mbedtls: some enhancement for PSA crypto core #80136
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Auto-select MBEDTLS_CIPHER_AES_ENABLED when AES support is requested through PSA (i.e. CONFIG_PSA_WANT_KEY_TYPE_AES) and the PSA support is provided through Mbed TLS itself (i.e. CONFIG_MBEDTLS_PSA_CRYPTO_C). This mimic what happens in Mbed TLS at build time: if AES support is required through PSA, but there's no one else providing it (i.e. no TF-M in Zephyr) then provide this support through legacy AES module. This is useful in samples/tests so that the user can simply use the PSA_WANT symbol to ask for AES support in PSA crypto and then tune the AES features (ex: CONFIG_MBEDTLS_AES_ROM_TABLES) without the need to also define CONFIG_MBEDTLS_CIPHER_AES_ENABLED. Signed-off-by: Valerio Setti <vsetti@baylibre.com>
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Adding new CONFIG_MBEDTLS_PSA_KEY_SLOT_COUNT to select the number of key slots in PSA core. The default value is 32 which is the same value used in Mbed TLS by default. Be aware that key slots consume RAM memory even if unused, so the proper value should be a compromise between the number of slots required by the application and the available RAM in the system. Signed-off-by: Valerio Setti <vsetti@baylibre.com>
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The main problem of MBEDTLS_PSA_CRYPTO_LEGACY_RNG is that it brings in some legacy modules (entropy + ctr_drbg/hmac_drbg) which means extra ROM/RAM footprint. MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG instead simply calls to the CSPRNG which makes it definitely smaller. Signed-off-by: Valerio Setti <vsetti@baylibre.com>
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CONFIG_MBEDTLS_CIPHER_AES_ENABLEDwhenCONFIG_PSA_WANT_KEY_TYPE_AESis set and Mbed TLS is the PSA crypto API provider (i.e.CONFIG_MBEDTLS_PSA_CRYPTO_C). This mimic what happens in Mbed TLS at build time.CONFIG_MBEDTLS_PSA_CRYPTO_EXTERNAL_RNGinstead ofCONFIG_MBEDTLS_PSA_CRYPTO_LEGACY_RNGif the platform has any CSPRNG enabled. This helps reducing RAM/ROM footprint.