#!/usr/local/bin/python3 print("udp fragments splitted after udp header") # |----| # |--------| import os from addr import * from scapy.all import * pid=os.getpid() uport=pid & 0xffff # inetd ignores UDP packets from privileged port or nfs if uport < 1024 or uport == 2049: uport+=1024 payload=b"ABCDEFGHIJKLMNOP" packet=IP(src=LOCAL_ADDR, dst=REMOTE_ADDR)/ \ UDP(sport=uport, dport=7)/payload frag=[] fid=pid & 0xffff frag.append(IP(src=LOCAL_ADDR, dst=REMOTE_ADDR, proto=17, id=fid, flags='MF')/bytes(packet)[20:28]) frag.append(IP(src=LOCAL_ADDR, dst=REMOTE_ADDR, proto=17, id=fid, frag=1)/bytes(packet)[28:44]) eth=[] for f in frag: eth.append(Ether(src=LOCAL_MAC, dst=REMOTE_MAC)/f) if os.fork() == 0: time.sleep(1) sendp(eth, iface=LOCAL_IF) os._exit(0) ans=sniff(iface=LOCAL_IF, timeout=3, filter= "ip and src "+REMOTE_ADDR+" and dst "+LOCAL_ADDR+" and udp") for a in ans: if a and a.type == ETH_P_IP and \ a.payload.proto == 17 and \ a.payload.frag == 0 and a.payload.flags == 0 and \ a.payload.payload.sport == 7: port=a.payload.payload.dport print("port=%d" % (port)) if port != uport: print("WRONG UDP ECHO REPLY PORT") exit(2) data=a.payload.payload.payload.load print("payload=%s" % (data)) if data == payload: exit(0) print("PAYLOAD!=%s" % (payload)) exit(1) print("NO UDP ECHO REPLY") exit(2)