fix: Allow OPTIONS method on every path

Signed-off-by: Célian Garcia <[email protected]>

Author: celian-garcia

Diff for: injectproxy/routes.go

@@ -315,21 +315,21 @@ func NewRoutes(upstream *url.URL, label string, extractLabeler ExtractLabeler, o
 	mux := newStrictMux(newInstrumentedMux(http.NewServeMux(), opt.registerer))
 
 	errs := merrors.New(
-		mux.Handle("/federate", r.el.ExtractLabel(enforceMethods(r.matcher, "GET"))),
-		mux.Handle("/api/v1/query", r.el.ExtractLabel(enforceMethods(r.query, "GET", "POST"))),
-		mux.Handle("/api/v1/query_range", r.el.ExtractLabel(enforceMethods(r.query, "GET", "POST"))),
-		mux.Handle("/api/v1/alerts", r.el.ExtractLabel(enforceMethods(r.passthrough, "GET"))),
-		mux.Handle("/api/v1/rules", r.el.ExtractLabel(enforceMethods(r.passthrough, "GET"))),
-		mux.Handle("/api/v1/series", r.el.ExtractLabel(enforceMethods(r.matcher, "GET", "POST"))),
-		mux.Handle("/api/v1/query_exemplars", r.el.ExtractLabel(enforceMethods(r.query, "GET", "POST"))),
+		mux.Handle("/federate", r.el.ExtractLabel(enforceMethods(r.matcher, "OPTIONS", "GET"))),
+		mux.Handle("/api/v1/query", r.el.ExtractLabel(enforceMethods(r.query, "OPTIONS", "GET", "POST"))),
+		mux.Handle("/api/v1/query_range", r.el.ExtractLabel(enforceMethods(r.query, "OPTIONS", "GET", "POST"))),
+		mux.Handle("/api/v1/alerts", r.el.ExtractLabel(enforceMethods(r.passthrough, "OPTIONS", "GET"))),
+		mux.Handle("/api/v1/rules", r.el.ExtractLabel(enforceMethods(r.passthrough, "OPTIONS", "GET"))),
+		mux.Handle("/api/v1/series", r.el.ExtractLabel(enforceMethods(r.matcher, "OPTIONS", "GET", "POST"))),
+		mux.Handle("/api/v1/query_exemplars", r.el.ExtractLabel(enforceMethods(r.query, "OPTIONS", "GET", "POST"))),
 	)
 
 	if opt.enableLabelAPIs {
 		errs.Add(
-			mux.Handle("/api/v1/labels", r.el.ExtractLabel(enforceMethods(r.matcher, "GET", "POST"))),
+			mux.Handle("/api/v1/labels", r.el.ExtractLabel(enforceMethods(r.matcher, "OPTIONS", "GET", "POST"))),
 			// Full path is /api/v1/label/<label_name>/values but http mux does not support patterns.
 			// This is fine though as we don't care about name for matcher injector.
-			mux.Handle("/api/v1/label/", r.el.ExtractLabel(enforceMethods(r.matcher, "GET"))),
+			mux.Handle("/api/v1/label/", r.el.ExtractLabel(enforceMethods(r.matcher, "OPTIONS", "GET"))),
 		)
 	}
 
@@ -340,20 +340,20 @@ func NewRoutes(upstream *url.URL, label string, extractLabeler ExtractLabeler, o
 			r.errorIfRegexpMatch(
 				enforceMethods(
 					assertSingleLabelValue(r.silences),
-					"GET", "POST",
+					"OPTIONS", "GET", "POST",
 				),
 			),
 		)),
 		mux.Handle("/api/v2/silence/", r.el.ExtractLabel(
 			r.errorIfRegexpMatch(
 				enforceMethods(
 					assertSingleLabelValue(r.deleteSilence),
-					"DELETE",
+					"OPTIONS", "DELETE",
 				),
 			),
 		)),
-		mux.Handle("/api/v2/alerts/groups", r.el.ExtractLabel(enforceMethods(r.enforceFilterParameter, "GET"))),
-		mux.Handle("/api/v2/alerts", r.el.ExtractLabel(enforceMethods(r.alerts, "GET"))),
+		mux.Handle("/api/v2/alerts/groups", r.el.ExtractLabel(enforceMethods(r.enforceFilterParameter, "OPTIONS", "GET"))),
+		mux.Handle("/api/v2/alerts", r.el.ExtractLabel(enforceMethods(r.alerts, "OPTIONS", "GET"))),
 	)
 
 	errs.Add(