Merge branch 'hans/ssh/random_modulus/OTP-13054' into maint

* hans/ssh/random_modulus/OTP-13054:
  ssh: correct a bad doc xref
  public_key: renamed priv/ssh_moduli -> priv/moduli
  ssh, public_key: updates after doc review
  ssh: changes after doc review
  ssh: extend 'dh_gex_limits' to server side
  ssh: option dh_gex_groups with tag ssh_moduli_file
  ssh, public_key: random selection of diffie-hellman moduli

7 files changed, 263 insertions, 146 deletions

diff --git a/lib/ssh/doc/src/ssh.xml b/lib/ssh/doc/src/ssh.xml
index 2b190c98b6..5c18c48f65 100644
--- a/lib/ssh/doc/src/ssh.xml
+++ b/lib/ssh/doc/src/ssh.xml
@@ -462,15 +462,45 @@ kex is implicit but public_key is set explicitly.</p>
 	</warning>
 	  </item>
 
-	  <tag><c><![CDATA[{dh_gex_groups, [{Size=integer(),G=integer(),P=integer()}] | {file,filename()} }]]></c></tag>
+	  <tag><c><![CDATA[{dh_gex_groups, [{Size=integer(),G=integer(),P=integer()}] | {file,filename()} {ssh_moduli_file,filename()} }]]></c></tag>
 	  <item>
-	    <p>Sets the groups that the server may choose among when diffie-hellman-group-exchange is negotiated.
-	    See RFC 4419 for details.
+	    <p>Defines the groups the server may choose among when diffie-hellman-group-exchange is negotiated.
+	    See RFC 4419 for details. The three variants of this option are:
 	    </p>
-	    <p>If the parameter is <c>{file,filename()}</c>, the file must exist and have one or more three-tuples terminated by a dot. The interpretation is as if the tuples had been given directly in the option.  The file is read when the daemon starts.
+	    <taglist>
+	      <tag><c>{Size=integer(),G=integer(),P=integer()}</c></tag>
+	      <item>The groups are given explicitly in this list. There may be several elements with the same <c>Size</c>.
+	      In such a case, the server will choose one randomly in the negotiated Size.
+	      </item>
+	      <tag><c>{file,filename()}</c></tag>
+	      <item>The file must have one or more three-tuples <c>{Size=integer(),G=integer(),P=integer()}</c> 
+	      terminated by a dot. The file is read when the daemon starts.
+	      </item>
+	      <tag><c>{ssh_moduli_file,filename()}</c></tag>
+	      <item>The file must be in
+	      <seealso marker="public_key:public_key#dh_gex_group/4">ssh-keygen moduli file format</seealso>.
+	      The file is read when the daemon starts.
+	      </item>
+	    </taglist>
+	    <p>The default list is fetched from the 
+	      <seealso marker="public_key:public_key#dh_gex_group/4">public_key</seealso> application.
 	    </p>
 	  </item>
 
+	  <tag><c><![CDATA[{dh_gex_limits,{Min=integer(),Max=integer()}}]]></c></tag>
+	  <item>
+	    <p>Limits what a client can ask for in diffie-hellman-group-exchange.
+	    The limits will be
+	    <c>{MaxUsed = min(MaxClient,Max), MinUsed = max(MinClient,Min)}</c> where <c>MaxClient</c> and 
+	    <c>MinClient</c> are the values proposed by a connecting client.
+	    </p>
+	    <p>The default value is <c>{0,infinity}</c>.
+	    </p>
+	    <p>If <c>MaxUsed &lt; MinUsed</c> in a key exchange, it will fail with a disconnect.
+	    </p>
+	    <p>See RFC 4419 for the function of the Max and Min values.</p>
+	  </item>
+
 	  <tag><c><![CDATA[{pwdfun, fun(User::string(), password::string()) -> boolean()}]]></c></tag>
 	  <item>
 	    <p>Provides a function for password validation. This function is called
diff --git a/lib/ssh/src/ssh.erl b/lib/ssh/src/ssh.erl
index 049018b21c..39cf441090 100644
--- a/lib/ssh/src/ssh.erl
+++ b/lib/ssh/src/ssh.erl
@@ -33,7 +33,8 @@
 	 default_algorithms/0,
 	 stop_listener/1, stop_listener/2,  stop_listener/3,
 	 stop_daemon/1, stop_daemon/2, stop_daemon/3,
-	 shell/1, shell/2, shell/3]).
+	 shell/1, shell/2, shell/3
+	]).
 
 %%--------------------------------------------------------------------
 -spec start() -> ok | {error, term()}.
@@ -420,27 +421,67 @@ handle_ssh_option({user_interaction, Value} = Opt) when is_boolean(Value) ->
     Opt;
 handle_ssh_option({preferred_algorithms,[_|_]} = Opt) -> 
     handle_pref_algs(Opt);
-handle_ssh_option({dh_gex_groups,L=[{I1,I2,I3}|_]}) when is_integer(I1), I1>0, 
-							 is_integer(I2), I2>0,
-							 is_integer(I3), I3>0 ->
-    {dh_gex_groups, lists:map(fun({N,G,P}) -> {N,{G,P}} end, L)};
-handle_ssh_option({dh_gex_groups,{file,File=[C|_]}}=Opt) when is_integer(C), C>0 ->
-    %% A string, (file name)
-    case file:consult(File) of
-	{ok, List} ->
-	    try handle_ssh_option({dh_gex_groups,List}) of
-		{dh_gex_groups,_} = NewOpt ->
-		    NewOpt
-	    catch
-		_:_ ->
-		    throw({error, {{eoptions, Opt}, "Bad format in file"}})
-	    end;
-	Error ->
-	    throw({error, {{eoptions, Opt},{"Error reading file",Error}}})
-    end;
+
+handle_ssh_option({dh_gex_groups,L0}) when is_list(L0) ->
+    {dh_gex_groups,
+     collect_per_size(
+       lists:foldl(
+	 fun({N,G,P}, Acc) when is_integer(N),N>0,
+				is_integer(G),G>0,
+				is_integer(P),P>0 -> 
+		 [{N,{G,P}} | Acc];
+	    ({N,{G,P}}, Acc) when is_integer(N),N>0,
+				  is_integer(G),G>0,
+				  is_integer(P),P>0 ->
+		 [{N,{G,P}} | Acc];
+	    ({N,GPs}, Acc) when is_list(GPs) ->
+		 lists:foldr(fun({Gi,Pi}, Acci) when is_integer(Gi),Gi>0,
+						     is_integer(Pi),Pi>0 -> 
+				     [{N,{Gi,Pi}} | Acci]
+			     end, Acc, GPs)
+	 end, [], L0))};
+
+handle_ssh_option({dh_gex_groups,{Tag,File=[C|_]}}=Opt) when is_integer(C), C>0,
+							      Tag == file ;
+							      Tag == ssh_moduli_file ->
+    {ok,GroupDefs} =
+	case Tag of
+	    file -> 
+		file:consult(File);
+	    ssh_moduli_file ->
+		case file:open(File,[read]) of
+		    {ok,D} ->
+			try
+			    {ok,Moduli} = read_moduli_file(D, 1, []),
+			    file:close(D),
+			    {ok, Moduli}
+			catch
+			    _:_ ->
+				throw({error, {{eoptions, Opt}, "Bad format in file "++File}})
+			end;
+		    {error,enoent} ->
+			throw({error, {{eoptions, Opt}, "File not found:"++File}});
+		    {error,Error} ->
+			throw({error, {{eoptions, Opt}, io_lib:format("Error reading file ~s: ~p",[File,Error])}})
+		end
+	end,
+
+    try
+	handle_ssh_option({dh_gex_groups,GroupDefs})
+    catch
+	_:_ ->
+	    throw({error, {{eoptions, Opt}, "Bad format in file: "++File}})
+    end;	    
+    
+
+handle_ssh_option({dh_gex_limits,{Min,Max}} = Opt) when is_integer(Min), Min>0, 
+							is_integer(Max), Max>=Min ->
+    %% Server
+    Opt;
 handle_ssh_option({dh_gex_limits,{Min,I,Max}} = Opt) when is_integer(Min), Min>0, 
 							  is_integer(I),   I>=Min,
 							  is_integer(Max), Max>=I ->
+    %% Client
     Opt;
 handle_ssh_option({connect_timeout, Value} = Opt) when is_integer(Value); Value == infinity ->
     Opt;
@@ -660,3 +701,33 @@ directory_exist_readable(Dir) ->
 		
 		    
 
+collect_per_size(L) ->
+    lists:foldr(
+      fun({Sz,GP}, [{Sz,GPs}|Acc]) -> [{Sz,[GP|GPs]}|Acc];
+	 ({Sz,GP}, Acc) -> [{Sz,[GP]}|Acc]
+      end, [], lists:sort(L)).
+
+read_moduli_file(D, I, Acc) ->
+    case io:get_line(D,"") of
+	{error,Error} ->
+	    {error,Error};
+	eof ->
+	    {ok, Acc};
+	"#" ++ _ -> read_moduli_file(D, I+1, Acc);
+	<<"#",_/binary>> ->  read_moduli_file(D, I+1, Acc);
+	Data ->
+	    Line = if is_binary(Data) -> binary_to_list(Data);
+		      is_list(Data) -> Data
+		   end,
+	    try
+		[_Time,_Type,_Tests,_Tries,Size,G,P] = string:tokens(Line," \r\n"),
+		M = {list_to_integer(Size),
+		     {list_to_integer(G), list_to_integer(P,16)}
+		    },
+		read_moduli_file(D, I+1, [M|Acc])
+	    catch
+		_:_ ->
+		    read_moduli_file(D, I+1, Acc)
+	    end
+    end.
+			   
diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl
index d622ec27fc..d61fc76c0a 100644
--- a/lib/ssh/src/ssh_transport.erl
+++ b/lib/ssh/src/ssh_transport.erl
@@ -441,19 +441,29 @@ handle_kexdh_reply(#ssh_msg_kexdh_reply{public_host_key = PeerPubHostKey,
 %%%
 %%% diffie-hellman-group-exchange-sha1
 %%% 
-handle_kex_dh_gex_request(#ssh_msg_kex_dh_gex_request{min = Min,
+handle_kex_dh_gex_request(#ssh_msg_kex_dh_gex_request{min = Min0,
 						      n   = NBits,
-						      max = Max}, 
-			  Ssh0=#ssh{opts=Opts}) when Min=<NBits, NBits=<Max ->
+						      max = Max0}, 
+			  Ssh0=#ssh{opts=Opts}) when Min0=<NBits, NBits=<Max0 ->
     %% server
-    {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 = {Min, Max, NBits}
-	    }};
+    {Min, Max} = adjust_gex_min_max(Min0, Max0, Opts),
+    case public_key:dh_gex_group(Min, NBits, Max,
+				 proplists:get_value(dh_gex_groups,Opts)) of
+	{ok, {_Sz, {G,P}}} ->
+	    {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 = {Min, Max, NBits}
+		    }};
+	{error,_} ->
+	    throw(#ssh_msg_disconnect{
+		     code = ?SSH_DISCONNECT_PROTOCOL_ERROR,
+		     description = "No possible diffie-hellman-group-exchange group found", 
+		     language = ""})
+    end;
+
 handle_kex_dh_gex_request(_, _) ->
   throw({{error,bad_ssh_msg_kex_dh_gex_request},
 	 #ssh_msg_disconnect{
@@ -462,6 +472,26 @@ handle_kex_dh_gex_request(_, _) ->
 	    language = ""}
 	}).
 
+
+adjust_gex_min_max(Min0, Max0, Opts) ->
+    case proplists:get_value(dh_gex_limits, Opts) of
+	undefined ->
+	    {Min0, Max0};
+	{Min1, Max1} ->
+	    Min2 = max(Min0, Min1),
+	    Max2 = min(Max0, Max1),
+	    if
+		Min2 =< Max2 ->
+		    {Min2, Max2};
+		Max2 < Min2 ->
+		    throw(#ssh_msg_disconnect{
+			     code = ?SSH_DISCONNECT_PROTOCOL_ERROR,
+			     description = "No possible diffie-hellman-group-exchange group possible", 
+			     language = ""})
+	    end
+    end.
+		    
+
 handle_kex_dh_gex_group(#ssh_msg_kex_dh_gex_group{p = P, g = G}, Ssh0) ->
     %% client
     {Public, Private} = generate_key(dh, [P,G]),
@@ -1482,44 +1512,10 @@ peer_name({Host, _}) ->
 %%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
-dh_group('diffie-hellman-group1-sha1') ->  element(2, ?dh_group1);
-dh_group('diffie-hellman-group14-sha1') -> element(2, ?dh_group14).
-
-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.
-    {_Size,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
-    end.
-
+dh_group('diffie-hellman-group1-sha1') ->  ?dh_group1;
+dh_group('diffie-hellman-group14-sha1') -> ?dh_group14.
 
+%%%----------------------------------------------------------------
 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/src/ssh_transport.hrl b/lib/ssh/src/ssh_transport.hrl
index 337f455279..fd43326f0d 100644
--- a/lib/ssh/src/ssh_transport.hrl
+++ b/lib/ssh/src/ssh_transport.hrl
@@ -229,40 +229,13 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 %%% rfc 2489, ch 6.2
+%%% Size 1024
 -define(dh_group1,
-	{1024,
-	 {2, 16#FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF}}).
+	 {2, 16#FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF}).
 
 %%% rfc 3526, ch3
+%%% Size 2048
 -define(dh_group14,
-	{2048,
-	 {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}}).
-
-%%% rfc 3526, ch4
--define(dh_group15,
-	{3072,
-	 {2, 16#FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D670C354E4ABC9804F1746C08CA18217C32905E462E36CE3BE39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF6955817183995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D04507A33A85521ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7DB3970F85A6E1E4C7ABF5AE8CDB0933D71E8C94E04A25619DCEE3D2261AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B18177B200CBBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFCE0FD108E4B82D120A93AD2CAFFFFFFFFFFFFFFFF}}).
-
-%%% rfc 3526, ch5
--define(dh_group16,
-	{4096,
-	 {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}}).
-
-%%% rfc 3526, ch6
--define(dh_group17,
-	{6144,
-	 {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}}).
-
-%%% rfc 3526, ch7
--define(dh_group18,
-	{8192,
-	 {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}}).
-
--define(dh_default_groups, [?dh_group1,
-			    ?dh_group14,
-			    ?dh_group15,
-			    ?dh_group16,
-			    ?dh_group17,
-			    ?dh_group18] ).
+	 {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}).
 
 -endif. % -ifdef(ssh_transport).
diff --git a/lib/ssh/test/ssh_algorithms_SUITE.erl b/lib/ssh/test/ssh_algorithms_SUITE.erl
index 2ab83d84e1..85415a17de 100644
--- a/lib/ssh/test/ssh_algorithms_SUITE.erl
+++ b/lib/ssh/test/ssh_algorithms_SUITE.erl
@@ -83,7 +83,7 @@ init_per_suite(Config) ->
 	    ssh_test_lib:default_algorithms(sshc),
 	    ssh_test_lib:default_algorithms(sshd),
 	    {?DEFAULT_DH_GROUP_MIN,?DEFAULT_DH_GROUP_NBITS,?DEFAULT_DH_GROUP_MAX},
-	    [KeyLen || {KeyLen,_} <- ?dh_default_groups],
+	    public_key:dh_gex_group_sizes(),
 	    ?MAX_NUM_ALGORITHMS
 	    ]),
     ct:log("all() ->~n    ~p.~n~ngroups()->~n    ~p.~n",[all(),groups()]),
@@ -172,19 +172,50 @@ simple_exec(Config) ->
     ssh_test_lib:std_simple_exec(Host, Port, Config).
 
 %%--------------------------------------------------------------------
+%% Testing if no group matches
+simple_exec_groups_no_match_too_small(Config) ->
+    try simple_exec_group({400,500,600}, Config)
+    of
+	_ -> ct:fail("Exec though no group available")
+    catch
+	error:{badmatch,{error,"No possible diffie-hellman-group-exchange group found"}} ->
+	    ok
+    end.
+
+simple_exec_groups_no_match_too_large(Config) ->
+    try simple_exec_group({9200,9500,9700}, Config)
+    of
+	_ -> ct:fail("Exec though no group available")
+    catch
+	error:{badmatch,{error,"No possible diffie-hellman-group-exchange group found"}} ->
+	    ok
+    end.
+
+%%--------------------------------------------------------------------
 %% Testing all default groups
-simple_exec_group14(Config) -> simple_exec_group(2048, Config).
-simple_exec_group15(Config) -> simple_exec_group(3072, Config).
-simple_exec_group16(Config) -> simple_exec_group(4096, Config).
-simple_exec_group17(Config) -> simple_exec_group(6144, Config).
-simple_exec_group18(Config) -> simple_exec_group(8192, Config).
-
-simple_exec_group(I, Config) ->
-    Min = I-100,
-    Max = I+100,
-    {Host,Port} = ?config(srvr_addr, Config),
-    ssh_test_lib:std_simple_exec(Host, Port, Config,
-				 [{dh_gex_limits,{Min,I,Max}}]).
+simple_exec_groups(Config) ->
+    Sizes = interpolate( public_key:dh_gex_group_sizes() ),
+    lists:foreach(
+      fun(Sz) ->
+	      ct:log("Try size ~p",[Sz]),
+	      ct:comment(Sz),
+	      case simple_exec_group(Sz, Config) of
+		  expected -> ct:log("Size ~p ok",[Sz]);
+		  _ -> ct:log("Size ~p not ok",[Sz])
+	      end
+      end, Sizes),
+    ct:comment("~p",[lists:map(fun({_,I,_}) -> I;
+				  (I) -> I
+			       end,Sizes)]).
+
+
+interpolate([I1,I2|Is]) ->
+    OneThird = (I2-I1) div 3,
+    [I1,
+     {I1, I1 + OneThird, I2},
+     {I1, I1 + 2*OneThird, I2} | interpolate([I2|Is])];
+interpolate(Is) ->
+    Is.
 
 %%--------------------------------------------------------------------
 %% Use the ssh client of the OS to connect
@@ -283,11 +314,10 @@ specific_test_cases(Tag, Alg, SshcAlgos, SshdAlgos) ->
 	case {Tag,Alg} of
 	    {kex,_} when Alg == 'diffie-hellman-group-exchange-sha1' ;
 			 Alg == 'diffie-hellman-group-exchange-sha256' ->
-		[simple_exec_group14,
-		 simple_exec_group15,
-		 simple_exec_group16,
-		 simple_exec_group17,
-		 simple_exec_group18];
+		[simple_exec_groups,
+		 simple_exec_groups_no_match_too_large,
+		 simple_exec_groups_no_match_too_small
+		];
 	    _ ->
 		[]
 	end.
@@ -331,3 +361,11 @@ setup_pubkey(Config) ->
     ssh_test_lib:setup_dsa_known_host(DataDir, UserDir),
     Config.
 
+
+simple_exec_group(I, Config) when is_integer(I) ->
+    simple_exec_group({I,I,I}, Config);
+simple_exec_group({Min,I,Max}, Config) ->
+    {Host,Port} = ?config(srvr_addr, Config),
+    ssh_test_lib:std_simple_exec(Host, Port, Config,
+				 [{dh_gex_limits,{Min,I,Max}}]).
+
diff --git a/lib/ssh/test/ssh_protocol_SUITE.erl b/lib/ssh/test/ssh_protocol_SUITE.erl
index b84ccac885..3a7f47c2dd 100644
--- a/lib/ssh/test/ssh_protocol_SUITE.erl
+++ b/lib/ssh/test/ssh_protocol_SUITE.erl
@@ -66,9 +66,9 @@ groups() ->
       
      {kex, [], [no_common_alg_server_disconnects,
 		no_common_alg_client_disconnects,
-		gex_client_init_default_noexact,
-		gex_client_init_default_exact,
 		gex_client_init_option_groups,
+		gex_server_gex_limit,
+		gex_client_init_option_groups_moduli_file,
 		gex_client_init_option_groups_file
 		]},
      {service_requests, [], [bad_service_name,
@@ -91,10 +91,10 @@ end_per_suite(Config) ->
 init_per_testcase(no_common_alg_server_disconnects, Config) ->
     start_std_daemon(Config, [{preferred_algorithms,[{public_key,['ssh-rsa']}]}]);
 
-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 ->
+init_per_testcase(TC, Config) when TC == gex_client_init_option_groups ;
+				   TC == gex_client_init_option_groups_moduli_file ;
+				   TC == gex_client_init_option_groups_file ;
+				   TC == gex_server_gex_limit ->
     Opts = case TC of
 	       gex_client_init_option_groups ->
 		   [{dh_gex_groups, [{2345, 3, 41}]}];
@@ -102,6 +102,16 @@ init_per_testcase(TC, Config) when TC == gex_client_init_default_noexact ;
 		   DataDir = ?config(data_dir, Config),
 		   F = filename:join(DataDir, "dh_group_test"),
 		   [{dh_gex_groups, {file,F}}];
+	       gex_client_init_option_groups_moduli_file ->
+		   DataDir = ?config(data_dir, Config),
+		   F = filename:join(DataDir, "dh_group_test.moduli"),
+		   [{dh_gex_groups, {ssh_moduli_file,F}}];
+	       gex_server_gex_limit ->
+		    [{dh_gex_groups, [{ 500, 3, 18},
+				      {1000, 7, 91},
+				      {3000, 5, 61}]},
+		     {dh_gex_limits,{500,1500}}
+		    ];
 	       _ ->
 		   []
 	   end,
@@ -113,10 +123,10 @@ init_per_testcase(_TestCase, Config) ->
 
 end_per_testcase(no_common_alg_server_disconnects, Config) ->
     stop_std_daemon(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 ->
+end_per_testcase(TC, Config) when TC == gex_client_init_option_groups ;
+				  TC == gex_client_init_option_groups_moduli_file ;
+				  TC == gex_client_init_option_groups_file ;
+				  TC == gex_server_gex_limit ->
     stop_std_daemon(Config);
 end_per_testcase(_TestCase, Config) ->
     check_std_daemon_works(Config, ?LINE).
@@ -332,28 +342,24 @@ no_common_alg_client_disconnects(Config) ->
     end.
 
 %%%--------------------------------------------------------------------
-gex_client_init_default_noexact(Config) ->
-    do_gex_client_init(Config, {2000, 3000, 4000},
-		       %% Warning, app knowledege:
-		       ?dh_group15).
-
-
-gex_client_init_default_exact(Config) ->
-    do_gex_client_init(Config, {2000, 2048, 4000},
-		       %% Warning, app knowledege:
-		       ?dh_group14).
-
-
 gex_client_init_option_groups(Config) ->
     do_gex_client_init(Config, {2000, 2048, 4000}, 
-		       {'n/a',{3,41}}).
-
+		       {3,41}).
 
 gex_client_init_option_groups_file(Config) ->
     do_gex_client_init(Config, {2000, 2048, 4000},
-		       {'n/a',{5,61}}).
+		       {5,61}).
+
+gex_client_init_option_groups_moduli_file(Config) ->
+    do_gex_client_init(Config, {2000, 2048, 4000},
+		       {5,16#B7}).
+
+gex_server_gex_limit(Config) ->
+    do_gex_client_init(Config, {1000, 3000, 4000},
+		       {7,91}).
+
 
-do_gex_client_init(Config, {Min,N,Max}, {_,{G,P}}) ->
+do_gex_client_init(Config, {Min,N,Max}, {G,P}) ->
     {ok,_} =
 	ssh_trpt_test_lib:exec(
 	  [{set_options, [print_ops, print_seqnums, print_messages]},
diff --git a/lib/ssh/test/ssh_protocol_SUITE_data/dh_group_test.moduli b/lib/ssh/test/ssh_protocol_SUITE_data/dh_group_test.moduli
new file mode 100644
index 0000000000..f6995ba4c9
--- /dev/null
+++ b/lib/ssh/test/ssh_protocol_SUITE_data/dh_group_test.moduli
@@ -0,0 +1,3 @@
+20151021104105 2 6 100 2222 5 B7
+20151021104106 2 6 100 1111 5 4F
+