ssh: implemented server side SSH_MSG_KEX_DH_GEX_REQUEST_OLD for putty client

2 files changed, 35 insertions, 0 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..1fbe50e758 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],