Correctly calculate base URL when behind multiple reverse proxies

Signed-off-by: Nathan Rennie-Waldock <nathan.renniewaldock@gmail.com>

libresonic-main/src/main/java/org/libresonic/player/service/NetworkService.java

@@ -60,8 +60,21 @@ public class NetworkService {
 
     private static URI calculateProxyUri(HttpServletRequest request) throws URISyntaxException {
         String xForardedHost = request.getHeader(X_FORWARDED_HOST);
+        // If the request has been through multiple reverse proxies,
+        // We need to return the original Host that the client used
+        if (xForardedHost != null) {
+            xForardedHost = xForardedHost.split(",")[0];
+        }
+
         if(!isValidXForwardedHost(xForardedHost)) {
             xForardedHost = request.getHeader(X_FORWARDED_SERVER);
+
+            // If the request has been through multiple reverse proxies,
+            // We need to return the original Host that the client used
+            if (xForardedHost != null) {
+                xForardedHost = xForardedHost.split(",")[0];
+            }
+
             if(!isValidXForwardedHost(xForardedHost)) {
                 throw new RuntimeException("Cannot calculate proxy uri without HTTP header " + X_FORWARDED_HOST);
             }