%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2007-2018. 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%
%%

%%----------------------------------------------------------------------
%% Purpose: Help funtions for handling the TLS (specific parts of)
%%% SSL/TLS/DTLS handshake protocol
%%----------------------------------------------------------------------

-module(tls_handshake).

-include("tls_handshake.hrl").
-include("tls_record.hrl").
-include("ssl_alert.hrl").
-include("ssl_internal.hrl").
-include("ssl_cipher.hrl").
-include("ssl_api.hrl").
-include_lib("public_key/include/public_key.hrl").

%% Handshake handling
-export([client_hello/8, hello/4]).

%% Handshake encoding
-export([encode_handshake/2]).

%% Handshake decodeing
-export([get_tls_handshake/4, decode_handshake/3]).

-type tls_handshake() :: #client_hello{} | ssl_handshake:ssl_handshake().

%%====================================================================
%% Handshake handling
%%====================================================================
%%--------------------------------------------------------------------
-spec client_hello(ssl:host(), inet:port_number(), ssl_record:connection_states(),
		   #ssl_options{}, integer(), atom(), boolean(), der_cert()) ->
			  #client_hello{}.
%%
%% Description: Creates a client hello message.
%%--------------------------------------------------------------------
client_hello(Host, Port, ConnectionStates,
	     #ssl_options{versions = Versions,
			  ciphers = UserSuites,
			  fallback = Fallback
			 } = SslOpts,
	     Cache, CacheCb, Renegotiation, OwnCert) ->
    Version = tls_record:highest_protocol_version(Versions),
    #{security_parameters := SecParams} = 
        ssl_record:pending_connection_state(ConnectionStates, read),
    AvailableCipherSuites = ssl_handshake:available_suites(UserSuites, Version),     
    Extensions = ssl_handshake:client_hello_extensions(Version, 
						       AvailableCipherSuites,
						       SslOpts, ConnectionStates, 
                                                       Renegotiation),
    CipherSuites = ssl_handshake:cipher_suites(AvailableCipherSuites, Renegotiation, Fallback),
    Id = ssl_session:client_id({Host, Port, SslOpts}, Cache, CacheCb, OwnCert),    
    #client_hello{session_id = Id,
		  client_version = Version,
		  cipher_suites = CipherSuites,
		  compression_methods = ssl_record:compressions(),
		  random = SecParams#security_parameters.client_random,
		  extensions = Extensions
		 }.

%%--------------------------------------------------------------------
-spec hello(#server_hello{} | #client_hello{}, #ssl_options{},
	    ssl_record:connection_states() | {inet:port_number(), #session{}, db_handle(),
				    atom(), ssl_record:connection_states(), 
				    binary() | undefined, ssl:kex_algo()},
	    boolean()) ->
		   {tls_record:tls_version(), ssl:session_id(), 
		    ssl_record:connection_states(), alpn | npn, binary() | undefined}|
		   {tls_record:tls_version(), {resumed | new, #session{}}, 
		    ssl_record:connection_states(), binary() | undefined, 
		    #hello_extensions{}, {ssl:hash(), ssl:sign_algo()} | 
                    undefined} | #alert{}.
%%
%% Description: Handles a received hello message
%%--------------------------------------------------------------------
hello(#server_hello{server_version = Version, random = Random,
		    cipher_suite = CipherSuite,
		    compression_method = Compression,
		    session_id = SessionId, extensions = HelloExt},
      #ssl_options{versions = SupportedVersions} = SslOpt,
      ConnectionStates0, Renegotiation) ->
    case tls_record:is_acceptable_version(Version, SupportedVersions) of
	true ->
	    handle_server_hello_extensions(Version, SessionId, Random, CipherSuite,
					   Compression, HelloExt, SslOpt, 
                                           ConnectionStates0, Renegotiation);
	false ->
	    ?ALERT_REC(?FATAL, ?PROTOCOL_VERSION)
    end;
			       
hello(#client_hello{client_version = ClientVersion,
		    cipher_suites = CipherSuites} = Hello,
      #ssl_options{versions = Versions} = SslOpts,
      Info, Renegotiation) ->
    try
	Version = ssl_handshake:select_version(tls_record, ClientVersion, Versions),
	case ssl_cipher:is_fallback(CipherSuites) of
	true -> 
		Highest = tls_record:highest_protocol_version(Versions),
		case tls_record:is_higher(Highest, Version) of
		    true ->
			?ALERT_REC(?FATAL, ?INAPPROPRIATE_FALLBACK);
		    false ->				     
			handle_client_hello(Version, Hello, SslOpts, Info, Renegotiation)
		end;
	    false ->
		handle_client_hello(Version, Hello, SslOpts, Info, Renegotiation)
	end
    catch
        error:{case_clause,{asn1, Asn1Reason}} ->
	    %% ASN-1 decode of certificate somehow failed
            ?ALERT_REC(?FATAL, ?INTERNAL_ERROR, {failed_to_decode_own_certificate, Asn1Reason});
	_:_ ->
	    ?ALERT_REC(?FATAL, ?HANDSHAKE_FAILURE, malformed_handshake_data)
    end.  


%%--------------------------------------------------------------------
%%% Handshake encodeing
%%--------------------------------------------------------------------

%%--------------------------------------------------------------------
-spec encode_handshake(tls_handshake(), tls_record:tls_version()) -> iolist().
%%     
%% Description: Encode a handshake packet
%%--------------------------------------------------------------------
encode_handshake(Package, Version) ->
    {MsgType, Bin} = enc_handshake(Package, Version),
    Len = byte_size(Bin),
    [MsgType, ?uint24(Len), Bin].


%%--------------------------------------------------------------------
%%% Handshake decodeing
%%--------------------------------------------------------------------

%%--------------------------------------------------------------------
-spec get_tls_handshake(tls_record:tls_version(), binary(), binary() | iolist(), 
                        #ssl_options{}) ->
     {[tls_handshake()], binary()}.
%%
%% Description: Given buffered and new data from ssl_record, collects
%% and returns it as a list of handshake messages, also returns leftover
%% data.
%%--------------------------------------------------------------------
get_tls_handshake(Version, Data, <<>>, Options) ->
    get_tls_handshake_aux(Version, Data, Options, []);
get_tls_handshake(Version, Data, Buffer, Options) ->
    get_tls_handshake_aux(Version, list_to_binary([Buffer, Data]), Options, []).

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
handle_client_hello(Version, 
                    #client_hello{session_id = SugesstedId,
                                  cipher_suites = CipherSuites,
                                  compression_methods = Compressions,
                                  random = Random,
                                  extensions = 
                                      #hello_extensions{elliptic_curves = Curves,
                                                        signature_algs = ClientHashSigns} 
                                  = HelloExt},
		    #ssl_options{versions = Versions,
				 signature_algs = SupportedHashSigns,
				 eccs = SupportedECCs,
				 honor_ecc_order = ECCOrder} = SslOpts,
		    {Port, Session0, Cache, CacheCb, ConnectionStates0, Cert, _}, 
                    Renegotiation) ->
    case tls_record:is_acceptable_version(Version, Versions) of
	true ->
	    AvailableHashSigns = ssl_handshake:available_signature_algs(
				   ClientHashSigns, SupportedHashSigns, Cert, Version),
	    ECCCurve = ssl_handshake:select_curve(Curves, SupportedECCs, ECCOrder),
	    {Type, #session{cipher_suite = CipherSuite} = Session1}
		= ssl_handshake:select_session(SugesstedId, CipherSuites, 
                                               AvailableHashSigns, Compressions,
					       Port, Session0#session{ecc = ECCCurve}, 
                                               Version, SslOpts, Cache, CacheCb, Cert),
	    case CipherSuite of 
		no_suite ->
                    ?ALERT_REC(?FATAL, ?INSUFFICIENT_SECURITY, no_suitable_ciphers);
		_ ->
		    #{key_exchange := KeyExAlg} = ssl_cipher_format:suite_definition(CipherSuite),
		    case ssl_handshake:select_hashsign(ClientHashSigns, Cert, KeyExAlg, 
                                                       SupportedHashSigns, Version) of
			#alert{} = Alert ->
			    Alert;
			HashSign ->
			    handle_client_hello_extensions(Version, Type, Random, 
                                                           CipherSuites, HelloExt,
							   SslOpts, Session1, 
                                                           ConnectionStates0,
							   Renegotiation, HashSign)
		    end
	    end;
	false ->
	    ?ALERT_REC(?FATAL, ?PROTOCOL_VERSION)
    end.

handle_client_hello_extensions(Version, Type, Random, CipherSuites,
                               HelloExt, SslOpts, Session0, ConnectionStates0, 
                               Renegotiation, HashSign) ->
    try ssl_handshake:handle_client_hello_extensions(tls_record, Random, CipherSuites,
						     HelloExt, Version, SslOpts,
						     Session0, ConnectionStates0, 
                                                     Renegotiation) of
	{Session, ConnectionStates, Protocol, ServerHelloExt} ->
	    {Version, {Type, Session}, ConnectionStates, Protocol, 
             ServerHelloExt, HashSign}
    catch throw:Alert ->
	    Alert
    end.


handle_server_hello_extensions(Version, SessionId, Random, CipherSuite,
			Compression, HelloExt, SslOpt, ConnectionStates0, Renegotiation) ->
    try ssl_handshake:handle_server_hello_extensions(tls_record, Random, CipherSuite,
						      Compression, HelloExt, Version,
						      SslOpt, ConnectionStates0, 
                                                     Renegotiation) of
	{ConnectionStates, ProtoExt, Protocol} ->
	    {Version, SessionId, ConnectionStates, ProtoExt, Protocol}
    catch throw:Alert ->
	    Alert
    end.
%%--------------------------------------------------------------------
enc_handshake(#hello_request{}, _Version) ->
    {?HELLO_REQUEST, <<>>};
enc_handshake(#client_hello{client_version = {Major, Minor},
		     random = Random,
		     session_id = SessionID,
		     cipher_suites = CipherSuites,
		     compression_methods = CompMethods, 
		     extensions = HelloExtensions}, _Version) ->
    SIDLength = byte_size(SessionID),
    BinCompMethods = list_to_binary(CompMethods),
    CmLength = byte_size(BinCompMethods),
    BinCipherSuites = list_to_binary(CipherSuites),
    CsLength = byte_size(BinCipherSuites),
    ExtensionsBin = ssl_handshake:encode_hello_extensions(HelloExtensions),

    {?CLIENT_HELLO, <<?BYTE(Major), ?BYTE(Minor), Random:32/binary,
		      ?BYTE(SIDLength), SessionID/binary,
		      ?UINT16(CsLength), BinCipherSuites/binary,
		      ?BYTE(CmLength), BinCompMethods/binary, ExtensionsBin/binary>>};

enc_handshake(HandshakeMsg, Version) ->
    ssl_handshake:encode_handshake(HandshakeMsg, Version).

%%--------------------------------------------------------------------
get_tls_handshake_aux(Version, <<?BYTE(Type), ?UINT24(Length),
				 Body:Length/binary,Rest/binary>>, 
                      Opts,  Acc) ->
    Raw = <<?BYTE(Type), ?UINT24(Length), Body/binary>>,
    try decode_handshake(Version, Type, Body) of
	Handshake ->
	    get_tls_handshake_aux(Version, Rest, Opts, [{Handshake,Raw} | Acc])
    catch
	_:_ ->
	    throw(?ALERT_REC(?FATAL, ?HANDSHAKE_FAILURE, handshake_decode_error))
    end;
get_tls_handshake_aux(_Version, Data, _, Acc) ->
    {lists:reverse(Acc), Data}.

decode_handshake(_, ?HELLO_REQUEST, <<>>) ->
    #hello_request{};
decode_handshake(_Version, ?CLIENT_HELLO, 
                 <<?BYTE(Major), ?BYTE(Minor), Random:32/binary,
                   ?BYTE(SID_length), Session_ID:SID_length/binary,
                   ?UINT16(Cs_length), CipherSuites:Cs_length/binary,
                   ?BYTE(Cm_length), Comp_methods:Cm_length/binary,
                   Extensions/binary>>) ->
    DecodedExtensions = ssl_handshake:decode_hello_extensions({client, Extensions}),
    #client_hello{
       client_version = {Major,Minor},
       random = Random,
       session_id = Session_ID,
       cipher_suites = ssl_handshake:decode_suites('2_bytes', CipherSuites),
       compression_methods = Comp_methods,
       extensions = DecodedExtensions
      };
decode_handshake(Version, Tag, Msg) ->
    ssl_handshake:decode_handshake(Version, Tag, Msg).


