[openvsx-proxy] Fix Access-Control-Allow-Origin header for cached values

Author: corneliusludmann

components/openvsx-proxy/pkg/errorhandler.go

@@ -62,6 +62,9 @@ func (o *OpenVSXProxy) ErrorHandler(rw http.ResponseWriter, r *http.Request, e e
 			}
 		}
 	}
+	if v := rw.Header().Get("Access-Control-Allow-Origin"); v != "" && v != "*" {
+		rw.Header().Set("Access-Control-Allow-Origin", r.Header.Get("Origin"))
+	}
 	rw.WriteHeader(cached.StatusCode)
 	rw.Write(cached.Body)
 	log.WithFields(logFields).Info("used cached response due to a proxy error")

components/openvsx-proxy/pkg/handler.go

@@ -85,6 +85,9 @@ func (o *OpenVSXProxy) Handler(p *httputil.ReverseProxy) func(http.ResponseWrite
 								}
 							}
 						}
+						if v := rw.Header().Get("Access-Control-Allow-Origin"); v != "" && v != "*" {
+							rw.Header().Set("Access-Control-Allow-Origin", r.Header.Get("Origin"))
+						}
 						rw.Header().Set("X-Cache", "HIT")
 						rw.WriteHeader(cached.StatusCode)
 						rw.Write(cached.Body)

components/openvsx-proxy/pkg/modifyresponse.go

@@ -81,6 +81,9 @@ func (o *OpenVSXProxy) ModifyResponse(r *http.Response) error {
 			return nil
 		}
 		r.Header = cached.Header
+		if v := r.Header.Get("Access-Control-Allow-Origin"); v != "" && v != "*" {
+			r.Header.Set("Access-Control-Allow-Origin", r.Header.Get("Origin"))
+		}
 		r.Body = ioutil.NopCloser(bytes.NewBuffer(cached.Body))
 		r.ContentLength = int64(len(cached.Body))
 		r.StatusCode = cached.StatusCode