Re: Use of auto-generation approach for mbedtls/mbed-crypto driver psa_crypto_driver_wrappers..h file
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From: Ruchika Gupta Sent: Friday, April 5, 2024 4:14 PM To: tf-m <"tf-m@lists.trustedfirmware.org <tf-m"@lists.trustedfirmware.org>; mbed-tls@lists.trustedfirmware.org; security-wg@lists.zephyrproject.org Subject: Use of auto-generation approach for mbedtls/mbed-crypto driver psa_crypto_driver_wrappers..h file
Hi All,
Apologies for the long email. I am adding all the 3 projects (TF-M, mbedTLS and Zephyr) to the mail chain because the issues I discuss below are inter-connected and affect all the three projects.
From mbedtls 3.5.0 version, the mbedtls project has migrated to auto-generated psa_crypto_driver_wrappers.h file. https://github.com/Mbed-TLS/mbedtls/blob/development/docs/psa-driver-example... https://github.com/Mbed-TLS/mbedtls/blob/development/docs/proposed/psa-drive...
On TF-M, mbed-crypto, there are 2 patches for the drivers given below which are still hardcoding their changes and not following the above approach.
1. PSA_CRYPTO_DRIVER_TFM_BUILTIN_KEY_LOADER (0001-Add-TF-M-Builtin-Key-Loader-driver-entry-points.patch) 2. PSA_CRYPTO_DRIVER_CC3XX (0005-Hardcode-CC3XX-entry-points.patch)
We at NXP, have migrated our psa crypto wrappers to the above approach using auto-generation. We want to maintain same code base for mbedtls for our SDK's, TFM mbed-crypto as well as align mbedTLS fork in Zephyr. We are increasingly finding it difficult to migrate to newer versions of mbedtls because of hardcoding of above drivers. The problem is specially on the Zephyr front, where in the mbedTLS fork in zephyr these patches from tfm are applied by default.
I have queries for all the 3 projects listed below :
TF-M --> Can you please let us know what are the plans to migrate these 2 drivers in tfm to the auto-generation approach. If these patches can be migrated to make changes in jinja files rather than hardcoding in psa_crypto_driver_wrappers , things would be much easier to integrate. Is somebody already working on it ? Are you open to accept patches for this change ?
mbedTLS --> What is the long term strategy from mbedTLS on this auto-generation ? We still have a lot of hard-coding in .jinja file rather than using drivers.json. Would mbedTLS/new PSA crypto repository start accepting patches for psa wrappers from platforms ? Can the patches which TF-M project maintains be merged in the mbedTLS ?
Zephyr --> On Zephyr front, what are the plans to align to this auto-generation approach ?
Regards, Ruchika
Hi Ruchika,
We are planning to complete the work to generate driver wrappers from the JSON, but we don't know when.
From a technical standpoint, we're likely to move away from the Jinja code and use only basic Python, with a function wrapper generator that we'll maintain and that we'll use for multiple purposes. So at this point we probably won't spend much effort on integrating patches to the Jinja templates or the corresponding Python code.
We do welcome reports and patches on how this works out for those of you who are maintaining drivers. Please let us know what does and doesn't work for you.
Best regards,
tf-m@lists.trustedfirmware.org
-
Gilles Peskine -
Ruchika Gupta