使用原始套接字制作 TCP 数据包

Question

I'm trying to make a SYN packet using a RAW socket. But every time I get this error. I tried many ways to solve this error but haven't got a solution.

server.sendto(packet, (dst_ip, 0)) OSError: [WinError 10022] An invalid argument was supplied

This is my complete code.

import socket
import struct


def checksum_calculator(header, size):

    checksum = 0
    pointer = 0

    while size > 1:
        checksum += int((str("%02x" % (header[pointer],)) +
                      str("%02x" % (header[pointer+1],))), 16)
        size -= 2
        pointer += 2

    if size: 
        checksum += header[pointer]

    checksum = (checksum >> 16) + (checksum & 0xffff)
    checksum += (checksum >> 16)

    return (~checksum) & 0xFFFF


# Create a raw socket.
server = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)

# Source IP and desination IP.
src_ip = socket.gethostbyname(socket.gethostname())
dst_ip = socket.gethostbyname('www.google.com')

# Let's create TCP header.
src_port = 4790
dst_port = 80
seq = 0
ack_numb = 0
doff = 80
placeholder = 0
protocol = socket.IPPROTO_TCP
tcp_len = 20

# TCP flags.
fin = 0
syn = 1
rst = 0
psh = 0
ack = 0
urg = 0

window = socket.htons(5840)
checksum = 0
urg_ptr = 0

tcp_flags = fin + (syn << 1) + (rst << 2) + \
    (psh << 3) + (ack << 4) + (urg << 5)

tcp_header = struct.pack('!4s4sBBHHHLLBBHHH', socket.inet_aton(src_ip), socket.inet_aton(
    dst_ip), placeholder, protocol, tcp_len, src_port, dst_port, seq, ack_numb, doff, tcp_flags, window, checksum, urg_ptr)

# For calculate real checksum value.
tcp_checksum = checksum_calculator(tcp_header, len(tcp_header))

packet = struct.pack('!HHLLBBHHH', src_port, dst_port, seq,
                     ack_numb, doff, tcp_flags, window, tcp_checksum, urg_ptr)

server.sendto(packet, (dst_ip, 0))

Please help me to solve this error or give me some resources to read more about this.

Answer 1

The problem is that the destination address must be an IP address in dotted decimal notation. You are passing it as a host name which will not work. Try changing your code like so:

dst_ip = socket.gethostbyname('www.google.com')

to this:

dst_ip = socket.gethostbyname('74.125.228.18')

That should fix the issue for you. If that doesn't work then try one of these two options:

Change the destination port number from 80 to another unused port such as 22.

Change the source port number from 4790 to something else. It seems like there might be a conflict with port 4790 somewhere along the line.

Hopefully those suggestions will resolve your issue. Good luck!