Add pwhash_SALTBYTES/0

c_src/enacl_nif.c

@@ -287,6 +287,7 @@ static ErlNifFunc nif_funcs[] = {
     {"crypto_verify_32", 2, enacl_crypto_verify_32},
     {"sodium_memzero", 1, enif_sodium_memzero},
 
+    {"crypto_pwhash_SALTBYTES", 0, enacl_crypto_pwhash_SALTBYTES},
     erl_nif_dirty_job_cpu_bound_macro("crypto_pwhash", 4, enacl_crypto_pwhash),
     erl_nif_dirty_job_cpu_bound_macro("crypto_pwhash_str", 3,
                                       enacl_crypto_pwhash_str),

c_src/pwhash.c

@@ -57,6 +57,12 @@ static size_t enacl_pwhash_memlimit(ErlNifEnv *env, ERL_NIF_TERM arg) {
   return 0;
 }
 
+
+ERL_NIF_TERM enacl_crypto_pwhash_SALTBYTES(ErlNifEnv *env, int argc,
+                                           ERL_NIF_TERM const argv[]) {
+  return enif_make_int64(env, crypto_pwhash_SALTBYTES);
+}
+
 ERL_NIF_TERM enacl_crypto_pwhash(ErlNifEnv *env, int argc,
                                  ERL_NIF_TERM const argv[]) {
   ErlNifBinary h, p, s;

c_src/pwhash.h

@@ -3,6 +3,9 @@
 
 #include <erl_nif.h>
 
+ERL_NIF_TERM enacl_crypto_pwhash_SALTBYTES(ErlNifEnv *env, int argc,
+                                           ERL_NIF_TERM const argv[]);
+
 ERL_NIF_TERM enacl_crypto_pwhash(ErlNifEnv *env, int argc,
                                  ERL_NIF_TERM const argv[]);
 

src/enacl.erl

@@ -116,6 +116,7 @@
          shorthash_size/0,
          shorthash/2,
 
+         pwhash_SALTBYTES/0,
          pwhash/4,
          pwhash_str/3,
 
@@ -395,6 +396,13 @@ generichash_final(State) ->
     enacl_nif:crypto_generichash_final(State).
 
 -type pwhash_limit() :: interactive | moderate | sensitive | pos_integer().
+
+%% @doc pwhash_SALTBYTES/0 returns the number of bytes required for salt.
+%% @end
+-spec pwhash_SALTBYTES() -> pos_integer().
+pwhash_SALTBYTES() ->
+    enacl_nif:crypto_pwhash_SALTBYTES().
+
 %% @doc pwhash/2 hash a password
 %%
 %% This function generates a fixed size salted hash of a user defined password.

src/enacl_nif.erl

@@ -147,6 +147,7 @@
 
 %% Password Hashing - Argon2 Algorithm
 -export([
+         crypto_pwhash_SALTBYTES/0,
          crypto_pwhash/4,
          crypto_pwhash_str/3,
          crypto_pwhash_str_verify/2
@@ -238,6 +239,7 @@ crypto_secretstream_xchacha20poly1305_init_pull(_Header, _Key) -> erlang:nif_err
 crypto_secretstream_xchacha20poly1305_pull(_Ref, _CipherText, _AD) -> erlang:nif_error(nif_not_loaded).
 crypto_secretstream_xchacha20poly1305_rekey(_Ref) -> erlang:nif_error(nif_not_loaded).
 
+crypto_pwhash_SALTBYTES() -> erlang:nif_error(nif_not_loaded).
 crypto_pwhash(_Password, _Salt, _Ops, _Mem) -> erlang:nif_error(nif_not_loaded).
 crypto_pwhash_str(_Password, _Ops, _Mem) -> erlang:nif_error(nif_not_loaded).
 crypto_pwhash_str_verify(_HashedPassword, _Password) -> erlang:nif_error(nif_not_loaded).

test/enacl_SUITE.erl

@@ -136,6 +136,7 @@ pwhash(_Config) ->
     Str1 = enacl:pwhash_str(PW),
     true = enacl:pwhash_str_verify(Str1, PW),
     false = enacl:pwhash_str_verify(Str1, <<PW/binary, 1>>),
+    16 = enacl:pwhash_SALTBYTES(),
     ok.
 
 sign(_Config) ->