[xDS] Protect RBAC audit logging options field with environment varia…

…ble. (#33004)

The protection is added at `xds_http_rbac_filter.cc` where we read the
new field. With this disabling the feature, nothing from things like
`xds_audit_logger_registry.cc` shall be invoked.

src/core/ext/xds/xds_http_rbac_filter.cc

@@ -49,13 +49,24 @@
 #include "src/core/ext/xds/xds_bootstrap_grpc.h"
 #include "src/core/ext/xds/xds_client.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/gpr/string.h"
+#include "src/core/lib/gprpp/env.h"
 #include "src/core/lib/json/json.h"
 #include "src/core/lib/json/json_writer.h"
 
 namespace grpc_core {
 
 namespace {
 
+// TODO(lwge): Remove once the feature is stable.
+bool XdsRbacAuditLoggingEnabled() {
+  auto value = GetEnv("GRPC_EXPERIMENTAL_XDS_RBAC_AUDIT_LOGGING");
+  if (!value.has_value()) return false;
+  bool parsed_value;
+  bool parse_succeeded = gpr_parse_bool_value(value->c_str(), &parsed_value);
+  return parse_succeeded && parsed_value;
+}
+
 Json ParseRegexMatcherToJson(
     const envoy_type_matcher_v3_RegexMatcher* regex_matcher) {
   return Json::FromObject(
@@ -453,7 +464,8 @@ Json ParseHttpRbacToJson(const XdsResourceType::DecodeContext& context,
                               Json::FromObject(std::move(policies_object)));
     }
     // Flatten the nested messages defined in rbac.proto
-    if (envoy_config_rbac_v3_RBAC_has_audit_logging_options(rules)) {
+    if (XdsRbacAuditLoggingEnabled() &&
+        envoy_config_rbac_v3_RBAC_has_audit_logging_options(rules)) {
       ValidationErrors::ScopedField field(errors, ".audit_logging_options");
       const auto* audit_logging_options =
           envoy_config_rbac_v3_RBAC_audit_logging_options(rules);

test/core/xds/BUILD

@@ -243,6 +243,7 @@ grpc_cc_test(
         "//src/proto/grpc/testing/xds/v3:stateful_session_proto",
         "//src/proto/grpc/testing/xds/v3:typed_struct_proto",
         "//test/core/util:grpc_test_util",
+        "//test/core/util:scoped_env_var",
         "//test/cpp/util:grpc_cli_utils",
     ],
 )

test/core/xds/xds_http_filters_test.cc

@@ -72,6 +72,7 @@
 #include "src/proto/grpc/testing/xds/v3/stateful_session_cookie.pb.h"
 #include "src/proto/grpc/testing/xds/v3/string.pb.h"
 #include "src/proto/grpc/testing/xds/v3/typed_struct.pb.h"
+#include "test/core/util/scoped_env_var.h"
 #include "test/core/util/test_config.h"
 
 // IWYU pragma: no_include <google/protobuf/message.h>
@@ -895,7 +896,31 @@ TEST_P(XdsRbacFilterConfigTest, AllPrincipalTypes) {
             "}}}}");
 }
 
+TEST_P(XdsRbacFilterConfigTest, AuditLoggingOptionsIgnoredWithFeatureDisabled) {
+  RBAC rbac;
+  auto* rules = rbac.mutable_rules();
+  rules->set_action(rules->ALLOW);
+  auto* logging_options = rules->mutable_audit_logging_options();
+  logging_options->set_audit_condition(
+      envoy::config::rbac::v3::RBAC_AuditLoggingOptions_AuditCondition_ON_DENY);
+  envoy::config::rbac::v3::RBAC_AuditLoggingOptions::AuditLoggerConfig
+      logger_config;
+  auto* audit_logger = logger_config.mutable_audit_logger();
+  audit_logger->mutable_typed_config()->set_type_url(
+      "/envoy.extensions.rbac.audit_loggers.stream.v3.StdoutAuditLog");
+  *logging_options->add_logger_configs() = logger_config;
+  auto config = GenerateConfig(rbac);
+  ASSERT_TRUE(errors_.ok()) << errors_.status(
+      absl::StatusCode::kInvalidArgument, "unexpected errors");
+  ASSERT_TRUE(config.has_value());
+  EXPECT_EQ(config->config_proto_type_name,
+            GetParam() ? filter_->OverrideConfigProtoName()
+                       : filter_->ConfigProtoName());
+  EXPECT_EQ(JsonDump(config->config), "{\"rules\":{\"action\":0}}");
+}
+
 TEST_P(XdsRbacFilterConfigTest, AuditLoggingOptions) {
+  ScopedExperimentalEnvVar env_var("GRPC_EXPERIMENTAL_XDS_RBAC_AUDIT_LOGGING");
   RBAC rbac;
   auto* rules = rbac.mutable_rules();
   rules->set_action(rules->ALLOW);
@@ -923,6 +948,7 @@ TEST_P(XdsRbacFilterConfigTest, AuditLoggingOptions) {
 }
 
 TEST_P(XdsRbacFilterConfigTest, InvalidAuditCondition) {
+  ScopedExperimentalEnvVar env_var("GRPC_EXPERIMENTAL_XDS_RBAC_AUDIT_LOGGING");
   RBAC rbac;
   auto* rules = rbac.mutable_rules();
   rules->set_action(rules->ALLOW);
@@ -945,6 +971,7 @@ TEST_P(XdsRbacFilterConfigTest, InvalidAuditCondition) {
 }
 
 TEST_P(XdsRbacFilterConfigTest, InvalidAuditLoggerConfig) {
+  ScopedExperimentalEnvVar env_var("GRPC_EXPERIMENTAL_XDS_RBAC_AUDIT_LOGGING");
   RBAC rbac;
   auto* rules = rbac.mutable_rules();
   rules->set_action(rules->ALLOW);