In the external RNG case, don't make mbedtls_psa_get_random() a
static inline function: this would likely result in identical
instances of this function in every module that uses it. Instead, make
it a single function with external linkage.
In the non-external case, instead of a trivial wrapper function, make
mbedtls_psa_get_random a constant pointer to whichever DRBG function
is being used.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Hide the obtention of the pointer to the RNG state behind a macro.
To make it possible to use this macro in a module other than
psa_crypto.c, which will happen in the future, make sure that the
definition of the macro does not reference internal variables of
psa_crypto.c. For this purpose, in the internal-DRBG case, export a
symbol containing the address of the DRBG state.
When the RNG state is a pointer a DRBG state, just keep this pointer
in a variable: there's no need to store a pointer to a larger structure.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
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>
