random and totp stuff

.gitignore

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+ebin/*
+.erlang.mk/
+utools.d

LICENSE

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+Copyright (c) 2022 Umgeher Torgersen <me@umgeher.org>
+
+Permission to use, copy, modify, and distribute this software for any
+purpose with or without fee is hereby granted, provided that the above
+copyright notice and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

src/utools.erl

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+-module(utools).
+
+-export([b32_decode/1]).
+-export([b32_encode/1]).
+-export([hotp/2]).
+-export([rand_bytes/0, rand_bytes/1]).
+-export([rand_chars/1]).
+-export([rand_hash/0]).
+-export([totp/1, totp/2]).
+-export([totp_generate/0]).
+
+b32_decode({<<V, "======">>, Bits}) ->
+    <<Bits/bits, (b32_std_dec(V) bsr 2):3>>;
+b32_decode({<<V, "====">>, Bits}) ->
+    <<Bits/bits, (b32_std_dec(V) bsr 4):1>>;
+b32_decode({<<V, "===">>, Bits}) ->
+    <<Bits/bits, (b32_std_dec(V) bsr 1):4>>;
+b32_decode({<<V, "=">>, Bits}) ->
+    <<Bits/bits, (b32_std_dec(V) bsr 3):2>>;
+b32_decode({<<V, R/binary>>, Bits}) ->
+    b32_decode({R, <<Bits/bits, (b32_std_dec(V)):5>>});
+b32_decode({<<>>, Bits}) ->
+    Bits;
+b32_decode(V) when is_list(V) ->
+    b32_decode(list_to_binary(V));
+b32_decode(V) when is_binary(V) ->
+    b32_decode({V, <<>>}).
+
+b32_encode({body, V}) ->
+    O = 5 * (byte_size(V) div 5),
+    <<Body:O/binary, R/binary>> = V,
+    {<< <<(b32_std_enc(X))>> || <<X:5>> <= Body>>, R};
+b32_encode({rest, V}) ->
+    O = 5 * (bit_size(V) div 5),
+    <<Body:O/bits, Rest/bits>> = V,
+    B0 = << <<(b32_std_enc(X))>> || <<X:5>> <= Body>>,
+    {B1, Pad} = case Rest of
+		    <<I:3>> -> {<<(b32_std_enc(I bsl 2))>>, 6};
+		    <<I:1>> -> {<<(b32_std_enc(I bsl 4))>>, 4};
+		    <<I:4>> -> {<<(b32_std_enc(I bsl 1))>>, 3};
+		    <<I:2>> -> {<<(b32_std_enc(I bsl 3))>>, 1};
+		    <<>> -> {<<>>, 0}
+		end,
+    {<<B0/binary, B1/binary>>, Pad};
+b32_encode(V) when is_list(V) ->
+    b32_encode(list_to_binary(V));
+b32_encode(V) when is_binary(V) ->
+    {EB, _R} = b32_encode({body, V}),
+    {ER, P} = b32_encode({rest, V}),
+    Padding = list_to_binary(lists:duplicate(P, $=)),
+    <<EB/binary, ER/binary, Padding/binary>>.
+
+b32_std_dec(I) when I >= $2 andalso I =< $7 -> 
+    I - 24;
+b32_std_dec(I) when I >= $a andalso I =< $z -> 
+    I - $a;
+b32_std_dec(I) when I >= $A andalso I =< $Z -> 
+    I - $A.
+
+b32_std_enc(I) when is_integer(I) andalso I >= 26 andalso I =< 31 ->
+    I + 24;
+b32_std_enc(I) when is_integer(I) andalso I >= 0 andalso I =< 25 ->
+    I + $a.
+
+hotp(Token, Time) ->
+  K = b32_decode(Token),
+  M = <<Time:8/big-unsigned-integer-unit:8>>,
+  D = crypto:mac(hmac, sha, K, M),
+  <<_:19/binary, _O:8>> = D,
+  O = _O band 15,
+  <<_TB:4/integer-unit:8>> = binary:part(D, O, 4),
+  TB = _TB band 16#7fffffff,
+  _T = TB rem trunc(math:pow(10, 6)),
+  T = integer_to_binary(_T),
+  P = << <<48:8>> || _ <- lists:seq(1, 6 - byte_size(T)) >>,
+  {ok, <<P/binary, T/binary>>}.
+
+rand_bytes() ->
+  rand_bytes(8).
+
+rand_bytes(N) when is_integer(N) ->
+  {ok, crypto:strong_rand_bytes(N)}.
+
+rand_chars({0, Swap}) ->
+  {ok, Swap};
+rand_chars({Size, <<Swap/binary>>}) when Size > 0 ->
+  Char = rand:uniform(26) + 96,
+  rand_chars({Size - 1, <<Swap/binary, Char>>});
+rand_chars(Size) when Size > 0 ->
+  rand_chars({Size, <<"">>}).
+
+rand_hash() ->
+  {ok, R} = rand_chars(64),
+  {ok, binary:encode_hex(crypto:hash(sha256, <<"utools:rand_hash(", R/binary, ")">>))}.
+
+totp_generate() ->
+  rand_chars(16).
+
+totp(<<Token/binary>>) ->
+  totp(Token, erlang:timestamp()).
+
+totp(<<Token/binary>>, {M, S, _}) ->
+  T = (M * 1000000 + S) / 30,
+  Time = trunc(T),
+  hotp(Token, Time).