Support using HMAC_DRBG instead of CTR_DRBG in the PSA subsystem.
Use HMAC_DRBG if CTR_DRBG is available. Choose between SHA-256 and
SHA-512 based on availability.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Implement support for MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG.
For test purposes, write an implementation that uses libc rand().
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Create wrapper functions around calls to CTR_DRBG and around calls to
entropy+DRBG. This is in preparation for allowing alternative DRBG
implementations that use the Mbed TLS entropy module, or complete RNG
implementations that bypass the entropy module as well.
This is purely a refactoring commit. No behavior change.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
