Change randombytes/1 so it always executes on a DS

Investigation shows erratic behaviour of the CSPRNG. It may block at times
because it needs to go to the kernel and obtain more random information in
the system. Once this happens, you are blocked for quite a long time, but
we don't generally know when this happens. So just execute these directly
on the dirty scheduler.

c_src/enacl_nif.c

@@ -1071,7 +1071,6 @@ static ErlNifFunc nif_funcs[] = {
 	{"crypto_sign_ed25519_PUBLICKEYBYTES", 0, enif_crypto_sign_ed25519_PUBLICKEYBYTES},
 	{"crypto_sign_ed25519_SECRETKEYBYTES", 0, enif_crypto_sign_ed25519_SECRETKEYBYTES},
 
-	{"randombytes_b", 1, enif_randombytes},
 	{"randombytes", 1, enif_randombytes, ERL_NIF_DIRTY_JOB_CPU_BOUND},
 
 	{"scramble_block_16", 2, enif_scramble_block_16}

src/enacl.erl

@@ -722,8 +722,6 @@ crypto_sign_ed25519_secret_size() ->
 %% you to the underlying system implementations for random data.
 %% @end
 -spec randombytes(non_neg_integer()) -> binary().
-randombytes(N) when N =< ?RANDOMBYTES_SIZE ->
-    bump(enacl_nif:randombytes_b(N), ?RANDOMBYTES_REDUCTIONS, ?RANDOMBYTES_SIZE, N);
 randombytes(N) ->
     enacl_nif:randombytes(N).
 

src/enacl_nif.erl

@@ -101,8 +101,7 @@
 
 %% Access to the RNG
 -export([
-	randombytes/1,
-	randombytes_b/1
+	randombytes/1
 ]).
 
 %% Undocumented features :>
@@ -199,6 +198,5 @@ crypto_verify_16(_X, _Y) -> erlang:nif_error(nif_not_loaded).
 crypto_verify_32(_X, _Y) -> erlang:nif_error(nif_not_loaded).
 
 randombytes(_RequestedSize) -> erlang:nif_error(nif_not_loaded).
-randombytes_b(_RequestedSize) -> erlang:nif_error(nif_not_loaded).
 
 scramble_block_16(_Block, _Key) -> erlang:nif_error(nif_not_loaded).