ssl: Add option to phase out support for sslv2 client hello

ssl servers can recognize sslv2 client hellos to interop with clients
that support higher version of SSL/TLS but also offers sslv2

Conflicts:
	lib/ssl/src/tls_connection.erl

4 files changed, 38 insertions, 27 deletions

diff --git a/lib/ssl/src/ssl.erl b/lib/ssl/src/ssl.erl
index 33d5c1c6d6..0058e5ec9a 100644
--- a/lib/ssl/src/ssl.erl
+++ b/lib/ssl/src/ssl.erl
@@ -732,7 +732,8 @@ handle_options(Opts0, Role) ->
 										     false, Role)),
 					     client, Role),
 		    crl_check = handle_option(crl_check, Opts, false),
-		    crl_cache = handle_option(crl_cache, Opts, {ssl_crl_cache, {internal, []}})
+		    crl_cache = handle_option(crl_cache, Opts, {ssl_crl_cache, {internal, []}}),
+		    v2_hello_compatible = handle_option(v2_hello_compatible, Opts, false)
 		   },
 
     CbInfo  = proplists:get_value(cb_info, Opts, {gen_tcp, tcp, tcp_closed, tcp_error}),
@@ -747,7 +748,7 @@ handle_options(Opts0, Role) ->
 		  alpn_preferred_protocols, next_protocols_advertised,
 		  client_preferred_next_protocols, log_alert,
 		  server_name_indication, honor_cipher_order, padding_check, crl_check, crl_cache,
-		  fallback, signature_algs, beast_mitigation],
+		  fallback, signature_algs, beast_mitigation, v2_hello_compatible],
 
     SockOpts = lists:foldl(fun(Key, PropList) ->
 				   proplists:delete(Key, PropList)
@@ -991,6 +992,8 @@ validate_option(beast_mitigation, Value) when Value == one_n_minus_one orelse
                                               Value == zero_n orelse
                                               Value == disabled ->
   Value;
+validate_option(v2_hello_compatible, Value) when is_boolean(Value)  ->
+    Value;
 validate_option(Opt, Value) ->
     throw({error, {options, {Opt, Value}}}).
 
diff --git a/lib/ssl/src/ssl_internal.hrl b/lib/ssl/src/ssl_internal.hrl
index dddcbdeeda..c19c1787ff 100644
--- a/lib/ssl/src/ssl_internal.hrl
+++ b/lib/ssl/src/ssl_internal.hrl
@@ -139,7 +139,8 @@
 	  fallback = false           :: boolean(),
 	  crl_check                  :: boolean() | peer | best_effort, 
 	  crl_cache,
-	  signature_algs
+	  signature_algs,
+	  v2_hello_compatible        :: boolean()
 	  }).
 
 -record(socket_options,
diff --git a/lib/ssl/src/tls_connection.erl b/lib/ssl/src/tls_connection.erl
index 56e516bce2..eaf2dd002d 100644
--- a/lib/ssl/src/tls_connection.erl
+++ b/lib/ssl/src/tls_connection.erl
@@ -399,9 +399,10 @@ handle_common_event(internal, #alert{} = Alert, StateName,
 handle_common_event(internal,  #ssl_tls{type = ?HANDSHAKE, fragment = Data}, 
 		    StateName, #state{protocol_buffers =
 					  #protocol_buffers{tls_handshake_buffer = Buf0} = Buffers,
-				      negotiated_version = Version} = State0) ->
-        try
-	{Packets, Buf} = tls_handshake:get_tls_handshake(Version,Data,Buf0),
+				      negotiated_version = Version,
+				      ssl_options = Options} = State0) ->
+    try
+	{Packets, Buf} = tls_handshake:get_tls_handshake(Version,Data,Buf0, Options),
 	State =
 	    State0#state{protocol_buffers =
 			     Buffers#protocol_buffers{tls_handshake_buffer = Buf}},
diff --git a/lib/ssl/src/tls_handshake.erl b/lib/ssl/src/tls_handshake.erl
index 871eb970eb..397f963ad5 100644
--- a/lib/ssl/src/tls_handshake.erl
+++ b/lib/ssl/src/tls_handshake.erl
@@ -33,7 +33,7 @@
 -include_lib("public_key/include/public_key.hrl").
 
 -export([client_hello/8, hello/4,
-	 get_tls_handshake/3, encode_handshake/2, decode_handshake/3]).
+	 get_tls_handshake/4, encode_handshake/2, decode_handshake/4]).
 
 -type tls_handshake() :: #client_hello{} | ssl_handshake:ssl_handshake().
 
@@ -133,17 +133,17 @@ encode_handshake(Package, Version) ->
     [MsgType, ?uint24(Len), Bin].
 
 %%--------------------------------------------------------------------
--spec get_tls_handshake(tls_record:tls_version(), binary(), binary() | iolist()) ->
+-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, <<>>) ->
-    get_tls_handshake_aux(Version, Data, []);
-get_tls_handshake(Version, Data, Buffer) ->
-    get_tls_handshake_aux(Version, list_to_binary([Buffer, 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
@@ -184,24 +184,24 @@ handle_client_hello(Version, #client_hello{session_id = SugesstedId,
     end.
 
 get_tls_handshake_aux(Version, <<?BYTE(Type), ?UINT24(Length),
-			Body:Length/binary,Rest/binary>>, Acc) ->
+				 Body:Length/binary,Rest/binary>>, #ssl_options{v2_hello_compatible = V2Hello} = Opts,  Acc) ->
     Raw = <<?BYTE(Type), ?UINT24(Length), Body/binary>>,
-    Handshake = decode_handshake(Version, Type, Body),
-    get_tls_handshake_aux(Version, Rest, [{Handshake,Raw} | Acc]);
-get_tls_handshake_aux(_Version, Data, Acc) ->
+    Handshake = decode_handshake(Version, Type, Body, V2Hello),
+    get_tls_handshake_aux(Version, Rest, Opts, [{Handshake,Raw} | Acc]);
+get_tls_handshake_aux(_Version, Data, _, Acc) ->
     {lists:reverse(Acc), Data}.
 
-decode_handshake(_, ?HELLO_REQUEST, <<>>) ->
+decode_handshake(_, ?HELLO_REQUEST, <<>>, _) ->
     #hello_request{};
 
 %% Client hello v2.
 %% The server must be able to receive such messages, from clients that
 %% are willing to use ssl v3 or higher, but have ssl v2 compatibility.
 decode_handshake(_Version, ?CLIENT_HELLO, <<?BYTE(Major), ?BYTE(Minor),
-				  ?UINT16(CSLength), ?UINT16(0),
-				  ?UINT16(CDLength),
-				  CipherSuites:CSLength/binary,
-				  ChallengeData:CDLength/binary>>) ->
+					    ?UINT16(CSLength), ?UINT16(0),
+					    ?UINT16(CDLength),
+					    CipherSuites:CSLength/binary,
+					    ChallengeData:CDLength/binary>>, true) ->
     #client_hello{client_version = {Major, Minor},
 		  random = ssl_v2:client_random(ChallengeData, CDLength),
 		  session_id = 0,
@@ -209,12 +209,18 @@ decode_handshake(_Version, ?CLIENT_HELLO, <<?BYTE(Major), ?BYTE(Minor),
 		  compression_methods = [?NULL],
 		  extensions = #hello_extensions{}
 		 };
+decode_handshake(_Version, ?CLIENT_HELLO, <<?BYTE(_), ?BYTE(_),
+					    ?UINT16(CSLength), ?UINT16(0),
+					    ?UINT16(CDLength),
+					    _CipherSuites:CSLength/binary,
+					    _ChallengeData:CDLength/binary>>, false) ->
+    throw(?ALERT_REC(?FATAL, ?PROTOCOL_VERSION, ssl_v2_client_hello_no_supported));
 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>>) ->
-
+					    ?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{
@@ -226,7 +232,7 @@ decode_handshake(_Version, ?CLIENT_HELLO, <<?BYTE(Major), ?BYTE(Minor), Random:3
        extensions = DecodedExtensions
       };
 
-decode_handshake(Version, Tag, Msg) ->
+decode_handshake(Version, Tag, Msg, _) ->
     ssl_handshake:decode_handshake(Version, Tag, Msg).
 
 enc_handshake(#hello_request{}, _Version) ->