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ssl: Reject unsupported previous version with protocol alert
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Change implementation use gen_statem postpone for hello message when users
want to pause handshake instead of legacy "reimplementation" of postpone

Closes erlang#5950
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@IngelaAndin
IngelaAndin committed Jun 5, 2022
1 parent 0863bd3 commit 82a0d24
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Showing 7 changed files with 182 additions and 100 deletions.
25 changes: 10 additions & 15 deletions lib/ssl/src/dtls_connection.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -325,13 +325,12 @@ hello(internal, #hello_verify_request{cookie = Cookie},
dtls_gen_connection:next_event(?FUNCTION_NAME, no_record, State, Actions);
hello(internal, #client_hello{extensions = Extensions} = Hello,
#state{ssl_options = #{handshake := hello},
handshake_env = HsEnv,
start_or_recv_from = From} = State0) ->
handshake_env = #handshake_env{handshake_continue = Continue},
start_or_recv_from = From} = State0) when Continue =/= continue ->
try tls_dtls_connection:handle_sni_extension(State0, Hello) of
#state{} = State ->
{next_state, user_hello, State#state{start_or_recv_from = undefined,
handshake_env = HsEnv#handshake_env{hello = Hello}},
[{reply, From, {ok, Extensions}}]}
{next_state, user_hello, State#state{start_or_recv_from = undefined},
[{postpone, true}, {reply, From, {ok, Extensions}}]}
catch throw:#alert{} = Alert ->
alert_or_reset_connection(Alert, ?FUNCTION_NAME, State0)
end;
Expand All @@ -354,16 +353,12 @@ hello(internal, #client_hello{cookie = Cookie} = Hello, #state{static_env = #sta
hello(internal, Hello#client_hello{cookie = <<>>}, State)
end
end;
hello(internal, #server_hello{extensions = Extensions} = Hello,
#state{ssl_options = #{
handshake := hello},
handshake_env = HsEnv,
start_or_recv_from = From} = State) ->
{next_state, user_hello, State#state{start_or_recv_from = undefined,
handshake_env = HsEnv#handshake_env{
hello = Hello}},
[{reply, From, {ok, Extensions}}]};

hello(internal, #server_hello{extensions = Extensions},
#state{ssl_options = #{handshake := hello},
handshake_env = #handshake_env{handshake_continue = Continue},
start_or_recv_from = From} = State) when Continue =/= continue ->
{next_state, user_hello, State#state{start_or_recv_from = undefined},
[{postpone, true},{reply, From, {ok, Extensions}}]};
hello(internal, #server_hello{} = Hello,
#state{
static_env = #static_env{role = client},
Expand Down
4 changes: 2 additions & 2 deletions lib/ssl/src/ssl_connection.hrl
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Original file line number Diff line number Diff line change
Expand Up @@ -55,7 +55,7 @@


-record(handshake_env, {
client_hello_version :: ssl_record:ssl_version() | 'undefined',
client_hello_version :: ssl_record:ssl_version() | 'undefined', %% Legacy client hello
unprocessed_handshake_events = 0 :: integer(),
tls_handshake_history :: ssl_handshake:ssl_handshake_history() | secret_printout()
| 'undefined',
Expand All @@ -67,7 +67,7 @@
early_data_accepted = false :: boolean(), %% TLS 1.3
allow_renegotiate = true ::boolean(),
%% Ext handling
hello, %%:: #client_hello{} | #server_hello{}
handshake_continue, %% undefined | client_hello_versions (when entering user_hello in TLS-1.3) | continue (after user_hello)
sni_hostname = undefined,
max_frag_enum :: undefined | {max_frag_enum, integer()},
expecting_next_protocol_negotiation = false ::boolean(),
Expand Down
24 changes: 11 additions & 13 deletions lib/ssl/src/tls_connection.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -111,7 +111,8 @@
%% Setup
-export([init/1]).

-export([renegotiate/2]).
-export([renegotiate/2,
choose_tls_fsm/2]).

%% gen_statem state functions
-export([initial_hello/3,
Expand Down Expand Up @@ -207,23 +208,20 @@ config_error(Type, Event, State) ->
#state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
hello(internal, #client_hello{extensions = Extensions} = Hello,
hello(internal, #client_hello{extensions = Extensions},
#state{ssl_options = #{handshake := hello},
static_env = #static_env{role = server},
handshake_env = HsEnv,
start_or_recv_from = From} = State) ->
{next_state, user_hello, State#state{start_or_recv_from = undefined,
handshake_env = HsEnv#handshake_env{hello = Hello}},
[{reply, From, {ok, Extensions}}]};
hello(internal, #server_hello{extensions = Extensions} = Hello,
handshake_env = #handshake_env{handshake_continue = Continue},
start_or_recv_from = From} = State) when Continue =/= continue ->
{next_state, user_hello, State#state{start_or_recv_from = undefined},
[{postpone, true}, {reply, From, {ok, Extensions}}]};
hello(internal, #server_hello{extensions = Extensions},
#state{ssl_options = #{handshake := hello},
handshake_env = #handshake_env{handshake_continue = Continue},
static_env = #static_env{role = client},
handshake_env = HsEnv,
start_or_recv_from = From} = State) ->
start_or_recv_from = From} = State) when Continue =/= continue ->
{next_state, user_hello,
State#state{start_or_recv_from = undefined,
handshake_env = HsEnv#handshake_env{
hello = Hello}}, [{reply, From, {ok, Extensions}}]};
State#state{start_or_recv_from = undefined}, [{postpone, true}, {reply, From, {ok, Extensions}}]};
hello(internal, #client_hello{client_version = ClientVersion} = Hello,
#state{static_env = #static_env{role = server}, connection_env = CEnv} = State0) ->
try
Expand Down
149 changes: 101 additions & 48 deletions lib/ssl/src/tls_connection_1_3.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -237,61 +237,94 @@ user_hello({call, From}, cancel, State) ->
ssl_gen_statem:handle_own_alert(?ALERT_REC(?FATAL, ?USER_CANCELED, user_canceled),
?FUNCTION_NAME, State);
user_hello({call, From}, {handshake_continue, NewOptions, Timeout},
#state{static_env = #static_env{role = Role},
handshake_env = #handshake_env{hello = Hello},
#state{static_env = #static_env{role = client = Role},
handshake_env = HSEnv,
ssl_options = Options0} = State0) ->
Options = ssl:handle_options(NewOptions, Role, Options0#{handshake => full}),
Options= ssl:handle_options(NewOptions, Role, Options0),
State = ssl_gen_statem:ssl_config(Options, Role, State0),
Next = case Role of
client ->
wait_sh;
server ->
start
end,
{next_state, Next, State#state{start_or_recv_from = From},
[{next_event, internal, Hello}, {{timeout, handshake}, Timeout, close}]};
{next_state, wait_sh, State#state{start_or_recv_from = From,
handshake_env = HSEnv#handshake_env{handshake_continue = continue}},
[{{timeout, handshake}, Timeout, close}]};
user_hello({call, From}, {handshake_continue, NewOptions, Timeout},
#state{static_env = #static_env{role = server = Role},
handshake_env = #handshake_env{handshake_continue = ClientVersions} = HSEnv,
ssl_options = Options0} = State0) ->
Options= #{versions := Versions} = ssl:handle_options(NewOptions, Role, Options0),
State = ssl_gen_statem:ssl_config(Options, Role, State0),
case ssl_handshake:select_supported_version(ClientVersions, Versions) of
{3,4} ->
{next_state, start, State#state{start_or_recv_from = From,
handshake_env = HSEnv#handshake_env{handshake_continue = continue}},
[{{timeout, handshake}, Timeout, close}]};
undefined ->
ssl_gen_statem:handle_own_alert(?ALERT_REC(?FATAL, ?PROTOCOL_VERSION), ?FUNCTION_NAME, State);
_Else ->
{next_state, hello, State#state{start_or_recv_from = From,
handshake_env = HSEnv#handshake_env{handshake_continue = continue}},
[{change_callback_module, tls_connection},
{{timeout, handshake}, Timeout, close}]}
end;
user_hello(info, {'DOWN', _, _, _, _} = Event, State) ->
ssl_gen_statem:handle_info(Event, ?FUNCTION_NAME, State);
user_hello(_, _, _) ->
{keep_state_and_data, [postpone]}.

start(internal, #change_cipher_spec{}, State) ->
tls_gen_connection:next_event(?FUNCTION_NAME, no_record, State);
start(internal, #client_hello{extensions = Extensions} = Hello,
#state{ssl_options = #{handshake := hello},
start(internal, #client_hello{extensions = #{client_hello_versions :=
#client_hello_versions{versions = ClientVersions}
}} = Hello,
#state{ssl_options = #{handshake := full}} = State) ->
case tls_record:is_acceptable_version({3,4}, ClientVersions) of
true ->
do_server_start(Hello, State);
false ->
ssl_gen_statem:handle_own_alert(?ALERT_REC(?FATAL, ?PROTOCOL_VERSION), ?FUNCTION_NAME, State)
end;
start(internal, #client_hello{extensions = #{client_hello_versions :=
#client_hello_versions{versions = ClientVersions}
}= Extensions},
#state{ssl_options = #{handshake := hello}, %% User requested pause to be able to react to hello extensions.
start_or_recv_from = From,
handshake_env = HsEnv} = State) ->
handshake_env = #handshake_env{handshake_continue = Continue} = HSEnv} = State) when Continue =/= continue ->
{next_state, user_hello,
State#state{start_or_recv_from = undefined,
handshake_env = HsEnv#handshake_env{
hello = Hello}}, [{reply, From, {ok, Extensions}}]};
start(internal, #client_hello{} = Hello, State0) ->
case tls_handshake_1_3:do_start(Hello, State0) of
#alert{} = Alert ->
ssl_gen_statem:handle_own_alert(Alert, start, State0);
{State, start} ->
{next_state, start, State, []};
{State, negotiated} ->
{next_state, negotiated, State, [{next_event, internal, {start_handshake, undefined}}]};
{State, negotiated, PSK} -> %% Session Resumption with PSK
{next_state, negotiated, State, [{next_event, internal, {start_handshake, PSK}}]}
State#state{start_or_recv_from = undefined, handshake_env = HSEnv#handshake_env{handshake_continue = ClientVersions}},
[{postpone, true}, {reply, From, {ok, Extensions}}]};
start(internal, #client_hello{} = Hello,
#state{handshake_env = #handshake_env{handshake_continue = continue}} = State) ->
do_server_start(Hello, State);
start(internal, #client_hello{}, State0) -> %% Missing mandantory TLS-1.3 extensions, so it is a previous version hello.
ssl_gen_statem:handle_own_alert(?ALERT_REC(?FATAL, ?PROTOCOL_VERSION), ?FUNCTION_NAME, State0);
start(internal, #server_hello{extensions = #{server_hello_selected_version :=
#server_hello_selected_version{selected_version = Version}}} = ServerHello,
#state{ssl_options = #{handshake := full,
versions := SupportedVersions}} = State) ->
case tls_record:is_acceptable_version(Version, SupportedVersions) of
true ->
do_client_start(ServerHello, State);
false ->
ssl_gen_statem:handle_own_alert(?ALERT_REC(?FATAL, ?PROTOCOL_VERSION), ?FUNCTION_NAME, State)
end;
start(internal, #server_hello{extensions = Extensions} = ServerHello,
#state{ssl_options = #{handshake := hello},
handshake_env = HsEnv,
start_or_recv_from = From}
= State) ->
{next_state, user_hello,
State#state{start_or_recv_from = undefined,
handshake_env = HsEnv#handshake_env{
hello = ServerHello}}, [{reply, From, {ok, Extensions}}]};
start(internal, #server_hello{} = ServerHello, State0) ->
case tls_handshake_1_3:do_start(ServerHello, State0) of
#alert{} = Alert ->
ssl_gen_statem:handle_own_alert(Alert, start, State0);
{State, NextState} ->
{next_state, NextState, State, []}
start(internal, #server_hello{extensions = #{server_hello_selected_version :=
#server_hello_selected_version{selected_version = Version}}
= Extensions},
#state{ssl_options = #{handshake := hello, %% User requested pause to be able to react to hello extensions.
versions := SupportedVersions},
start_or_recv_from = From,
handshake_env = #handshake_env{handshake_continue = Continue}}
= State) when Continue =/= continue ->
case tls_record:is_acceptable_version(Version, SupportedVersions) of
true ->
{next_state, user_hello,
State#state{start_or_recv_from = undefined}, [{postpone, true}, {reply, From, {ok, Extensions}}]};
false ->
ssl_gen_statem:handle_own_alert(?ALERT_REC(?FATAL, ?PROTOCOL_VERSION), ?FUNCTION_NAME, State)
end;
start(internal, #server_hello{} = ServerHello,
#state{handshake_env = #handshake_env{handshake_continue = continue}} = State) ->
do_client_start(ServerHello, State);
start(internal, #server_hello{}, State0) -> %% Missing mandantory TLS-1.3 extensions, so it is a previous version hello.
ssl_gen_statem:handle_own_alert(?ALERT_REC(?FATAL, ?PROTOCOL_VERSION), ?FUNCTION_NAME, State0);
start(info, Msg, State) ->
tls_gen_connection:handle_info(Msg, ?FUNCTION_NAME, State);
start(Type, Msg, State) ->
Expand Down Expand Up @@ -359,13 +392,12 @@ wait_finished(Type, Msg, State) ->

wait_sh(internal, #change_cipher_spec{}, State) ->
tls_gen_connection:next_event(?FUNCTION_NAME, no_record, State);
wait_sh(internal, #server_hello{extensions = Extensions} = Hello, #state{ssl_options = #{handshake := hello},
start_or_recv_from = From,
handshake_env = HsEnv} = State) ->
wait_sh(internal, #server_hello{extensions = Extensions},
#state{ssl_options = #{handshake := hello},
handshake_env = #handshake_env{handshake_continue = Continue},
start_or_recv_from = From} = State) when Continue =/= continue ->
{next_state, user_hello,
State#state{start_or_recv_from = undefined,
handshake_env = HsEnv#handshake_env{
hello = Hello}}, [{reply, From, {ok, Extensions}}]};
State#state{start_or_recv_from = undefined}, [{postpone, true},{reply, From, {ok, Extensions}}]};
wait_sh(internal, #server_hello{} = Hello, State0) ->
case tls_handshake_1_3:do_wait_sh(Hello, State0) of
#alert{} = Alert ->
Expand Down Expand Up @@ -464,6 +496,27 @@ downgrade(Type, Event, State) ->
%--------------------------------------------------------------------
%% internal functions
%%--------------------------------------------------------------------

do_server_start(ClientHello, State0) ->
case tls_handshake_1_3:do_start(ClientHello, State0) of
#alert{} = Alert ->
ssl_gen_statem:handle_own_alert(Alert, start, State0);
{State, start} ->
{next_state, start, State, []};
{State, negotiated} ->
{next_state, negotiated, State, [{next_event, internal, {start_handshake, undefined}}]};
{State, negotiated, PSK} -> %% Session Resumption with PSK
{next_state, negotiated, State, [{next_event, internal, {start_handshake, PSK}}]}
end.

do_client_start(ServerHello, State0) ->
case tls_handshake_1_3:do_start(ServerHello, State0) of
#alert{} = Alert ->
ssl_gen_statem:handle_own_alert(Alert, start, State0);
{State, NextState} ->
{next_state, NextState, State, []}
end.

initial_state(Role, Sender, Host, Port, Socket, {SSLOptions, SocketOptions, Trackers}, User,
{CbModule, DataTag, CloseTag, ErrorTag, PassiveTag}) ->
#{erl_dist := IsErlDist,
Expand Down
10 changes: 6 additions & 4 deletions lib/ssl/src/tls_dtls_connection.erl
View file
Original file line number Diff line number Diff line change
Expand Up @@ -168,12 +168,14 @@ user_hello({call, From}, cancel, _State) ->
throw(?ALERT_REC(?FATAL, ?USER_CANCELED, user_canceled));
user_hello({call, From}, {handshake_continue, NewOptions, Timeout},
#state{static_env = #static_env{role = Role},
handshake_env = #handshake_env{hello = Hello},
handshake_env = HSEnv,
ssl_options = Options0} = State0) ->
Options = ssl:handle_options(NewOptions, Role, Options0#{handshake => full}),
Options = ssl:handle_options(NewOptions, Role, Options0),
State = ssl_gen_statem:ssl_config(Options, Role, State0),
{next_state, hello, State#state{start_or_recv_from = From},
[{next_event, internal, Hello}, {{timeout, handshake}, Timeout, close}]};
{next_state, hello, State#state{start_or_recv_from = From,
handshake_env = HSEnv#handshake_env{handshake_continue = continue}
},
[{{timeout, handshake}, Timeout, close}]};
user_hello(info, {'DOWN', _, _, _, _} = Event, State) ->
ssl_gen_statem:handle_info(Event, ?FUNCTION_NAME, State);
user_hello(_, _, _) ->
Expand Down
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