fix(emqx_schema): move tls version gap validation to emqx_schema

apps/emqx/src/emqx_schema.erl

@@ -2679,10 +2679,30 @@ validate_ciphers(Ciphers) ->
 validate_tls_versions(Collection, Versions) ->
     AvailableVersions = available_tls_vsns(Collection),
     case lists:filter(fun(V) -> not lists:member(V, AvailableVersions) end, Versions) of
-        [] -> ok;
+        [] -> validate_tls_version_gap(Versions);
         Vs -> {error, {unsupported_tls_versions, Vs}}
     end.
 
+%% See also `validate_version_gap/1` in OTP ssl.erl,
+%% e.g: https://github.com/emqx/otp/blob/emqx-OTP-25.1.2/lib/ssl/src/ssl.erl#L2566.
+%% Do not allow configuration of TLS 1.3 with a gap where TLS 1.2 is not supported
+%% as that configuration can trigger the built in version downgrade protection
+%% mechanism and the handshake can fail with an Illegal Parameter alert.
+validate_tls_version_gap(Versions) ->
+    case lists:member('tlsv1.3', Versions) of
+        true when length(Versions) >= 2 ->
+            case lists:member('tlsv1.2', Versions) of
+                true ->
+                    ok;
+                false ->
+                    {error,
+                        "Using multiple versions that include tlsv1.3 but "
+                        "exclude tlsv1.2 is not allowed"}
+            end;
+        _ ->
+            ok
+    end.
+
 validations() ->
     [
         {check_process_watermark, fun check_process_watermark/1},

apps/emqx/src/emqx_tls_lib.erl

@@ -556,33 +556,9 @@ resolve_cert_path_for_read_strict(Path) ->
 resolve_cert_path_for_read(Path) ->
     emqx_schema:naive_env_interpolation(Path).
 
-ensure_valid_options(Options, Versions0) ->
-    Versions = validate_version_gap(Versions0),
+ensure_valid_options(Options, Versions) ->
     ensure_valid_options(Options, Versions, []).
 
-%% See also lib/ssl/src/ssl.erl#L2617.
-%% Do not allow configuration of TLS 1.3 with a gap where TLS 1.2 is not supported
-%% as that configuration can trigger the built in version downgrade protection
-%% mechanism and the handshake can fail with an Illegal Parameter alert.
-validate_version_gap(Versions) ->
-    case lists:member('tlsv1.3', Versions) of
-        true when length(Versions) >= 2 ->
-            case lists:member('tlsv1.2', Versions) of
-                true ->
-                    Versions;
-                false ->
-                    NewVersions = ['tlsv1.3'],
-                    ?SLOG(warning, #{
-                        msg => "tlsv13_version_gap",
-                        versions => Versions,
-                        new_versions => NewVersions
-                    }),
-                    NewVersions
-            end;
-        _ ->
-            Versions
-    end.
-
 ensure_valid_options([], _, Acc) ->
     lists:reverse(Acc);
 ensure_valid_options([{_, undefined} | T], Versions, Acc) ->
@@ -607,7 +583,7 @@ ensure_valid_options([{K, V} | T], Versions, Acc) ->
             end
     end.
 
-%% see lib/ssl/src/ssl.erl, assert_option_dependency/4
+%% see otp/lib/ssl/src/ssl.erl, `assert_option_dependency/4`
 tls_option_compatible_versions(beast_mitigation) ->
     [dtlsv1, 'tlsv1'];
 tls_option_compatible_versions(padding_check) ->

apps/emqx/test/emqx_schema_tests.erl

@@ -94,6 +94,18 @@ ssl_opts_tls_psk_test() ->
     Checked = validate(Sc, #{<<"versions">> => [<<"tlsv1.2">>]}),
     ?assertMatch(#{versions := ['tlsv1.2']}, Checked).
 
+ssl_opts_version_gap_test_() ->
+    Sc = emqx_schema:server_ssl_opts_schema(#{}, false),
+    RanchSc = emqx_schema:server_ssl_opts_schema(#{}, true),
+    Reason = "Using multiple versions that include tlsv1.3 but exclude tlsv1.2 is not allowed",
+    [
+        ?_assertThrow(
+            {_, [#{kind := validation_error, reason := Reason}]},
+            validate(S, #{<<"versions">> => [<<"tlsv1.1">>, <<"tlsv1.3">>]})
+        )
+     || S <- [Sc, RanchSc]
+    ].
+
 bad_cipher_test() ->
     Sc = emqx_schema:server_ssl_opts_schema(#{}, false),
     Reason = {bad_ciphers, ["foo"]},

changes/ce/fix-11028.en.md

@@ -0,0 +1,7 @@
+Disallow using multiple TLS versions in the listener config that include tlsv1.3 but exclude tlsv1.2.
+
+Using TLS configuration with such version gap caused connection errors.
+Additionally, drop and log TLS options that are incompatible with the selected TLS version(s).
+
+Note: any old listener configuration with the version gap described above will fail to load
+after applying this fix and must be manually fixed.