Harden NTFS SMB login retry

LiamNtfs/cNtfsBase.cs

@@ -17,6 +17,9 @@ namespace LiamNtfs
 {
     public class cNtfsBase
     {
+        private const int ErrorSessionCredentialConflict = 1219;
+        private const int ErrorNotConnected = 2250;
+
         private cNtfsLogonInfo privLogonInfo = null;
         private int scanningDepth;
         public PrincipalContext adContext = null;
@@ -58,15 +61,40 @@ namespace LiamNtfs
                     LogonInfo.UserSecret,
                     LogonInfo.User,
                     0);
-                if(result == 1219)
+
+                if (result == ErrorSessionCredentialConflict)
                 {
-                    result = WNetCancelConnection2(LogonInfo.TargetNetworkName,0,true);
-                    if (result == 0)
-                        return await privLogonAsync(LogonInfo);
+                    var originalResult = result;
+                    var cancelResult = WNetCancelConnection2(LogonInfo.TargetNetworkName, 0, true);
+
+                    if (cancelResult == 0 || cancelResult == ErrorNotConnected)
+                    {
+                        result = WNetAddConnection2(
+                            netResource,
+                            LogonInfo.UserSecret,
+                            LogonInfo.User,
+                            0);
+
+                        if (result == 0)
+                        {
+                            cLogManager.LogEntry(
+                                $"NTFS login retry succeeded after SMB conflict on '{LogonInfo.TargetNetworkName}'. Initial add returned {originalResult} ({BuildWin32Message(originalResult)}), cancel returned {cancelResult} ({BuildWin32Message(cancelResult)}).",
+                                LogLevels.Debug);
+                        }
+                        else
+                        {
+                            throw CreateNtfsLoginException(LogonInfo, originalResult, cancelResult, result);
+                        }
+                    }
+                    else
+                    {
+                        throw CreateNtfsLoginException(LogonInfo, originalResult, cancelResult, null);
+                    }
                 }
+
                 if (result != 0)
                 {
-                    throw new Win32Exception(result);
+                    throw CreateNtfsLoginException(LogonInfo, result, null, null);
                 }
                 var FSLogon =  true;
 
@@ -83,6 +111,39 @@ namespace LiamNtfs
             return false;
         }
 
+        private static Exception CreateNtfsLoginException(cNtfsLogonInfo logonInfo, int addResult, int? cancelResult, int? retryResult)
+        {
+            var stages = new List<string>
+            {
+                $"WNetAddConnection2={addResult} ({BuildWin32Message(addResult)})"
+            };
+
+            if (cancelResult.HasValue)
+                stages.Add($"WNetCancelConnection2('{logonInfo?.TargetNetworkName}')={cancelResult.Value} ({BuildWin32Message(cancelResult.Value)})");
+
+            if (retryResult.HasValue)
+                stages.Add($"RetryAdd={retryResult.Value} ({BuildWin32Message(retryResult.Value)})");
+
+            var details = string.Join(", ", stages);
+            var message = $"NTFS login to '{logonInfo?.TargetNetworkName}' for user '{logonInfo?.User}' failed. {details}.";
+
+            if (addResult == ErrorSessionCredentialConflict)
+            {
+                message += " This usually indicates an existing SMB/DFS session to the same server with a different credential context.";
+
+                if (cancelResult == ErrorNotConnected)
+                    message += " The exact DFS/share path was not registered as a disconnectable connection, so the conflicting session is likely held under a different remote name or DFS target.";
+            }
+
+            var nativeResult = retryResult ?? cancelResult ?? addResult;
+            return new InvalidOperationException(message, new Win32Exception(nativeResult));
+        }
+
+        private static string BuildWin32Message(int errorCode)
+        {
+            return new Win32Exception(errorCode).Message;
+        }
+
         private async Task<bool> privRelogon()
         {
             if (privLogonInfo == null)