RedirectScheme redirects based on X-Forwarded-Proto header

docs/content/middlewares/http/redirectscheme.md

@@ -12,7 +12,17 @@ Redirecting the Client to a Different Scheme/Port
 TODO: add schema
 -->
 
-RedirectScheme redirects requests from a scheme/port to another.
+The RedirectScheme middleware redirects the request if the request scheme is different from the configured scheme.
+The middleware does not work for websocket requests. 
+
+!!! warning "When behind another reverse-proxy"
+
+    When there is at least one other reverse-proxy between the client and Traefik, 
+    the other reverse-proxy (i.e. the last hop) needs to be a [trusted](../../routing/entrypoints.md#forwarded-headers) one. 
+    
+    Otherwise, Traefik would clean up the X-Forwarded headers coming from this last hop, 
+    and as the RedirectScheme middleware relies on them to determine the scheme used,
+    it would not function as intended.
 
 ## Configuration Examples
 

pkg/middlewares/redirect/redirect_scheme.go

@@ -13,8 +13,9 @@ import (
 )
 
 const (
-	typeSchemeName = "RedirectScheme"
-	uriPattern     = `^(https?:\/\/)?(\[[\w:.]+\]|[\w\._-]+)?(:\d+)?(.*)$`
+	typeSchemeName  = "RedirectScheme"
+	uriPattern      = `^(https?:\/\/)?(\[[\w:.]+\]|[\w\._-]+)?(:\d+)?(.*)$`
+	xForwardedProto = "X-Forwarded-Proto"
 )
 
 // NewRedirectScheme creates a new RedirectScheme middleware.
@@ -63,7 +64,11 @@ func rawURLScheme(req *http.Request) string {
 		scheme = schemeHTTPS
 	}
 
-	if scheme == schemeHTTP && port == ":80" || scheme == schemeHTTPS && port == ":443" || port == "" {
+	if value := req.Header.Get(xForwardedProto); value != "" {
+		scheme = value
+	}
+
+	if scheme == schemeHTTP && port == ":80" || scheme == schemeHTTPS && port == ":443" {
 		port = ""
 	}
 

pkg/middlewares/redirect/redirect_scheme_test.go

@@ -47,11 +47,22 @@ func TestRedirectSchemeHandler(t *testing.T) {
 			},
 			url: "http://foo",
 			headers: map[string]string{
-				"X-Forwarded-Proto": "https",
+				"X-Forwarded-Proto": "http",
 			},
 			expectedURL:    "https://foo",
 			expectedStatus: http.StatusFound,
 		},
+		{
+			desc: "HTTP to HTTPS, with X-Forwarded-Proto to HTTPS",
+			config: dynamic.RedirectScheme{
+				Scheme: "https",
+			},
+			url: "http://foo",
+			headers: map[string]string{
+				"X-Forwarded-Proto": "https",
+			},
+			expectedStatus: http.StatusOK,
+		},
 		{
 			desc: "HTTP with port to HTTPS without port",
 			config: dynamic.RedirectScheme{