Add disable client-initiated renegotiation option

Client-initiated renegotiation is more costly for the server than the
client, and this feature can be abused in denial of service attempts.
Although the ssl application already takes counter-measure for these
(via cooldown periods between renegotiations), it can be useful to
disable the feature entirely.

This patch adds the `{client_renegotiation, boolean()}' option to the
server-side of the SSL application (defaulting to `true' to be
compatible with the current behaviour).

The option disables the ability to do any renegotiation at all in the
protocol's state, reusing the existing denial code, but without opening
the code path that sets up a timed message to eventually reopen it up.

1 files changed, 53 insertions, 4 deletions

diff --git a/lib/ssl/test/ssl_basic_SUITE.erl b/lib/ssl/test/ssl_basic_SUITE.erl
index df9432a43b..4d5966fed9 100644
--- a/lib/ssl/test/ssl_basic_SUITE.erl
+++ b/lib/ssl/test/ssl_basic_SUITE.erl
@@ -162,7 +162,8 @@ renegotiate_tests() ->
      client_no_wrap_sequence_number,
      server_no_wrap_sequence_number,
      renegotiate_dos_mitigate_active,
-     renegotiate_dos_mitigate_passive].
+     renegotiate_dos_mitigate_passive,
+     renegotiate_dos_mitigate_absolute].
 
 cipher_tests() ->
     [cipher_suites,
@@ -2955,8 +2956,36 @@ renegotiate_dos_mitigate_passive(Config) when is_list(Config) ->
     ssl_test_lib:close(Client).
 
 %%--------------------------------------------------------------------
+renegotiate_dos_mitigate_absolute() ->
+    [{doc, "Mitigate DOS computational attack by not allowing client to initiate renegotiation"}].
+renegotiate_dos_mitigate_absolute(Config) when is_list(Config) ->
+    ServerOpts = ?config(server_opts, Config),
+    ClientOpts = ?config(client_opts, Config),
+
+    {ClientNode, ServerNode, Hostname} = ssl_test_lib:run_where(Config),
+
+    Server =
+	ssl_test_lib:start_server([{node, ServerNode}, {port, 0},
+				   {from, self()},
+				   {mfa, {ssl_test_lib, send_recv_result_active, []}},
+				   {options, [{client_renegotiation, false} | ServerOpts]}]),
+    Port = ssl_test_lib:inet_port(Server),
+
+    Client = ssl_test_lib:start_client([{node, ClientNode}, {port, Port},
+					{host, Hostname},
+					{from, self()},
+					{mfa, {?MODULE,
+					       renegotiate_rejected,
+					       []}},
+					{options, ClientOpts}]),
+
+    ssl_test_lib:check_result(Client, ok, Server, ok),
+    ssl_test_lib:close(Server),
+    ssl_test_lib:close(Client).
+
+%%--------------------------------------------------------------------
 tcp_error_propagation_in_active_mode() ->
-    [{doc,"Test that process recives {ssl_error, Socket, closed} when tcp error ocurres"}].
+    [{doc,"Test that process recives {ssl_error, Socket, closed} when tcp error occurs"}].
 tcp_error_propagation_in_active_mode(Config) when is_list(Config) ->
     ClientOpts = ?config(client_opts, Config),
     ServerOpts = ?config(server_opts, Config),
@@ -3390,12 +3419,12 @@ renegotiate_reuse_session(Socket, Data) ->
     renegotiate(Socket, Data).
 
 renegotiate_immediately(Socket) ->
-    receive 
+    receive
 	{ssl, Socket, "Hello world"} ->
 	    ok;
 	%% Handle 1/n-1 splitting countermeasure Rizzo/Duong-Beast
 	{ssl, Socket, "H"} ->
-	    receive 
+	    receive
 		{ssl, Socket, "ello world"} ->
 		    ok
 	    end
@@ -3407,6 +3436,26 @@ renegotiate_immediately(Socket) ->
     ct:log("Renegotiated again"),
     ssl:send(Socket, "Hello world"),
     ok.
+
+renegotiate_rejected(Socket) ->
+    receive
+	{ssl, Socket, "Hello world"} ->
+	    ok;
+	%% Handle 1/n-1 splitting countermeasure Rizzo/Duong-Beast
+	{ssl, Socket, "H"} ->
+	    receive
+		{ssl, Socket, "ello world"} ->
+		    ok
+	    end
+    end,
+    {error, renegotiation_rejected} = ssl:renegotiate(Socket),
+    {error, renegotiation_rejected} = ssl:renegotiate(Socket),
+    ct:sleep(?RENEGOTIATION_DISABLE_TIME +1),
+    {error, renegotiation_rejected} = ssl:renegotiate(Socket),
+    ct:log("Failed to renegotiate again"),
+    ssl:send(Socket, "Hello world"),
+    ok.
+
     
 new_config(PrivDir, ServerOpts0) ->
     CaCertFile = proplists:get_value(cacertfile, ServerOpts0),