feat(tls-partial-chain): support CAcert renewal

The listener could support two versions of CAcerts if partial_chain is set to `two_cacerts_from_cacertfile`

src/emqx_const_v2.erl

@@ -21,7 +21,25 @@
 -export([ make_tls_root_fun/2
         ]).
 
-make_tls_root_fun(cacert_from_cacertfile, CADer) ->
+%% @doc Build a root fun for verify TLS partial_chain.
-    fun(_InputChain) ->
+%% The `InputChain' is composed by OTP SSL with local cert store
-            {trusted_ca, CADer}
+%% AND the cert (chain if any) from the client.
-    end.
+%% @end
+make_tls_root_fun(cacert_from_cacertfile, [Trusted]) ->
+  %% Allow only one trusted ca cert, and just return the defined trusted CA cert,
+  fun(_InputChain) ->
+      %% Note, returing `trusted_ca` doesn't really mean it accepts the connection
+      %% OTP SSL app will do the path validation, signature validation subsequently.
+      {trusted_ca, Trusted}
+  end;
+make_tls_root_fun(cacert_from_cacertfile, [TrustedOne, TrustedTwo]) ->
+  %% Allow two trusted CA certs in case of CA cert renewal
+  %% This is a little expensive call as it compares the binaries.
+  fun(InputChain) ->
+      case lists:member(TrustedOne, InputChain) of
+        true ->
+          {trusted_ca, TrustedOne};
+        false ->
+          {trusted_ca, TrustedTwo}
+      end
+  end.

src/emqx_tls_lib.erl

@@ -191,26 +191,31 @@ opt_partial_chain(SslOpts) ->
         false ->
             SslOpts;
         V when V =:= cacert_from_cacertfile orelse V == true ->
-            replace(SslOpts, partial_chain, rootfun_trusted_ca_from_cacertfile(SslOpts))
+            replace(SslOpts, partial_chain, rootfun_trusted_ca_from_cacertfile(1, SslOpts));
+        V when V =:= two_cacerts_from_cacertfile -> %% for certificate rotations
+            replace(SslOpts, partial_chain, rootfun_trusted_ca_from_cacertfile(2, SslOpts))
     end.
 
 replace(Opts, Key, Value) -> [{Key, Value} | proplists:delete(Key, Opts)].
 
 %% @doc Helper, make TLS root_fun
-rootfun_trusted_ca_from_cacertfile(SslOpts) ->
+rootfun_trusted_ca_from_cacertfile(NumOfCerts, SslOpts) ->
     Cacertfile = proplists:get_value(cacertfile, SslOpts, undefined),
-    try do_rootfun_trusted_ca_from_cacertfile(Cacertfile)
+    try do_rootfun_trusted_ca_from_cacertfile(NumOfCerts, Cacertfile)
     catch _Error:_Info:ST ->
             %% The cacertfile will be checked by OTP SSL as well and OTP choice to be silent on this.
             %% We are touching security sutffs, don't leak extra info..
             ?LOG(error, "Failed to look for trusted cacert from cacertfile. Stacktrace: ~p", [ST]),
             throw({error, ?FUNCTION_NAME})
     end.
-do_rootfun_trusted_ca_from_cacertfile(Cacertfile) ->
+do_rootfun_trusted_ca_from_cacertfile(NumOfCerts, Cacertfile) ->
     {ok, PemBin} = file:read_file(Cacertfile),
-    %% The last one should be the top parent in the chain if it is a chain
+    %% The last one or two should be the top parent in the chain if it is a chain
-    {'Certificate', CADer, _} = lists:last(public_key:pem_decode(PemBin)),
+    Certs = public_key:pem_decode(PemBin),
-    emqx_const_v2:make_tls_root_fun(cacert_from_cacertfile, CADer).
+    Pos = length(Certs) - NumOfCerts + 1,
+    Trusted = [ CADer || {'Certificate', CADer, _} <-
+                             lists:sublist(public_key:pem_decode(PemBin), Pos, NumOfCerts)],
+    emqx_const_v2:make_tls_root_fun(cacert_from_cacertfile, Trusted).
 
 -if(?OTP_RELEASE > 22).
 -ifdef(TEST).

test/emqx_listener_tls_verify_partial_chain_SUITE.erl

@@ -115,7 +115,56 @@ t_conn_fail_with_renewed_intermediate_cacert_and_client_using_old_bundle(Config)
   fail_when_no_ssl_alert(Socket, unknown_ca),
   ssl:close(Socket).
 
-%%@TODO limitation: EMQX is not able to check if the trusted CAcert and the old CAcert belongs to same CA.
+t_conn_success_with_old_and_renewed_intermediate_cacert_and_client_provides_renewed_client_cert(Config) ->
+  Port = emqx_test_tls_certs_helper:select_free_port(ssl),
+  DataDir = ?config(data_dir, Config),
+  Options = [{ssl_options, [ {cacertfile, filename:join(DataDir, "intermediate2_renewed_old-bundle.pem")}
+                           , {certfile, filename:join(DataDir, "server2.pem")}
+                           , {keyfile, filename:join(DataDir, "server2.key")}
+                           , {partial_chain, two_cacerts_from_cacertfile}
+                           | ?config(ssl_config, Config)
+                           ]}],
+  emqx_listeners:start_listener(ssl, Port, Options),
+  {ok, Socket} = ssl:connect({127, 0, 0, 1}, Port, [{keyfile,  filename:join(DataDir, "client2.key")},
+                                                    {certfile, filename:join(DataDir, "client2_renewed.pem")}
+                                                   ], 1000),
+  fail_when_ssl_error(Socket),
+  ssl:close(Socket).
+
+%% Note, this is good to have for usecase coverage
+t_conn_success_with_new_intermediate_cacert_and_client_provides_renewed_client_cert_signed_by_old_intermediate(Config) ->
+  Port = emqx_test_tls_certs_helper:select_free_port(ssl),
+  DataDir = ?config(data_dir, Config),
+  Options = [{ssl_options, [ {cacertfile, filename:join(DataDir, "intermediate2_renewed.pem")}
+                           , {certfile, filename:join(DataDir, "server2.pem")}
+                           , {keyfile, filename:join(DataDir, "server2.key")}
+                           | ?config(ssl_config, Config)
+                           ]}],
+  emqx_listeners:start_listener(ssl, Port, Options),
+  {ok, Socket} = ssl:connect({127, 0, 0, 1}, Port, [{keyfile,  filename:join(DataDir, "client2.key")},
+                                                    {certfile, filename:join(DataDir, "client2_renewed.pem")}
+                                                   ], 1000),
+  fail_when_ssl_error(Socket),
+  ssl:close(Socket).
+
+%% @doc server should build a partial_chain with old version of ca cert.
+t_conn_success_with_old_and_renewed_intermediate_cacert_and_client_provides_client_cert(Config) ->
+  Port = emqx_test_tls_certs_helper:select_free_port(ssl),
+  DataDir = ?config(data_dir, Config),
+  Options = [{ssl_options, [ {cacertfile, filename:join(DataDir, "intermediate2_renewed_old-bundle.pem")}
+                           , {certfile, filename:join(DataDir, "server2.pem")}
+                           , {keyfile, filename:join(DataDir, "server2.key")}
+                           , {partial_chain, two_cacerts_from_cacertfile}
+                           | ?config(ssl_config, Config)
+                           ]}],
+  emqx_listeners:start_listener(ssl, Port, Options),
+  {ok, Socket} = ssl:connect({127, 0, 0, 1}, Port, [{keyfile,  filename:join(DataDir, "client2.key")},
+                                                    {certfile, filename:join(DataDir, "client2.pem")}
+                                                   ], 1000),
+  fail_when_ssl_error(Socket),
+  ssl:close(Socket).
+
+%% @doc verify when config does not allow two versions of certs from same trusted CA.
 t_conn_fail_with_renewed_and_old_intermediate_cacert_and_client_using_old_bundle(Config) ->
   Port = emqx_test_tls_certs_helper:select_free_port(ssl),
   DataDir = ?config(data_dir, Config),
@@ -131,6 +180,44 @@ t_conn_fail_with_renewed_and_old_intermediate_cacert_and_client_using_old_bundle
   fail_when_no_ssl_alert(Socket, unknown_ca),
   ssl:close(Socket).
 
+%% @doc verify when config (two_cacerts_from_cacertfile) allows two versions of certs from same trusted CA.
+t_conn_success_with_old_and_renewed_intermediate_cacert_bundle_and_client_using_old_bundle(Config) ->
+  Port = emqx_test_tls_certs_helper:select_free_port(ssl),
+  DataDir = ?config(data_dir, Config),
+  Options = [{ssl_options, [ {cacertfile, filename:join(DataDir, "intermediate2_renewed_old-bundle.pem")}
+                           , {certfile, filename:join(DataDir, "server2.pem")}
+                           , {keyfile, filename:join(DataDir, "server2.key")}
+                           , {partial_chain, two_cacerts_from_cacertfile}
+                           | ?config(ssl_config, Config)
+                           ]}],
+  emqx_listeners:start_listener(ssl, Port, Options),
+  {ok, Socket} = ssl:connect({127, 0, 0, 1}, Port, [{keyfile,  filename:join(DataDir, "client2.key")},
+                                                    {certfile, filename:join(DataDir, "client2-intermediate2-bundle.pem")}
+                                                   ], 1000),
+  fail_when_ssl_error(Socket),
+  ssl:close(Socket).
+
+%% @doc: verify even if listener has old/new intermediate2 certs,
+%%       client1 should not able to connect with old intermediate2 cert.
+%%  In this case, listener verify_fun returns {trusted_ca, Oldintermediate2Cert} but OTP should still fail the validation
+%%  since the client1 cert is not signed by Oldintermediate2Cert (trusted CA cert).
+%% @end
+t_fail_success_with_old_and_renewed_intermediate_cacert_bundle_and_client_using_all_CAcerts(Config) ->
+  Port = emqx_test_tls_certs_helper:select_free_port(ssl),
+  DataDir = ?config(data_dir, Config),
+  Options = [{ssl_options, [ {cacertfile, filename:join(DataDir, "intermediate2_renewed_old-bundle.pem")}
+                           , {certfile, filename:join(DataDir, "server2.pem")}
+                           , {keyfile, filename:join(DataDir, "server2.key")}
+                           , {partial_chain, two_cacerts_from_cacertfile}
+                           | ?config(ssl_config, Config)
+                           ]}],
+  emqx_listeners:start_listener(ssl, Port, Options),
+  {ok, Socket} = ssl:connect({127, 0, 0, 1}, Port, [{keyfile,  filename:join(DataDir, "client1.key")},
+                                                    {certfile, filename:join(DataDir, "all-CAcerts-bundle.pem")}
+                                                   ], 1000),
+  fail_when_no_ssl_alert(Socket, unknown_ca),
+  ssl:close(Socket).
+
 t_conn_fail_with_renewed_intermediate_cacert_other_client(Config) ->
   Port = emqx_test_tls_certs_helper:select_free_port(ssl),
   DataDir = ?config(data_dir, Config),

test/emqx_test_tls_certs_helper.erl

@@ -214,6 +214,8 @@ generate_tls_certs(Config) ->
   gen_host_cert("client1", "intermediate1", DataDir),
   gen_host_cert("server2", "intermediate2", DataDir),
   gen_host_cert("client2", "intermediate2", DataDir),
+
+  %% Build bundles below
   os:cmd(io_lib:format("cat ~p ~p ~p > ~p", [filename:join(DataDir, "client2.pem"),
                                              filename:join(DataDir, "intermediate2.pem"),
                                              filename:join(DataDir, "root.pem"),