278e5ebf78
Driver developer's guide: introduction on how to write a driver. Driver integration guide: how to build Mbed TLS with drivers. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
45 lines
2.1 KiB
Markdown
45 lines
2.1 KiB
Markdown
Building Mbed TLS with PSA cryptoprocessor drivers
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==================================================
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**This is a specification of work in progress. The implementation is not yet merged into Mbed TLS.**
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This document describes how to build Mbed TLS with additional cryptoprocessor drivers that follow the PSA cryptoprocessor driver interface.
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The interface is not fully implemented in Mbed TLS yet and is disabled by default. You can enable the experimental work in progress by setting `MBEDTLS_PSA_CRYPTO_DRIVERS` in the compile-time configuration. Please note that the interface may still change: until further notice, we do not guarantee backward compatibility with existing driver code when `MBEDTLS_PSA_CRYPTO_DRIVERS` is enabled.
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## Introduction
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The PSA cryptography driver interface provides a way to build Mbed TLS with additional code that implements certain cryptographic primitives. This is primarily intended to support platform-specific hardware.
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Note that such drivers are only available through the PSA cryptography API (crypto functions beginning with `psa_`, and X.509 and TLS interfaces that reference PSA types).
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Concretely speaking, a driver consists of one or more **driver description files** in JSON format and some code to include in the build. The driver code can either be provided in binary form as additional object file to link, or in source form.
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## How to build Mbed TLS with drivers
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To build Mbed TLS with drivers:
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1. Activate `MBEDTLS_PSA_CRYPTO_DRIVERS` in the library configuration.
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```
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cd /path/to/mbedtls
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scripts/config.py set MBEDTLS_PSA_CRYPTO_DRIVERS
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```
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2. Pass the driver description files through the Make variable `PSA_DRIVERS` when building the library.
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```
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cd /path/to/mbedtls
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make PSA_DRIVERS="/path/to/acme/driver.json /path/to/nadir/driver.json" lib
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```
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3. Link your application with the implementation of the driver functions.
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```
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cd /path/to/application
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ld myapp.o -L/path/to/acme -lacmedriver -L/path/to/nadir -lnadirdriver -L/path/to/mbedtls -lmbedcrypto
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```
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<!-- TODO: what if the driver is provided as C source code? -->
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<!-- TODO: what about additional include files? -->
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