feat(TLS): veriy client cert keyusage

changes/v4.4.19-en.md

@@ -20,6 +20,8 @@
 - Adds a new feature to enable partial certificate chain validation for TLS listeners[#10553](https://github.com/emqx/emqx/pull/10553).
   If partial_chain is set to 'true', the last certificate in cacertfile is treated as the terminal of the certificate trust-chain. That is, the TLS handshake does not require full trust-chain, and EMQX will not try to validate the chain all the way up to the root CA.
 
+- Adds a new feature to enable client certificate extended key usage validation for TLS listeners[#10669](https://github.com/emqx/emqx/pull/10669).
+
 ## Bug fixes
 
 - Fixed an issue where the rule engine was unable to access variables exported by `FOREACH` in the `DO` clause [#10620](https://github.com/emqx/emqx/pull/10620).

changes/v4.4.19-zh.md

@@ -19,6 +19,8 @@
 
 - 增加了一个新的功能，为 TLS 监听器启用部分证书链验证[#10553](https://github.com/emqx/emqx/pull/10553)。
   如果 partial_chain 设置为“true”，cacertfile 中的最后一个证书将被视为证书信任链的顶端证书。 也就是说，TLS 握手不需要完整的链，并且 EMQX 不会尝试一直验证链直到根 CA。
+
+- 增加了一个新功能，为 TLS 监听器启用客户端证书扩展密钥使用验证 [#10669](https://github.com/emqx/emqx/pull/10669)。
 
 ## 修复
 

priv/emqx.schema

@@ -1650,6 +1650,11 @@ end}.
   {datatype, atom}
 ]}.
 
+{mapping, "listener.ssl.$name.verify_peer_ext_key_usage", "emqx.listeners", [
+  {datatype, string},
+  {default, undefined}
+]}.
+
 {mapping, "listener.ssl.$name.fail_if_no_peer_cert", "emqx.listeners", [
   {datatype, {enum, [true, false]}}
 ]}.
@@ -2382,6 +2387,7 @@ end}.
                           {cacertfile, cuttlefish:conf_get(Prefix ++ ".cacertfile", Conf, undefined)},
                           {verify,     cuttlefish:conf_get(Prefix ++ ".verify", Conf, undefined)},
                           {partial_chain, cuttlefish:conf_get(Prefix ++ ".partial_chain", Conf, undefined)},
+                          {verify_peer_ext_key_usage, cuttlefish:conf_get(Prefix ++ ".verify_peer_ext_key_usage", Conf, undefined)},
                           {fail_if_no_peer_cert, cuttlefish:conf_get(Prefix ++ ".fail_if_no_peer_cert", Conf, undefined)},
                           {secure_renegotiate, cuttlefish:conf_get(Prefix ++ ".secure_renegotiate", Conf, undefined)},
                           {reuse_sessions, cuttlefish:conf_get(Prefix ++ ".reuse_sessions", Conf, undefined)},

src/emqx_const_v2.erl

@@ -19,8 +19,10 @@
 -module(emqx_const_v2).
 
 -export([ make_tls_root_fun/2
+        , make_tls_verify_fun/2
         ]).
 
+-include_lib("public_key/include/public_key.hrl").
 %% @doc Build a root fun for verify TLS partial_chain.
 %% The `InputChain' is composed by OTP SSL with local cert store
 %% AND the cert (chain if any) from the client.
@@ -43,3 +45,73 @@ make_tls_root_fun(cacert_from_cacertfile, [TrustedOne, TrustedTwo]) ->
           {trusted_ca, TrustedTwo}
       end
   end.
+
+make_tls_verify_fun(verify_cert_extKeyUsage, KeyUsages) ->
+  AllowedKeyUsages = ext_key_opts(KeyUsages),
+  {fun verify_fun_peer_extKeyUsage/3, AllowedKeyUsages}.
+
+verify_fun_peer_extKeyUsage(_, {bad_cert, invalid_ext_key_usage}, UserState) ->
+  %% !! Override OTP verify peer default
+  %% OTP SSL is unhappy with the ext_key_usage but we will check on our own.
+  {unknown, UserState};
+verify_fun_peer_extKeyUsage(_, {bad_cert, _} = Reason, _UserState) ->
+  %% OTP verify_peer default
+  {fail, Reason};
+verify_fun_peer_extKeyUsage(_, {extension, _}, UserState) ->
+  %% OTP verify_peer default
+  {unknown, UserState};
+verify_fun_peer_extKeyUsage(_, valid, UserState) ->
+  %% OTP verify_peer default
+  {valid, UserState};
+verify_fun_peer_extKeyUsage(#'OTPCertificate'{tbsCertificate = #'OTPTBSCertificate'{extensions = ExtL}},
+                            valid_peer,  %% valid peer cert
+                            AllowedKeyUsages) ->
+  %% override OTP verify_peer default
+  %% must have id-ce-extKeyUsage
+  case lists:keyfind(?'id-ce-extKeyUsage', 2, ExtL) of
+    #'Extension'{extnID = ?'id-ce-extKeyUsage', extnValue = VL} ->
+      case do_verify_ext_key_usage(VL, AllowedKeyUsages) of
+        true ->
+          %% pass the check,
+          %% fallback to OTP verify_peer default
+          {valid, AllowedKeyUsages};
+        false ->
+          {fail, extKeyUsage_unmatched}
+      end;
+    _ ->
+      {fail, extKeyUsage_not_set}
+  end.
+
+%% @doc check required extkeyUsages are presented in the cert
+do_verify_ext_key_usage(_, []) ->
+    %% Verify finished
+    true;
+do_verify_ext_key_usage(CertExtL, [Usage | T] = _Required) ->
+    case lists:member(Usage, CertExtL) of
+        true ->
+            do_verify_ext_key_usage(CertExtL, T);
+        false ->
+            false
+    end.
+
+%% @doc Helper tls cert extension
+-spec ext_key_opts(string()) -> [OidString::string() | public_key:oid()];
+                  (undefined) -> undefined.
+ext_key_opts(Str) ->
+    Usages = string:tokens(Str, ","),
+    lists:map(fun("clientAuth") ->
+                      ?'id-kp-clientAuth';
+                 ("serverAuth") ->
+                      ?'id-kp-serverAuth';
+                 ("codeSigning") ->
+                      ?'id-kp-codeSigning';
+                 ("emailProtection") ->
+                      ?'id-kp-emailProtection';
+                 ("timeStamping") ->
+                      ?'id-kp-timeStamping';
+                 ("ocspSigning") ->
+                      ?'id-kp-OCSPSigning';
+                 ([$O,$I,$D,$: | OidStr]) ->
+                      OidList = string:tokens(OidStr, "."),
+                      list_to_tuple(lists:map(fun list_to_integer/1, OidList))
+              end, Usages).

src/emqx_listeners.erl

@@ -139,7 +139,8 @@ start_listener(Proto, ListenOn, Options0) when Proto == ssl; Proto == tls ->
     ListenerID = proplists:get_value(listener_id, Options0),
     Options1 = proplists:delete(listener_id, Options0),
     Options2 = emqx_ocsp_cache:inject_sni_fun(ListenerID, Options1),
-    Options = emqx_tls_lib:inject_root_fun(Options2),
+    Options3 = emqx_tls_lib:inject_root_fun(Options2),
+    Options = emqx_tls_lib:inject_verify_fun(Options3),
     ok = maybe_register_crl_urls(Options),
     start_mqtt_listener('mqtt:ssl', ListenOn, Options);
 

src/emqx_tls_lib.erl

@@ -23,10 +23,13 @@
         , integral_ciphers/2
         , drop_tls13_for_old_otp/1
         , inject_root_fun/1
+        , inject_verify_fun/1
         , opt_partial_chain/1
+        , opt_verify_fun/1
         ]).
 
 -include("logger.hrl").
+-include_lib("public_key/include/public_key.hrl").
 
 %% non-empty string
 -define(IS_STRING(L), (is_list(L) andalso L =/= [] andalso is_integer(hd(L)))).
@@ -182,6 +185,14 @@ inject_root_fun(Options) ->
             replace(Options, ssl_options, opt_partial_chain(SslOpts))
     end.
 
+inject_verify_fun(Options) ->
+    case proplists:get_value(ssl_options, Options) of
+        undefined ->
+            Options;
+        SslOpts ->
+            replace(Options, ssl_options, emqx_tls_lib:opt_verify_fun(SslOpts))
+    end.
+
 %% @doc enable TLS partial_chain validation if set.
 -spec opt_partial_chain(SslOpts :: proplists:proplist()) -> NewSslOpts :: proplists:proplist().
 opt_partial_chain(SslOpts) ->
@@ -196,6 +207,17 @@ opt_partial_chain(SslOpts) ->
             replace(SslOpts, partial_chain, rootfun_trusted_ca_from_cacertfile(2, SslOpts))
     end.
 
+
+-spec opt_verify_fun(SslOpts :: proplists:proplist()) -> NewSslOpts :: proplists:proplist().
+opt_verify_fun(SslOpts) ->
+    case proplists:get_value(verify_peer_ext_key_usage, SslOpts, undefined) of
+        undefined ->
+            SslOpts;
+        V ->
+            VerifyFun = emqx_const_v2:make_tls_verify_fun(verify_cert_extKeyUsage, V),
+            replace(SslOpts, verify_fun, VerifyFun)
+    end.
+
 replace(Opts, Key, Value) -> [{Key, Value} | proplists:delete(Key, Opts)].
 
 %% @doc Helper, make TLS root_fun