%% Taken from erlang stdlib implementation.
%% Adapted by mmzeeman@xs4all.nl to encode and decode base64url. This is
%% a url and filename friendly version of base64. See also RFC4648.
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2007-2009. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
%% Description: Implements base 64 encode and decode. See RFC4648.
-module(base64url).
-export([encode/1, decode/1, mime_decode/1,
encode_to_string/1, decode_to_string/1, mime_decode_to_string/1]).
%%-------------------------------------------------------------------------
%% The following type is a subtype of string() for return values
%% of (some) functions of this module.
%%-------------------------------------------------------------------------
-type ascii_string() :: [1..255].
%%-------------------------------------------------------------------------
%% encode_to_string(ASCII) -> Base64String
%% ASCII - string() | binary()
%% Base64String - string()
%%
%% Description: Encodes a plain ASCII string (or binary) into base64.
%%-------------------------------------------------------------------------
-spec encode_to_string(string() | binary()) -> ascii_string().
encode_to_string(Bin) when is_binary(Bin) ->
encode_to_string(binary_to_list(Bin));
encode_to_string(List) when is_list(List) ->
encode_l(List).
%%-------------------------------------------------------------------------
%% encode(ASCII) -> Base64
%% ASCII - string() | binary()
%% Base64 - binary()
%%
%% Description: Encodes a plain ASCII string (or binary) into base64.
%%-------------------------------------------------------------------------
-spec encode(string() | binary()) -> binary().
encode(Bin) when is_binary(Bin) ->
encode_binary(Bin);
encode(List) when is_list(List) ->
list_to_binary(encode_l(List)).
-spec encode_l(string()) -> ascii_string().
encode_l([]) ->
[];
encode_l([A]) ->
[b64e(A bsr 2),
b64e((A band 3) bsl 4)];
encode_l([A, B]) ->
[b64e(A bsr 2),
b64e(((A band 3) bsl 4) bor (B bsr 4)),
b64e((B band 15) bsl 2)];
encode_l([A, B, C | Ls]) ->
BB = (A bsl 16) bor (B bsl 8) bor C,
[b64e(BB bsr 18),
b64e((BB bsr 12) band 63),
b64e((BB bsr 6) band 63),
b64e(BB band 63) | encode_l(Ls)].
encode_binary(Bin) ->
Split = 3 * (byte_size(Bin) div 3),
<<Main0:Split/binary, Rest/binary>> = Bin,
Main = <<<<(b64e(C)):8>> || <<C:6>> <= Main0>>,
case Rest of
<<A:6, B:6, C:4>> ->
<<Main/binary, (b64e(A)):8, (b64e(B)):8, (b64e(C bsl 2)):8>>;
<<A:6, B:2>> ->
<<Main/binary, (b64e(A)):8, (b64e(B bsl 4)):8>>;
<<>> ->
Main
end.
%%-------------------------------------------------------------------------
%% mime_decode(Base64) -> ASCII
%% decode(Base64) -> ASCII
%% Base64 - string() | binary()
%% ASCII - binary()
%%
%% Description: Decodes an base64 encoded string to plain ASCII.
%% mime_decode strips away all characters not Base64 before converting,
%% whereas decode crashes if an illegal character is found
%%-------------------------------------------------------------------------
-spec decode(string() | binary()) -> binary().
decode(Bin) when is_binary(Bin) ->
PaddingSize = 4 - (size(Bin) rem 4),
Padding = padding_b(PaddingSize),
decode_binary(<<>>, <<Bin/binary, Padding/binary>>);
decode(List) when is_list(List) ->
PaddingSize = 4 - (length(List) rem 4),
Padding = padding_l(PaddingSize),
list_to_binary(decode_l(List ++ Padding)).
padding_b(2) ->
<<"==">>;
padding_b(1) ->
<<"=">>;
padding_b(Int) when Int == 0; Int == 4 ->
<<>>.
padding_l(2) ->
"==";
padding_l(1) ->
"=";
padding_l(Int) when Int == 0; Int == 4 ->
"".
-spec mime_decode(string() | binary()) -> binary().
mime_decode(Bin) when is_binary(Bin) ->
mime_decode_binary(<<>>, Bin);
mime_decode(List) when is_list(List) ->
list_to_binary(mime_decode_l(List)).
-spec decode_l(string()) -> string().
decode_l(List) ->
L = strip_spaces(List, []),
decode(L, []).
-spec mime_decode_l(string()) -> string().
mime_decode_l(List) ->
L = strip_illegal(List, []),
decode(L, []).
%%-------------------------------------------------------------------------
%% mime_decode_to_string(Base64) -> ASCII
%% decode_to_string(Base64) -> ASCII
%% Base64 - string() | binary()
%% ASCII - binary()
%%
%% Description: Decodes an base64 encoded string to plain ASCII.
%% mime_decode strips away all characters not Base64 before converting,
%% whereas decode crashes if an illegal character is found
%%-------------------------------------------------------------------------
-spec decode_to_string(string() | binary()) -> string().
decode_to_string(Bin) when is_binary(Bin) ->
decode_to_string(binary_to_list(Bin));
decode_to_string(List) when is_list(List) ->
decode_l(List).
-spec mime_decode_to_string(string() | binary()) -> string().
mime_decode_to_string(Bin) when is_binary(Bin) ->
mime_decode_to_string(binary_to_list(Bin));
mime_decode_to_string(List) when is_list(List) ->
mime_decode_l(List).
%% One-based decode map.
-define(DECODE_MAP,
{bad, bad, bad, bad, bad, bad, bad, bad, ws, ws, bad, bad, ws, bad, bad, %1-15
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, %16-31
ws, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, 62, bad, bad, %32-47
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, bad, bad, bad, eq, bad, bad, %48-63
bad, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, %64-79
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, bad, bad, bad, bad, 63, % 80-95
bad, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad,
bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad, bad}).
decode_binary(Result0, <<C:8, T0/bits>>) ->
case element(C, ?DECODE_MAP) of
bad ->
erlang:error({badarg, C});
ws ->
decode_binary(Result0, T0);
eq ->
case strip_ws(T0) of
<<$=:8, T/binary>> ->
<<>> = strip_ws(T),
Split = byte_size(Result0) - 1,
<<Result:Split/bytes, _:4>> = Result0,
Result;
T ->
<<>> = strip_ws(T),
Split = byte_size(Result0) - 1,
<<Result:Split/bytes, _:2>> = Result0,
Result
end;
Bits ->
decode_binary(<<Result0/bits, Bits:6>>, T0)
end;
decode_binary(Result, <<>>) ->
true = is_binary(Result),
Result.
mime_decode_binary(Result, <<0:8, T/bits>>) ->
mime_decode_binary(Result, T);
mime_decode_binary(Result0, <<C:8, T/bits>>) ->
case element(C, ?DECODE_MAP) of
Bits when is_integer(Bits) ->
mime_decode_binary(<<Result0/bits, Bits:6>>, T);
eq ->
case tail_contains_equal(T) of
true ->
Split = byte_size(Result0) - 1,
<<Result:Split/bytes, _:4>> = Result0,
Result;
false ->
Split = byte_size(Result0) - 1,
<<Result:Split/bytes, _:2>> = Result0,
Result
end;
_ ->
mime_decode_binary(Result0, T)
end;
mime_decode_binary(Result, <<>>) ->
true = is_binary(Result),
Result.
decode([], A) -> A;
decode([$=, $=, C2, C1 | Cs], A) ->
Bits2x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12),
Octet1 = Bits2x6 bsr 16,
decode(Cs, [Octet1 | A]);
decode([$=, C3, C2, C1 | Cs], A) ->
Bits3x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12)
bor (b64d(C3) bsl 6),
Octet1 = Bits3x6 bsr 16,
Octet2 = (Bits3x6 bsr 8) band 16#ff,
decode(Cs, [Octet1, Octet2 | A]);
decode([C4, C3, C2, C1 | Cs], A) ->
Bits4x6 = (b64d(C1) bsl 18) bor (b64d(C2) bsl 12)
bor (b64d(C3) bsl 6) bor b64d(C4),
Octet1 = Bits4x6 bsr 16,
Octet2 = (Bits4x6 bsr 8) band 16#ff,
Octet3 = Bits4x6 band 16#ff,
decode(Cs, [Octet1, Octet2, Octet3 | A]).
%%%========================================================================
%%% Internal functions
%%%========================================================================
strip_spaces([], A) -> A;
strip_spaces([$\s | Cs], A) -> strip_spaces(Cs, A);
strip_spaces([$\t | Cs], A) -> strip_spaces(Cs, A);
strip_spaces([$\r | Cs], A) -> strip_spaces(Cs, A);
strip_spaces([$\n | Cs], A) -> strip_spaces(Cs, A);
strip_spaces([C | Cs], A) -> strip_spaces(Cs, [C | A]).
strip_ws(<<$\t, T/binary>>) ->
strip_ws(T);
strip_ws(<<$\n, T/binary>>) ->
strip_ws(T);
strip_ws(<<$\r, T/binary>>) ->
strip_ws(T);
strip_ws(<<$\s, T/binary>>) ->
strip_ws(T);
strip_ws(T) -> T.
strip_illegal([0 | Cs], A) ->
strip_illegal(Cs, A);
strip_illegal([C | Cs], A) ->
case element(C, ?DECODE_MAP) of
bad -> strip_illegal(Cs, A);
ws -> strip_illegal(Cs, A);
eq -> strip_illegal_end(Cs, [$= | A]);
_ -> strip_illegal(Cs, [C | A])
end;
strip_illegal([], A) -> A.
strip_illegal_end([0 | Cs], A) ->
strip_illegal_end(Cs, A);
strip_illegal_end([C | Cs], A) ->
case element(C, ?DECODE_MAP) of
bad -> strip_illegal(Cs, A);
ws -> strip_illegal(Cs, A);
eq -> [C | A];
_ -> strip_illegal(Cs, [C | A])
end;
strip_illegal_end([], A) -> A.
tail_contains_equal(<<$=, _/binary>>) -> true;
tail_contains_equal(<<_, T/binary>>) -> tail_contains_equal(T);
tail_contains_equal(<<>>) -> false.
%% accessors
b64e(X) ->
element(X + 1,
{$A, $B, $C, $D, $E, $F, $G, $H, $I, $J, $K, $L, $M, $N,
$O, $P, $Q, $R, $S, $T, $U, $V, $W, $X, $Y, $Z,
$a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l, $m, $n,
$o, $p, $q, $r, $s, $t, $u, $v, $w, $x, $y, $z,
$0, $1, $2, $3, $4, $5, $6, $7, $8, $9, $-, $_}).
b64d(X) ->
b64d_ok(element(X, ?DECODE_MAP)).
b64d_ok(I) when is_integer(I) -> I.
