Log Real IP on Authentication failure in case of a reverse proxy

(cherry picked from commit 686a14cdff63fcffe4fceee1f9a06d0b2dc3e813)

src/Lidarr.Http/Authentication/AuthenticationService.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Linq;
+using System.Net;
 using System.Security.Claims;
 using System.Security.Principal;
 using Lidarr.Http.Extensions;
@@ -208,27 +209,70 @@ namespace Lidarr.Http.Authentication
 
         public void LogUnauthorized(NancyContext context)
         {
-            _authLogger.Info("Auth-Unauthorized ip {0} url '{1}'", context.Request.UserHostAddress, context.Request.Url.ToString());
+            _authLogger.Info("Auth-Unauthorized ip {0} url '{1}'", GetRemoteIP(context), context.Request.Url.ToString());
         }
 
         private void LogInvalidated(NancyContext context)
         {
-            _authLogger.Info("Auth-Invalidated ip {0}", context.Request.UserHostAddress);
+            _authLogger.Info("Auth-Invalidated ip {0}", GetRemoteIP(context));
         }
 
         private void LogFailure(NancyContext context, string username)
         {
-            _authLogger.Warn("Auth-Failure ip {0} username '{1}'", context.Request.UserHostAddress, username);
+            _authLogger.Warn("Auth-Failure ip {0} username '{1}'", GetRemoteIP(context), username);
         }
 
         private void LogSuccess(NancyContext context, string username)
         {
-            _authLogger.Info("Auth-Success ip {0} username '{1}'", context.Request.UserHostAddress, username);
+            _authLogger.Info("Auth-Success ip {0} username '{1}'", GetRemoteIP(context), username);
         }
 
         private void LogLogout(NancyContext context, string username)
         {
-            _authLogger.Info("Auth-Logout ip {0} username '{1}'", context.Request.UserHostAddress, username);
+            _authLogger.Info("Auth-Logout ip {0} username '{1}'", GetRemoteIP(context), username);
+        }
+
+        private string GetRemoteIP(NancyContext context)
+        {
+            if (context == null || context.Request == null)
+            {
+                return "Unknown";
+            }
+
+            var remoteAddress = context.Request.UserHostAddress;
+            IPAddress remoteIP;
+
+            // Only check if forwarded by a local network reverse proxy
+            if (IPAddress.TryParse(remoteAddress, out remoteIP) && remoteIP.IsLocalAddress())
+            {
+                var realIPHeader = context.Request.Headers["X-Real-IP"];
+                if (realIPHeader.Any())
+                {
+                    return realIPHeader.First().ToString();
+                }
+
+                var forwardedForHeader = context.Request.Headers["X-Forwarded-For"];
+                if (forwardedForHeader.Any())
+                {
+                    // Get the first address that was forwarded by a local IP to prevent remote clients faking another proxy
+                    foreach (var forwardedForAddress in forwardedForHeader.SelectMany(v => v.Split(',')).Select(v => v.Trim()).Reverse())
+                    {
+                        if (!IPAddress.TryParse(forwardedForAddress, out remoteIP))
+                        {
+                            return remoteAddress;
+                        }
+
+                        if (!remoteIP.IsLocalAddress())
+                        {
+                            return forwardedForAddress;
+                        }
+
+                        remoteAddress = forwardedForAddress;
+                    }
+                }
+            }
+
+            return remoteAddress;
         }
     }
 }

src/NzbDrone.Common/Extensions/IpAddressExtensions.cs

@@ -1,4 +1,5 @@
 using System.Net;
+using System.Net.Sockets;
 
 namespace NzbDrone.Common.Extensions
 {
@@ -6,11 +7,18 @@ namespace NzbDrone.Common.Extensions
     {
         public static bool IsLocalAddress(this IPAddress ipAddress)
         {
-            if (ipAddress.ToString() == "::1")
+            if (ipAddress.IsIPv6LinkLocal)
             {
                 return true;
             }
 
+            if (IPAddress.IsLoopback(ipAddress))
+            {
+                return true;
+            }
+
+            if (ipAddress.AddressFamily == AddressFamily.InterNetwork)
+            {
                 byte[] bytes = ipAddress.GetAddressBytes();
                 switch (bytes[0])
                 {
@@ -25,5 +33,8 @@ namespace NzbDrone.Common.Extensions
                         return false;
                 }
             }
+
+            return false;
+        }
     }
 }

src/NzbDrone.Core/Security/X509CertificateValidationService.cs

@@ -50,7 +50,7 @@ namespace NzbDrone.Core.Security
             }
 
             if (certificateValidation == CertificateValidationType.DisabledForLocalAddresses &&
-                ipAddresses.All(i => i.IsIPv6LinkLocal || i.IsLocalAddress()))
+                ipAddresses.All(i => i.IsLocalAddress()))
             {
                 return true;
             }