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src/stun_codec.erl
%%%-------------------------------------------------------------------
%%% File : stun_codec.erl
%%% Author : Evgeniy Khramtsov <ekhramtsov@process-one.net>
%%% Description : STUN codec
%%% Created : 7 Aug 2009 by Evgeniy Khramtsov <ekhramtsov@process-one.net>
%%%
%%%
%%% Copyright (C) 2002-2021 ProcessOne, SARL. All Rights Reserved.
%%%
%%% Licensed under the Apache License, Version 2.0 (the "License");
%%% you may not use this file except in compliance with the License.
%%% You may obtain a copy of the License at
%%%
%%% http://www.apache.org/licenses/LICENSE-2.0
%%%
%%% Unless required by applicable law or agreed to in writing, software
%%% distributed under the License is distributed on an "AS IS" BASIS,
%%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%%% See the License for the specific language governing permissions and
%%% limitations under the License.
%%%
%%%-------------------------------------------------------------------
-module(stun_codec).
%% API
-export([decode/2, encode/1, encode/2, version/1, error/1, check_integrity/2,
add_fingerprint/1, generate_user_password/2, pp/1]).
-include("stun.hrl").
%%====================================================================
%% API
%%====================================================================
decode(<<0:2, Type:14, Len:16, Magic:32, TrID:96, Body:Len/binary, Tail/binary>> = Data,
Transport) ->
case catch decode(Type, Magic, TrID, Body) of
{'EXIT', _} ->
{error, unparsed};
{Res, RawSize} when Transport == datagram ->
{ok, add_raw(Res, Data, RawSize)};
{Res, RawSize} ->
{ok, add_raw(Res, Data, RawSize), Tail}
end;
decode(<<1:2, _:6, _/binary>> = Pkt, datagram) ->
case Pkt of
<<Channel:16, Len:16, Data:Len/binary, _/binary>> ->
{ok, #turn{channel = Channel, data = Data}};
_ ->
{error, unparsed}
end;
decode(<<1:2, _:6, _/binary>> = Pkt, stream) ->
case Pkt of
<<Channel:16, Len:16, Rest/binary>> ->
PaddLen = padd_len(Len),
case Rest of
<<Data:Len/binary, _:PaddLen, Tail/binary>> ->
{ok, #turn{channel = Channel, data = Data}, Tail};
_ ->
more
end;
_ ->
more
end;
decode(<<0:2, _:6, _/binary>>, stream) ->
more;
decode(<<>>, stream) ->
empty;
decode(_, _Transport) ->
{error, unparsed}.
encode(Msg) ->
encode(Msg, undefined).
encode(#turn{channel = Channel, data = Data}, _Password) ->
Len = size(Data),
PaddLen = padd_len(Len),
<<Channel:16, Len:16, Data/binary, 0:PaddLen>>;
encode(#stun{class = Class,
method = Method,
magic = Magic,
trid = TrID} =
Msg,
Key) ->
ClassCode =
case Class of
request ->
0;
indication ->
1;
response ->
2;
error ->
3
end,
Type = ?STUN_TYPE(ClassCode, Method),
Attrs = enc_attrs(Msg),
Len = size(Attrs),
if Key /= undefined ->
NewKey =
case Key of
{User, Realm, Password} ->
crypto:hash(md5, [User, $:, Realm, $:, Password]);
_ ->
Key
end,
Data = <<0:2, Type:14, (Len + 24):16, Magic:32, TrID:96, Attrs/binary>>,
MessageIntegrity = crypto:mac(hmac, sha, NewKey, Data),
<<Data/binary, ?STUN_ATTR_MESSAGE_INTEGRITY:16, 20:16, MessageIntegrity/binary>>;
true ->
<<0:2, Type:14, Len:16, Magic:32, TrID:96, Attrs/binary>>
end.
add_fingerprint(<<T:16, L:16, Tail/binary>>) ->
Data = <<T:16, (L + 8):16, Tail/binary>>,
Fingerprint = erlang:crc32(Data) bxor 16#5354554e,
<<Data/binary, ?STUN_ATTR_FINGERPRINT:16, 4:16, Fingerprint:32>>.
generate_user_password(Secret, Username) ->
Hash = crypto:mac(hmac, sha, Secret, Username),
base64:encode(Hash).
check_integrity(#stun{raw = Raw, 'MESSAGE-INTEGRITY' = MI}, Key)
when is_binary(Raw), is_binary(MI), Key /= undefined ->
NewKey =
case Key of
{User, Realm, Password} ->
crypto:hash(md5, [User, $:, Realm, $:, Password]);
_ ->
Key
end,
crypto:mac(hmac, sha, NewKey, Raw) == MI;
check_integrity(_Msg, _Key) ->
false.
pp(Term) ->
io_lib_pretty:print(Term, fun pp/2).
version(#stun{magic = ?STUN_MAGIC}) ->
new;
version(#stun{}) ->
old.
error(300) ->
{300, <<"Try Alternate">>};
error(400) ->
{400, <<"Bad Request">>};
error(401) ->
{401, <<"Unauthorized">>};
error(403) ->
{403, <<"Forbidden">>};
error(405) ->
{405, <<"Method Not Allowed">>};
error(420) ->
{420, <<"Unknown Attribute">>};
error(437) ->
{437, <<"Allocation Mismatch">>};
error(438) ->
{438, <<"Stale Nonce">>};
error(440) ->
{440, <<"Address Family not Supported">>};
error(441) ->
{441, <<"Wrong Credentials">>};
error(442) ->
{442, <<"Unsupported Transport Protocol">>};
error(443) ->
{443, <<"Peer Address Family Mismatch">>};
error(486) ->
{486, <<"Allocation Quota Reached">>};
error(487) ->
{487, <<"Role Conflict">>};
error(500) ->
{500, <<"Server Error">>};
error(508) ->
{508, <<"Insufficient Capacity">>};
error(Int) ->
{Int, <<"Undefined Error">>}.
%%====================================================================
%% Internal functions
%%====================================================================
decode(Type, Magic, TrID, Body) ->
Method = ?STUN_METHOD(Type),
Class =
case ?STUN_CLASS(Type) of
0 ->
request;
1 ->
indication;
2 ->
response;
3 ->
error
end,
dec_attrs(Body,
20,
#stun{class = Class,
method = Method,
magic = Magic,
trid = TrID}).
dec_attrs(<<Type:16, Len:16, Rest/binary>>, Bytes, Msg) ->
PaddLen = padd_len(Len),
<<Val:Len/binary, _:PaddLen, Tail/binary>> = Rest,
NewMsg = dec_attr(Type, Val, Msg),
if Type == ?STUN_ATTR_MESSAGE_INTEGRITY ->
{NewMsg, Bytes};
true ->
NewBytes = Bytes + 4 + Len + PaddLen div 8,
dec_attrs(Tail, NewBytes, NewMsg)
end;
dec_attrs(<<>>, _Bytes, Msg) ->
{Msg, 0}.
enc_attrs(Msg) ->
iolist_to_binary([enc_attr(?STUN_ATTR_SOFTWARE, Msg#stun.'SOFTWARE'),
enc_addr(?STUN_ATTR_MAPPED_ADDRESS, Msg#stun.'MAPPED-ADDRESS'),
enc_xor_addr(?STUN_ATTR_XOR_MAPPED_ADDRESS,
Msg#stun.magic,
Msg#stun.trid,
Msg#stun.'XOR-MAPPED-ADDRESS'),
enc_xor_addr(?STUN_ATTR_XOR_RELAYED_ADDRESS,
Msg#stun.magic,
Msg#stun.trid,
Msg#stun.'XOR-RELAYED-ADDRESS'),
enc_xor_peer_addr(Msg#stun.magic, Msg#stun.trid, Msg#stun.'XOR-PEER-ADDRESS'),
enc_req_family(Msg#stun.'REQUESTED-ADDRESS-FAMILY'),
enc_req_trans(Msg#stun.'REQUESTED-TRANSPORT'),
enc_attr(?STUN_ATTR_DATA, Msg#stun.'DATA'),
enc_df(Msg#stun.'DONT-FRAGMENT'),
enc_addr(?STUN_ATTR_ALTERNATE_SERVER, Msg#stun.'ALTERNATE-SERVER'),
enc_attr(?STUN_ATTR_USERNAME, Msg#stun.'USERNAME'),
enc_attr(?STUN_ATTR_REALM, Msg#stun.'REALM'),
enc_attr(?STUN_ATTR_NONCE, Msg#stun.'NONCE'),
enc_error_code(Msg#stun.'ERROR-CODE'),
enc_uint32(?STUN_ATTR_LIFETIME, Msg#stun.'LIFETIME'),
enc_chan(Msg#stun.'CHANNEL-NUMBER'),
enc_use_cand(Msg#stun.'USE-CANDIDATE'),
enc_ice_controlled(Msg#stun.'ICE-CONTROLLED'),
enc_ice_controlling(Msg#stun.'ICE-CONTROLLING'),
enc_priority(Msg#stun.'PRIORITY'),
enc_unknown_attrs(Msg#stun.'UNKNOWN-ATTRIBUTES')]).
dec_attr(?STUN_ATTR_MAPPED_ADDRESS, Val, Msg) ->
<<_, Family, Port:16, AddrBin/binary>> = Val,
Addr = dec_addr(Family, AddrBin),
Msg#stun{'MAPPED-ADDRESS' = {Addr, Port}};
dec_attr(?STUN_ATTR_XOR_MAPPED_ADDRESS, Val, Msg) ->
AddrPort = dec_xor_addr(Val, Msg),
Msg#stun{'XOR-MAPPED-ADDRESS' = AddrPort};
dec_attr(?STUN_ATTR_SOFTWARE, Val, Msg) ->
Msg#stun{'SOFTWARE' = Val};
dec_attr(?STUN_ATTR_USERNAME, Val, Msg) ->
Msg#stun{'USERNAME' = Val};
dec_attr(?STUN_ATTR_REALM, Val, Msg) ->
Msg#stun{'REALM' = Val};
dec_attr(?STUN_ATTR_NONCE, Val, Msg) ->
Msg#stun{'NONCE' = Val};
dec_attr(?STUN_ATTR_MESSAGE_INTEGRITY, Val, Msg) ->
Msg#stun{'MESSAGE-INTEGRITY' = Val};
dec_attr(?STUN_ATTR_ALTERNATE_SERVER, Val, Msg) ->
<<_, Family, Port:16, Address/binary>> = Val,
IP = dec_addr(Family, Address),
Msg#stun{'ALTERNATE-SERVER' = {IP, Port}};
dec_attr(?STUN_ATTR_ERROR_CODE, Val, Msg) ->
<<_:21, Class:3, Number:8, Reason/binary>> = Val,
if Class >= 3, Class =< 6, Number >= 0, Number =< 99 ->
Code = Class * 100 + Number,
Msg#stun{'ERROR-CODE' = {Code, Reason}}
end;
dec_attr(?STUN_ATTR_UNKNOWN_ATTRIBUTES, Val, Msg) ->
Attrs = dec_unknown_attrs(Val, []),
Msg#stun{'UNKNOWN-ATTRIBUTES' = Attrs};
dec_attr(?STUN_ATTR_XOR_RELAYED_ADDRESS, Val, Msg) ->
AddrPort = dec_xor_addr(Val, Msg),
Msg#stun{'XOR-RELAYED-ADDRESS' = AddrPort};
dec_attr(?STUN_ATTR_XOR_PEER_ADDRESS, Val, Msg) ->
AddrPort = dec_xor_addr(Val, Msg),
Tail = Msg#stun.'XOR-PEER-ADDRESS',
Msg#stun{'XOR-PEER-ADDRESS' = [AddrPort | Tail]};
dec_attr(?STUN_ATTR_REQUESTED_ADDRESS_FAMILY, Val, Msg) ->
Family =
case Val of
<<1:8, _:3/binary>> ->
ipv4;
<<2:8, _:3/binary>> ->
ipv6
end,
Msg#stun{'REQUESTED-ADDRESS-FAMILY' = Family};
dec_attr(?STUN_ATTR_REQUESTED_TRANSPORT, Val, Msg) ->
<<ProtoInt, _:3/binary>> = Val,
Proto =
case ProtoInt of
17 ->
udp;
_ ->
unknown
end,
Msg#stun{'REQUESTED-TRANSPORT' = Proto};
dec_attr(?STUN_ATTR_DATA, Val, Msg) ->
Msg#stun{'DATA' = Val};
dec_attr(?STUN_ATTR_LIFETIME, Val, Msg) ->
<<Seconds:32>> = Val,
Msg#stun{'LIFETIME' = Seconds};
dec_attr(?STUN_ATTR_DONT_FRAGMENT, _Val, Msg) ->
Msg#stun{'DONT-FRAGMENT' = true};
dec_attr(?STUN_ATTR_CHANNEL_NUMBER, Val, Msg) ->
<<Channel:16, _:16>> = Val,
Msg#stun{'CHANNEL-NUMBER' = Channel};
dec_attr(?STUN_ATTR_USE_CANDIDATE, _Val, Msg) ->
Msg#stun{'USE-CANDIDATE' = true};
dec_attr(?STUN_ATTR_ICE_CONTROLLED, _Val, Msg) ->
Msg#stun{'ICE-CONTROLLED' = true};
dec_attr(?STUN_ATTR_ICE_CONTROLLING, _Val, Msg) ->
Msg#stun{'ICE-CONTROLLING' = true};
dec_attr(?STUN_ATTR_PRIORITY, Val, Msg) ->
<<Priority:32>> = Val,
Msg#stun{'PRIORITY' = Priority};
dec_attr(Attr, _Val, #stun{unsupported = Attrs} = Msg) when Attr < 16#8000 ->
Msg#stun{unsupported = [Attr | Attrs]};
dec_attr(_Attr, _Val, Msg) ->
Msg.
dec_addr(1, <<A1, A2, A3, A4>>) ->
{A1, A2, A3, A4};
dec_addr(2, <<A1:16, A2:16, A3:16, A4:16, A5:16, A6:16, A7:16, A8:16>>) ->
{A1, A2, A3, A4, A5, A6, A7, A8}.
dec_xor_addr(<<_, Family, XPort:16, XAddr/binary>>, Msg) ->
Magic = Msg#stun.magic,
Port = XPort bxor (Magic bsr 16),
Addr = dec_xor_addr(Family, Magic, Msg#stun.trid, XAddr),
{Addr, Port}.
dec_xor_addr(1, Magic, _TrID, <<XAddr:32>>) ->
Addr = XAddr bxor Magic,
dec_addr(1, <<Addr:32>>);
dec_xor_addr(2, Magic, TrID, <<XAddr:128>>) ->
Addr = XAddr bxor (Magic bsl 96 bor TrID),
dec_addr(2, <<Addr:128>>).
dec_unknown_attrs(<<Attr:16, Tail/binary>>, Acc) ->
dec_unknown_attrs(Tail, [Attr | Acc]);
dec_unknown_attrs(<<>>, Acc) ->
lists:reverse(Acc).
enc_attr(_Attr, undefined) ->
<<>>;
enc_attr(Attr, Val) ->
Len = size(Val),
PaddLen = padd_len(Len),
<<Attr:16, Len:16, Val/binary, 0:PaddLen>>.
enc_addr(_Type, undefined) ->
<<>>;
enc_addr(Type, {{A1, A2, A3, A4}, Port}) ->
enc_attr(Type, <<0, 1, Port:16, A1, A2, A3, A4>>);
enc_addr(Type, {{A1, A2, A3, A4, A5, A6, A7, A8}, Port}) ->
enc_attr(Type, <<0, 2, Port:16, A1:16, A2:16, A3:16, A4:16, A5:16, A6:16, A7:16, A8:16>>).
enc_xor_addr(_Type, _Magic, _TrID, undefined) ->
<<>>;
enc_xor_addr(Type, Magic, _TrID, {{A1, A2, A3, A4}, Port}) ->
XPort = Port bxor (Magic bsr 16),
<<Addr:32>> = <<A1, A2, A3, A4>>,
XAddr = Addr bxor Magic,
enc_attr(Type, <<0, 1, XPort:16, XAddr:32>>);
enc_xor_addr(Type, Magic, TrID, {{A1, A2, A3, A4, A5, A6, A7, A8}, Port}) ->
XPort = Port bxor (Magic bsr 16),
<<Addr:128>> = <<A1:16, A2:16, A3:16, A4:16, A5:16, A6:16, A7:16, A8:16>>,
XAddr = Addr bxor (Magic bsl 96 bor TrID),
enc_attr(Type, <<0, 2, XPort:16, XAddr:128>>).
enc_xor_peer_addr(Magic, TrID, AddrPortList) ->
[enc_xor_addr(?STUN_ATTR_XOR_PEER_ADDRESS, Magic, TrID, AddrPort)
|| AddrPort <- AddrPortList].
enc_error_code(undefined) ->
<<>>;
enc_error_code({undefined, _Sth}) ->
<<>>;
enc_error_code({Code, Reason}) ->
Class = Code div 100,
Number = Code rem 100,
enc_attr(?STUN_ATTR_ERROR_CODE, <<0:21, Class:3, Number:8, Reason/binary>>).
enc_unknown_attrs([]) ->
<<>>;
enc_unknown_attrs(Attrs) ->
enc_attr(?STUN_ATTR_UNKNOWN_ATTRIBUTES, iolist_to_binary([<<Attr:16>> || Attr <- Attrs])).
enc_uint32(_Type, undefined) ->
<<>>;
enc_uint32(Type, Seconds) ->
enc_attr(Type, <<Seconds:32>>).
enc_req_family(undefined) ->
<<>>;
enc_req_family(ipv4) ->
enc_attr(?STUN_ATTR_REQUESTED_ADDRESS_FAMILY, <<1, 0:24>>);
enc_req_family(ipv6) ->
enc_attr(?STUN_ATTR_REQUESTED_ADDRESS_FAMILY, <<2, 0:24>>).
enc_req_trans(undefined) ->
<<>>;
enc_req_trans(udp) ->
enc_attr(?STUN_ATTR_REQUESTED_TRANSPORT, <<17, 0:24>>).
enc_df(false) ->
<<>>;
enc_df(true) ->
enc_attr(?STUN_ATTR_DONT_FRAGMENT, <<>>).
enc_use_cand(false) ->
<<>>;
enc_use_cand(true) ->
enc_attr(?STUN_ATTR_USE_CANDIDATE, <<>>).
enc_ice_controlled(false) ->
<<>>;
enc_ice_controlled(true) ->
enc_attr(?STUN_ATTR_ICE_CONTROLLED, <<>>).
enc_ice_controlling(false) ->
<<>>;
enc_ice_controlling(true) ->
enc_attr(?STUN_ATTR_ICE_CONTROLLING, <<>>).
enc_priority(undefined) ->
<<>>;
enc_priority(Priority) ->
enc_attr(?STUN_ATTR_PRIORITY, <<Priority:32>>).
enc_chan(undefined) ->
<<>>;
enc_chan(Channel) ->
enc_attr(?STUN_ATTR_CHANNEL_NUMBER, <<Channel:16, 0:16>>).
%%====================================================================
%% Auxiliary functions
%%====================================================================
pp(Tag, N) ->
try
pp1(Tag, N)
catch
_:_ ->
no
end.
pp1(stun, N) ->
N = record_info(size, stun) - 1,
record_info(fields, stun);
pp1(turn, N) ->
N = record_info(size, turn) - 1,
record_info(fields, turn);
pp1(_, _) ->
no.
add_raw(Msg, _Data, 0) ->
Msg;
add_raw(Msg, Data, Size) ->
<<Head:Size/binary, _/binary>> = Data,
<<Type:16, _:16, Tail/binary>> = Head,
Raw = <<Type:16, (Size + 4):16, Tail/binary>>,
Msg#stun{raw = Raw}.
%% Workaround for stupid clients.
-ifdef(NO_PADDING).
padd_len(_Len) ->
0.
-else.
padd_len(Len) ->
case Len rem 4 of
0 ->
0;
N ->
8 * (4 - N)
end.
-endif.