rbac: add method name to :path in headers

internal/xds/rbac/rbac_engine.go

@@ -219,6 +219,9 @@ func newRPCData(ctx context.Context) (*rpcData, error) {
 	if !ok {
 		return nil, errors.New("missing method in incoming context")
 	}
+	// gRPC-Go strips :path from the headers given to the application, but RBAC should be
+	// able to match against it.
+	md[":path"] = []string{mn}
 
 	// The connection is needed in order to find the destination address and
 	// port of the incoming RPC Call.

test/xds/xds_server_rbac_test.go

@@ -478,6 +478,30 @@ func (s) TestRBACHTTPFilter(t *testing.T) {
 			wantStatusEmptyCall: codes.PermissionDenied,
 			wantStatusUnaryCall: codes.OK,
 		},
+		// This test tests an RBAC HTTP Filter which is configured to allow only
+		// RPC's with certain paths ("UnaryCall") via the ":path" header. Only
+		// unary calls passing through this RBAC HTTP Filter should proceed as
+		// normal, and any others should be denied.
+		{
+			name: "allow-certain-path-by-header",
+			rbacCfg: &rpb.RBAC{
+				Rules: &v3rbacpb.RBAC{
+					Action: v3rbacpb.RBAC_ALLOW,
+					Policies: map[string]*v3rbacpb.Policy{
+						"certain-path": {
+							Permissions: []*v3rbacpb.Permission{
+								{Rule: &v3rbacpb.Permission_Header{Header: &v3routepb.HeaderMatcher{Name: ":path", HeaderMatchSpecifier: &v3routepb.HeaderMatcher_ExactMatch{ExactMatch: "/grpc.testing.TestService/UnaryCall"}}}},
+							},
+							Principals: []*v3rbacpb.Principal{
+								{Identifier: &v3rbacpb.Principal_Any{Any: true}},
+							},
+						},
+					},
+				},
+			},
+			wantStatusEmptyCall: codes.PermissionDenied,
+			wantStatusUnaryCall: codes.OK,
+		},
 		// This test that a RBAC Config with nil rules means that every RPC is
 		// allowed. This maps to the line "If absent, no enforcing RBAC policy
 		// will be applied" from the RBAC Proto documentation for the Rules