From a528fe4f942af8fc03973ac3925ee2649387fb32 Mon Sep 17 00:00:00 2001
From: Olivier Lemasle <olivier.lemasle@apalia.net>
Date: Mon, 2 Jan 2023 17:21:55 +0100
Subject: [PATCH] Fix panic for some invalid custom metric requests

This refactors the handling of metrics related to namespaces, by moving
the logic from the storage part to the handler. This allows the handler
to perform validation of the request.
---
 pkg/apiserver/endpoints/handlers/get.go    | 23 ++++++++++++++++++++++
 pkg/registry/custom_metrics/reststorage.go |  9 ---------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/pkg/apiserver/endpoints/handlers/get.go b/pkg/apiserver/endpoints/handlers/get.go
index 0f4ad95b..1ce71623 100644
--- a/pkg/apiserver/endpoints/handlers/get.go
+++ b/pkg/apiserver/endpoints/handlers/get.go
@@ -41,6 +41,29 @@ func ListResourceWithOptions(r cm_rest.ListerWithOptions, scope handlers.Request
 		// For performance tracking purposes.
 		trace := utiltrace.New("List " + req.URL.Path)
 
+		requestInfo, ok := request.RequestInfoFrom(req.Context())
+		if !ok {
+			err := errors.NewBadRequest("missing requestInfo")
+			writeError(&scope, err, w, req)
+			return
+		}
+
+		// handle metrics describing namespaces
+		if requestInfo.Namespace != "" && requestInfo.Resource == "metrics" {
+			requestInfo.Subresource = requestInfo.Name
+			requestInfo.Name = requestInfo.Namespace
+			requestInfo.Resource = "namespaces"
+			requestInfo.Namespace = ""
+			requestInfo.Parts = append([]string{"namespaces", requestInfo.Name}, requestInfo.Parts[1:]...)
+		}
+
+		// handle invalid requests, e.g. /namespaces/name/foo
+		if len(requestInfo.Parts) < 3 {
+			err := errors.NewBadRequest("invalid request path")
+			writeError(&scope, err, w, req)
+			return
+		}
+
 		namespace, err := scope.Namer.Namespace(req)
 		if err != nil {
 			writeError(&scope, err, w, req)
diff --git a/pkg/registry/custom_metrics/reststorage.go b/pkg/registry/custom_metrics/reststorage.go
index 79b27a23..1b703eef 100644
--- a/pkg/registry/custom_metrics/reststorage.go
+++ b/pkg/registry/custom_metrics/reststorage.go
@@ -112,15 +112,6 @@ func (r *REST) List(ctx context.Context, options *metainternalversion.ListOption
 
 	groupResource := schema.ParseGroupResource(resourceRaw)
 
-	// handle metrics describing namespaces
-	if namespace != "" && resourceRaw == "metrics" {
-		// namespace-describing metrics have a path of /namespaces/$NS/metrics/$metric,
-		groupResource = schema.GroupResource{Resource: "namespaces"}
-		metricName = name
-		name = namespace
-		namespace = ""
-	}
-
 	var res *custom_metrics.MetricValueList
 	var err error