feat(googlereader)!: remove CORS handler

The Google Reader API is not supposed to be used by web clients.

Removing CORS should not break any Google Reader client and it
reduces the attack surface.

internal/googlereader/handler.go

@@ -47,9 +47,7 @@ func Serve(router *mux.Router, store *storage.Storage) {
 
 	middleware := newMiddleware(store)
 	sr := router.PathPrefix("/reader/api/0").Subrouter()
-	sr.Use(middleware.handleCORS)
 	sr.Use(middleware.apiKeyAuth)
-	sr.Methods(http.MethodOptions)
 	sr.HandleFunc("/token", handler.tokenHandler).Methods(http.MethodGet).Name("Token")
 	sr.HandleFunc("/edit-tag", handler.editTagHandler).Methods(http.MethodPost).Name("EditTag")
 	sr.HandleFunc("/rename-tag", handler.renameTagHandler).Methods(http.MethodPost).Name("Rename Tag")

internal/googlereader/middleware.go

@@ -25,19 +25,6 @@ func newMiddleware(s *storage.Storage) *middleware {
 	return &middleware{s}
 }
 
-func (m *middleware) handleCORS(next http.Handler) http.Handler {
-	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		w.Header().Set("Access-Control-Allow-Origin", "*")
-		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
-		w.Header().Set("Access-Control-Allow-Headers", "Authorization")
-		if r.Method == http.MethodOptions {
-			w.WriteHeader(http.StatusOK)
-			return
-		}
-		next.ServeHTTP(w, r)
-	})
-}
-
 func (m *middleware) apiKeyAuth(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		clientIP := request.ClientIP(r)