Added IP check on loopback

LightlessSyncServer/LightlessSyncAuthService/Utils/HttpContextAccessorExtensions.cs

@@ -0,0 +1,26 @@
+using System.Net;
+
+namespace LightlessSyncAuthService.Utils
+{
+    public static class HttpContextAccessorExtensions
+    {
+        public static IPAddress? GetClientIpAddress(this IHttpContextAccessor accessor)
+        {
+            var context = accessor.HttpContext;
+            if (context == null) return null;
+
+            string[] headerKeys = { "CF-Connecting-IP", "X-Forwarded-For", "X-Real-IP" };
+            foreach (var key in headerKeys)
+            {
+                if (context.Request.Headers.TryGetValue(key, out var values))
+                {
+                    var ipCandidate = values.FirstOrDefault()?.Split(',').FirstOrDefault()?.Trim();
+                    if (IPAddress.TryParse(ipCandidate, out var parsed))
+                        return parsed;
+                }
+            }
+
+            return context.Connection?.RemoteIpAddress;
+        }
+    }
+}