ssh: Repair/add experimental diffie-hellman-group-exchange-sha1 support

DO NOT USE IN PRODUCTION!!!

This is a bug fixing of the previously partly impelmented kex algorithm.
There are more things to do, for example genrate/select better g,p pair obeying the min||n||max request.
It is not enabled by default, but may be enabled with the option
  {preferred_algorithms, [{kex, ['diffie-hellman-group-exchange-sha1']}]}

5 files changed, 303 insertions, 115 deletions

diff --git a/lib/ssh/src/ssh_connection_handler.erl b/lib/ssh/src/ssh_connection_handler.erl
index a9c60d0674..c059834b27 100644
--- a/lib/ssh/src/ssh_connection_handler.erl
+++ b/lib/ssh/src/ssh_connection_handler.erl
@@ -46,7 +46,9 @@
 	 get_print_info/1]).
 
 %% gen_fsm callbacks
--export([hello/2, kexinit/2, key_exchange/2, new_keys/2,
+-export([hello/2, kexinit/2, key_exchange/2, 
+	 key_exchange_dh_gex_init/2, key_exchange_dh_gex_reply/2,
+	 new_keys/2,
 	 userauth/2, connected/2,
 	 error/2]).
 
@@ -417,27 +419,39 @@ key_exchange(#ssh_msg_kexdh_reply{} = Msg,
     send_msg(NewKeys, State),
     {next_state, new_keys, next_packet(State#state{ssh_params = Ssh})};
 
-key_exchange(#ssh_msg_kex_dh_gex_group{} = Msg, 
+key_exchange(#ssh_msg_kex_dh_gex_request{} = Msg, 
 	     #state{ssh_params = #ssh{role = server} = Ssh0} = State) ->
-    {ok, NextKexMsg, Ssh1} = ssh_transport:handle_kex_dh_gex_group(Msg, Ssh0),
-    send_msg(NextKexMsg, State),
-    {ok, NewKeys, Ssh} = ssh_transport:new_keys_message(Ssh1),
-    send_msg(NewKeys, State),
-    {next_state, new_keys, next_packet(State#state{ssh_params = Ssh})};
+    {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_request{} = Msg, 
+key_exchange(#ssh_msg_kex_dh_gex_group{} = Msg, 
 	     #state{ssh_params = #ssh{role = client} = Ssh0} = State) ->
-    {ok, NextKexMsg, Ssh} = ssh_transport:handle_kex_dh_gex_request(Msg, Ssh0),
-    send_msg(NextKexMsg, State),
-    {next_state, new_keys, next_packet(State#state{ssh_params = Ssh})};
+    {ok, KexGexInit, Ssh} = ssh_transport:handle_kex_dh_gex_group(Msg, Ssh0),
+    send_msg(KexGexInit, State),
+    {next_state, key_exchange_dh_gex_reply, next_packet(State#state{ssh_params = Ssh})}.
 
-key_exchange(#ssh_msg_kex_dh_gex_reply{} = Msg, 
-	     #state{ssh_params = #ssh{role = client} = Ssh0} = State) ->
-    {ok, NewKeys, Ssh} = ssh_transport:handle_kex_dh_gex_reply(Msg, Ssh0),
+%%--------------------------------------------------------------------
+-spec key_exchange_dh_gex_init(#ssh_msg_kex_dh_gex_init{}, #state{}) -> gen_fsm_state_return().
+%%--------------------------------------------------------------------
+key_exchange_dh_gex_init(#ssh_msg_kex_dh_gex_init{} = Msg,
+			 #state{ssh_params = #ssh{role = server} = Ssh0} = State) ->
+    {ok, KexGexReply, Ssh1} =  ssh_transport:handle_kex_dh_gex_init(Msg, Ssh0),
+    send_msg(KexGexReply, State),
+    {ok, NewKeys, Ssh} = ssh_transport:new_keys_message(Ssh1),
     send_msg(NewKeys, State),
     {next_state, new_keys, next_packet(State#state{ssh_params = Ssh})}.
 
 %%--------------------------------------------------------------------
+-spec key_exchange_dh_gex_reply(#ssh_msg_kex_dh_gex_reply{}, #state{}) -> gen_fsm_state_return().
+%%--------------------------------------------------------------------
+key_exchange_dh_gex_reply(#ssh_msg_kex_dh_gex_reply{} = Msg,
+			  #state{ssh_params = #ssh{role = client} = Ssh0} = State) ->
+    {ok, NewKeys, Ssh1} =  ssh_transport:handle_kex_dh_gex_reply(Msg, Ssh0),
+    send_msg(NewKeys, State),
+    {next_state, new_keys, next_packet(State#state{ssh_params = Ssh1})}.
+
+%%--------------------------------------------------------------------
 -spec new_keys(#ssh_msg_newkeys{}, #state{}) -> gen_fsm_state_return().
 %%--------------------------------------------------------------------
 
diff --git a/lib/ssh/src/ssh_message.erl b/lib/ssh/src/ssh_message.erl
index 1f0f6fb15f..7b786b8fff 100644
--- a/lib/ssh/src/ssh_message.erl
+++ b/lib/ssh/src/ssh_message.erl
@@ -237,7 +237,7 @@ encode(#ssh_msg_kex_dh_gex_request{
 	  max = Max
 	 }) ->
     ssh_bits:encode([?SSH_MSG_KEX_DH_GEX_REQUEST, Min, N, Max],
-		    [byte, uint32, uint32, uint32, uint32]);
+		    [byte, uint32, uint32, uint32]);
 encode(#ssh_msg_kex_dh_gex_request_old{n = N}) ->
     ssh_bits:encode([?SSH_MSG_KEX_DH_GEX_REQUEST_OLD, N],
 		    [byte, uint32]);
@@ -257,7 +257,7 @@ encode(#ssh_msg_kex_dh_gex_reply{
 	 }) ->
     EncKey = encode_host_key(Key),
     EncSign = encode_sign(Key, Signature),
-    ssh_bits:encode([?SSH_MSG_KEXDH_REPLY, EncKey, F, EncSign], [byte, binary, mpint, binary]);
+    ssh_bits:encode([?SSH_MSG_KEX_DH_GEX_REPLY, EncKey, F, EncSign], [byte, binary, mpint, binary]);
 
 encode(#ssh_msg_ignore{data = Data}) ->
     ssh_bits:encode([?SSH_MSG_IGNORE, Data], [byte, string]);
@@ -442,6 +442,19 @@ decode(<<?BYTE(?SSH_MSG_KEX_DH_GEX_GROUP),
        p = Prime,
        g = Generator
       };
+decode(<<?BYTE(?SSH_MSG_KEX_DH_GEX_INIT), ?UINT32(Len), E:Len/big-signed-integer-unit:8>>) ->
+    #ssh_msg_kex_dh_gex_init{
+       e = E
+      };
+decode(<<?BYTE(?SSH_MSG_KEX_DH_GEX_REPLY), 
+	 ?UINT32(Len0), Key:Len0/binary,
+	 ?UINT32(Len1), F:Len1/big-signed-integer-unit:8,
+	 ?UINT32(Len2), Hashsign:Len2/binary>>) ->
+    #ssh_msg_kex_dh_gex_reply{
+       public_host_key = decode_host_key(Key),
+       f = F,
+       h_sig = decode_sign(Hashsign)
+      };
 decode(<<?BYTE(?SSH_MSG_KEXDH_REPLY), ?UINT32(Len0), Key:Len0/binary,
 	 ?UINT32(Len1), F:Len1/big-signed-integer-unit:8,
 	 ?UINT32(Len2), Hashsign:Len2/binary>>) ->
diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl
index 2e7391e1f8..ce0762bf96 100644
--- a/lib/ssh/src/ssh_transport.erl
+++ b/lib/ssh/src/ssh_transport.erl
@@ -39,7 +39,7 @@
 	 key_exchange_init_msg/1,
 	 key_init/3, new_keys_message/1,
 	 handle_kexinit_msg/3, handle_kexdh_init/2,
-	 handle_kex_dh_gex_group/2, handle_kex_dh_gex_reply/2,
+	 handle_kex_dh_gex_group/2, handle_kex_dh_gex_init/2, handle_kex_dh_gex_reply/2,
 	 handle_new_keys/2, handle_kex_dh_gex_request/2,
 	 handle_kexdh_reply/2, 
 	 unpack/3, decompress/2, ssh_packet/2, pack/2, msg_data/1,
@@ -66,6 +66,8 @@ algo_classes() -> [kex, public_key, cipher, mac, compression].
 default_algorithms(compression) ->
     %% Do not announce '[email protected]' because there seem to be problems
     supported_algorithms(compression, same(['[email protected]']));
+default_algorithms(kex) ->
+    supported_algorithms(kex, ['diffie-hellman-group-exchange-sha1']);
 default_algorithms(Alg) ->
     supported_algorithms(Alg).
 
@@ -73,7 +75,8 @@ default_algorithms(Alg) ->
 supported_algorithms() -> [{K,supported_algorithms(K)} || K <- algo_classes()].
 
 supported_algorithms(kex) ->
-    ['diffie-hellman-group1-sha1'];
+    ['diffie-hellman-group1-sha1',
+     'diffie-hellman-group-exchange-sha1'];
 supported_algorithms(public_key) ->
     ssh_auth:default_public_key_algorithms();
 supported_algorithms(cipher) ->
@@ -135,7 +138,7 @@ ssh_vsn() ->
 	_:_ -> ""
     end.
     
-random_id(Nlo, Nup) -> 
+random_id(Nlo, Nup) ->
     [crypto:rand_uniform($a,$z+1) || _<- lists:duplicate(crypto:rand_uniform(Nlo,Nup+1),x)  ].
 
 hello_version_msg(Data) ->
@@ -144,7 +147,7 @@ hello_version_msg(Data) ->
 next_seqnum(SeqNum) ->
     (SeqNum + 1) band 16#ffffffff.
 
-decrypt_first_block(Bin, #ssh{decrypt_block_size = BlockSize} = Ssh0) -> 
+decrypt_first_block(Bin, #ssh{decrypt_block_size = BlockSize} = Ssh0) ->
     <<EncBlock:BlockSize/binary, EncData/binary>> = Bin,
     {Ssh, <<?UINT32(PacketLen), _/binary>> = DecData} =
 	decrypt(Ssh0, EncBlock),
@@ -282,9 +285,14 @@ verify_algorithm(#alg{kex = 'diffie-hellman-group1-sha1'}) -> true;
 verify_algorithm(#alg{kex = 'diffie-hellman-group-exchange-sha1'}) -> true;
 verify_algorithm(_) -> false.
 
+%%%----------------------------------------------------------------
+%%%
+%%% Key exchange initialization
+%%%
 key_exchange_first_msg('diffie-hellman-group1-sha1', Ssh0) ->
     {G, P} = dh_group1(),
     {Private, Public} = dh_gen_key(G, P, 1024),
+    %% Public = G^Private mod P  (def)
     {SshPacket, Ssh1} = ssh_packet(#ssh_msg_kexdh_init{e = Public}, Ssh0),
     {ok, SshPacket, 
      Ssh1#ssh{keyex_key = {{Private, Public}, {G, P}}}};
@@ -295,13 +303,18 @@ key_exchange_first_msg('diffie-hellman-group-exchange-sha1', Ssh0) ->
     Max = ?DEFAULT_DH_GROUP_MAX,
     {SshPacket, Ssh1} = 
 	ssh_packet(#ssh_msg_kex_dh_gex_request{min = Min, 
-					       n = NBits, max = Max}, 
+					       n = NBits,
+					       max = Max}, 
 		   Ssh0),
     {ok, SshPacket, 
      Ssh1#ssh{keyex_info = {Min, Max, NBits}}}. 
 
-
+%%%----------------------------------------------------------------
+%%%
+%%% diffie-hellman-group1-sha1
+%%% 
 handle_kexdh_init(#ssh_msg_kexdh_init{e = E}, Ssh0) ->
+    %% server
     {G, P} = dh_group1(),
     if
 	1=<E, E=<(P-1) ->
@@ -314,101 +327,176 @@ handle_kexdh_init(#ssh_msg_kexdh_init{e = E}, Ssh0) ->
 								f = Public,
 								h_sig = H_SIG
 							       }, Ssh0),
-	    
 	    {ok, SshPacket, Ssh1#ssh{keyex_key = {{Private, Public}, {G, P}},
 				     shared_secret = K,
 				     exchanged_hash = H,
 				     session_id = sid(Ssh1, H)}};
+
 	true ->
-	    Error = {error,bad_e_from_peer},
-	    Disconnect = #ssh_msg_disconnect{
-			    code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
-			    description = "Key exchange failed, 'f' out of bounds",
-			    language = "en"},
-	    throw({Error, Disconnect})
+	    throw({{error,bad_e_from_peer},
+		   #ssh_msg_disconnect{
+		      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+		      description = "Key exchange failed, 'e' out of bounds",
+		      language = ""}
+		   })
     end.
 
-handle_kex_dh_gex_group(#ssh_msg_kex_dh_gex_group{p = P, g = G}, Ssh0) ->
-    {Private, Public} = dh_gen_key(G,P,1024),
-    {SshPacket, Ssh1} = 
-	ssh_packet(#ssh_msg_kex_dh_gex_init{e = Public}, Ssh0),
-    {ok, SshPacket, 
-     Ssh1#ssh{keyex_key = {{Private, Public}, {G, P}}}}.
+handle_kexdh_reply(#ssh_msg_kexdh_reply{public_host_key = HostKey,
+					f = F,
+					h_sig = H_SIG}, 
+		   #ssh{keyex_key = {{Private, Public}, {_G, P}}} = Ssh0) ->
+    %% client
+    if 
+	1=<F, F=<(P-1)->
+	    K = ssh_math:ipow(F, Private, P),
+	    H = kex_h(Ssh0, HostKey, Public, F, K),
+
+	    case verify_host_key(Ssh0, HostKey, H, H_SIG) of
+		ok ->
+		    {SshPacket, Ssh} = ssh_packet(#ssh_msg_newkeys{}, Ssh0),
+		    {ok, SshPacket, Ssh#ssh{shared_secret  = K,
+					    exchanged_hash = H,
+					    session_id = sid(Ssh, H)}};
+		Error ->
+		    throw({Error,
+			   #ssh_msg_disconnect{
+			      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+			      description = "Key exchange failed",
+			      language = "en"}
+			  })
+	    end;
 
-handle_new_keys(#ssh_msg_newkeys{}, Ssh0) ->
-    try install_alg(Ssh0) of
-	#ssh{} = Ssh ->
-	    {ok, Ssh}
-    catch 
-	error:_Error -> %% TODO: Throw earlier ....
-	    throw(#ssh_msg_disconnect{code = ?SSH_DISCONNECT_PROTOCOL_ERROR,
-				      description = "Install alg failed", 
-				      language = "en"})
-    end. 
+	true ->
+	    throw({{error,bad_f_from_peer},
+		   #ssh_msg_disconnect{
+		      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+		      description = "Key exchange failed, 'f' out of bounds",
+		      language = ""}
+		   })
+    end.
 
 
-%% %% Select algorithms
-handle_kexdh_reply(#ssh_msg_kexdh_reply{public_host_key = HostKey, f = F,
-					h_sig = H_SIG}, 
-		   #ssh{keyex_key = {{Private, Public}, {_G, P}}} = Ssh0) when 1=<F, F=<(P-1)->
-    K = ssh_math:ipow(F, Private, P),
-    H = kex_h(Ssh0, HostKey, Public, F, K),
-
-    case verify_host_key(Ssh0, HostKey, H, H_SIG) of
-	ok ->
-	    {SshPacket, Ssh} = ssh_packet(#ssh_msg_newkeys{}, Ssh0),
-	    {ok, SshPacket, Ssh#ssh{shared_secret  = K,
-				    exchanged_hash = H,
-				    session_id = sid(Ssh, H)}};
-	Error ->
-	    Disconnect = #ssh_msg_disconnect{
-	      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
-	      description = "Key exchange failed",
-	      language = "en"},
-	    throw({Error, Disconnect})
-    end;
-handle_kexdh_reply(#ssh_msg_kexdh_reply{}, _SSH) ->
-    Error = {error,bad_f_from_peer},
-    Disconnect = #ssh_msg_disconnect{
-		    code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
-		    description = "Key exchange failed, 'f' out of bounds",
-		    language = "en"},
-    throw({Error, Disconnect}).
-
-
-handle_kex_dh_gex_request(#ssh_msg_kex_dh_gex_request{min = _Min,
-						      n   = _NBits,
-						      max = _Max}, Ssh0) ->
+%%%----------------------------------------------------------------
+%%%
+%%% diffie-hellman-group-exchange-sha1
+%%% 
+handle_kex_dh_gex_request(#ssh_msg_kex_dh_gex_request{min = Min,
+						      n   = NBits,
+						      max = Max}, Ssh0) ->
+    %% server
     {G,P} = dh_group1(), %% TODO real imp this seems to be a hack?!
     {Private, Public} = dh_gen_key(G, P, 1024),
     {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}}}}.
+     Ssh#ssh{keyex_key = {{Private, Public}, {G, P}},
+	     keyex_info = {Min, Max, NBits}
+	    }}.
+
+handle_kex_dh_gex_group(#ssh_msg_kex_dh_gex_group{p = P, g = G}, Ssh0) ->
+    %% client
+    {Private, Public} = dh_gen_key(G, P, 1024),
+    {SshPacket, Ssh1} = 
+	ssh_packet(#ssh_msg_kex_dh_gex_init{e = Public}, Ssh0),	% Pub = G^Priv mod P (def)
+
+    {ok, SshPacket, 
+     Ssh1#ssh{keyex_key = {{Private, Public}, {G, P}}}}.
+
+handle_kex_dh_gex_init(#ssh_msg_kex_dh_gex_init{e = E}, 
+		       #ssh{keyex_key = {{Private, Public}, {G, P}},
+			    keyex_info = {Min, Max, NBits}} = 
+			   Ssh0) ->
+    %% server
+    if
+	1=<E, E=<(P-1) ->
+	    K = ssh_math:ipow(E, Private, P),
+	    if
+		1<K, K<(P-1) ->
+		    HostKey = get_host_key(Ssh0),
+		    H = kex_h(Ssh0, HostKey, Min, NBits, Max, P, G, E, Public, K),
+		    H_SIG = sign_host_key(Ssh0, HostKey, H),
+		    {SshPacket, Ssh} = 
+			ssh_packet(#ssh_msg_kex_dh_gex_reply{public_host_key = HostKey, 
+							     f = Public,
+							     h_sig = H_SIG}, Ssh0),
+		    {ok, SshPacket, Ssh#ssh{shared_secret = K,
+					    exchanged_hash = H,
+					    session_id = sid(Ssh, H)
+					   }};
+		true ->
+		    throw({{error,bad_K},
+			   #ssh_msg_disconnect{
+			      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+			      description = "Key exchange failed, 'K' out of bounds",
+			      language = ""}
+			  })
+	    end;
+	true ->
+	    throw({{error,bad_e_from_peer},
+		   #ssh_msg_disconnect{
+		      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+		      description = "Key exchange failed, 'e' out of bounds",
+		      language = ""}
+		  })
+    end.
 
 handle_kex_dh_gex_reply(#ssh_msg_kex_dh_gex_reply{public_host_key = HostKey, 
 						  f = F,
 						  h_sig = H_SIG},
 			#ssh{keyex_key = {{Private, Public}, {G, P}},
 			     keyex_info = {Min, Max, NBits}} = 
-		 	Ssh0) ->
-    K = ssh_math:ipow(F, Private, P),
-    H = kex_h(Ssh0, HostKey, Min, NBits, Max, P, G, Public, F, K),
-
-    case verify_host_key(Ssh0, HostKey, H, H_SIG) of
-	ok ->
-	    {SshPacket, Ssh} = ssh_packet(#ssh_msg_newkeys{}, Ssh0),
-	    {ok, SshPacket, Ssh#ssh{shared_secret  = K,
-			  exchanged_hash = H,
-			  session_id = sid(Ssh, H)}};
-	_Error ->
-	    Disconnect = #ssh_msg_disconnect{
-	      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
-	      description = "Key exchange failed",
-	      language = "en"},
-	    throw(Disconnect)
+			    Ssh0) ->
+    %% client
+    if 
+	1=<F, F=<(P-1)->
+	    K = ssh_math:ipow(F, Private, P),
+	    if
+		1<K, K<(P-1) ->
+		    H = kex_h(Ssh0, HostKey, Min, NBits, Max, P, G, Public, F, K),
+
+		    case verify_host_key(Ssh0, HostKey, H, H_SIG) of
+			ok ->
+			    {SshPacket, Ssh} = ssh_packet(#ssh_msg_newkeys{}, Ssh0),
+			    {ok, SshPacket, Ssh#ssh{shared_secret  = K,
+						    exchanged_hash = H,
+						    session_id = sid(Ssh, H)}};
+			_Error ->
+			    throw(#ssh_msg_disconnect{
+				     code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+				     description = "Key exchange failed",
+				     language = ""}
+				 )
+		    end;
+
+		true ->
+		    throw({{error,bad_K},
+			   #ssh_msg_disconnect{
+			      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+			      description = "Key exchange failed, 'K' out of bounds",
+			      language = ""}
+			  })
+	    end;
+	true ->
+	    throw({{error,bad_f_from_peer},
+		   #ssh_msg_disconnect{
+		      code = ?SSH_DISCONNECT_KEY_EXCHANGE_FAILED,
+		      description = "Key exchange failed, 'f' out of bounds",
+		      language = ""}
+		  })
     end.	       
 
+%%%----------------------------------------------------------------
+handle_new_keys(#ssh_msg_newkeys{}, Ssh0) ->
+    try install_alg(Ssh0) of
+	#ssh{} = Ssh ->
+	    {ok, Ssh}
+    catch 
+	error:_Error -> %% TODO: Throw earlier ....
+	    throw(#ssh_msg_disconnect{code = ?SSH_DISCONNECT_PROTOCOL_ERROR,
+				      description = "Install alg failed", 
+				      language = "en"})
+    end. 
+
 %% select session id
 sid(#ssh{session_id = undefined}, H) -> 
     H;
@@ -511,7 +599,6 @@ select_algorithm(Role, Client, Server) ->
 	       decompress = Decompression,
 	       c_lng = C_Lng,
 	       s_lng = S_Lng},
-%%ct:pal("~p~n Client=~p~n Server=~p~n    Alg=~p~n",[Role,Client,Server,Alg]),
     {ok, Alg}.
 
 select_encrypt_decrypt(client, Client, Server) ->
@@ -1001,7 +1088,7 @@ recv_mac_init(SSH) ->
 recv_mac_final(SSH) ->
     {ok, SSH#ssh { recv_mac = none, recv_mac_key = undefined }}.
 
-mac(none, _ , _, _) ->  
+mac(none, _ , _, _) ->
     <<>>;
 mac('hmac-sha1', Key, SeqNum, Data) ->
     crypto:hmac(sha, Key, [<<?UINT32(SeqNum)>>, Data]);
diff --git a/lib/ssh/test/ssh_basic_SUITE.erl b/lib/ssh/test/ssh_basic_SUITE.erl
index bf9fe54c57..c71463db30 100644
--- a/lib/ssh/test/ssh_basic_SUITE.erl
+++ b/lib/ssh/test/ssh_basic_SUITE.erl
@@ -42,6 +42,7 @@ suite() ->
 all() -> 
     [app_test,
      appup_test,
+     {group, 'diffie-hellman-group-exchange-sha1'},
      {group, dsa_key},
      {group, rsa_key},
      {group, dsa_pass_key},
@@ -92,6 +93,8 @@ groups() ->
 			    max_sessions_sftp_start_channel_parallel,
 			    max_sessions_sftp_start_channel_sequential
 			   ]},
+     {'diffie-hellman-group-exchange-sha1', [], ['diffie-hellman-group-exchange-sha1'
+						]},
      {dir_options, [], [user_dir_option,
 			system_dir_option]}
     ].
@@ -146,6 +149,17 @@ init_per_group(internal_error, Config) ->
     ssh_test_lib:setup_dsa(DataDir, PrivDir),
     file:delete(filename:join(PrivDir, "system/ssh_host_dsa_key")),
     Config;
+init_per_group('diffie-hellman-group-exchange-sha1', Config) ->
+    case lists:member('diffie-hellman-group-exchange-sha1',
+		      ssh_transport:supported_algorithms(kex)) of
+	true ->
+	    DataDir = ?config(data_dir, Config),
+	    PrivDir = ?config(priv_dir, Config),
+	    ssh_test_lib:setup_rsa(DataDir, PrivDir),
+	    Config;
+	false ->
+	    {skip,"diffie-hellman-group-exchange-sha1 is not supported"}
+    end;
 init_per_group(dir_options, Config) ->
     PrivDir = ?config(priv_dir, Config),
     %% Make unreadable dir:
@@ -818,6 +832,43 @@ ssh_msg_debug_fun_option_client(Config) ->
     end.
 
 %%--------------------------------------------------------------------
+'diffie-hellman-group-exchange-sha1'(Config) ->
+    process_flag(trap_exit, true),
+    SystemDir = filename:join(?config(priv_dir, Config), system),
+    UserDir = ?config(priv_dir, Config), 
+
+    {Pid, Host, Port} = ssh_test_lib:daemon([{system_dir, SystemDir},
+					     {user_dir, UserDir},
+					     {user_passwords, [{"foo", "bar"}]},
+					     {preferred_algorithms,
+					      [{kex, ['diffie-hellman-group-exchange-sha1']}]},
+					     {failfun, fun ssh_test_lib:failfun/2}]),
+    
+    ConnectionRef =
+	ssh_test_lib:connect(Host, Port, [{silently_accept_hosts, true},
+					  {user, "foo"},
+					  {password, "bar"},
+					  {user_dir, UserDir},
+					  {preferred_algorithms,
+					   [{kex, ['diffie-hellman-group-exchange-sha1']}]},
+					  {user_interaction, false}]),
+    check(ConnectionRef, Pid).
+
+check(ConnectionRef, Pid) ->
+    {ok, ChannelId} = ssh_connection:session_channel(ConnectionRef, infinity),
+    success = ssh_connection:exec(ConnectionRef, ChannelId,
+				  "1+1.", infinity),
+    Data = {ssh_cm, ConnectionRef, {data, ChannelId, 0, <<"2\n">>}},
+    case ssh_test_lib:receive_exec_result(Data) of
+	expected ->
+	    ok;
+	Other ->
+	    ct:fail(Other)
+    end,
+    ssh_test_lib:receive_exec_end(ConnectionRef, ChannelId),
+    ssh:stop_daemon(Pid).
+
+%%--------------------------------------------------------------------
 connectfun_disconnectfun_server(Config) ->
     PrivDir = ?config(priv_dir, Config),
     UserDir = filename:join(PrivDir, nopubkey), % to make sure we don't use public-key-auth
diff --git a/lib/ssh/test/ssh_sftp_SUITE.erl b/lib/ssh/test/ssh_sftp_SUITE.erl
index 6c631e6f6e..86ab503c20 100644
--- a/lib/ssh/test/ssh_sftp_SUITE.erl
+++ b/lib/ssh/test/ssh_sftp_SUITE.erl
@@ -64,12 +64,16 @@ end_per_suite(Config) ->
 groups() -> 
     [{not_unicode, [], [{group,erlang_server},
 			{group,openssh_server},
+			{group,'diffie-hellman-group-exchange-sha1'},
 			sftp_nonexistent_subsystem]},
 
      {unicode, [], [{group,erlang_server},
 		    {group,openssh_server},
 		    sftp_nonexistent_subsystem]},
      
+     {'diffie-hellman-group-exchange-sha1', [], [{group,erlang_server},
+						 {group,openssh_server}]},
+
      {erlang_server, [], [{group,write_read_tests},
 			  version_option,
 			  {group,remote_tar}]},
@@ -142,22 +146,26 @@ init_per_group(erlang_server, Config) ->
     User = ?config(user, Config),
     Passwd = ?config(passwd, Config),
     Sftpd = {_, HostX, PortX} =
-	ssh_test_lib:daemon([{system_dir, SysDir},
-			     {user_dir, PrivDir},
-			     {user_passwords,
-			      [{User, Passwd}]}]),
+	ssh_test_lib:daemon(extra_opts(Config) ++
+				[{system_dir, SysDir},
+				 {user_dir, PrivDir},
+				 {user_passwords,
+				  [{User, Passwd}]}]),
     [{peer, {fmt_host(HostX),PortX}}, {group, erlang_server}, {sftpd, Sftpd} | Config];
 
 init_per_group(openssh_server, Config) ->
     ct:comment("Begin ~p",[grps(Config)]),
     Host = ssh_test_lib:hostname(),
-    case (catch ssh_sftp:start_channel(Host,					      
-				       [{user_interaction, false},
-					{silently_accept_hosts, true}])) of
+    case (catch ssh_sftp:start_channel(Host,
+				       extra_opts(Config) ++
+					   [{user_interaction, false},
+					    {silently_accept_hosts, true}])) of
 	{ok, _ChannelPid, Connection} ->
 	    [{peer, {_HostName,{IPx,Portx}}}] = ssh:connection_info(Connection,[peer]),
 	    ssh:close(Connection),
 	    [{peer, {fmt_host(IPx),Portx}}, {group, openssh_server} | Config];
+	{error,"Key exchange failed"} ->
+	    {skip, "openssh server lacks 'diffie-hellman-group-exchange-sha1'"};
 	_ ->
 	    {skip, "No openssh server"} 
     end;
@@ -172,10 +180,11 @@ init_per_group(remote_tar, Config) ->
 	case ?config(group, Config) of
 	    erlang_server ->
 		ssh:connect(Host, Port,
-			    [{user, User},
-			     {password, Passwd},
-			     {user_interaction, false},
-			     {silently_accept_hosts, true}]);
+			    extra_opts(Config) ++
+				[{user, User},
+				 {password, Passwd},
+				 {user_interaction, false},
+				 {silently_accept_hosts, true}]);
 	    openssh_server ->
 		ssh:connect(Host, Port,
 			    [{user_interaction, false},
@@ -184,6 +193,17 @@ init_per_group(remote_tar, Config) ->
     [{remote_tar, true}, 
      {connection, Connection} | Config];
 
+init_per_group('diffie-hellman-group-exchange-sha1', Config) ->
+    case lists:member('diffie-hellman-group-exchange-sha1',
+		      ssh_transport:supported_algorithms(kex)) of
+	true ->
+	    [{extra_opts, [{preferred_algorithms, [{kex,['diffie-hellman-group-exchange-sha1']}]}]}
+	     | Config]; 
+
+	false ->
+	     {skip,"'diffie-hellman-group-exchange-sha1' not supported by this version of erlang ssh"}
+    end;
+
 init_per_group(write_read_tests, Config) ->
     ct:comment("Begin ~p",[grps(Config)]),
     Config.
@@ -194,7 +214,6 @@ grps(Config) ->
       lists:flatten([proplists:get_value(tc_group_properties,Config,[]),
 		     proplists:get_value(tc_group_path,Config,[])])).
 
-
 end_per_group(erlang_server, Config) ->
     ct:comment("End ~p",[grps(Config)]),
     Config;
@@ -249,10 +268,12 @@ init_per_testcase(Case, Config0) ->
 		{_,Host, Port} =  ?config(sftpd, Config2),
 		{ok, ChannelPid, Connection}  = 
 		    ssh_sftp:start_channel(Host, Port,
-					   [{user, User},
-					    {password, Passwd},
-					    {user_interaction, false},
-					    {silently_accept_hosts, true}]),
+					   extra_opts(Config2) ++
+					       [{user, User},
+						{password, Passwd},
+						{user_interaction, false},
+						{silently_accept_hosts, true}]
+					  ),
 		Sftp = {ChannelPid, Connection},
 		[{sftp, Sftp}, {watchdog, Dog} | Config2];
 	    openssh_server when Case == links ->
@@ -261,8 +282,9 @@ init_per_testcase(Case, Config0) ->
 		Host = ssh_test_lib:hostname(),
 		{ok, ChannelPid, Connection} = 
 		    ssh_sftp:start_channel(Host, 
-					   [{user_interaction, false},
-					    {silently_accept_hosts, true}]), 
+					    extra_opts(Config2) ++
+					       [{user_interaction, false},
+						{silently_accept_hosts, true}]), 
 		Sftp = {ChannelPid, Connection},
 		[{sftp, Sftp}, {watchdog, Dog} | Config2]
 	end,
@@ -910,7 +932,8 @@ prep(Config) ->
     ok = file:write_file_info(TestFile,
 			      FileInfo#file_info{mode = Mode}).
 
-
+extra_opts(Config) ->
+    proplists:get_value(extra_opts, Config, []).
 
 chk_tar(Items, Config) ->
     chk_tar(Items, Config, []).