%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2013-2013. 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%
%%
%%----------------------------------------------------------------------
%% Purpose: Handle DTLS record protocol. (Parts that are not shared with SSL/TLS)
%%----------------------------------------------------------------------
-module(dtls_record).
-include("dtls_record.hrl").
-include("ssl_internal.hrl").
-include("ssl_alert.hrl").
-include("dtls_handshake.hrl").
-include("ssl_cipher.hrl").
%% Handling of incoming data
-export([get_dtls_records/2]).
%% Decoding
-export([decode_cipher_text/2]).
%% Encoding
-export([encode_plain_text/4]).
%% Protocol version handling
-export([protocol_version/1, lowest_protocol_version/2,
highest_protocol_version/1, supported_protocol_versions/0,
is_acceptable_version/2]).
%% DTLS Epoch handling
-export([init_connection_state_seq/2, current_connection_state_epoch/2,
set_connection_state_by_epoch/3, connection_state_by_epoch/3]).
-compile(inline).
%%====================================================================
%% Internal application API
%%====================================================================
%%--------------------------------------------------------------------
-spec get_dtls_records(binary(), binary()) -> {[binary()], binary()} | #alert{}.
%%
%% Description: Given old buffer and new data from UDP/SCTP, packs up a records
%% and returns it as a list of tls_compressed binaries also returns leftover
%% data
%%--------------------------------------------------------------------
get_dtls_records(Data, <<>>) ->
get_dtls_records_aux(Data, []);
get_dtls_records(Data, Buffer) ->
get_dtls_records_aux(list_to_binary([Buffer, Data]), []).
get_dtls_records_aux(<<?BYTE(?APPLICATION_DATA),?BYTE(MajVer),?BYTE(MinVer),
?UINT16(Epoch), ?UINT48(SequenceNumber),
?UINT16(Length), Data:Length/binary, Rest/binary>>,
Acc) ->
get_dtls_records_aux(Rest, [#ssl_tls{type = ?APPLICATION_DATA,
version = {MajVer, MinVer},
epoch = Epoch, record_seq = SequenceNumber,
fragment = Data} | Acc]);
get_dtls_records_aux(<<?BYTE(?HANDSHAKE),?BYTE(MajVer),?BYTE(MinVer),
?UINT16(Epoch), ?UINT48(SequenceNumber),
?UINT16(Length),
Data:Length/binary, Rest/binary>>, Acc) when MajVer >= 128 ->
get_dtls_records_aux(Rest, [#ssl_tls{type = ?HANDSHAKE,
version = {MajVer, MinVer},
epoch = Epoch, record_seq = SequenceNumber,
fragment = Data} | Acc]);
get_dtls_records_aux(<<?BYTE(?ALERT),?BYTE(MajVer),?BYTE(MinVer),
?UINT16(Epoch), ?UINT48(SequenceNumber),
?UINT16(Length), Data:Length/binary,
Rest/binary>>, Acc) ->
get_dtls_records_aux(Rest, [#ssl_tls{type = ?ALERT,
version = {MajVer, MinVer},
epoch = Epoch, record_seq = SequenceNumber,
fragment = Data} | Acc]);
get_dtls_records_aux(<<?BYTE(?CHANGE_CIPHER_SPEC),?BYTE(MajVer),?BYTE(MinVer),
?UINT16(Epoch), ?UINT48(SequenceNumber),
?UINT16(Length), Data:Length/binary, Rest/binary>>,
Acc) ->
get_dtls_records_aux(Rest, [#ssl_tls{type = ?CHANGE_CIPHER_SPEC,
version = {MajVer, MinVer},
epoch = Epoch, record_seq = SequenceNumber,
fragment = Data} | Acc]);
get_dtls_records_aux(<<0:1, _CT:7, ?BYTE(_MajVer), ?BYTE(_MinVer),
?UINT16(Length), _/binary>>,
_Acc) when Length > ?MAX_CIPHER_TEXT_LENGTH ->
?ALERT_REC(?FATAL, ?RECORD_OVERFLOW);
get_dtls_records_aux(<<1:1, Length0:15, _/binary>>,_Acc)
when Length0 > ?MAX_CIPHER_TEXT_LENGTH ->
?ALERT_REC(?FATAL, ?RECORD_OVERFLOW);
get_dtls_records_aux(Data, Acc) ->
case size(Data) =< ?MAX_CIPHER_TEXT_LENGTH + ?INITIAL_BYTES of
true ->
{lists:reverse(Acc), Data};
false ->
?ALERT_REC(?FATAL, ?UNEXPECTED_MESSAGE)
end.
encode_plain_text(Type, Version, Data,
#connection_states{current_write=#connection_state{
epoch = Epoch,
sequence_number = Seq,
compression_state=CompS0,
security_parameters=
#security_parameters{compression_algorithm=CompAlg}
}= WriteState0} = ConnectionStates) ->
{Comp, CompS1} = ssl_record:compress(CompAlg, Data, CompS0),
WriteState1 = WriteState0#connection_state{compression_state = CompS1},
MacHash = calc_mac_hash(WriteState1, Type, Version, Epoch, Seq, Comp),
{CipherFragment, WriteState} = ssl_record:cipher(Version, Comp, WriteState1, MacHash),
CipherText = encode_tls_cipher_text(Type, Version, Epoch, Seq, CipherFragment),
{CipherText, ConnectionStates#connection_states{current_write =
WriteState#connection_state{sequence_number = Seq +1}}}.
decode_cipher_text(#ssl_tls{type = Type, version = Version,
epoch = Epoch,
record_seq = Seq,
fragment = CipherFragment} = CipherText,
#connection_states{current_read =
#connection_state{compression_state = CompressionS0,
security_parameters = SecParams} = ReadState0}
= ConnnectionStates0) ->
CompressAlg = SecParams#security_parameters.compression_algorithm,
{PlainFragment, Mac, ReadState1} = ssl_record:decipher(dtls_v1:corresponding_tls_version(Version),
CipherFragment, ReadState0),
MacHash = calc_mac_hash(Type, Version, Epoch, Seq, PlainFragment, ReadState1),
case ssl_record:is_correct_mac(Mac, MacHash) of
true ->
{Plain, CompressionS1} = ssl_record:uncompress(CompressAlg,
PlainFragment, CompressionS0),
ConnnectionStates = ConnnectionStates0#connection_states{
current_read = ReadState1#connection_state{
compression_state = CompressionS1}},
{CipherText#ssl_tls{fragment = Plain}, ConnnectionStates};
false ->
?ALERT_REC(?FATAL, ?BAD_RECORD_MAC)
end.
%%--------------------------------------------------------------------
-spec protocol_version(tls_atom_version() | tls_version()) ->
tls_version() | tls_atom_version().
%%
%% Description: Creates a protocol version record from a version atom
%% or vice versa.
%%--------------------------------------------------------------------
protocol_version('dtlsv1.2') ->
{254, 253};
protocol_version(dtlsv1) ->
{254, 255};
protocol_version({254, 253}) ->
'dtlsv1.2';
protocol_version({254, 255}) ->
dtlsv1.
%%--------------------------------------------------------------------
-spec lowest_protocol_version(tls_version(), tls_version()) -> tls_version().
%%
%% Description: Lowes protocol version of two given versions
%%--------------------------------------------------------------------
lowest_protocol_version(Version = {M, N}, {M, O}) when N > O ->
Version;
lowest_protocol_version({M, _}, Version = {M, _}) ->
Version;
lowest_protocol_version(Version = {M,_}, {N, _}) when M > N ->
Version;
lowest_protocol_version(_,Version) ->
Version.
%%--------------------------------------------------------------------
-spec highest_protocol_version([tls_version()]) -> tls_version().
%%
%% Description: Highest protocol version present in a list
%%--------------------------------------------------------------------
highest_protocol_version([Ver | Vers]) ->
highest_protocol_version(Ver, Vers).
highest_protocol_version(Version, []) ->
Version;
highest_protocol_version(Version = {N, M}, [{N, O} | Rest]) when M < O ->
highest_protocol_version(Version, Rest);
highest_protocol_version({M, _}, [Version = {M, _} | Rest]) ->
highest_protocol_version(Version, Rest);
highest_protocol_version(Version = {M,_}, [{N,_} | Rest]) when M < N ->
highest_protocol_version(Version, Rest);
highest_protocol_version(_, [Version | Rest]) ->
highest_protocol_version(Version, Rest).
%%--------------------------------------------------------------------
-spec supported_protocol_versions() -> [tls_version()].
%%
%% Description: Protocol versions supported
%%--------------------------------------------------------------------
supported_protocol_versions() ->
Fun = fun(Version) ->
protocol_version(Version)
end,
case application:get_env(ssl, dtls_protocol_version) of
undefined ->
lists:map(Fun, supported_protocol_versions([]));
{ok, []} ->
lists:map(Fun, supported_protocol_versions([]));
{ok, Vsns} when is_list(Vsns) ->
supported_protocol_versions(Vsns);
{ok, Vsn} ->
supported_protocol_versions([Vsn])
end.
supported_protocol_versions([]) ->
Vsns = supported_connection_protocol_versions([]),
application:set_env(ssl, dtls_protocol_version, Vsns),
Vsns;
supported_protocol_versions([_|_] = Vsns) ->
Vsns.
supported_connection_protocol_versions([]) ->
?ALL_DATAGRAM_SUPPORTED_VERSIONS.
%%--------------------------------------------------------------------
-spec is_acceptable_version(tls_version(), Supported :: [tls_version()]) -> boolean().
%%
%% Description: ssl version 2 is not acceptable security risks are too big.
%%
%%--------------------------------------------------------------------
is_acceptable_version(Version, Versions) ->
lists:member(Version, Versions).
%%--------------------------------------------------------------------
-spec init_connection_state_seq(tls_version(), #connection_states{}) ->
#connection_state{}.
%%
%% Description: Copy the read sequence number to the write sequence number
%% This is only valid for DTLS in the first client_hello
%%--------------------------------------------------------------------
init_connection_state_seq({254, _},
#connection_states{
current_read = Read = #connection_state{epoch = 0},
current_write = Write = #connection_state{epoch = 0}} = CS0) ->
CS0#connection_states{current_write =
Write#connection_state{
sequence_number = Read#connection_state.sequence_number}};
init_connection_state_seq(_, CS) ->
CS.
%%--------------------------------------------------------
-spec current_connection_state_epoch(#connection_states{}, read | write) ->
integer().
%%
%% Description: Returns the epoch the connection_state record
%% that is currently defined as the current conection state.
%%--------------------------------------------------------------------
current_connection_state_epoch(#connection_states{current_read = Current},
read) ->
Current#connection_state.epoch;
current_connection_state_epoch(#connection_states{current_write = Current},
write) ->
Current#connection_state.epoch.
%%--------------------------------------------------------------------
-spec connection_state_by_epoch(#connection_states{}, integer(), read | write) ->
#connection_state{}.
%%
%% Description: Returns the instance of the connection_state record
%% that is defined by the Epoch.
%%--------------------------------------------------------------------
connection_state_by_epoch(#connection_states{current_read = CS}, Epoch, read)
when CS#connection_state.epoch == Epoch ->
CS;
connection_state_by_epoch(#connection_states{pending_read = CS}, Epoch, read)
when CS#connection_state.epoch == Epoch ->
CS;
connection_state_by_epoch(#connection_states{current_write = CS}, Epoch, write)
when CS#connection_state.epoch == Epoch ->
CS;
connection_state_by_epoch(#connection_states{pending_write = CS}, Epoch, write)
when CS#connection_state.epoch == Epoch ->
CS.
%%--------------------------------------------------------------------
-spec set_connection_state_by_epoch(#connection_states{},
#connection_state{}, read | write)
-> #connection_states{}.
%%
%% Description: Returns the instance of the connection_state record
%% that is defined by the Epoch.
%%--------------------------------------------------------------------
set_connection_state_by_epoch(ConnectionStates0 =
#connection_states{current_read = CS},
NewCS = #connection_state{epoch = Epoch}, read)
when CS#connection_state.epoch == Epoch ->
ConnectionStates0#connection_states{current_read = NewCS};
set_connection_state_by_epoch(ConnectionStates0 =
#connection_states{pending_read = CS},
NewCS = #connection_state{epoch = Epoch}, read)
when CS#connection_state.epoch == Epoch ->
ConnectionStates0#connection_states{pending_read = NewCS};
set_connection_state_by_epoch(ConnectionStates0 =
#connection_states{current_write = CS},
NewCS = #connection_state{epoch = Epoch}, write)
when CS#connection_state.epoch == Epoch ->
ConnectionStates0#connection_states{current_write = NewCS};
set_connection_state_by_epoch(ConnectionStates0 =
#connection_states{pending_write = CS},
NewCS = #connection_state{epoch = Epoch}, write)
when CS#connection_state.epoch == Epoch ->
ConnectionStates0#connection_states{pending_write = NewCS}.
%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
encode_tls_cipher_text(Type, {MajVer, MinVer}, Epoch, Seq, Fragment) ->
Length = erlang:iolist_size(Fragment),
[<<?BYTE(Type), ?BYTE(MajVer), ?BYTE(MinVer), ?UINT16(Epoch),
?UINT48(Seq), ?UINT16(Length)>>, Fragment].
calc_mac_hash(#connection_state{mac_secret = MacSecret,
security_parameters = #security_parameters{mac_algorithm = MacAlg}},
Type, Version, Epoch, SeqNo, Fragment) ->
Length = erlang:iolist_size(Fragment),
NewSeq = (Epoch bsl 48) + SeqNo,
mac_hash(Version, MacAlg, MacSecret, NewSeq, Type,
Length, Fragment).
mac_hash(Version, MacAlg, MacSecret, SeqNo, Type, Length, Fragment) ->
dtls_v1:mac_hash(MacAlg, MacSecret, SeqNo, Type, Version,
Length, Fragment).
