
Please check commits messages for details.

These changes were tested with zephyr/samples/net/openthread/coap/ on 2x nrf52840dk boards .

doc/releases/migration-guide-4.3.rst

rlubos · 2025-10-31T11:26:51Z

samples/net/openthread/coap/prj.conf

 CONFIG_OPENTHREAD_NETWORK_NAME="OpenThreadDemo"
+
+# Use ZMS as storage backend for Secure Storage
+CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_ZMS=y


Wouldn't we need this in other samples as well? And those generic networking samples that have overlay-ot.conf?

This is still no clear to me, do we need thsoe configs in other samples/OT overlays as well?

I'm still working on making other samples building properly :). I think the CI is not even testing them and they need fixes for sure.
I just pushed the PR to let @tomi-font and other reviewers see requested changes in place ;)

I added the DNM label to ensure that this PR is not merged accidentally before we're happy with test coverage

I'd say just enable the Settings backend instead, it's the simplest to enable, just a Kconfig option, no DT overlay.

Even with CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_SETTINGS you need to select the backend for Settings, otherwise CONFIG_SETTINGS_NONE would be used.
Then if I enable Settings to use ZMS as backend, why not using ZMS directly from Secure Storage and save some footprint?

This is still no clear to me, do we need thsoe configs in other samples/OT overlays as well?

@rlubos I finally had the time to check this question.
Apparently samples/net/openthread/border_router already enables NVS so we don't need ZMS in this case. The same holds also for samples/net/openthread/coprocessor and for samples/net/openthread/shell.

For sake of uniformity I think it's better to enable NVS also in the samples/net/openthread/border_router instead of ZMS as I did previously.

Cristib05 · 2025-11-25T09:11:40Z

Hi @valeriosetti. I have been debugging more in OpenThread border router application from samples/net/openthread/border_router.
At the moment, I have found one issue, related to TREL:
Here is the app call stack:

One issue is in psa_key_derivation_setup function. At the moment, the result is return PSA_ERROR_NOT_SUPPORTED;

It seems like AT_LEAST_ONE_BUILTIN_KDF has to be defined for an actual call to be made, but I am not sure what flag is required to have this enabled.

The question is what flag I should define not to break the functionality and enable the computation of key?

valeriosetti · 2025-11-25T15:43:44Z

It seems like AT_LEAST_ONE_BUILTIN_KDF has to be defined for an actual call to be made, but I am not sure what flag is required to have this enabled.

This is an amazing feedback, thanks! I added a new commit in the series which hopefully should enable what was missing. Can you please give it another try?

Cristib05 · 2025-11-25T15:53:40Z

It seems like AT_LEAST_ONE_BUILTIN_KDF has to be defined for an actual call to be made, but I am not sure what flag is required to have this enabled.

This is an amazing feedback, thanks! I added a new commit in the series which hopefully should enable what was missing. Can you please give it another try?

Meanwhile I have managed to have a working joiner-commissioner scenario on OpenThread Border Router sample. I will compare my changes with yours and let you know. Thanks for the new commit!

Cristib05 · 2025-11-26T08:14:47Z

It seems like AT_LEAST_ONE_BUILTIN_KDF has to be defined for an actual call to be made, but I am not sure what flag is required to have this enabled.

This is an amazing feedback, thanks! I added a new commit in the series which hopefully should enable what was missing. Can you please give it another try?

Meanwhile I have managed to have a working joiner-commissioner scenario on OpenThread Border Router sample. I will compare my changes with yours and let you know. Thanks for the new commit!

Hi @valeriosetti,
For the joiner-commissioner scenario, I have found that those settings are required:
select PSA_WANT_ALG_TLS12_PRF if OPENTHREAD_COMMISSIONER_JOINER
select PSA_WANT_ALG_TLS12_ECJPAKE_TO_PMS if OPENTHREAD_COMMISSIONER_JOINER
I also needed to increase CONFIG_MBEDTLS_HEAP_SIZE from 10240 to 15360, but I guess this can be further optimized.

Related to your commit from yesterday,
select PSA_WANT_ALG_HKDF if OPENTHREAD_COMMISSIONER_JOINER
select PSA_WANT_ALG_HKDF_EXTRACT if OPENTHREAD_COMMISSIONER_JOINER
select PSA_WANT_ALG_HKDF_EXPAND if OPENTHREAD_COMMISSIONER_JOINER,
I think that those are not required by OPENTHREAD_COMMISSIONER_JOINER. Maybe this should fall under something related to TREL or Border Router, as HKDF-SHA256 is required by TREL.

Related to TREL initialization, I made use of PSA switch proposal from OpenThread, openthread/openthread@3a6573f#diff-8d6dc63e1ec9adacf9f4215b293513b17f39a8127ea4b89100db42976adace44,
and for KeyManager::ComputeTrelKey to work, a small addition is required in https://github.com/zephyrproject-rtos/zephyr/blob/main/modules/openthread/platform/crypto_psa.c#L97, OT_CRYPTO_KEY_USAGE_DERIVE should also be added to the list of supported flags.

valeriosetti · 2025-11-26T14:37:59Z

I think that those are not required by OPENTHREAD_COMMISSIONER_JOINER. Maybe this should fall under something related to TREL or Border Router, as HKDF-SHA256 is required by TREL.

Thanks for the suggestion. I updated the commit with the information you provided.

Related to TREL initialization, I made use of PSA switch proposal from OpenThread, openthread/openthread@3a6573f#diff-8d6dc63e1ec9adacf9f4215b293513b17f39a8127ea4b89100db42976adace44, and for KeyManager::ComputeTrelKey to work

I updated the companion PR to entirely cherry-pick the commit from the PR on the official OT repo. Previously I only took some part of it.

a small addition is required in https://github.com/zephyrproject-rtos/zephyr/blob/main/modules/openthread/platform/crypto_psa.c#L97, OT_CRYPTO_KEY_USAGE_DERIVE should also be added to the list of supported flags.

Done. Thanks.

valeriosetti · 2025-12-05T16:45:12Z

@Cristib05 did you have a chance to retest this PR after I applied all the changes you proposed in your last message?
I would like to keep this PR progressing and having it completed asap

Cristib05 · 2025-12-08T07:09:01Z

@Cristib05 did you have a chance to retest this PR after I applied all the changes you proposed in your last message? I would like to keep this PR progressing and having it completed asap

Hi @valeriosetti, I managed to re-test using your latest changes. I have tested the following:

joiner-commissioner on 15.4 https://github.com/openthread/openthread/blob/main/src/cli/README_COMMISSIONING.md
external commissioner on Border Router
TREL communication between RW612 Zephyr OTBR and RPI
SRP service registration between RW612 Zephyr OTBR and RPI

Thanks for your updates!

tomi-font

OpenThread needs a PSA ITS provider when using PSA Crypto API, therefore we enable Secure Storage in builds without TF-M. Signed-off-by: Valerio Setti <[email protected]>

Make CONFIG_OPENTHREAD_CRYPTO_PSA as enabled by default in order to use PSA Crypto API instead of legacy Mbed TLS' crypto. This is done with the final goal to deprecate and remove usage of legacy crypto support in the near future from Zephyr codebase. Signed-off-by: Valerio Setti <[email protected]>

Secure Storage is used as PSA ITS in builds where TF-M is not enabled, but it needs a storage backend where to physically save data. If CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_ZMS is used then its "depends on" guarantee that there is a partition to use as physical storage. If CONFIG_SECURE_STORAGE_ITS_STORE_IMPLEMENTATION_SETTINGS is used instead we want to ensure that CONFIG_SETTINGS_NONE doesn't gets selected which would result in Settings not being able to store data anywhere. This commit add a depends_on for this last case. Signed-off-by: Valerio Setti <[email protected]>

Allow MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED to work with either legacy crypto (i.e. MBEDTLS_ECJPAKE_C) or PSA Crypto API (i.e. PSA_WANT_ALG_JPAKE). Signed-off-by: Valerio Setti <[email protected]>

When PSA Crypto API are used they need a PSA ITS implementation and this is provided by Secure Storage if TF-M is not enabled in the build. Secure Storage can use Settings as backend and Settings, on its turn, can use several other backends to store data (ex: ZMS, NVS, etc). Since NVS is already enabled in other OpenThread Zephyr samples, let's enable NVS also for this sample. While at it, also slightly re-organize "sample.yaml" to share more data between tests and allow building and testing also on the nrf52840dk board. Signed-off-by: Valerio Setti <[email protected]>

crypto_psa.c was missing an implementation for the following functions: - otPlatCryptoHkdfInit - otPlatCryptoHkdfExtract - otPlatCryptoHkdfExpand - otPlatCryptoHkdfDeinit which provide support for HKDF using PSA Crypto API. This commit fill this gap by copying the implementation from upstream PR 11445. Signed-off-by: Valerio Setti <[email protected]>

Select proper PSA_WANT requirements in CONFIG_OPENTHREAD_CRYPTO_PSA_CONFIG in order to enable KDF algorithms. Signed-off-by: Valerio Setti <[email protected]>

Increase heap memory when OpenThread is enabled and either "commissioner" or "joiner" roles are used. Signed-off-by: Valerio Setti <[email protected]>

Simply move the definition of OPENTHREAD_CRYPTO_PSA Konfig before crypto configuration related Kconfigs. Signed-off-by: Valerio Setti <[email protected]>

Include new definitions in crypto.h in order support HKDF algorithm. Signed-off-by: Valerio Setti <[email protected]>

sonarqubecloud · 2025-12-10T12:15:13Z

Quality Gate passed

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0 New issues
0 Accepted issues

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0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

valeriosetti force-pushed the openthread-use-psa branch 2 times, most recently from 5cdcab8 to 0086bd8 Compare October 30, 2025 22:14

valeriosetti marked this pull request as ready for review October 30, 2025 22:45

zephyrbot added area: Samples Samples area: OpenThread area: mbedTLS / PSA Crypto area: Networking Release Notes To be mentioned in the release notes labels Oct 30, 2025

zephyrbot requested review from canisLupus1313, ceolin, cfriedt, d3zd3z, edmont, ithinuel, jhedberg, jukkar, maciejbaczmanski, mariuszpos, pdgendt, rlubos, ssharks, tomi-font and wearyzen October 30, 2025 22:46

zephyrbot assigned rlubos Oct 30, 2025

valeriosetti force-pushed the openthread-use-psa branch from 0086bd8 to 2ea6432 Compare October 31, 2025 08:08

zephyrbot requested a review from kartben October 31, 2025 08:10

valeriosetti force-pushed the openthread-use-psa branch 3 times, most recently from 3f04640 to 481eed1 Compare October 31, 2025 11:14

rlubos reviewed Oct 31, 2025

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valeriosetti force-pushed the openthread-use-psa branch from 5d37bbe to b710852 Compare November 25, 2025 15:39

valeriosetti force-pushed the openthread-use-psa branch from b710852 to f709285 Compare November 25, 2025 15:45

valeriosetti force-pushed the openthread-use-psa branch from f709285 to fe92598 Compare November 26, 2025 14:37

valeriosetti force-pushed the openthread-use-psa branch from fe92598 to f602249 Compare November 26, 2025 15:35

valeriosetti mentioned this pull request Dec 5, 2025

include: platform: crypto: add support for HKDF zephyrproject-rtos/openthread#210

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valeriosetti requested a review from tomi-font December 9, 2025 03:55

tomi-font requested changes Dec 9, 2025

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valeriosetti added 10 commits December 10, 2025 12:42

modules: openthread: select Secure Storage when using PSA without TF-M

0ee1e64

OpenThread needs a PSA ITS provider when using PSA Crypto API, therefore we enable Secure Storage in builds without TF-M. Signed-off-by: Valerio Setti <[email protected]>

modules: mbedtls: allow ECJPAKE keyexchange to work through PSA API

e12c5eb

Allow MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED to work with either legacy crypto (i.e. MBEDTLS_ECJPAKE_C) or PSA Crypto API (i.e. PSA_WANT_ALG_JPAKE). Signed-off-by: Valerio Setti <[email protected]>

modules: openthread: select PSA_WANT deps for KDF algorithms

778b40d

Select proper PSA_WANT requirements in CONFIG_OPENTHREAD_CRYPTO_PSA_CONFIG in order to enable KDF algorithms. Signed-off-by: Valerio Setti <[email protected]>

modules: mbedtls: increase heap memory for OpenThread

7a2b496

Increase heap memory when OpenThread is enabled and either "commissioner" or "joiner" roles are used. Signed-off-by: Valerio Setti <[email protected]>

modules: openthread: move definition of OPENTHREAD_CRYPTO_PSA

4e9f2a1

Simply move the definition of OPENTHREAD_CRYPTO_PSA Konfig before crypto configuration related Kconfigs. Signed-off-by: Valerio Setti <[email protected]>

manifest: openthread: include updates for HKDF support

307ff11

Include new definitions in crypto.h in order support HKDF algorithm. Signed-off-by: Valerio Setti <[email protected]>

valeriosetti force-pushed the openthread-use-psa branch from f602249 to 307ff11 Compare December 10, 2025 11:47

valeriosetti requested a review from tomi-font December 10, 2025 11:48

tomi-font approved these changes Dec 11, 2025

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LuDuda approved these changes Dec 12, 2025

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jukkar approved these changes Dec 12, 2025

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modules: openthread: use PSA Crypto API as default choice for crypto #98088

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