Adds RFC7239 checks to the new location middleware.

The RFC7239 is the standard way to define headers about reverse proxy
redirections. It replaces all the X-Forwarded-* previous way of defining them.
We let the previous implementations exist to avoid breaking existant installations.

router/middleware/location/location.go

@@ -15,6 +15,27 @@ func Resolve(c *gin.Context) {
 	c.Next()
 }
 
+// parseHeader parses non unique headers value
+// from a http.Request and return a slice of the values
+// queried from the header
+func parseHeader(r *http.Request, header string, token string) (val []string) {
+	for _, v := range r.Header[header] {
+		options := strings.Split(v, ";")
+		for _, o := range options {
+			keyvalue := strings.Split(o, "=")
+			var key, value string
+			if len(keyvalue) > 1 {
+				key, value = strings.TrimSpace(keyvalue[0]), strings.TrimSpace(keyvalue[1])
+			}
+			key = strings.ToLower(key)
+			if key == token {
+				val = append(val, value)
+			}
+		}
+	}
+	return
+}
+
 // resolveScheme is a helper function that evaluates the http.Request
 // and returns the scheme, HTTP or HTTPS. It is able to detect,
 // using the X-Forwarded-Proto, if the original request was HTTPS
@@ -29,6 +50,8 @@ func resolveScheme(r *http.Request) string {
 		return "https"
 	case r.Header.Get("X-Forwarded-Proto") == "https":
 		return "https"
+	case len(r.Header.Get("Forwarded")) != 0 && len(parseHeader(r, "Forwarded", "proto")) != 0 && parseHeader(r, "Forwarded", "proto")[0] == "https":
+		return "https"
 	default:
 		return "http"
 	}
@@ -46,8 +69,12 @@ func resolveHost(r *http.Request) string {
 		return r.URL.Host
 	case len(r.Header.Get("X-Forwarded-For")) != 0:
 		return r.Header.Get("X-Forwarded-For")
+	case len(r.Header.Get("Forwarded")) != 0 && len(parseHeader(r, "Forwarded", "for")) != 0:
+		return parseHeader(r, "Forwarded", "for")[0]
 	case len(r.Header.Get("X-Host")) != 0:
 		return r.Header.Get("X-Host")
+	case len(r.Header.Get("Forwarded")) != 0 && len(parseHeader(r, "Forwarded", "host")) != 0:
+		return parseHeader(r, "Forwarded", "host")[0]
 	case len(r.Header.Get("XFF")) != 0:
 		return r.Header.Get("XFF")
 	case len(r.Header.Get("X-Real-IP")) != 0: