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Diffstat (limited to 'src')
| -rw-r--r-- | src/cow_ws.erl | 308 |
1 files changed, 308 insertions, 0 deletions
diff --git a/src/cow_ws.erl b/src/cow_ws.erl new file mode 100644 index 0000000..de7d0b5 --- /dev/null +++ b/src/cow_ws.erl @@ -0,0 +1,308 @@ +%% Copyright (c) 2015, Loïc Hoguin <[email protected]> +%% +%% Permission to use, copy, modify, and/or 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. + +-module(cow_ws). + +-export([parse_header/3]). +-export([parse_close_code/2]). +-export([parse_payload/9]). +-export([frame/2]). + +-type close_code() :: 1000..1003 | 1006..1011 | 3000..4999. +-export_type([close_code/0]). + +-type frag_state() :: undefined | {fin | nofin, text | binary}. +-export_type([frag_state/0]). + +-type frame() :: close | ping | pong + | {text | binary | close | ping | pong, iodata()} + | {close, close_code(), iodata()}. +-export_type([frame/0]). + +-type extensions() :: map(). +-type frame_type() :: fragment | text | binary | close | ping | pong. +-type mask_key() :: undefined | 0..16#ffffffff. +-type rsv() :: <<_:3>>. +-type utf8_state() :: <<>> | <<_:8>> | <<_:16>> | <<_:24>>. + +%% @doc Parse and validate the Websocket frame header. +%% +%% This function also updates the fragmentation state according to +%% information found in the frame's header. + +-spec parse_header(binary(), extensions(), frag_state()) + -> error | more | {frame_type(), frag_state(), rsv(), non_neg_integer(), mask_key(), binary()}. +%% RSV bits MUST be 0 unless an extension is negotiated +%% that defines meanings for non-zero values. +parse_header(<< _:1, Rsv:3, _/bits >>, Extensions, _) when Extensions =:= #{}, Rsv =/= 0 -> error; +%% Last 2 RSV bits MUST be 0 if deflate-frame extension is used. +parse_header(<< _:2, 1:1, _/bits >>, #{deflate_frame := _}, _) -> error; +parse_header(<< _:3, 1:1, _/bits >>, #{deflate_frame := _}, _) -> error; +%% Invalid opcode. Note that these opcodes may be used by extensions. +parse_header(<< _:4, 3:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 4:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 5:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 6:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 7:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 11:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 12:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 13:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 14:4, _/bits >>, _, _) -> error; +parse_header(<< _:4, 15:4, _/bits >>, _, _) -> error; +%% Control frames MUST NOT be fragmented. +parse_header(<< 0:1, _:3, Opcode:4, _/bits >>, _, _) when Opcode >= 8 -> error; +%% A frame MUST NOT use the zero opcode unless fragmentation was initiated. +parse_header(<< _:4, 0:4, _/bits >>, _, undefined) -> error; +%% Non-control opcode when expecting control message or next fragment. +parse_header(<< _:4, 1:4, _/bits >>, _, {_, _}) -> error; +parse_header(<< _:4, 2:4, _/bits >>, _, {_, _}) -> error; +parse_header(<< _:4, 3:4, _/bits >>, _, {_, _}) -> error; +parse_header(<< _:4, 4:4, _/bits >>, _, {_, _}) -> error; +parse_header(<< _:4, 5:4, _/bits >>, _, {_, _}) -> error; +parse_header(<< _:4, 6:4, _/bits >>, _, {_, _}) -> error; +parse_header(<< _:4, 7:4, _/bits >>, _, {_, _}) -> error; +%% Close control frame length MUST be 0 or >= 2. +parse_header(<< _:4, 8:4, _:1, 1:7, _/bits >>, _, _) -> error; +%% Close control frame with incomplete close code. Need more data. +parse_header(Data = << _:4, 8:4, 0:1, Len:7, _/bits >>, _, _) when Len > 1, byte_size(Data) < 4 -> more; +parse_header(Data = << _:4, 8:4, 1:1, Len:7, _/bits >>, _, _) when Len > 1, byte_size(Data) < 8 -> more; +%% 7 bits payload length. +parse_header(<< Fin:1, Rsv:3/bits, Opcode:4, 0:1, Len:7, Rest/bits >>, _, FragState) when Len < 126 -> + parse_header(Opcode, Fin, FragState, Rsv, Len, undefined, Rest); +parse_header(<< Fin:1, Rsv:3/bits, Opcode:4, 1:1, Len:7, MaskKey:32, Rest/bits >>, _, FragState) when Len < 126 -> + parse_header(Opcode, Fin, FragState, Rsv, Len, MaskKey, Rest); +%% 16 bits payload length. +parse_header(<< Fin:1, Rsv:3/bits, Opcode:4, 0:1, 126:7, Len:16, Rest/bits >>, _, FragState) when Len > 125, Opcode < 8 -> + parse_header(Opcode, Fin, FragState, Rsv, Len, undefined, Rest); +parse_header(<< Fin:1, Rsv:3/bits, Opcode:4, 1:1, 126:7, Len:16, MaskKey:32, Rest/bits >>, _, FragState) when Len > 125, Opcode < 8 -> + parse_header(Opcode, Fin, FragState, Rsv, Len, MaskKey, Rest); +%% 63 bits payload length. +parse_header(<< Fin:1, Rsv:3/bits, Opcode:4, 0:1, 127:7, 0:1, Len:63, Rest/bits >>, _, FragState) when Len > 16#ffff, Opcode < 8 -> + parse_header(Opcode, Fin, FragState, Rsv, Len, undefined, Rest); +parse_header(<< Fin:1, Rsv:3/bits, Opcode:4, 1:1, 127:7, 0:1, Len:63, MaskKey:32, Rest/bits >>, _, FragState) when Len > 16#ffff, Opcode < 8 -> + parse_header(Opcode, Fin, FragState, Rsv, Len, MaskKey, Rest); +%% When payload length is over 63 bits, the most significant bit MUST be 0. +parse_header(<< _:9, 127:7, 1:1, _/bits >>, _, _) -> error; +%% For the next two clauses, it can be one of the following: +%% +%% * The minimal number of bytes MUST be used to encode the length +%% * All control frames MUST have a payload length of 125 bytes or less +parse_header(<< _:8, 0:1, 126:7, _:16, _/bits >>, _, _) -> error; +parse_header(<< _:8, 1:1, 126:7, _:48, _/bits >>, _, _) -> error; +parse_header(<< _:8, 0:1, 127:7, _:64, _/bits >>, _, _) -> error; +parse_header(<< _:8, 1:1, 127:7, _:96, _/bits >>, _, _) -> error; +%% Need more data. +parse_header(_, _, _) -> more. + +parse_header(Opcode, Fin, FragState, Rsv, Len, MaskKey, Rest) -> + Type = opcode_to_frame_type(Opcode), + Type2 = case Fin of + 0 -> fragment; + 1 -> Type + end, + {Type2, frag_state(Type, Fin, FragState), Rsv, Len, MaskKey, Rest}. + +opcode_to_frame_type(0) -> fragment; +opcode_to_frame_type(1) -> text; +opcode_to_frame_type(2) -> binary; +opcode_to_frame_type(8) -> close; +opcode_to_frame_type(9) -> ping; +opcode_to_frame_type(10) -> pong. + +frag_state(Type, 0, undefined) -> {nofin, Type}; +frag_state(fragment, 0, FragState = {nofin, _}) -> FragState; +frag_state(fragment, 1, {nofin, Type}) -> {fin, Type}; +frag_state(_, 1, FragState) -> FragState. + +%% @doc Parse and validate the close frame's close code. +%% +%% The close code is part of the payload and must therefore be unmasked. + +-spec parse_close_code(binary(), mask_key()) -> {ok, close_code(), binary()} | error. +parse_close_code(<< MaskedCode:2/binary, Rest/bits >>, MaskKey) -> + << Code:16 >> = unmask(MaskedCode, MaskKey, 0), + if + Code < 1000; Code =:= 1004; Code =:= 1005; Code =:= 1006; + (Code > 1011) and (Code < 3000); Code > 4999 -> + error; + true -> + {ok, Code, Rest} + end. + +%% @doc Parse and validate the frame's payload. +%% +%% Validation is only required for text and close frames which feature +%% a UTF-8 payload. + +-spec parse_payload(binary(), mask_key(), utf8_state(), non_neg_integer(), + frame_type(), non_neg_integer(), frag_state(), extensions(), rsv()) + -> {ok, binary(), utf8_state(), binary()} | {more, binary(), utf8_state()} | error. +parse_payload(Data, MaskKey, Utf8State, ParsedLen, Type, Len, FragState, #{deflate_frame := Inflate}, << 1:1, 0:2 >>) -> + {Data2, Rest, Eof} = split_payload(Data, Len), + Payload = inflate_frame(unmask(Data2, MaskKey, ParsedLen), Inflate, FragState, Eof), + validate_payload(Payload, Rest, Utf8State, ParsedLen, Type, FragState, Eof); +parse_payload(Data, MaskKey, Utf8State, ParsedLen, Type, Len, FragState, _, << 0:3 >>) -> + {Data2, Rest, Eof} = split_payload(Data, Len), + Payload = unmask(Data2, MaskKey, ParsedLen), + validate_payload(Payload, Rest, Utf8State, ParsedLen, Type, FragState, Eof). + +split_payload(Data, Len) -> + case byte_size(Data) of + Len -> + {Data, <<>>, true}; + DataLen when DataLen < Len -> + {Data, <<>>, false}; + _ -> + << Data2:Len/binary, Rest/bits >> = Data, + {Data2, Rest, true} + end. + +unmask(Data, MaskKey, 0) -> + do_unmask(Data, MaskKey, <<>>); +%% We unmask on the fly so we need to continue from the right mask byte. +unmask(Data, MaskKey, UnmaskedLen) -> + Left = UnmaskedLen rem 4, + Right = 4 - Left, + MaskKey2 = (MaskKey bsl (Left * 8)) + (MaskKey bsr (Right * 8)), + do_unmask(Data, MaskKey2, <<>>). + +do_unmask(<<>>, _, Unmasked) -> + Unmasked; +do_unmask(<< O:32, Rest/bits >>, MaskKey, Acc) -> + T = O bxor MaskKey, + do_unmask(Rest, MaskKey, << Acc/binary, T:32 >>); +do_unmask(<< O:24 >>, MaskKey, Acc) -> + << MaskKey2:24, _:8 >> = << MaskKey:32 >>, + T = O bxor MaskKey2, + << Acc/binary, T:24 >>; +do_unmask(<< O:16 >>, MaskKey, Acc) -> + << MaskKey2:16, _:16 >> = << MaskKey:32 >>, + T = O bxor MaskKey2, + << Acc/binary, T:16 >>; +do_unmask(<< O:8 >>, MaskKey, Acc) -> + << MaskKey2:8, _:24 >> = << MaskKey:32 >>, + T = O bxor MaskKey2, + << Acc/binary, T:8 >>. + +%% @todo Try using iodata() and see if it improves anything. +inflate_frame(Data, Inflate, fin, true) -> + iolist_to_binary(zlib:inflate(Inflate, << Data/binary, 0, 0, 255, 255 >>)); +inflate_frame(Data, Inflate, _, _) -> + iolist_to_binary(zlib:inflate(Inflate, Data)). + +%% Text frames and close control frames MUST have a payload that is valid UTF-8. +validate_payload(Payload, Rest, Utf8State, _, Type, _, Eof) when Type =:= text; Type =:= close -> + case validate_utf8(<< Utf8State/binary, Payload/binary >>) of + false -> error; + Utf8State when not Eof -> {more, Payload, Utf8State}; + <<>> when Eof -> {ok, Payload, <<>>, Rest}; + _ -> error + end; +validate_payload(Payload, Rest, Utf8State, _, fragment, {Fin, text}, Eof) -> + case validate_utf8(<< Utf8State/binary, Payload/binary >>) of + false -> error; + <<>> when Eof -> {ok, Payload, <<>>, Rest}; + Utf8State2 when Eof, Fin =:= nofin -> {ok, Payload, Utf8State2, Rest}; + Utf8State2 when not Eof -> {more, Payload, Utf8State2}; + _ -> error + end; +validate_payload(Payload, _, Utf8State, _, _, _, false) -> + {more, Payload, Utf8State}; +validate_payload(Payload, Rest, Utf8State, _, _, _, true) -> + {ok, Payload, Utf8State, Rest}. + +%% Returns <<>> if the argument is valid UTF-8, false if not, +%% or the incomplete part of the argument if we need more data. +validate_utf8(Valid = <<>>) -> + Valid; +validate_utf8(<< _/utf8, Rest/bits >>) -> + validate_utf8(Rest); +%% 2 bytes. Codepages C0 and C1 are invalid; fail early. +validate_utf8(<< 2#1100000:7, _/bits >>) -> + false; +validate_utf8(Incomplete = << 2#110:3, _:5 >>) -> + Incomplete; +%% 3 bytes. +validate_utf8(Incomplete = << 2#1110:4, _:4 >>) -> + Incomplete; +validate_utf8(Incomplete = << 2#1110:4, _:4, 2#10:2, _:6 >>) -> + Incomplete; +%% 4 bytes. Codepage F4 may have invalid values greater than 0x10FFFF. +validate_utf8(<< 2#11110100:8, 2#10:2, High:6, _/bits >>) when High >= 2#10000 -> + false; +validate_utf8(Incomplete = << 2#11110:5, _:3 >>) -> + Incomplete; +validate_utf8(Incomplete = << 2#11110:5, _:3, 2#10:2, _:6 >>) -> + Incomplete; +validate_utf8(Incomplete = << 2#11110:5, _:3, 2#10:2, _:6, 2#10:2, _:6 >>) -> + Incomplete; +%% Invalid. +validate_utf8(_) -> + false. + +%% @doc Construct an unmasked Websocket frame. + +-spec frame(frame(), extensions()) -> iodata(). +%% Control frames. Control packets must not be > 125 in length. +frame(close, _) -> + << 1:1, 0:3, 8:4, 0:8 >>; +frame(ping, _) -> + << 1:1, 0:3, 9:4, 0:8 >>; +frame(pong, _) -> + << 1:1, 0:3, 10:4, 0:8 >>; +frame({close, Payload}, Extensions) -> + frame({close, 1000, Payload}, Extensions); +frame({close, StatusCode, Payload}, _) -> + Len = 2 + iolist_size(Payload), + true = Len =< 125, + [<< 1:1, 0:3, 8:4, 0:1, Len:7, StatusCode:16 >>, Payload]; +frame({ping, Payload}, _) -> + Len = iolist_size(Payload), + true = Len =< 125, + [<< 1:1, 0:3, 9:4, 0:1, Len:7 >>, Payload]; +frame({pong, Payload}, _) -> + Len = iolist_size(Payload), + true = Len =< 125, + [<< 1:1, 0:3, 10:4, 0:1, Len:7 >>, Payload]; +%% Data frames, deflate-frame extension. +frame({text, Payload}, #{deflate_frame := Deflate}) -> + Payload2 = deflate_frame(Payload, Deflate), + Len = payload_length(Payload2), + [<< 1:1, 1:1, 0:2, 1:4, 0:1, Len/bits >>, Payload2]; +frame({binary, Payload}, #{deflate_frame := Deflate}) -> + Payload2 = deflate_frame(Payload, Deflate), + Len = payload_length(Payload2), + [<< 1:1, 1:1, 0:2, 2:4, 0:1, Len/bits >>, Payload2]; +%% Data frames. +frame({text, Payload}, _) -> + Len = payload_length(Payload), + [<< 1:1, 0:3, 1:4, 0:1, Len/bits >>, Payload]; +frame({binary, Payload}, _) -> + Len = payload_length(Payload), + [<< 1:1, 0:3, 2:4, 0:1, Len/bits >>, Payload]. + +payload_length(Payload) -> + case byte_size(Payload) of + N when N =< 125 -> << N:7 >>; + N when N =< 16#ffff -> << 126:7, N:16 >>; + N when N =< 16#7fffffffffffffff -> << 127:7, N:64 >> + end. + +deflate_frame(Payload, Deflate) -> + Deflated = iolist_to_binary(zlib:deflate(Deflate, Payload, sync)), + Len = byte_size(Deflated) - 4, + case Deflated of + << Body:Len/binary, 0:8, 0:8, 255:8, 255:8 >> -> Body; + _ -> Deflated + end. |