rbac: add support for matching on route metadata (#36957)

## Background

This PR adds a new option called `sourced_metadata` to RBAC permissions
and principals which allows specifying an optional source for the
metadata to be matched. Currently it only supports Dynamic Metadata and
Route Metadata. More options could be added later.

**Fixes:** #34913

---

**Commit Message:** rbac: add support for matching on route metadata
**Additional Description:** This PR adds a new option called
`sourced_metadata` to RBAC permissions and principals which allows
specifying an optional source for the metadata to be matched.
**Risk Level:** Low
**Testing:** Added Unit & Integration Tests
**Docs Changes:** Added
**Release Notes:** Added

---------

Signed-off-by: Rohit Agrawal <rohit.agrawal@databricks.com>

Mirrored from https://github.com/envoyproxy/envoy @ 8aabe0f9ae2834985f92b6a5e378a8c93bce0c7c

envoy/config/rbac/v3/rbac.proto

@@ -28,6 +28,14 @@ option (udpa.annotations.file_status).package_version_status = ACTIVE;
 
 // [#protodoc-title: Role Based Access Control (RBAC)]
 
+enum MetadataSource {
+  // Query :ref:`dynamic metadata <well_known_dynamic_metadata>`
+  DYNAMIC = 0;
+
+  // Query :ref:`route metadata <envoy_v3_api_field_config.route.v3.Route.metadata>`
+  ROUTE = 1;
+}
+
 // Role Based Access Control (RBAC) provides service-level and method-level access control for a
 // service. Requests are allowed or denied based on the ``action`` and whether a matching policy is
 // found. For instance, if the action is ALLOW and a matching policy is found the request should be
@@ -193,8 +201,27 @@ message Policy {
       [(udpa.annotations.field_migrate).oneof_promotion = "expression_specifier"];
 }
 
+// SourcedMetadata enables matching against metadata from different sources in the request processing
+// pipeline. It extends the base MetadataMatcher functionality by allowing specification of where the
+// metadata should be sourced from, rather than only matching against dynamic metadata.
+//
+// The matcher can be configured to look up metadata from:
+// * Dynamic metadata: Runtime metadata added by filters during request processing
+// * Route metadata: Static metadata configured on the route entry
+message SourcedMetadata {
+  // Metadata matcher configuration that defines what metadata to match against. This includes the filter name,
+  // metadata key path, and expected value.
+  type.matcher.v3.MetadataMatcher metadata_matcher = 1
+      [(validate.rules).message = {required: true}];
+
+  // Specifies which metadata source should be used for matching. If not set,
+  // defaults to DYNAMIC (dynamic metadata). Set to ROUTE to match against
+  // static metadata configured on the route entry.
+  MetadataSource metadata_source = 2 [(validate.rules).enum = {defined_only: true}];
+}
+
 // Permission defines an action (or actions) that a principal can take.
-// [#next-free-field: 14]
+// [#next-free-field: 15]
 message Permission {
   option (udpa.annotations.versioning).previous_message_type = "envoy.config.rbac.v2.Permission";
 
@@ -237,8 +264,10 @@ message Permission {
     // A port number range that describes a range of destination ports connecting to.
     type.v3.Int32Range destination_port_range = 11;
 
-    // Metadata that describes additional information about the action.
-    type.matcher.v3.MetadataMatcher metadata = 7;
+    // Metadata that describes additional information about the action. This field is deprecated; please use
+    // :ref:`sourced_metadata<envoy_v3_api_field_config.rbac.v3.Permission.sourced_metadata>` instead.
+    type.matcher.v3.MetadataMatcher metadata = 7
+        [deprecated = true, (envoy.annotations.deprecated_at_minor_version) = "3.0"];
 
     // Negates matching the provided permission. For instance, if the value of
     // ``not_rule`` would match, this permission would not match. Conversely, if
@@ -274,12 +303,16 @@ message Permission {
     // URI template path matching.
     // [#extension-category: envoy.path.match]
     core.v3.TypedExtensionConfig uri_template = 13;
+
+    // Matches against metadata from either dynamic state or route configuration. Preferred over the
+    // ``metadata`` field as it provides more flexibility in metadata source selection.
+    SourcedMetadata sourced_metadata = 14;
   }
 }
 
 // Principal defines an identity or a group of identities for a downstream
 // subject.
-// [#next-free-field: 13]
+// [#next-free-field: 14]
 message Principal {
   option (udpa.annotations.versioning).previous_message_type = "envoy.config.rbac.v2.Principal";
 
@@ -356,8 +389,10 @@ message Principal {
     // A URL path on the incoming HTTP request. Only available for HTTP.
     type.matcher.v3.PathMatcher url_path = 9;
 
-    // Metadata that describes additional information about the principal.
-    type.matcher.v3.MetadataMatcher metadata = 7;
+    // Metadata that describes additional information about the principal. This field is deprecated; please use
+    // :ref:`sourced_metadata<envoy_v3_api_field_config.rbac.v3.Principal.sourced_metadata>` instead.
+    type.matcher.v3.MetadataMatcher metadata = 7
+        [deprecated = true, (envoy.annotations.deprecated_at_minor_version) = "3.0"];
 
     // Identifies the principal using a filter state object.
     type.matcher.v3.FilterStateMatcher filter_state = 12;
@@ -366,6 +401,10 @@ message Principal {
     // ``not_id`` would match, this principal would not match. Conversely, if the
     // value of ``not_id`` would not match, this principal would match.
     Principal not_id = 8;
+
+    // Matches against metadata from either dynamic state or route configuration. Preferred over the
+    // ``metadata`` field as it provides more flexibility in metadata source selection.
+    SourcedMetadata sourced_metadata = 13;
   }
 }