DRBG: fix reseeding via RAND_add()/RAND_seed() with large input
In pull request #4328 the seeding of the DRBG via RAND_add()/RAND_seed() was implemented by buffering the data in a random pool where it is picked up later by the rand_drbg_get_entropy() callback. This buffer was limited to the size of 4096 bytes. When a larger input was added via RAND_add() or RAND_seed() to the DRBG, the reseeding failed, but the error returned by the DRBG was ignored by the two calling functions, which both don't return an error code. As a consequence, the data provided by the application was effectively ignored. This commit fixes the problem by a more efficient implementation which does not copy the data in memory and by raising the buffer the size limit to INT32_MAX (2 gigabytes). This is less than the NIST limit of 2^35 bits but it was chosen intentionally to avoid platform dependent problems like integer sizes and/or signed/unsigned conversion. Additionally, the DRBG is now less permissive on errors: In addition to ...
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