From 8c7eee2ba9c9b06d5781b794718359bf5f8e550a Mon Sep 17 00:00:00 2001
From: Oliver Gugger <gugger@gmail.com>
Date: Thu, 6 Feb 2020 11:48:09 +0100
Subject: [PATCH 1/2] loopd: add option to configure CORS origin

---
 loopd/config.go |  1 +
 loopd/daemon.go | 15 ++++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/loopd/config.go b/loopd/config.go
index 3fb05fb..9aa313b 100644
--- a/loopd/config.go
+++ b/loopd/config.go
@@ -35,6 +35,7 @@ type config struct {
 	TLSPathSwapSrv string `long:"tlspathswapserver" description:"Path to swap server tls certificate. Only needed if the swap server uses a self-signed certificate."`
 	RPCListen      string `long:"rpclisten" description:"Address to listen on for gRPC clients"`
 	RESTListen     string `long:"restlisten" description:"Address to listen on for REST clients"`
+	CORSOrigin     string `long:"corsorigin" description:"The value to send in the Access-Control-Allow-Origin header. Header will be omitted if empty."`
 
 	LogDir         string `long:"logdir" description:"Directory to log output."`
 	MaxLogFiles    int    `long:"maxlogfiles" description:"Maximum logfiles to keep (0 for no rotation)"`
diff --git a/loopd/daemon.go b/loopd/daemon.go
index 358841e..f226331 100644
--- a/loopd/daemon.go
+++ b/loopd/daemon.go
@@ -119,6 +119,10 @@ func daemon(config *config, lisCfg *listenerCfg) error {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 	mux := proxy.NewServeMux(customMarshalerOption)
+	var restHandler http.Handler = mux
+	if config.CORSOrigin != "" {
+		restHandler = allowCORS(restHandler, config.CORSOrigin)
+	}
 	proxyOpts := []grpc.DialOption{
 		grpc.WithInsecure(),
 		grpc.WithDefaultCallOptions(maxMsgRecvSize),
@@ -141,7 +145,7 @@ func daemon(config *config, lisCfg *listenerCfg) error {
 		log.Infof("Starting REST proxy listener")
 
 		defer restListener.Close()
-		proxy := &http.Server{Handler: mux}
+		proxy := &http.Server{Handler: restHandler}
 
 		go func() {
 			err := proxy.Serve(restListener)
@@ -225,3 +229,12 @@ func daemon(config *config, lisCfg *listenerCfg) error {
 
 	return nil
 }
+
+// allowCORS wraps the given http.Handler with a function that adds the
+// Access-Control-Allow-Origin header to the response.
+func allowCORS(handler http.Handler, origin string) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Access-Control-Allow-Origin", origin)
+		handler.ServeHTTP(w, r)
+	})
+}

From ae376a49ba75c4fc68015a91e612736a081e5be6 Mon Sep 17 00:00:00 2001
From: Oliver Gugger <gugger@gmail.com>
Date: Thu, 6 Feb 2020 11:59:48 +0100
Subject: [PATCH 2/2] loopd: fix linter issue

---
 loopd/daemon.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/loopd/daemon.go b/loopd/daemon.go
index f226331..9ba8e76 100644
--- a/loopd/daemon.go
+++ b/loopd/daemon.go
@@ -218,7 +218,7 @@ func daemon(config *config, lisCfg *listenerCfg) error {
 		// Debug code to dump goroutines on hanging exit.
 		go func() {
 			time.Sleep(5 * time.Second)
-			pprof.Lookup("goroutine").WriteTo(os.Stdout, 1)
+			_ = pprof.Lookup("goroutine").WriteTo(os.Stdout, 1)
 		}()
 
 		cancel()