%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2013-2017. 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.
%%
%% %CopyrightEnd%
%%
-module(dtls_connection).
%% Internal application API
-behaviour(gen_statem).
-include("dtls_connection.hrl").
-include("dtls_handshake.hrl").
-include("ssl_alert.hrl").
-include("dtls_record.hrl").
-include("ssl_cipher.hrl").
-include("ssl_api.hrl").
-include("ssl_internal.hrl").
-include("ssl_srp.hrl").
-include_lib("public_key/include/public_key.hrl").
%% Internal application API
%% Setup
-export([start_fsm/8, start_link/7, init/1]).
%% State transition handling
-export([next_record/1, next_event/3, next_event/4, handle_common_event/4]).
%% Handshake handling
-export([renegotiate/2, send_handshake/2,
queue_handshake/2, queue_change_cipher/2,
reinit_handshake_data/1, select_sni_extension/1, empty_connection_state/2]).
%% Alert and close handling
-export([encode_alert/3,send_alert/2, close/5, protocol_name/0]).
%% Data handling
-export([encode_data/3, passive_receive/2, next_record_if_active/1,
send/3, socket/5, setopts/3, getopts/3]).
%% gen_statem state functions
-export([init/3, error/3, downgrade/3, %% Initiation and take down states
hello/3, certify/3, cipher/3, abbreviated/3, %% Handshake states
connection/3]).
%% gen_statem callbacks
-export([callback_mode/0, terminate/3, code_change/4, format_status/2]).
%%====================================================================
%% Internal application API
%%====================================================================
%%====================================================================
%% Setup
%%====================================================================
start_fsm(Role, Host, Port, Socket, {#ssl_options{erl_dist = false},_, Tracker} = Opts,
User, {CbModule, _,_, _} = CbInfo,
Timeout) ->
try
{ok, Pid} = dtls_connection_sup:start_child([Role, Host, Port, Socket,
Opts, User, CbInfo]),
{ok, SslSocket} = ssl_connection:socket_control(?MODULE, Socket, Pid, CbModule, Tracker),
ok = ssl_connection:handshake(SslSocket, Timeout),
{ok, SslSocket}
catch
error:{badmatch, {error, _} = Error} ->
Error
end.
%%--------------------------------------------------------------------
-spec start_link(atom(), host(), inet:port_number(), port(), list(), pid(), tuple()) ->
{ok, pid()} | ignore | {error, reason()}.
%%
%% Description: Creates a gen_statem process which calls Module:init/1 to
%% initialize.
%%--------------------------------------------------------------------
start_link(Role, Host, Port, Socket, Options, User, CbInfo) ->
{ok, proc_lib:spawn_link(?MODULE, init, [[Role, Host, Port, Socket, Options, User, CbInfo]])}.
init([Role, Host, Port, Socket, Options, User, CbInfo]) ->
process_flag(trap_exit, true),
State0 = initial_state(Role, Host, Port, Socket, Options, User, CbInfo),
try
State = ssl_connection:ssl_config(State0#state.ssl_options, Role, State0),
gen_statem:enter_loop(?MODULE, [], init, State)
catch
throw:Error ->
gen_statem:enter_loop(?MODULE, [], error, {Error,State0})
end.
%%====================================================================
%% State transition handling
%%====================================================================
next_record(#state{unprocessed_handshake_events = N} = State) when N > 0 ->
{no_record, State#state{unprocessed_handshake_events = N-1}};
next_record(#state{protocol_buffers =
#protocol_buffers{dtls_cipher_texts = [#ssl_tls{epoch = Epoch} = CT | Rest]}
= Buffers,
connection_states = #{current_read := #{epoch := Epoch}} = ConnectionStates} = State) ->
CurrentRead = dtls_record:get_connection_state_by_epoch(Epoch, ConnectionStates, read),
case dtls_record:replay_detect(CT, CurrentRead) of
false ->
decode_cipher_text(State#state{connection_states = ConnectionStates}) ;
true ->
%% Ignore replayed record
next_record(State#state{protocol_buffers =
Buffers#protocol_buffers{dtls_cipher_texts = Rest},
connection_states = ConnectionStates})
end;
next_record(#state{protocol_buffers =
#protocol_buffers{dtls_cipher_texts = [#ssl_tls{epoch = Epoch} | Rest]}
= Buffers,
connection_states = #{current_read := #{epoch := CurrentEpoch}} = ConnectionStates} = State)
when Epoch > CurrentEpoch ->
%% TODO Buffer later Epoch message, drop it for now
next_record(State#state{protocol_buffers =
Buffers#protocol_buffers{dtls_cipher_texts = Rest},
connection_states = ConnectionStates});
next_record(#state{protocol_buffers =
#protocol_buffers{dtls_cipher_texts = [ _ | Rest]}
= Buffers,
connection_states = ConnectionStates} = State) ->
%% Drop old epoch message
next_record(State#state{protocol_buffers =
Buffers#protocol_buffers{dtls_cipher_texts = Rest},
connection_states = ConnectionStates});
next_record(#state{role = server,
socket = {Listener, {Client, _}},
transport_cb = gen_udp} = State) ->
dtls_udp_listener:active_once(Listener, Client, self()),
{no_record, State};
next_record(#state{role = client,
socket = {_Server, Socket},
transport_cb = Transport} = State) ->
dtls_socket:setopts(Transport, Socket, [{active,once}]),
{no_record, State};
next_record(State) ->
{no_record, State}.
next_event(StateName, Record, State) ->
next_event(StateName, Record, State, []).
next_event(connection = StateName, no_record,
#state{connection_states = #{current_read := #{epoch := CurrentEpoch}}} = State0, Actions) ->
case next_record_if_active(State0) of
{no_record, State} ->
ssl_connection:hibernate_after(StateName, State, Actions);
{#ssl_tls{epoch = CurrentEpoch,
type = ?HANDSHAKE,
version = Version} = Record, State1} ->
State = dtls_version(StateName, Version, State1),
{next_state, StateName, State,
[{next_event, internal, {protocol_record, Record}} | Actions]};
{#ssl_tls{epoch = CurrentEpoch} = Record, State} ->
{next_state, StateName, State, [{next_event, internal, {protocol_record, Record}} | Actions]};
{#ssl_tls{epoch = Epoch,
type = ?HANDSHAKE,
version = _Version}, State1} = _Record when Epoch == CurrentEpoch-1 ->
{State2, MoreActions} = send_handshake_flight(State1, CurrentEpoch),
{NextRecord, State} = next_record(State2),
next_event(StateName, NextRecord, State, Actions ++ MoreActions);
%% From FLIGHT perspective CHANGE_CIPHER_SPEC is treated as a handshake
{#ssl_tls{epoch = Epoch,
type = ?CHANGE_CIPHER_SPEC,
version = _Version}, State1} = _Record when Epoch == CurrentEpoch-1 ->
{State2, MoreActions} = send_handshake_flight(State1, CurrentEpoch),
{NextRecord, State} = next_record(State2),
next_event(StateName, NextRecord, State, Actions ++ MoreActions);
{#ssl_tls{epoch = _Epoch,
version = _Version}, State1} ->
%% TODO maybe buffer later epoch
{Record, State} = next_record(State1),
next_event(StateName, Record, State, Actions);
{#alert{} = Alert, State} ->
{next_state, StateName, State, [{next_event, internal, Alert} | Actions]}
end;
next_event(connection = StateName, Record,
#state{connection_states = #{current_read := #{epoch := CurrentEpoch}}} = State0, Actions) ->
case Record of
#ssl_tls{epoch = CurrentEpoch,
type = ?HANDSHAKE,
version = Version} = Record ->
State = dtls_version(StateName, Version, State0),
{next_state, StateName, State,
[{next_event, internal, {protocol_record, Record}} | Actions]};
#ssl_tls{epoch = CurrentEpoch} ->
{next_state, StateName, State0, [{next_event, internal, {protocol_record, Record}} | Actions]};
#ssl_tls{epoch = Epoch,
type = ?HANDSHAKE,
version = _Version} when Epoch == CurrentEpoch-1 ->
{State1, MoreActions} = send_handshake_flight(State0, CurrentEpoch),
{NextRecord, State} = next_record(State1),
next_event(StateName, NextRecord, State, Actions ++ MoreActions);
%% From FLIGHT perspective CHANGE_CIPHER_SPEC is treated as a handshake
#ssl_tls{epoch = Epoch,
type = ?CHANGE_CIPHER_SPEC,
version = _Version} when Epoch == CurrentEpoch-1 ->
{State1, MoreActions} = send_handshake_flight(State0, CurrentEpoch),
{NextRecord, State} = next_record(State1),
next_event(StateName, NextRecord, State, Actions ++ MoreActions);
_ ->
next_event(StateName, no_record, State0, Actions)
end;
next_event(StateName, Record,
#state{connection_states = #{current_read := #{epoch := CurrentEpoch}}} = State0, Actions) ->
case Record of
no_record ->
{next_state, StateName, State0, Actions};
#ssl_tls{epoch = CurrentEpoch,
version = Version} = Record ->
State = dtls_version(StateName, Version, State0),
{next_state, StateName, State,
[{next_event, internal, {protocol_record, Record}} | Actions]};
#ssl_tls{epoch = _Epoch,
version = _Version} = _Record ->
%% TODO maybe buffer later epoch
{Record, State} = next_record(State0),
next_event(StateName, Record, State, Actions);
#alert{} = Alert ->
{next_state, StateName, State0, [{next_event, internal, Alert} | Actions]}
end.
handle_call(Event, From, StateName, State) ->
ssl_connection:handle_call(Event, From, StateName, State, ?MODULE).
handle_common_event(internal, #alert{} = Alert, StateName,
#state{negotiated_version = Version} = State) ->
handle_own_alert(Alert, Version, StateName, State);
%%% DTLS record protocol level handshake messages
handle_common_event(internal, #ssl_tls{type = ?HANDSHAKE,
fragment = Data},
StateName,
#state{protocol_buffers = Buffers0,
negotiated_version = Version} = State0) ->
try
case dtls_handshake:get_dtls_handshake(Version, Data, Buffers0) of
{[], Buffers} ->
{Record, State} = next_record(State0#state{protocol_buffers = Buffers}),
next_event(StateName, Record, State);
{Packets, Buffers} ->
State = State0#state{protocol_buffers = Buffers},
Events = dtls_handshake_events(Packets),
{next_state, StateName,
State#state{unprocessed_handshake_events = unprocessed_events(Events)}, Events}
end
catch throw:#alert{} = Alert ->
handle_own_alert(Alert, Version, StateName, State0)
end;
%%% DTLS record protocol level application data messages
handle_common_event(internal, #ssl_tls{type = ?APPLICATION_DATA, fragment = Data}, StateName, State) ->
{next_state, StateName, State, [{next_event, internal, {application_data, Data}}]};
%%% DTLS record protocol level change cipher messages
handle_common_event(internal, #ssl_tls{type = ?CHANGE_CIPHER_SPEC, fragment = Data}, StateName, State) ->
{next_state, StateName, State, [{next_event, internal, #change_cipher_spec{type = Data}}]};
%%% DTLS record protocol level Alert messages
handle_common_event(internal, #ssl_tls{type = ?ALERT, fragment = EncAlerts}, StateName,
#state{negotiated_version = Version} = State) ->
case decode_alerts(EncAlerts) of
Alerts = [_|_] ->
handle_alerts(Alerts, {next_state, StateName, State});
#alert{} = Alert ->
handle_own_alert(Alert, Version, StateName, State)
end;
%% Ignore unknown TLS record level protocol messages
handle_common_event(internal, #ssl_tls{type = _Unknown}, StateName, State) ->
{next_state, StateName, State}.
%%====================================================================
%% Handshake handling
%%====================================================================
renegotiate(#state{role = client} = State, Actions) ->
%% Handle same way as if server requested
%% the renegotiation
{next_state, connection, State,
[{next_event, internal, #hello_request{}} | Actions]};
renegotiate(#state{role = server} = State0, Actions) ->
HelloRequest = ssl_handshake:hello_request(),
State1 = prepare_flight(State0),
{State2, MoreActions} = send_handshake(HelloRequest, State1),
{Record, State} = next_record(State2),
next_event(hello, Record, State, Actions ++ MoreActions).
send_handshake(Handshake, #state{connection_states = ConnectionStates} = State) ->
#{epoch := Epoch} = ssl_record:current_connection_state(ConnectionStates, write),
send_handshake_flight(queue_handshake(Handshake, State), Epoch).
queue_handshake(Handshake0, #state{tls_handshake_history = Hist0,
negotiated_version = Version,
flight_buffer = #{handshakes := HsBuffer0,
change_cipher_spec := undefined,
next_sequence := Seq} = Flight0} = State) ->
Handshake = dtls_handshake:encode_handshake(Handshake0, Version, Seq),
Hist = update_handshake_history(Handshake0, Handshake, Hist0),
State#state{flight_buffer = Flight0#{handshakes => [Handshake | HsBuffer0],
next_sequence => Seq +1},
tls_handshake_history = Hist};
queue_handshake(Handshake0, #state{tls_handshake_history = Hist0,
negotiated_version = Version,
flight_buffer = #{handshakes_after_change_cipher_spec := Buffer0,
next_sequence := Seq} = Flight0} = State) ->
Handshake = dtls_handshake:encode_handshake(Handshake0, Version, Seq),
Hist = update_handshake_history(Handshake0, Handshake, Hist0),
State#state{flight_buffer = Flight0#{handshakes_after_change_cipher_spec => [Handshake | Buffer0],
next_sequence => Seq +1},
tls_handshake_history = Hist}.
queue_change_cipher(ChangeCipher, #state{flight_buffer = Flight,
connection_states = ConnectionStates0} = State) ->
ConnectionStates =
dtls_record:next_epoch(ConnectionStates0, write),
State#state{flight_buffer = Flight#{change_cipher_spec => ChangeCipher},
connection_states = ConnectionStates}.
reinit_handshake_data(#state{protocol_buffers = Buffers} = State) ->
State#state{premaster_secret = undefined,
public_key_info = undefined,
tls_handshake_history = ssl_handshake:init_handshake_history(),
flight_state = {retransmit, ?INITIAL_RETRANSMIT_TIMEOUT},
flight_buffer = new_flight(),
protocol_buffers =
Buffers#protocol_buffers{
dtls_handshake_next_seq = 0,
dtls_handshake_next_fragments = [],
dtls_handshake_later_fragments = []
}}.
select_sni_extension(#client_hello{extensions = HelloExtensions}) ->
HelloExtensions#hello_extensions.sni;
select_sni_extension(_) ->
undefined.
empty_connection_state(ConnectionEnd, BeastMitigation) ->
Empty = ssl_record:empty_connection_state(ConnectionEnd, BeastMitigation),
dtls_record:empty_connection_state(Empty).
%%====================================================================
%% Alert and close handling
%%====================================================================
encode_alert(#alert{} = Alert, Version, ConnectionStates) ->
dtls_record:encode_alert_record(Alert, Version, ConnectionStates).
send_alert(Alert, #state{negotiated_version = Version,
socket = Socket,
transport_cb = Transport,
connection_states = ConnectionStates0} = State0) ->
{BinMsg, ConnectionStates} =
encode_alert(Alert, Version, ConnectionStates0),
send(Transport, Socket, BinMsg),
State0#state{connection_states = ConnectionStates}.
close(downgrade, _,_,_,_) ->
ok;
%% Other
close(_, Socket, Transport, _,_) ->
dtls_socket:close(Transport,Socket).
protocol_name() ->
"DTLS".
%%====================================================================
%% Data handling
%%====================================================================
encode_data(Data, Version, ConnectionStates0)->
dtls_record:encode_data(Data, Version, ConnectionStates0).
passive_receive(State0 = #state{user_data_buffer = Buffer}, StateName) ->
case Buffer of
<<>> ->
{Record, State} = next_record(State0),
next_event(StateName, Record, State);
_ ->
{Record, State} = ssl_connection:read_application_data(<<>>, State0),
next_event(StateName, Record, State)
end.
next_record_if_active(State =
#state{socket_options =
#socket_options{active = false}}) ->
{no_record ,State};
next_record_if_active(State) ->
next_record(State).
send(Transport, {_, {{_,_}, _} = Socket}, Data) ->
send(Transport, Socket, Data);
send(Transport, Socket, Data) ->
dtls_socket:send(Transport, Socket, Data).
socket(Pid, Transport, Socket, Connection, _) ->
dtls_socket:socket(Pid, Transport, Socket, Connection).
setopts(Transport, Socket, Other) ->
dtls_socket:setopts(Transport, Socket, Other).
getopts(Transport, Socket, Tag) ->
dtls_socket:getopts(Transport, Socket, Tag).
%%--------------------------------------------------------------------
%% State functions
%%--------------------------------------------------------------------
%%--------------------------------------------------------------------
-spec init(gen_statem:event_type(),
{start, timeout()} | term(), #state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
init(enter, _, State) ->
{keep_state, State};
init({call, From}, {start, Timeout},
#state{host = Host, port = Port, role = client,
ssl_options = SslOpts,
session = #session{own_certificate = Cert} = Session0,
connection_states = ConnectionStates0,
renegotiation = {Renegotiation, _},
session_cache = Cache,
session_cache_cb = CacheCb
} = State0) ->
Timer = ssl_connection:start_or_recv_cancel_timer(Timeout, From),
Hello = dtls_handshake:client_hello(Host, Port, ConnectionStates0, SslOpts,
Cache, CacheCb, Renegotiation, Cert),
Version = Hello#client_hello.client_version,
HelloVersion = dtls_record:hello_version(Version, SslOpts#ssl_options.versions),
State1 = prepare_flight(State0#state{negotiated_version = Version}),
{State2, Actions} = send_handshake(Hello, State1#state{negotiated_version = HelloVersion}),
State3 = State2#state{negotiated_version = Version, %% Requested version
session =
Session0#session{session_id = Hello#client_hello.session_id},
start_or_recv_from = From,
timer = Timer,
flight_state = {retransmit, ?INITIAL_RETRANSMIT_TIMEOUT}
},
{Record, State} = next_record(State3),
next_event(hello, Record, State, Actions);
init({call, _} = Type, Event, #state{role = server, transport_cb = gen_udp} = State) ->
Result = ssl_connection:?FUNCTION_NAME(Type, Event,
State#state{flight_state = {retransmit, ?INITIAL_RETRANSMIT_TIMEOUT},
protocol_specific = #{current_cookie_secret => dtls_v1:cookie_secret(),
previous_cookie_secret => <<>>,
ignored_alerts => 0,
max_ignored_alerts => 10}},
?MODULE),
erlang:send_after(dtls_v1:cookie_timeout(), self(), new_cookie_secret),
Result;
init({call, _} = Type, Event, #state{role = server} = State) ->
%% I.E. DTLS over sctp
ssl_connection:?FUNCTION_NAME(Type, Event, State#state{flight_state = reliable}, ?MODULE);
init(Type, Event, State) ->
ssl_connection:?FUNCTION_NAME(Type, Event, State, ?MODULE).
%%--------------------------------------------------------------------
-spec error(gen_statem:event_type(),
{start, timeout()} | term(), #state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
error(enter, _, State) ->
{keep_state, State};
error({call, From}, {start, _Timeout}, {Error, State}) ->
{stop_and_reply, normal, {reply, From, {error, Error}}, State};
error({call, From}, Msg, State) ->
handle_call(Msg, From, ?FUNCTION_NAME, State);
error(_, _, _) ->
{keep_state_and_data, [postpone]}.
%%--------------------------------------------------------------------
-spec hello(gen_statem:event_type(),
#hello_request{} | #client_hello{} | #server_hello{} | term(),
#state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
hello(enter, _, #state{role = server} = State) ->
{keep_state, State};
hello(enter, _, #state{role = client} = State0) ->
{State, Actions} = handle_flight_timer(State0),
{keep_state, State, Actions};
hello(internal, #client_hello{cookie = <<>>,
client_version = Version} = Hello, #state{role = server,
transport_cb = Transport,
socket = Socket,
protocol_specific = #{current_cookie_secret := Secret}} = State0) ->
{ok, {IP, Port}} = dtls_socket:peername(Transport, Socket),
Cookie = dtls_handshake:cookie(Secret, IP, Port, Hello),
%% FROM RFC 6347 regarding HelloVerifyRequest message:
%% The server_version field has the same syntax as in TLS. However, in
%% order to avoid the requirement to do version negotiation in the
%% initial handshake, DTLS 1.2 server implementations SHOULD use DTLS
%% version 1.0 regardless of the version of TLS that is expected to be
%% negotiated.
VerifyRequest = dtls_handshake:hello_verify_request(Cookie, ?HELLO_VERIFY_REQUEST_VERSION),
State1 = prepare_flight(State0#state{negotiated_version = Version}),
{State2, Actions} = send_handshake(VerifyRequest, State1),
{Record, State} = next_record(State2),
next_event(?FUNCTION_NAME, Record, State#state{tls_handshake_history = ssl_handshake:init_handshake_history()}, Actions);
hello(internal, #client_hello{cookie = Cookie} = Hello, #state{role = server,
transport_cb = Transport,
socket = Socket,
protocol_specific = #{current_cookie_secret := Secret,
previous_cookie_secret := PSecret}} = State0) ->
{ok, {IP, Port}} = dtls_socket:peername(Transport, Socket),
case dtls_handshake:cookie(Secret, IP, Port, Hello) of
Cookie ->
handle_client_hello(Hello, State0);
_ ->
case dtls_handshake:cookie(PSecret, IP, Port, Hello) of
Cookie ->
handle_client_hello(Hello, State0);
_ ->
%% Handle bad cookie as new cookie request RFC 6347 4.1.2
hello(internal, Hello#client_hello{cookie = <<>>}, State0)
end
end;
hello(internal, #hello_verify_request{cookie = Cookie}, #state{role = client,
host = Host, port = Port,
ssl_options = SslOpts,
session = #session{own_certificate = OwnCert}
= Session0,
connection_states = ConnectionStates0,
renegotiation = {Renegotiation, _},
session_cache = Cache,
session_cache_cb = CacheCb
} = State0) ->
Hello = dtls_handshake:client_hello(Host, Port, Cookie, ConnectionStates0,
SslOpts,
Cache, CacheCb, Renegotiation, OwnCert),
Version = Hello#client_hello.client_version,
State1 = prepare_flight(State0#state{tls_handshake_history = ssl_handshake:init_handshake_history()}),
{State2, Actions} = send_handshake(Hello, State1),
State3 = State2#state{negotiated_version = Version, %% Requested version
session =
Session0#session{session_id =
Hello#client_hello.session_id}},
{Record, State} = next_record(State3),
next_event(?FUNCTION_NAME, Record, State, Actions);
hello(internal, #server_hello{} = Hello,
#state{connection_states = ConnectionStates0,
negotiated_version = ReqVersion,
role = client,
renegotiation = {Renegotiation, _},
ssl_options = SslOptions} = State) ->
case dtls_handshake:hello(Hello, SslOptions, ConnectionStates0, Renegotiation) of
#alert{} = Alert ->
handle_own_alert(Alert, ReqVersion, ?FUNCTION_NAME, State);
{Version, NewId, ConnectionStates, ProtoExt, Protocol} ->
ssl_connection:handle_session(Hello,
Version, NewId, ConnectionStates, ProtoExt, Protocol, State)
end;
hello(internal, {handshake, {#client_hello{cookie = <<>>} = Handshake, _}}, State) ->
%% Initial hello should not be in handshake history
{next_state, ?FUNCTION_NAME, State, [{next_event, internal, Handshake}]};
hello(internal, {handshake, {#hello_verify_request{} = Handshake, _}}, State) ->
%% hello_verify should not be in handshake history
{next_state, ?FUNCTION_NAME, State, [{next_event, internal, Handshake}]};
hello(info, Event, State) ->
handle_info(Event, ?FUNCTION_NAME, State);
hello(state_timeout, Event, State) ->
handle_state_timeout(Event, ?FUNCTION_NAME, State);
hello(Type, Event, State) ->
ssl_connection:?FUNCTION_NAME(Type, Event, State, ?MODULE).
%%--------------------------------------------------------------------
-spec abbreviated(gen_statem:event_type(), term(), #state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
abbreviated(enter, _, State0) ->
{State, Actions} = handle_flight_timer(State0),
{keep_state, State, Actions};
abbreviated(info, Event, State) ->
handle_info(Event, ?FUNCTION_NAME, State);
abbreviated(internal = Type,
#change_cipher_spec{type = <<1>>} = Event,
#state{connection_states = ConnectionStates0} = State) ->
ConnectionStates1 = dtls_record:save_current_connection_state(ConnectionStates0, read),
ConnectionStates = dtls_record:next_epoch(ConnectionStates1, read),
ssl_connection:?FUNCTION_NAME(Type, Event, State#state{connection_states = ConnectionStates}, ?MODULE);
abbreviated(internal = Type, #finished{} = Event, #state{connection_states = ConnectionStates} = State) ->
ssl_connection:?FUNCTION_NAME(Type, Event,
prepare_flight(State#state{connection_states = ConnectionStates,
flight_state = connection}), ?MODULE);
abbreviated(state_timeout, Event, State) ->
handle_state_timeout(Event, ?FUNCTION_NAME, State);
abbreviated(Type, Event, State) ->
ssl_connection:?FUNCTION_NAME(Type, Event, State, ?MODULE).
%%--------------------------------------------------------------------
-spec certify(gen_statem:event_type(), term(), #state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
certify(enter, _, State0) ->
{State, Actions} = handle_flight_timer(State0),
{keep_state, State, Actions};
certify(info, Event, State) ->
handle_info(Event, ?FUNCTION_NAME, State);
certify(internal = Type, #server_hello_done{} = Event, State) ->
ssl_connection:certify(Type, Event, prepare_flight(State), ?MODULE);
certify(state_timeout, Event, State) ->
handle_state_timeout(Event, ?FUNCTION_NAME, State);
certify(Type, Event, State) ->
ssl_connection:?FUNCTION_NAME(Type, Event, State, ?MODULE).
%%--------------------------------------------------------------------
-spec cipher(gen_statem:event_type(), term(), #state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
cipher(enter, _, State0) ->
{State, Actions} = handle_flight_timer(State0),
{keep_state, State, Actions};
cipher(info, Event, State) ->
handle_info(Event, ?FUNCTION_NAME, State);
cipher(internal = Type, #change_cipher_spec{type = <<1>>} = Event,
#state{connection_states = ConnectionStates0} = State) ->
ConnectionStates1 = dtls_record:save_current_connection_state(ConnectionStates0, read),
ConnectionStates = dtls_record:next_epoch(ConnectionStates1, read),
ssl_connection:?FUNCTION_NAME(Type, Event, State#state{connection_states = ConnectionStates}, ?MODULE);
cipher(internal = Type, #finished{} = Event, #state{connection_states = ConnectionStates} = State) ->
ssl_connection:?FUNCTION_NAME(Type, Event,
prepare_flight(State#state{connection_states = ConnectionStates,
flight_state = connection}),
?MODULE);
cipher(state_timeout, Event, State) ->
handle_state_timeout(Event, ?FUNCTION_NAME, State);
cipher(Type, Event, State) ->
ssl_connection:?FUNCTION_NAME(Type, Event, State, ?MODULE).
%%--------------------------------------------------------------------
-spec connection(gen_statem:event_type(),
#hello_request{} | #client_hello{}| term(), #state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
connection(enter, _, State) ->
{keep_state, State};
connection(info, Event, State) ->
handle_info(Event, ?FUNCTION_NAME, State);
connection(internal, #hello_request{}, #state{host = Host, port = Port,
session = #session{own_certificate = Cert} = Session0,
session_cache = Cache, session_cache_cb = CacheCb,
ssl_options = SslOpts,
connection_states = ConnectionStates0,
renegotiation = {Renegotiation, _}} = State0) ->
Hello = dtls_handshake:client_hello(Host, Port, ConnectionStates0, SslOpts,
Cache, CacheCb, Renegotiation, Cert),
Version = Hello#client_hello.client_version,
HelloVersion = dtls_record:hello_version(Version, SslOpts#ssl_options.versions),
State1 = prepare_flight(State0),
{State2, Actions} = send_handshake(Hello, State1#state{negotiated_version = HelloVersion}),
{Record, State} =
next_record(
State2#state{flight_state = {retransmit, ?INITIAL_RETRANSMIT_TIMEOUT},
session = Session0#session{session_id
= Hello#client_hello.session_id}}),
next_event(hello, Record, State, Actions);
connection(internal, #client_hello{} = Hello, #state{role = server, allow_renegotiate = true} = State) ->
%% Mitigate Computational DoS attack
%% http://www.educatedguesswork.org/2011/10/ssltls_and_computational_dos.html
%% http://www.thc.org/thc-ssl-dos/ Rather than disabling client
%% initiated renegotiation we will disallow many client initiated
%% renegotiations immediately after each other.
erlang:send_after(?WAIT_TO_ALLOW_RENEGOTIATION, self(), allow_renegotiate),
{next_state, hello, State#state{allow_renegotiate = false, renegotiation = {true, peer}},
[{next_event, internal, Hello}]};
connection(internal, #client_hello{}, #state{role = server, allow_renegotiate = false} = State0) ->
Alert = ?ALERT_REC(?WARNING, ?NO_RENEGOTIATION),
State1 = send_alert(Alert, State0),
{Record, State} = ssl_connection:prepare_connection(State1, ?MODULE),
next_event(?FUNCTION_NAME, Record, State);
connection(Type, Event, State) ->
ssl_connection:?FUNCTION_NAME(Type, Event, State, ?MODULE).
%%TODO does this make sense for DTLS ?
%%--------------------------------------------------------------------
-spec downgrade(gen_statem:event_type(), term(), #state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
downgrade(enter, _, State) ->
{keep_state, State};
downgrade(Type, Event, State) ->
ssl_connection:?FUNCTION_NAME(Type, Event, State, ?MODULE).
%%--------------------------------------------------------------------
%% gen_statem callbacks
%%--------------------------------------------------------------------
callback_mode() ->
[state_functions, state_enter].
terminate(Reason, StateName, State) ->
ssl_connection:terminate(Reason, StateName, State).
code_change(_OldVsn, StateName, State, _Extra) ->
{ok, StateName, State}.
format_status(Type, Data) ->
ssl_connection:format_status(Type, Data).
%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
initial_state(Role, Host, Port, Socket, {SSLOptions, SocketOptions, _}, User,
{CbModule, DataTag, CloseTag, ErrorTag}) ->
#ssl_options{beast_mitigation = BeastMitigation} = SSLOptions,
ConnectionStates = dtls_record:init_connection_states(Role, BeastMitigation),
SessionCacheCb = case application:get_env(ssl, session_cb) of
{ok, Cb} when is_atom(Cb) ->
Cb;
_ ->
ssl_session_cache
end,
Monitor = erlang:monitor(process, User),
#state{socket_options = SocketOptions,
%% We do not want to save the password in the state so that
%% could be written in the clear into error logs.
ssl_options = SSLOptions#ssl_options{password = undefined},
session = #session{is_resumable = new},
transport_cb = CbModule,
data_tag = DataTag,
close_tag = CloseTag,
error_tag = ErrorTag,
role = Role,
host = Host,
port = Port,
socket = Socket,
connection_states = ConnectionStates,
protocol_buffers = #protocol_buffers{},
user_application = {Monitor, User},
user_data_buffer = <<>>,
session_cache_cb = SessionCacheCb,
renegotiation = {false, first},
allow_renegotiate = SSLOptions#ssl_options.client_renegotiation,
start_or_recv_from = undefined,
protocol_cb = ?MODULE,
flight_buffer = new_flight(),
flight_state = {retransmit, ?INITIAL_RETRANSMIT_TIMEOUT}
}.
next_dtls_record(Data, #state{protocol_buffers = #protocol_buffers{
dtls_record_buffer = Buf0,
dtls_cipher_texts = CT0} = Buffers} = State0) ->
case dtls_record:get_dtls_records(Data, Buf0) of
{Records, Buf1} ->
CT1 = CT0 ++ Records,
next_record(State0#state{protocol_buffers =
Buffers#protocol_buffers{dtls_record_buffer = Buf1,
dtls_cipher_texts = CT1}});
#alert{} = Alert ->
Alert
end.
dtls_handshake_events(Packets) ->
lists:map(fun(Packet) ->
{next_event, internal, {handshake, Packet}}
end, Packets).
decode_cipher_text(#state{protocol_buffers = #protocol_buffers{dtls_cipher_texts = [ CT | Rest]} = Buffers,
connection_states = ConnStates0} = State) ->
case dtls_record:decode_cipher_text(CT, ConnStates0) of
{Plain, ConnStates} ->
{Plain, State#state{protocol_buffers =
Buffers#protocol_buffers{dtls_cipher_texts = Rest},
connection_states = ConnStates}};
#alert{} = Alert ->
{Alert, State}
end.
dtls_version(hello, Version, #state{role = server} = State) ->
State#state{negotiated_version = Version}; %%Inital version
dtls_version(_,_, State) ->
State.
handle_client_hello(#client_hello{client_version = ClientVersion} = Hello,
#state{connection_states = ConnectionStates0,
port = Port, session = #session{own_certificate = Cert} = Session0,
renegotiation = {Renegotiation, _},
session_cache = Cache,
session_cache_cb = CacheCb,
negotiated_protocol = CurrentProtocol,
key_algorithm = KeyExAlg,
ssl_options = SslOpts} = State0) ->
case dtls_handshake:hello(Hello, SslOpts, {Port, Session0, Cache, CacheCb,
ConnectionStates0, Cert, KeyExAlg}, Renegotiation) of
#alert{} = Alert ->
handle_own_alert(Alert, ClientVersion, hello, State0);
{Version, {Type, Session},
ConnectionStates, Protocol0, ServerHelloExt, HashSign} ->
Protocol = case Protocol0 of
undefined -> CurrentProtocol;
_ -> Protocol0
end,
State = prepare_flight(State0#state{connection_states = ConnectionStates,
negotiated_version = Version,
hashsign_algorithm = HashSign,
client_hello_version = ClientVersion,
session = Session,
negotiated_protocol = Protocol}),
ssl_connection:hello(internal, {common_client_hello, Type, ServerHelloExt},
State, ?MODULE)
end.
%% raw data from socket, unpack records
handle_info({Protocol, _, _, _, Data}, StateName,
#state{data_tag = Protocol} = State0) ->
case next_dtls_record(Data, State0) of
{Record, State} ->
next_event(StateName, Record, State);
#alert{} = Alert ->
ssl_connection:handle_normal_shutdown(Alert, StateName, State0),
{stop, {shutdown, own_alert}}
end;
handle_info({CloseTag, Socket}, StateName,
#state{socket = Socket,
socket_options = #socket_options{active = Active},
protocol_buffers = #protocol_buffers{dtls_cipher_texts = CTs},
close_tag = CloseTag,
negotiated_version = Version} = State) ->
%% Note that as of DTLS 1.2 (TLS 1.1),
%% failure to properly close a connection no longer requires that a
%% session not be resumed. This is a change from DTLS 1.0 to conform
%% with widespread implementation practice.
case (Active == false) andalso (CTs =/= []) of
false ->
case Version of
{254, N} when N =< 253 ->
ok;
_ ->
%% As invalidate_sessions here causes performance issues,
%% we will conform to the widespread implementation
%% practice and go aginst the spec
%%invalidate_session(Role, Host, Port, Session)
ok
end,
ssl_connection:handle_normal_shutdown(?ALERT_REC(?FATAL, ?CLOSE_NOTIFY), StateName, State),
{stop, {shutdown, transport_closed}};
true ->
%% Fixes non-delivery of final DTLS record in {active, once}.
%% Basically allows the application the opportunity to set {active, once} again
%% and then receive the final message.
next_event(StateName, no_record, State)
end;
handle_info(new_cookie_secret, StateName,
#state{protocol_specific = #{current_cookie_secret := Secret} = CookieInfo} = State) ->
erlang:send_after(dtls_v1:cookie_timeout(), self(), new_cookie_secret),
{next_state, StateName, State#state{protocol_specific =
CookieInfo#{current_cookie_secret => dtls_v1:cookie_secret(),
previous_cookie_secret => Secret}}};
handle_info(Msg, StateName, State) ->
ssl_connection:handle_info(Msg, StateName, State).
handle_state_timeout(flight_retransmission_timeout, StateName,
#state{flight_state = {retransmit, NextTimeout}} = State0) ->
{State1, Actions} = send_handshake_flight(State0#state{flight_state = {retransmit, NextTimeout}},
retransmit_epoch(StateName, State0)),
{Record, State} = next_record(State1),
next_event(StateName, Record, State, Actions).
handle_alerts([], Result) ->
Result;
handle_alerts(_, {stop,_} = Stop) ->
Stop;
handle_alerts([Alert | Alerts], {next_state, StateName, State}) ->
handle_alerts(Alerts, ssl_connection:handle_alert(Alert, StateName, State));
handle_alerts([Alert | Alerts], {next_state, StateName, State, _Actions}) ->
handle_alerts(Alerts, ssl_connection:handle_alert(Alert, StateName, State)).
handle_own_alert(Alert, Version, StateName, #state{transport_cb = gen_udp,
role = Role,
ssl_options = Options} = State0) ->
case ignore_alert(Alert, State0) of
{true, State} ->
log_ignore_alert(Options#ssl_options.log_alert, StateName, Alert, Role),
{next_state, StateName, State};
{false, State} ->
ssl_connection:handle_own_alert(Alert, Version, StateName, State)
end;
handle_own_alert(Alert, Version, StateName, State) ->
ssl_connection:handle_own_alert(Alert, Version, StateName, State).
encode_handshake_flight(Flight, Version, MaxFragmentSize, Epoch, ConnectionStates) ->
Fragments = lists:map(fun(Handshake) ->
dtls_handshake:fragment_handshake(Handshake, MaxFragmentSize)
end, Flight),
dtls_record:encode_handshake(Fragments, Version, Epoch, ConnectionStates).
encode_change_cipher(#change_cipher_spec{}, Version, Epoch, ConnectionStates) ->
dtls_record:encode_change_cipher_spec(Version, Epoch, ConnectionStates).
decode_alerts(Bin) ->
ssl_alert:decode(Bin).
unprocessed_events(Events) ->
%% The first handshake event will be processed immediately
%% as it is entered first in the event queue and
%% when it is processed there will be length(Events)-1
%% handshake events left to process before we should
%% process more TLS-records received on the socket.
erlang:length(Events)-1.
update_handshake_history(#hello_verify_request{}, _, Hist) ->
Hist;
update_handshake_history(_, Handshake, Hist) ->
%% DTLS never needs option "v2_hello_compatible" to be true
ssl_handshake:update_handshake_history(Hist, iolist_to_binary(Handshake), false).
prepare_flight(#state{flight_buffer = Flight,
connection_states = ConnectionStates0,
protocol_buffers =
#protocol_buffers{} = Buffers} = State) ->
ConnectionStates = dtls_record:save_current_connection_state(ConnectionStates0, write),
State#state{flight_buffer = next_flight(Flight),
connection_states = ConnectionStates,
protocol_buffers = Buffers#protocol_buffers{
dtls_handshake_next_fragments = [],
dtls_handshake_later_fragments = []}}.
new_flight() ->
#{next_sequence => 0,
handshakes => [],
change_cipher_spec => undefined,
handshakes_after_change_cipher_spec => []}.
next_flight(Flight) ->
Flight#{handshakes => [],
change_cipher_spec => undefined,
handshakes_after_change_cipher_spec => []}.
handle_flight_timer(#state{transport_cb = gen_udp,
flight_state = {retransmit, Timeout}} = State) ->
start_retransmision_timer(Timeout, State);
handle_flight_timer(#state{transport_cb = gen_udp,
flight_state = connection} = State) ->
{State, []};
handle_flight_timer(State) ->
%% No retransmision needed i.e DTLS over SCTP
{State#state{flight_state = reliable}, []}.
start_retransmision_timer(Timeout, State) ->
{State#state{flight_state = {retransmit, new_timeout(Timeout)}},
[{state_timeout, Timeout, flight_retransmission_timeout}]}.
new_timeout(N) when N =< 30 ->
N * 2;
new_timeout(_) ->
60.
send_handshake_flight(#state{socket = Socket,
transport_cb = Transport,
flight_buffer = #{handshakes := Flight,
change_cipher_spec := undefined},
negotiated_version = Version,
connection_states = ConnectionStates0} = State0, Epoch) ->
%% TODO remove hardcoded Max size
{Encoded, ConnectionStates} =
encode_handshake_flight(lists:reverse(Flight), Version, 1400, Epoch, ConnectionStates0),
send(Transport, Socket, Encoded),
{State0#state{connection_states = ConnectionStates}, []};
send_handshake_flight(#state{socket = Socket,
transport_cb = Transport,
flight_buffer = #{handshakes := [_|_] = Flight0,
change_cipher_spec := ChangeCipher,
handshakes_after_change_cipher_spec := []},
negotiated_version = Version,
connection_states = ConnectionStates0} = State0, Epoch) ->
{HsBefore, ConnectionStates1} =
encode_handshake_flight(lists:reverse(Flight0), Version, 1400, Epoch, ConnectionStates0),
{EncChangeCipher, ConnectionStates} = encode_change_cipher(ChangeCipher, Version, Epoch, ConnectionStates1),
send(Transport, Socket, [HsBefore, EncChangeCipher]),
{State0#state{connection_states = ConnectionStates}, []};
send_handshake_flight(#state{socket = Socket,
transport_cb = Transport,
flight_buffer = #{handshakes := [_|_] = Flight0,
change_cipher_spec := ChangeCipher,
handshakes_after_change_cipher_spec := Flight1},
negotiated_version = Version,
connection_states = ConnectionStates0} = State0, Epoch) ->
{HsBefore, ConnectionStates1} =
encode_handshake_flight(lists:reverse(Flight0), Version, 1400, Epoch-1, ConnectionStates0),
{EncChangeCipher, ConnectionStates2} =
encode_change_cipher(ChangeCipher, Version, Epoch-1, ConnectionStates1),
{HsAfter, ConnectionStates} =
encode_handshake_flight(lists:reverse(Flight1), Version, 1400, Epoch, ConnectionStates2),
send(Transport, Socket, [HsBefore, EncChangeCipher, HsAfter]),
{State0#state{connection_states = ConnectionStates}, []};
send_handshake_flight(#state{socket = Socket,
transport_cb = Transport,
flight_buffer = #{handshakes := [],
change_cipher_spec := ChangeCipher,
handshakes_after_change_cipher_spec := Flight1},
negotiated_version = Version,
connection_states = ConnectionStates0} = State0, Epoch) ->
{EncChangeCipher, ConnectionStates1} =
encode_change_cipher(ChangeCipher, Version, Epoch-1, ConnectionStates0),
{HsAfter, ConnectionStates} =
encode_handshake_flight(lists:reverse(Flight1), Version, 1400, Epoch, ConnectionStates1),
send(Transport, Socket, [EncChangeCipher, HsAfter]),
{State0#state{connection_states = ConnectionStates}, []}.
retransmit_epoch(_StateName, #state{connection_states = ConnectionStates}) ->
#{epoch := Epoch} =
ssl_record:current_connection_state(ConnectionStates, write),
Epoch.
ignore_alert(#alert{level = ?FATAL}, #state{protocol_specific = #{ignored_alerts := N,
max_ignored_alerts := N}} = State) ->
{false, State};
ignore_alert(#alert{level = ?FATAL} = Alert,
#state{protocol_specific = #{ignored_alerts := N} = PS} = State) ->
case is_ignore_alert(Alert) of
true ->
{true, State#state{protocol_specific = PS#{ignored_alerts => N+1}}};
false ->
{false, State}
end;
ignore_alert(_, State) ->
{false, State}.
%% RFC 6347 4.1.2.7. Handling Invalid Records
%% recommends to silently ignore invalid DTLS records when
%% upd is the transport. Note we do not support compression so no need
%% include ?DECOMPRESSION_FAILURE
is_ignore_alert(#alert{description = ?BAD_RECORD_MAC}) ->
true;
is_ignore_alert(#alert{description = ?RECORD_OVERFLOW}) ->
true;
is_ignore_alert(#alert{description = ?DECODE_ERROR}) ->
true;
is_ignore_alert(#alert{description = ?DECRYPT_ERROR}) ->
true;
is_ignore_alert(#alert{description = ?ILLEGAL_PARAMETER}) ->
true;
is_ignore_alert(_) ->
false.
log_ignore_alert(true, StateName, Alert, Role) ->
Txt = ssl_alert:alert_txt(Alert),
error_logger:format("DTLS over UDP ~p: In state ~p ignored to send ALERT ~s as DoS-attack mitigation \n",
[Role, StateName, Txt]);
log_ignore_alert(false, _, _,_) ->
ok.
