From 729b6d2d0876f9c835e83f09b164827ad66e0136 Mon Sep 17 00:00:00 2001
From: Umputun <umputun@gmail.com>
Date: Mon, 27 Jul 2020 16:58:47 -0500
Subject: [PATCH] add `--proxy-cors` $PROXY_CORS disabling internal cors
 middleware #749

---
 README.md                    |  1 +
 backend/app/cmd/server.go    |  2 ++
 backend/app/rest/api/rest.go | 23 ++++++++++++++---------
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/README.md b/README.md
index ba8991e7..a1208adb 100644
--- a/README.md
+++ b/README.md
@@ -187,6 +187,7 @@ _this is the recommended way to run remark42_
 | image-proxy.cache-external | IMAGE_PROXY_CACHE_EXTERNAL | `false`            | enable caching external images to current image storage |
 | emoji                   | EMOJI                   | `false`                  | enable emoji support                            |
 | simple-view             | SIMPLE_VIEW             | `false`                  | minimized UI with basic info only               |
+| proxy-cors              | PROXY_CORS              | `false`                  | disable internal CORS and delegate it to proxy  |
 | port                    | REMARK_PORT             | `8080`                   | web server port                                 |
 | web-root                | REMARK_WEB_ROOT         | `./web`                  | web server root directory                       |
 | update-limit            | UPDATE_LIMIT            | `0.5`                    | updates/sec limit                               |
diff --git a/backend/app/cmd/server.go b/backend/app/cmd/server.go
index be109042..3c291716 100644
--- a/backend/app/cmd/server.go
+++ b/backend/app/cmd/server.go
@@ -75,6 +75,7 @@ type ServerCommand struct {
 	RestrictedWords  []string      `long:"restricted-words" env:"RESTRICTED_WORDS" description:"words prohibited to use in comments" env-delim:","`
 	EnableEmoji      bool          `long:"emoji" env:"EMOJI" description:"enable emoji"`
 	SimpleView       bool          `long:"simpler-view" env:"SIMPLE_VIEW" description:"minimal comment editor mode"`
+	ProxyCORS        bool          `long:"proxy-cors" env:"PROXY_CORS" description:"disable internal CORS and delegate it to proxy"`
 
 	Auth struct {
 		TTL struct {
@@ -453,6 +454,7 @@ func (s *ServerCommand) newServerApp() (*serverApp, error) {
 		EmojiEnabled:       s.EnableEmoji,
 		AnonVote:           s.AnonymousVote && s.RestrictVoteIP,
 		SimpleView:         s.SimpleView,
+		ProxyCORS:          s.ProxyCORS,
 	}
 
 	// enable admin notifications only if admin email is set
diff --git a/backend/app/rest/api/rest.go b/backend/app/rest/api/rest.go
index 5d6fdfb6..f79404fb 100644
--- a/backend/app/rest/api/rest.go
+++ b/backend/app/rest/api/rest.go
@@ -62,6 +62,7 @@ type Rest struct {
 	EmailNotifications bool
 	EmojiEnabled       bool
 	SimpleView         bool
+	ProxyCORS          bool
 
 	SSLConfig   SSLConfig
 	httpsServer *http.Server
@@ -187,15 +188,19 @@ func (s *Rest) routes() chi.Router {
 
 	s.pubRest, s.privRest, s.adminRest, s.rssRest = s.controllerGroups() // assign controllers for groups
 
-	corsMiddleware := cors.New(cors.Options{
-		AllowedOrigins:   []string{"*"},
-		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
-		AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "X-XSRF-Token", "X-JWT"},
-		ExposedHeaders:   []string{"Authorization"},
-		AllowCredentials: true,
-		MaxAge:           300,
-	})
-	router.Use(corsMiddleware.Handler)
+	if s.ProxyCORS {
+		log.Printf("[WARN] internal CORS disabled")
+	} else {
+		corsMiddleware := cors.New(cors.Options{
+			AllowedOrigins:   []string{"*"},
+			AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
+			AllowedHeaders:   []string{"Accept", "Authorization", "Content-Type", "X-XSRF-Token", "X-JWT"},
+			ExposedHeaders:   []string{"Authorization"},
+			AllowCredentials: true,
+			MaxAge:           300,
+		})
+		router.Use(corsMiddleware.Handler)
+	}
 
 	ipFn := func(ip string) string { return store.HashValue(ip, s.SharedSecret)[:12] } // logger uses it for anonymization
 	logInfoWithBody := logger.New(logger.Log(log.Default()), logger.WithBody, logger.IPfn(ipFn), logger.Prefix("[INFO]")).Handler