ssl: Align code of TLS/DTLS record handling

3 files changed, 283 insertions, 249 deletions

diff --git a/lib/ssl/src/dtls_record.erl b/lib/ssl/src/dtls_record.erl
index a8520717e5..2dcc6efc91 100644
--- a/lib/ssl/src/dtls_record.erl
+++ b/lib/ssl/src/dtls_record.erl
@@ -32,13 +32,15 @@
 %% Handling of incoming data
 -export([get_dtls_records/2,  init_connection_states/2, empty_connection_state/1]).
 
-%% Decoding
--export([decode_cipher_text/2]).
+-export([save_current_connection_state/2, next_epoch/2, get_connection_state_by_epoch/3, replay_detect/2,
+         init_connection_state_seq/2, current_connection_state_epoch/2]).
 
 %% Encoding
 -export([encode_handshake/4, encode_alert_record/3,
-	 encode_change_cipher_spec/3, encode_data/3]).
--export([encode_plain_text/5]).
+	 encode_change_cipher_spec/3, encode_data/3, encode_plain_text/5]).
+
+%% Decoding
+-export([decode_cipher_text/2]).
 
 %% Protocol version handling
 -export([protocol_version/1, lowest_protocol_version/1, lowest_protocol_version/2,
@@ -46,9 +48,6 @@
 	 is_higher/2, supported_protocol_versions/0,
 	 is_acceptable_version/2, hello_version/2]).
 
--export([save_current_connection_state/2, next_epoch/2, get_connection_state_by_epoch/3, replay_detect/2]).
-
--export([init_connection_state_seq/2, current_connection_state_epoch/2]).
 
 -export_type([dtls_version/0, dtls_atom_version/0]).
 
@@ -60,7 +59,7 @@
 -compile(inline).
 
 %%====================================================================
-%% Internal application API
+%%  Handling of incoming data
 %%====================================================================
 %%--------------------------------------------------------------------
 -spec init_connection_states(client | server, one_n_minus_one | zero_n | disabled) ->
@@ -86,7 +85,6 @@ init_connection_states(Role, BeastMitigation) ->
 empty_connection_state(Empty) ->    
     Empty#{epoch => undefined, replay_window => init_replay_window(?REPLAY_WINDOW_SIZE)}.
 
-
 %%--------------------------------------------------------------------
 -spec save_current_connection_state(ssl_record:connection_states(), read | write) ->
 				      ssl_record:connection_states().
@@ -137,6 +135,34 @@ set_connection_state_by_epoch(ReadState, Epoch, #{saved_read := #{epoch := Epoch
     States#{saved_read := ReadState}.
 
 %%--------------------------------------------------------------------
+-spec init_connection_state_seq(dtls_version(), ssl_record:connection_states()) ->
+				       ssl_record: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, _},
+			  #{current_read := #{epoch := 0, sequence_number := Seq},
+			    current_write := #{epoch := 0} = Write} = ConnnectionStates0) ->
+    ConnnectionStates0#{current_write => Write#{sequence_number => Seq}};
+init_connection_state_seq(_, ConnnectionStates) ->
+    ConnnectionStates.
+
+%%--------------------------------------------------------
+-spec current_connection_state_epoch(ssl_record:connection_states(), read | write) ->
+					    integer().
+%%
+%% Description: Returns the epoch the connection_state record
+%% that is currently defined as the current connection state.
+%%--------------------------------------------------------------------
+current_connection_state_epoch(#{current_read := #{epoch := Epoch}},
+			       read) ->
+    Epoch;
+current_connection_state_epoch(#{current_write := #{epoch := Epoch}},
+			       write) ->
+    Epoch.
+
+%%--------------------------------------------------------------------
 -spec get_dtls_records(binary(), binary()) -> {[binary()], binary()} | #alert{}.
 %%
 %% Description: Given old buffer and new data from UDP/SCTP, packs up a records
@@ -148,55 +174,10 @@ get_dtls_records(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, sequence_number = 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, sequence_number = 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, sequence_number = 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, sequence_number = 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.
+%%====================================================================
+%% Encoding DTLS records
+%%====================================================================
 
 %%--------------------------------------------------------------------
 -spec encode_handshake(iolist(), dtls_version(), integer(), ssl_record:connection_states()) ->
@@ -245,11 +226,19 @@ encode_plain_text(Type, Version, Epoch, Data, ConnectionStates) ->
     {CipherText, Write} = encode_dtls_cipher_text(Type, Version, CipherFragment, Write1),
     {CipherText, set_connection_state_by_epoch(Write, Epoch, ConnectionStates, write)}.
 
+%%====================================================================
+%% Decoding 
+%%====================================================================
 
 decode_cipher_text(#ssl_tls{epoch = Epoch} = CipherText, ConnnectionStates0) ->
     ReadState = get_connection_state_by_epoch(Epoch, ConnnectionStates0, read),
     decode_cipher_text(CipherText, ReadState, ConnnectionStates0).
 
+
+%%====================================================================
+%% Protocol version handling
+%%====================================================================
+
 %%--------------------------------------------------------------------
 -spec protocol_version(dtls_atom_version() | dtls_version()) ->
 			      dtls_version() | dtls_atom_version().
@@ -381,35 +370,6 @@ supported_protocol_versions([_|_] = Vsns) ->
 is_acceptable_version(Version, Versions) ->
     lists:member(Version, Versions).
 
-
-%%--------------------------------------------------------------------
--spec init_connection_state_seq(dtls_version(), ssl_record:connection_states()) ->
-				       ssl_record: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, _},
-			  #{current_read := #{epoch := 0, sequence_number := Seq},
-			    current_write := #{epoch := 0} = Write} = ConnnectionStates0) ->
-    ConnnectionStates0#{current_write => Write#{sequence_number => Seq}};
-init_connection_state_seq(_, ConnnectionStates) ->
-    ConnnectionStates.
-
-%%--------------------------------------------------------
--spec current_connection_state_epoch(ssl_record:connection_states(), read | write) ->
-					    integer().
-%%
-%% Description: Returns the epoch the connection_state record
-%% that is currently defined as the current connection state.
-%%--------------------------------------------------------------------
-current_connection_state_epoch(#{current_read := #{epoch := Epoch}},
-			       read) ->
-    Epoch;
-current_connection_state_epoch(#{current_write := #{epoch := Epoch}},
-			       write) ->
-    Epoch.
-
 -spec hello_version(dtls_version(), [dtls_version()]) -> dtls_version().
 hello_version(Version, Versions) ->
     case dtls_v1:corresponding_tls_version(Version) of
@@ -438,15 +398,93 @@ initial_connection_state(ConnectionEnd, BeastMitigation) ->
       server_verify_data => undefined
      }.
 
-lowest_list_protocol_version(Ver, []) ->
-    Ver;
-lowest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
-    lowest_list_protocol_version(lowest_protocol_version(Ver1, Ver2), Rest).
+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, sequence_number = 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, sequence_number = 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, sequence_number = 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, sequence_number = SequenceNumber,
+					 fragment = Data} | Acc]);
 
-highest_list_protocol_version(Ver, []) ->
-    Ver;
-highest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
-    highest_list_protocol_version(highest_protocol_version(Ver1, Ver2), Rest).
+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.
+%%--------------------------------------------------------------------
+
+init_replay_window(Size) ->
+    #{size => Size,
+      top => Size,
+      bottom => 0,
+      mask => 0 bsl 64
+     }.
+
+replay_detect(#ssl_tls{sequence_number = SequenceNumber}, #{replay_window := Window}) ->
+    is_replay(SequenceNumber, Window).
+
+
+is_replay(SequenceNumber, #{bottom := Bottom}) when SequenceNumber < Bottom ->
+    true;
+is_replay(SequenceNumber, #{size := Size,
+                            top := Top,
+                            bottom := Bottom,
+                            mask :=  Mask})  when (SequenceNumber >= Bottom) andalso (SequenceNumber =< Top) ->
+    Index = (SequenceNumber rem Size),
+    (Index band Mask) == 1;
+
+is_replay(_, _) ->
+    false.
+
+update_replay_window(SequenceNumber,  #{replay_window := #{size := Size,
+                                                           top := Top,
+                                                           bottom := Bottom,
+                                                           mask :=  Mask0} = Window0} = ConnectionStates) ->
+    NoNewBits = SequenceNumber - Top,
+    Index = SequenceNumber rem Size,
+    Mask = (Mask0 bsl NoNewBits) bor Index,
+    Window =  Window0#{top => SequenceNumber,
+                       bottom => Bottom + NoNewBits,
+                       mask => Mask},
+    ConnectionStates#{replay_window := Window}.
+
+%%--------------------------------------------------------------------
 
 encode_dtls_cipher_text(Type, {MajVer, MinVer}, Fragment, 
 		       #{epoch := Epoch, sequence_number := Seq} = WriteState) ->
@@ -490,6 +528,7 @@ encode_plain_text(Type, Version, Fragment, #{compression_state := CompS0,
 	ssl_cipher:cipher(BulkCipherAlgo, CipherS0, MAC, Fragment, TLSVersion),
     {CipherFragment,  WriteState0#{cipher_state => CipherS1}}.
 
+%%--------------------------------------------------------------------
 decode_cipher_text(#ssl_tls{type = Type, version = Version,
 			    epoch = Epoch,
 			    sequence_number = Seq,
@@ -541,6 +580,7 @@ decode_cipher_text(#ssl_tls{type = Type, version = Version,
 	false ->
 	    ?ALERT_REC(?FATAL, ?BAD_RECORD_MAC)
     end.
+%%--------------------------------------------------------------------
 
 calc_mac_hash(Type, Version, #{mac_secret := MacSecret,
 			       security_parameters := #security_parameters{mac_algorithm = MacAlg}},
@@ -549,16 +589,6 @@ calc_mac_hash(Type, Version, #{mac_secret := MacSecret,
     mac_hash(Version, MacAlg, MacSecret, Epoch, SeqNo, Type,
 	     Length, Fragment).
 
-highest_protocol_version() ->
-    highest_protocol_version(supported_protocol_versions()).
-
-lowest_protocol_version() ->
-    lowest_protocol_version(supported_protocol_versions()).
-
-sufficient_dtlsv1_2_crypto_support() ->
-    CryptoSupport = crypto:supports(),
-    proplists:get_bool(sha256, proplists:get_value(hashs, CryptoSupport)).
-
 mac_hash({Major, Minor}, MacAlg, MacSecret, Epoch, SeqNo, Type, Length, Fragment) ->
     Value = [<<?UINT16(Epoch), ?UINT48(SeqNo), ?BYTE(Type),
        ?BYTE(Major), ?BYTE(Minor), ?UINT16(Length)>>,
@@ -568,37 +598,25 @@ mac_hash({Major, Minor}, MacAlg, MacSecret, Epoch, SeqNo, Type, Length, Fragment
 calc_aad(Type, {MajVer, MinVer}, Epoch, SeqNo) ->
     <<?UINT16(Epoch), ?UINT48(SeqNo), ?BYTE(Type), ?BYTE(MajVer), ?BYTE(MinVer)>>.
 
-init_replay_window(Size) ->
-    #{size => Size,
-      top => Size,
-      bottom => 0,
-      mask => 0 bsl 64
-     }.
+%%--------------------------------------------------------------------
 
-replay_detect(#ssl_tls{sequence_number = SequenceNumber}, #{replay_window := Window}) ->
-    is_replay(SequenceNumber, Window).
+lowest_list_protocol_version(Ver, []) ->
+    Ver;
+lowest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
+    lowest_list_protocol_version(lowest_protocol_version(Ver1, Ver2), Rest).
 
+highest_list_protocol_version(Ver, []) ->
+    Ver;
+highest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
+    highest_list_protocol_version(highest_protocol_version(Ver1, Ver2), Rest).
 
-is_replay(SequenceNumber, #{bottom := Bottom}) when SequenceNumber < Bottom ->
-    true;
-is_replay(SequenceNumber, #{size := Size,
-                            top := Top,
-                            bottom := Bottom,
-                            mask :=  Mask})  when (SequenceNumber >= Bottom) andalso (SequenceNumber =< Top) ->
-    Index = (SequenceNumber rem Size),
-    (Index band Mask) == 1;
+highest_protocol_version() ->
+    highest_protocol_version(supported_protocol_versions()).
 
-is_replay(_, _) ->
-    false.
+lowest_protocol_version() ->
+    lowest_protocol_version(supported_protocol_versions()).
+
+sufficient_dtlsv1_2_crypto_support() ->
+    CryptoSupport = crypto:supports(),
+    proplists:get_bool(sha256, proplists:get_value(hashs, CryptoSupport)).
 
-update_replay_window(SequenceNumber,  #{replay_window := #{size := Size,
-                                                           top := Top,
-                                                           bottom := Bottom,
-                                                           mask :=  Mask0} = Window0} = ConnectionStates) ->
-    NoNewBits = SequenceNumber - Top,
-    Index = SequenceNumber rem Size,
-    Mask = (Mask0 bsl NoNewBits) bor Index,
-    Window =  Window0#{top => SequenceNumber,
-                       bottom => Bottom + NoNewBits,
-                       mask => Mask},
-    ConnectionStates#{replay_window := Window}.
diff --git a/lib/ssl/src/ssl_record.erl b/lib/ssl/src/ssl_record.erl
index 003ad4994b..dd6a3e8521 100644
--- a/lib/ssl/src/ssl_record.erl
+++ b/lib/ssl/src/ssl_record.erl
@@ -53,11 +53,11 @@
 -type ssl_atom_version() :: tls_record:tls_atom_version().
 -type connection_states() :: term(). %% Map
 -type connection_state() :: term(). %% Map
+
 %%====================================================================
-%% Internal application API
+%% Connection state handling
 %%====================================================================
 
-
 %%--------------------------------------------------------------------
 -spec current_connection_state(connection_states(), read | write) ->
 				      connection_state().
@@ -267,6 +267,9 @@ set_pending_cipher_state(#{pending_read := Read,
       pending_read => Read#{cipher_state => ServerState},
       pending_write => Write#{cipher_state => ClientState}}.
 
+%%====================================================================
+%% Compression
+%%====================================================================
 
 uncompress(?NULL, Data, CS) ->
     {Data, CS}.
@@ -282,6 +285,11 @@ compress(?NULL, Data, CS) ->
 compressions() ->
     [?byte(?NULL)].
 
+
+%%====================================================================
+%% Payload encryption/decryption
+%%====================================================================
+
 %%--------------------------------------------------------------------
 -spec cipher(ssl_version(), iodata(), connection_state(), MacHash::binary()) ->
 		    {CipherFragment::binary(), connection_state()}.
diff --git a/lib/ssl/src/tls_record.erl b/lib/ssl/src/tls_record.erl
index 4ac6cdc6b5..ab179c1bf0 100644
--- a/lib/ssl/src/tls_record.erl
+++ b/lib/ssl/src/tls_record.erl
@@ -39,15 +39,15 @@
 	 encode_change_cipher_spec/2, encode_data/3]).
 -export([encode_plain_text/4]).
 
+%% Decoding
+-export([decode_cipher_text/3]).
+
 %% Protocol version handling
 -export([protocol_version/1,  lowest_protocol_version/1, lowest_protocol_version/2,
 	 highest_protocol_version/1, highest_protocol_version/2,
 	 is_higher/2, supported_protocol_versions/0,
 	 is_acceptable_version/1, is_acceptable_version/2, hello_version/2]).
 
-%% Decoding
--export([decode_cipher_text/3]).
-
 -export_type([tls_version/0, tls_atom_version/0]).
 
 -type tls_version()       :: ssl_record:ssl_version().
@@ -56,13 +56,12 @@
 -compile(inline).
 
 %%====================================================================
-%% Internal application API
+%% Handling of incoming data
 %%====================================================================
 %%--------------------------------------------------------------------
 -spec init_connection_states(client | server, one_n_minus_one | zero_n | disabled) ->
  				    ssl_record:connection_states().
-%% %
-						%
+%% 
 %% Description: Creates a connection_states record with appropriate
 %% values for the initial SSL connection setup.
 %%--------------------------------------------------------------------
@@ -87,6 +86,10 @@ get_tls_records(Data, <<>>) ->
 get_tls_records(Data, Buffer) ->
     get_tls_records_aux(list_to_binary([Buffer, Data]), []).
 
+%%====================================================================
+%% Encoding
+%%====================================================================
+
 %%--------------------------------------------------------------------
 -spec encode_handshake(iolist(), tls_version(), ssl_record:connection_states()) ->
 			      {iolist(), ssl_record:connection_states()}.
@@ -141,6 +144,74 @@ encode_data(Frag, Version,
     Data = split_bin(Frag, ?MAX_PLAIN_TEXT_LENGTH, Version, BCA, BeastMitigation),
     encode_iolist(?APPLICATION_DATA, Data, Version, ConnectionStates).
 
+%%====================================================================
+%% Decoding
+%%====================================================================
+
+%%--------------------------------------------------------------------
+-spec decode_cipher_text(#ssl_tls{}, ssl_record:connection_states(), boolean()) ->
+				{#ssl_tls{}, ssl_record:connection_states()}| #alert{}.
+%%
+%% Description: Decode cipher text
+%%--------------------------------------------------------------------
+decode_cipher_text(#ssl_tls{type = Type, version = Version,
+			    fragment = CipherFragment} = CipherText,
+		   #{current_read :=
+			 #{compression_state := CompressionS0,
+			   sequence_number := Seq,
+                           cipher_state := CipherS0,
+			   security_parameters :=
+			       #security_parameters{
+				  cipher_type = ?AEAD,
+                                  bulk_cipher_algorithm =
+                                      BulkCipherAlgo,
+				  compression_algorithm = CompAlg}
+			  } = ReadState0} = ConnnectionStates0, _) ->
+    AAD = calc_aad(Type, Version, ReadState0),
+    case ssl_cipher:decipher_aead(BulkCipherAlgo, CipherS0, Seq, AAD, CipherFragment, Version) of
+	{PlainFragment, CipherS1} ->
+	    {Plain, CompressionS1} = ssl_record:uncompress(CompAlg,
+							   PlainFragment, CompressionS0),
+	    ConnnectionStates = ConnnectionStates0#{
+				  current_read => ReadState0#{
+                                                    cipher_state => CipherS1,
+                                                    sequence_number => Seq + 1,
+                                                    compression_state => CompressionS1}},
+	    {CipherText#ssl_tls{fragment = Plain}, ConnnectionStates};
+	#alert{} = Alert ->
+	    Alert
+    end;
+
+decode_cipher_text(#ssl_tls{type = Type, version = Version,
+			    fragment = CipherFragment} = CipherText,
+		   #{current_read :=
+			 #{compression_state := CompressionS0,
+			   sequence_number := Seq,
+			   security_parameters :=
+			       #security_parameters{compression_algorithm = CompAlg}
+			  } = ReadState0} = ConnnectionStates0, PaddingCheck) ->
+    case ssl_record:decipher(Version, CipherFragment, ReadState0, PaddingCheck) of
+	{PlainFragment, Mac, ReadState1} ->
+	    MacHash = ssl_cipher:calc_mac_hash(Type, Version, PlainFragment, ReadState1),
+	    case ssl_record:is_correct_mac(Mac, MacHash) of
+		true ->
+		    {Plain, CompressionS1} = ssl_record:uncompress(CompAlg,
+								   PlainFragment, CompressionS0),
+		    ConnnectionStates = ConnnectionStates0#{
+					  current_read => ReadState1#{
+							    sequence_number => Seq + 1,
+							    compression_state => CompressionS1}},
+		    {CipherText#ssl_tls{fragment = Plain}, ConnnectionStates};
+		false ->
+			?ALERT_REC(?FATAL, ?BAD_RECORD_MAC)
+	    end;
+	    #alert{} = Alert ->
+	    Alert
+    end.
+
+%%====================================================================
+%% Protocol version handling
+%%====================================================================
 
 %%--------------------------------------------------------------------
 -spec protocol_version(tls_atom_version() | tls_version()) -> 
@@ -278,11 +349,6 @@ supported_protocol_versions([_|_] = Vsns) ->
 	    end
     end.
 
-%%--------------------------------------------------------------------
-%%     
-%% Description: ssl version 2 is not acceptable security risks are too big.
-%% 
-%%--------------------------------------------------------------------
 -spec is_acceptable_version(tls_version()) -> boolean().
 is_acceptable_version({N,_}) 
   when N >= ?LOWEST_MAJOR_SUPPORTED_VERSION ->
@@ -302,6 +368,7 @@ hello_version(Version, _) when Version >= {3, 3} ->
     Version;
 hello_version(_, Versions) ->
     lowest_protocol_version(Versions).
+
 %%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------
@@ -376,37 +443,17 @@ get_tls_records_aux(Data, Acc) ->
 	false ->
 	    ?ALERT_REC(?FATAL, ?UNEXPECTED_MESSAGE)
 	end.
-
+%%--------------------------------------------------------------------
 encode_plain_text(Type, Version, Data, #{current_write := Write0} = ConnectionStates) ->
     {CipherFragment, Write1} = do_encode_plain_text(Type, Version, Data, Write0),
     {CipherText, Write} = encode_tls_cipher_text(Type, Version, CipherFragment, Write1),
     {CipherText, ConnectionStates#{current_write => Write}}.
 
-lowest_list_protocol_version(Ver, []) ->
-    Ver;
-lowest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
-    lowest_list_protocol_version(lowest_protocol_version(Ver1, Ver2), Rest).
-
-highest_list_protocol_version(Ver, []) ->
-    Ver;
-highest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
-    highest_list_protocol_version(highest_protocol_version(Ver1, Ver2), Rest).
-
 encode_tls_cipher_text(Type, {MajVer, MinVer}, Fragment, #{sequence_number := Seq} = Write) ->
     Length = erlang:iolist_size(Fragment),
     {[<<?BYTE(Type), ?BYTE(MajVer), ?BYTE(MinVer), ?UINT16(Length)>>, Fragment],
      Write#{sequence_number => Seq +1}}.
 
-highest_protocol_version() ->
-    highest_protocol_version(supported_protocol_versions()).
-
-lowest_protocol_version() ->
-    lowest_protocol_version(supported_protocol_versions()).
-
-sufficient_tlsv1_2_crypto_support() ->
-    CryptoSupport = crypto:supports(),
-    proplists:get_bool(sha256, proplists:get_value(hashs, CryptoSupport)).
-
 encode_iolist(Type, Data, Version, ConnectionStates0) ->
     {ConnectionStates, EncodedMsg} =
         lists:foldl(fun(Text, {CS0, Encoded}) ->
@@ -415,6 +462,31 @@ encode_iolist(Type, Data, Version, ConnectionStates0) ->
 			    {CS1, [Enc | Encoded]}
 		    end, {ConnectionStates0, []}, Data),
     {lists:reverse(EncodedMsg), ConnectionStates}.
+%%--------------------------------------------------------------------
+do_encode_plain_text(Type, Version, Data, #{compression_state := CompS0,
+					 security_parameters :=
+					     #security_parameters{
+						cipher_type = ?AEAD,
+						compression_algorithm = CompAlg}
+					} = WriteState0) ->
+    {Comp, CompS1} = ssl_record:compress(CompAlg, Data, CompS0),
+    WriteState1 = WriteState0#{compression_state => CompS1},
+    AAD = calc_aad(Type, Version, WriteState1),
+    ssl_record:cipher_aead(Version, Comp, WriteState1, AAD);
+do_encode_plain_text(Type, Version, Data, #{compression_state := CompS0,
+					 security_parameters :=
+					     #security_parameters{compression_algorithm = CompAlg}
+					}= WriteState0) ->
+    {Comp, CompS1} = ssl_record:compress(CompAlg, Data, CompS0),
+    WriteState1 = WriteState0#{compression_state => CompS1},
+    MacHash = ssl_cipher:calc_mac_hash(Type, Version, Comp, WriteState1),
+    ssl_record:cipher(Version, Comp, WriteState1, MacHash);
+do_encode_plain_text(_,_,_,CS) ->
+    exit({cs, CS}).
+%%--------------------------------------------------------------------
+calc_aad(Type, {MajVer, MinVer},
+	 #{sequence_number := SeqNo}) ->
+    <<?UINT64(SeqNo), ?BYTE(Type), ?BYTE(MajVer), ?BYTE(MinVer)>>.
 
 %% 1/n-1 splitting countermeasure Rizzo/Duong-Beast, RC4 chiphers are
 %% not vulnerable to this attack.
@@ -440,89 +512,25 @@ do_split_bin(Bin, ChunkSize, Acc) ->
         _ ->
             lists:reverse(Acc, [Bin])
     end.
-
 %%--------------------------------------------------------------------
--spec decode_cipher_text(#ssl_tls{}, ssl_record:connection_states(), boolean()) ->
-				{#ssl_tls{}, ssl_record:connection_states()}| #alert{}.
-%%
-%% Description: Decode cipher text
-%%--------------------------------------------------------------------
-decode_cipher_text(#ssl_tls{type = Type, version = Version,
-			    fragment = CipherFragment} = CipherText,
-		   #{current_read :=
-			 #{compression_state := CompressionS0,
-			   sequence_number := Seq,
-                           cipher_state := CipherS0,
-			   security_parameters :=
-			       #security_parameters{
-				  cipher_type = ?AEAD,
-                                  bulk_cipher_algorithm =
-                                      BulkCipherAlgo,
-				  compression_algorithm = CompAlg}
-			  } = ReadState0} = ConnnectionStates0, _) ->
-    AAD = calc_aad(Type, Version, ReadState0),
-    case ssl_cipher:decipher_aead(BulkCipherAlgo, CipherS0, Seq, AAD, CipherFragment, Version) of
-	{PlainFragment, CipherS1} ->
-	    {Plain, CompressionS1} = ssl_record:uncompress(CompAlg,
-							   PlainFragment, CompressionS0),
-	    ConnnectionStates = ConnnectionStates0#{
-				  current_read => ReadState0#{
-                                                    cipher_state => CipherS1,
-                                                    sequence_number => Seq + 1,
-                                                    compression_state => CompressionS1}},
-	    {CipherText#ssl_tls{fragment = Plain}, ConnnectionStates};
-	#alert{} = Alert ->
-	    Alert
-    end;
+lowest_list_protocol_version(Ver, []) ->
+    Ver;
+lowest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
+    lowest_list_protocol_version(lowest_protocol_version(Ver1, Ver2), Rest).
 
-decode_cipher_text(#ssl_tls{type = Type, version = Version,
-			    fragment = CipherFragment} = CipherText,
-		   #{current_read :=
-			 #{compression_state := CompressionS0,
-			   sequence_number := Seq,
-			   security_parameters :=
-			       #security_parameters{compression_algorithm = CompAlg}
-			  } = ReadState0} = ConnnectionStates0, PaddingCheck) ->
-    case ssl_record:decipher(Version, CipherFragment, ReadState0, PaddingCheck) of
-	{PlainFragment, Mac, ReadState1} ->
-	    MacHash = ssl_cipher:calc_mac_hash(Type, Version, PlainFragment, ReadState1),
-	    case ssl_record:is_correct_mac(Mac, MacHash) of
-		true ->
-		    {Plain, CompressionS1} = ssl_record:uncompress(CompAlg,
-								   PlainFragment, CompressionS0),
-		    ConnnectionStates = ConnnectionStates0#{
-					  current_read => ReadState1#{
-							    sequence_number => Seq + 1,
-							    compression_state => CompressionS1}},
-		    {CipherText#ssl_tls{fragment = Plain}, ConnnectionStates};
-		false ->
-			?ALERT_REC(?FATAL, ?BAD_RECORD_MAC)
-	    end;
-	    #alert{} = Alert ->
-	    Alert
-    end.
+highest_list_protocol_version(Ver, []) ->
+    Ver;
+highest_list_protocol_version(Ver1,  [Ver2 | Rest]) ->
+    highest_list_protocol_version(highest_protocol_version(Ver1, Ver2), Rest).
+
+highest_protocol_version() ->
+    highest_protocol_version(supported_protocol_versions()).
+
+lowest_protocol_version() ->
+    lowest_protocol_version(supported_protocol_versions()).
+
+sufficient_tlsv1_2_crypto_support() ->
+    CryptoSupport = crypto:supports(),
+    proplists:get_bool(sha256, proplists:get_value(hashs, CryptoSupport)).
 
-do_encode_plain_text(Type, Version, Data, #{compression_state := CompS0,
-					 security_parameters :=
-					     #security_parameters{
-						cipher_type = ?AEAD,
-						compression_algorithm = CompAlg}
-					} = WriteState0) ->
-    {Comp, CompS1} = ssl_record:compress(CompAlg, Data, CompS0),
-    WriteState1 = WriteState0#{compression_state => CompS1},
-    AAD = calc_aad(Type, Version, WriteState1),
-    ssl_record:cipher_aead(Version, Comp, WriteState1, AAD);
-do_encode_plain_text(Type, Version, Data, #{compression_state := CompS0,
-					 security_parameters :=
-					     #security_parameters{compression_algorithm = CompAlg}
-					}= WriteState0) ->
-    {Comp, CompS1} = ssl_record:compress(CompAlg, Data, CompS0),
-    WriteState1 = WriteState0#{compression_state => CompS1},
-    MacHash = ssl_cipher:calc_mac_hash(Type, Version, Comp, WriteState1),
-    ssl_record:cipher(Version, Comp, WriteState1, MacHash);
-do_encode_plain_text(_,_,_,CS) ->
-    exit({cs, CS}).
 
-calc_aad(Type, {MajVer, MinVer},
-	 #{sequence_number := SeqNo}) ->
-    <<?UINT64(SeqNo), ?BYTE(Type), ?BYTE(MajVer), ?BYTE(MinVer)>>.