python如何使用raw socket进行TCP SYN扫描

#!/usr/bin/env python
# -*- coding: UTF-8 -*- 

# 必须以root权限运行

import socket
import sys
import time

from struct import *

# 计算校验和
def checksum(msg):
  s = 0
  # 每次取2个字节
  for i in range(0,len(msg),2):
    w = (ord(msg[i]) << 8) + (ord(msg[i+1]))
    s = s+w

  s = (s>>16) + (s & 0xffff)
  s = ~s & 0xffff

  return s

def CreateSocket(source_ip,dest_ip):
  try:
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)
  except socket.error, msg:
    print 'Socket create error: ',str(msg[0]),'message: ',msg[1]
    sys.exit()

  # 设置手工提供IP头部
  s.setsockopt(socket.IPPROTO_TCP, socket.IP_HDRINCL, 1)
  return s

# 创建IP头部
def CreateIpHeader(source_ip, dest_ip):
  packet = ''

  # ip 头部选项
  headerlen = 5
  version = 4
  tos = 0
  tot_len = 20 + 20
  id = random.randrange(18000,65535,1)
  frag_off = 0
  ttl = 255
  protocol = socket.IPPROTO_TCP
  check = 10
  saddr = socket.inet_aton ( source_ip )
  daddr = socket.inet_aton ( dest_ip )
  hl_version = (version << 4) + headerlen
  ip_header = pack('!BBHHHBBH4s4s', hl_version, tos, tot_len, id, frag_off, ttl, protocol, check, saddr, daddr)

  return ip_header

# 创建TCP头部
def create_tcp_syn_header(source_ip, dest_ip, dest_port):
  # tcp 头部选项
  source = random.randrange(32000,62000,1)  # 随机化一个源端口
  seq = 0
  ack_seq = 0
  doff = 5
  # tcp flags
  fin = 0
  syn = 1
  rst = 0
  psh = 0
  ack = 0
  urg = 0
  window = socket.htons (8192)  # 最大窗口大小
  check = 0
  urg_ptr = 0
  offset_res = (doff << 4) + 0
  tcp_flags = fin + (syn<<1) + (rst<<2) + (psh<<3) + (ack<<4) + (urg<<5)
  tcp_header = pack('!HHLLBBHHH', source, dest_port, seq, ack_seq, offset_res, tcp_flags, window, check, urg_ptr)
  # 伪头部选项
  source_address = socket.inet_aton( source_ip )
  dest_address = socket.inet_aton( dest_ip )
  placeholder = 0
  protocol = socket.IPPROTO_TCP
  tcp_length = len(tcp_header)
  psh = pack('!4s4sBBH', source_address, dest_address, placeholder, protocol, tcp_length);
  psh = psh + tcp_header;
  tcp_checksum = checksum(psh)

  # 重新打包TCP头部，并填充正确地校验和
  tcp_header = pack('!HHLLBBHHH', source, dest_port, seq, ack_seq, offset_res, tcp_flags, window, tcp_checksum, urg_ptr)
  return tcp_header

def range_scan(source_ip, dest_ip, start_port, end_port) :
  syn_ack_received = []  # 开放端口存储列表

  for j in range (start_port, end_port) :
    s = CreateSocket(source_ip, dest_ip)
    ip_header = CreateIpHeader(source_ip, dest_ip)
    tcp_header = create_tcp_syn_header(source_ip, dest_ip,j)
    packet = ip_header + tcp_header

    s.sendto(packet, (dest_ip, 0))

    data = s.recvfrom(1024) [0][0:]

    ip_header_len = (ord(data[0]) & 0x0f) * 4
    ip_header_ret = data[0: ip_header_len - 1]
    tcp_header_len = (ord(data[32]) & 0xf0)>>2
    tcp_header_ret = data[ip_header_len:ip_header_len+tcp_header_len - 1]

    if ord(tcp_header_ret[13]) == 0x12: # SYN/ACK flags 
      syn_ack_received.append(j)
  return syn_ack_received

# 程序从这里开始:
open_port_list = []
ipsource = '192.168.1.95'
ipdest = '192.168.1.31'
start = 100
stop = 450
step = (stop-start)/10
scan_ports = range(start, stop, step)
if scan_ports[len(scan_ports)-1] < stop:
  scan_ports.append(stop)
for i in range(len(scan_ports)-1):
  opl = range_scan(ipsource, ipdest, scan_ports[i], scan_ports[i+1])
  open_port_list.append(opl)
for i in range(len(open_port_list)):
  print 'Process #: ',i,' Open ports: ',open_port_list[i]
print 'A list of all open ports found: '
for i in range(len(open_port_list)):
  for j in range(len(open_port_list[i])):
    print open_port_list[i][j],', '