Add missing unit test and docs entry for -m 21420

docs/changes.txt

@@ -6,6 +6,7 @@
 
 - Added hash-mode: Exodus Desktop Wallet (scrypt)
 - Added hash-mode: Teamspeak 3 (channel hash)
+- Added hash-mode: sha256($salt.sha256_bin($pass))
 
 ##
 ## Features

docs/readme.txt

@@ -110,6 +110,7 @@ NVIDIA GPUs require "NVIDIA Driver" (440.64 or later) and "CUDA Toolkit" (9.0 or
 - sha256($salt.$pass)
 - sha256($salt.$pass.$salt)
 - sha256($salt.sha256($pass))
+- sha256($salt.sha256_bin($pass))
 - sha256($salt.utf16le($pass))
 - sha256(md5($pass))
 - sha256(sha256($pass).$salt)

tools/test_modules/m21420.pm

@@ -0,0 +1,45 @@
+#!/usr/bin/env perl
+
+##
+## Author......: See docs/credits.txt
+## License.....: MIT
+##
+
+use strict;
+use warnings;
+
+use Digest::SHA  qw (sha256);
+
+sub module_constraints { [[0, 256], [0, 256], [-1, -1], [-1, -1], [-1, -1]] }
+
+sub module_generate_hash
+{
+  my $word = shift;
+  my $salt = shift;
+
+print unpack ("H*", sha256 ($word)), "\n";
+  my $digest = sha256 ($salt . sha256 ($word));
+
+  my $hash = sprintf ("%s:%s", unpack ("H*", $digest), $salt);
+
+  return $hash;
+}
+
+sub module_verify_hash
+{
+  my $line = shift;
+
+  my ($digest, $salt, $word) = split (':', $line);
+
+  return unless defined $digest;
+  return unless defined $salt;
+  return unless defined $word;
+
+  my $word_packed = pack_if_HEX_notation ($word);
+
+  my $new_hash = module_generate_hash ($word_packed, $salt);
+
+  return ($new_hash, $word);
+}
+
+1;