Merge branch 'hans/ssh/dh_gex_request_old/OTP-13140' into maint-18

* hans/ssh/dh_gex_request_old/OTP-13140:
  ssh: vsn.mk updated
  ssh: New test cases for SSH_MSG_KEX_DH_GEX_REQUEST_OLD
  ssh: update existing testcases
  ssh: Improve group selection
  ssh: implemented server side SSH_MSG_KEX_DH_GEX_REQUEST_OLD for putty client

4 files changed, 88 insertions, 34 deletions

diff --git a/lib/ssh/src/ssh_connection_handler.erl b/lib/ssh/src/ssh_connection_handler.erl
index fcd66b80c0..5b4f6081c1 100644
--- a/lib/ssh/src/ssh_connection_handler.erl
+++ b/lib/ssh/src/ssh_connection_handler.erl
@@ -425,6 +425,12 @@ key_exchange(#ssh_msg_kex_dh_gex_request{} = Msg,
     send_msg(GexGroup, State),
     {next_state, key_exchange_dh_gex_init, next_packet(State#state{ssh_params = Ssh})};
 
+key_exchange(#ssh_msg_kex_dh_gex_request_old{} = Msg, 
+	     #state{ssh_params = #ssh{role = server} = Ssh0} = State) ->
+    {ok, GexGroup, Ssh} = ssh_transport:handle_kex_dh_gex_request(Msg, Ssh0),
+    send_msg(GexGroup, State),
+    {next_state, key_exchange_dh_gex_init, next_packet(State#state{ssh_params = Ssh})};
+
 key_exchange(#ssh_msg_kex_dh_gex_group{} = Msg, 
 	     #state{ssh_params = #ssh{role = client} = Ssh0} = State) ->
     {ok, KexGexInit, Ssh} = ssh_transport:handle_kex_dh_gex_group(Msg, Ssh0),
diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl
index 2b6f0a3cdc..e3ee399b8e 100644
--- a/lib/ssh/src/ssh_transport.erl
+++ b/lib/ssh/src/ssh_transport.erl
@@ -427,6 +427,32 @@ handle_kex_dh_gex_request(#ssh_msg_kex_dh_gex_request{min = Min,
      Ssh#ssh{keyex_key = {{Private, Public}, {G, P}},
 	     keyex_info = {Min, Max, NBits}
 	    }};
+
+handle_kex_dh_gex_request(#ssh_msg_kex_dh_gex_request_old{n = NBits}, 
+			  Ssh0=#ssh{opts=Opts}) ->
+    %% server
+    %%
+    %% This message was in the draft-00 of rfc4419
+    %% (https://tools.ietf.org/html/draft-ietf-secsh-dh-group-exchange-00)
+    %% In later drafts and the rfc is "is used for backward compatibility".
+    %% Unfortunatly the rfc does not specify how to treat the parameter n
+    %% if there is no group of that modulus length :(
+    %% The draft-00 however specifies that n is the "... number of bits
+    %% the subgroup should have at least".
+    %% Further, it says that "Servers and clients SHOULD support groups
+    %% with a modulus length of k bits, where 1024 <= k <= 8192."
+    %%
+    Min = NBits,
+    Max = 8192,
+    {G, P} = dh_gex_group(Min, NBits, Max, proplists:get_value(dh_gex_groups,Opts)),
+    {Public, Private} = generate_key(dh, [P,G]),
+    {SshPacket, Ssh} = 
+	ssh_packet(#ssh_msg_kex_dh_gex_group{p = P, g = G}, Ssh0),
+    {ok, SshPacket, 
+     Ssh#ssh{keyex_key = {{Private, Public}, {G, P}},
+	     keyex_info = {-1, -1, NBits} % flag for kex_h hash calc
+	    }};
+
 handle_kex_dh_gex_request(_, _) ->
   throw({{error,bad_ssh_msg_kex_dh_gex_request},
 	 #ssh_msg_disconnect{
@@ -1286,6 +1312,9 @@ kex_h(SSH, Curve, Key, Q_c, Q_s, K) ->
 
 kex_h(SSH, Key, Min, NBits, Max, Prime, Gen, E, F, K) ->
     L = if Min==-1; Max==-1 ->
+		%% flag from 'ssh_msg_kex_dh_gex_request_old'
+		%% It was like this before that message was supported,
+		%% why?
 		Ts = [string,string,binary,binary,binary,
 		      uint32,
 		      mpint,mpint,mpint,mpint,mpint],
@@ -1349,35 +1378,23 @@ dh_gex_default_groups() -> ?dh_default_groups.
 dh_gex_group(Min, N, Max, undefined) ->
     dh_gex_group(Min, N, Max, dh_gex_default_groups());
 dh_gex_group(Min, N, Max, Groups) ->
-    %% First try to find an exact match. If not an exact match, select the largest possible.
-    {_,Group} =
-	lists:foldl(
-	  fun(_, {I,G}) when I==N ->
-		  %% If we have an exact match already: use that one
-		  {I,G};
-	     ({I,G}, _) when I==N ->
-		  %% If we now found an exact match: use that very one
-		  {I,G};
-	     ({I,G}, {Imax,_Gmax}) when Min=<I,I=<Max, % a) {I,G} fullfills the requirements
-				        I>Imax ->      % b) {I,G} is larger than current max
-		  %% A group within the limits and better than the one we have
-		  {I,G};
-	     (_, IGmax) ->
-		  %% Keep the one we have
-		  IGmax
-	  end, {-1,undefined}, Groups),
-
-    case Group of
-	undefined ->
-	    throw(#ssh_msg_disconnect{
-		     code = ?SSH_DISCONNECT_PROTOCOL_ERROR,
-		     description = "No possible diffie-hellman-group-exchange group found", 
-		     language = ""});
-	_ ->
-	    Group
+    %% Try to find an exact match. If not an exact match, select the first found.
+    case lists:keyfind(N, 1, Groups) of
+	{N,Grp} -> 
+	    Grp;
+	false -> 
+	    case lists:dropwhile(fun({I,_}) -> I < Min-1 orelse I > Max+1 end,
+				 Groups) of
+		[{_,Grp}|_] ->
+		    Grp;
+		[] ->
+		    throw(#ssh_msg_disconnect{
+			     code = ?SSH_DISCONNECT_PROTOCOL_ERROR,
+			     description = "No possible diffie-hellman-group-exchange group found", 
+			     language = ""})
+	    end
     end.
 
-
 generate_key(Algorithm, Args) ->
     {Public,Private} = crypto:generate_key(Algorithm, Args),
     {crypto:bytes_to_integer(Public), crypto:bytes_to_integer(Private)}.
diff --git a/lib/ssh/test/ssh_protocol_SUITE.erl b/lib/ssh/test/ssh_protocol_SUITE.erl
index d8e99799e2..dd0adda2dc 100644
--- a/lib/ssh/test/ssh_protocol_SUITE.erl
+++ b/lib/ssh/test/ssh_protocol_SUITE.erl
@@ -60,7 +60,9 @@ groups() ->
 		gex_client_init_default_noexact,
 		gex_client_init_default_exact,
 		gex_client_init_option_groups,
-		gex_client_init_option_groups_file
+		gex_client_init_option_groups_file,
+		gex_client_old_request_exact,
+		gex_client_old_request_noexact
 		]}
     ].
 
@@ -79,7 +81,9 @@ init_per_testcase(no_common_alg_server_disconnects, Config) ->
 init_per_testcase(TC, Config) when TC == gex_client_init_default_noexact ;
 				   TC == gex_client_init_default_exact ;
 				   TC == gex_client_init_option_groups ;
-				   TC == gex_client_init_option_groups_file ->
+				   TC == gex_client_init_option_groups_file ;
+				   TC == gex_client_old_request_exact ;
+				   TC == gex_client_old_request_noexact ->
     Opts = case TC of
 	       gex_client_init_option_groups ->
 		   [{dh_gex_groups, [{2345, 3, 41}]}];
@@ -101,7 +105,9 @@ end_per_testcase(no_common_alg_server_disconnects, Config) ->
 end_per_testcase(TC, Config) when TC == gex_client_init_default_noexact ;
 				  TC == gex_client_init_default_exact ;
 				  TC == gex_client_init_option_groups ;
-				  TC == gex_client_init_option_groups_file ->
+				  TC == gex_client_init_option_groups_file ;
+				  TC == gex_client_old_request_exact ;
+				  TC == gex_client_old_request_noexact ->
     stop_std_daemon(Config);
 end_per_testcase(_TestCase, Config) ->
     check_std_daemon_works(Config, ?LINE).
@@ -333,13 +339,13 @@ no_common_alg_client_disconnects(Config) ->
 gex_client_init_default_noexact(Config) ->
     do_gex_client_init(Config, {2000, 3000, 4000},
 		       %% Warning, app knowledege:
-		       ?dh_group15).
+		       ?dh_group14).
 
 
 gex_client_init_default_exact(Config) ->
-    do_gex_client_init(Config, {2000, 2048, 4000},
+    do_gex_client_init(Config, {2000, 3072, 4000},
 		       %% Warning, app knowledege:
-		       ?dh_group14).
+		       ?dh_group15).
 
 
 gex_client_init_option_groups(Config) ->
@@ -373,6 +379,31 @@ do_gex_client_init(Config, {Min,N,Max}, {_,{G,P}}) ->
 	  ]
 	 ).
 
+%%%--------------------------------------------------------------------
+gex_client_old_request_exact(Config) -> do_gex_client_init_old(Config, 2048, ?dh_group14).
+gex_client_old_request_noexact(Config) -> do_gex_client_init_old(Config, 1000, ?dh_group1).
+    
+do_gex_client_init_old(Config, N, {_,{G,P}}) ->
+    {ok,_} =
+	ssh_trpt_test_lib:exec(
+	  [{set_options, [print_ops, print_seqnums, print_messages]},
+	   {connect,
+	    server_host(Config),server_port(Config),
+	    [{silently_accept_hosts, true},
+	     {user_dir, user_dir(Config)},
+	     {user_interaction, false},
+	     {preferred_algorithms,[{kex,['diffie-hellman-group-exchange-sha1']}]}
+	    ]},
+	   receive_hello,
+	   {send, hello},
+	   {send, ssh_msg_kexinit},
+	   {match, #ssh_msg_kexinit{_='_'}, receive_msg},
+	   {send, #ssh_msg_kex_dh_gex_request_old{n = N}},
+	   {match, #ssh_msg_kex_dh_gex_group{p=P, g=G, _='_'},  receive_msg}
+	  ]
+	 ).
+
+
 %%%================================================================
 %%%==== Internal functions ========================================
 %%%================================================================
diff --git a/lib/ssh/vsn.mk b/lib/ssh/vsn.mk
index 5bb18a656a..762bd9b208 100644
--- a/lib/ssh/vsn.mk
+++ b/lib/ssh/vsn.mk
@@ -1,4 +1,4 @@
 #-*-makefile-*-   ; force emacs to enter makefile-mode
 
-SSH_VSN = 4.1.2
+SSH_VSN = 4.1.3
 APP_VSN    = "ssh-$(SSH_VSN)"