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censor2.py
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censor2.py
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"""
Censor 2 ----> CENSOR 1
Designed to be run by the evaluator.
TCP Censor that synchronizes on first SYN only, works 100% of the time, sends 5 RSTs to client.
"""
import layers.packet
import logging
logging.getLogger("scapy.runtime").setLevel(logging.ERROR)
from scapy.all import IP, TCP
from censors.censor import Censor
class Censor2(Censor):
def __init__(self, environment_id, forbidden, log_dir, log_level, port, queue_num):
Censor.__init__(self, environment_id, log_dir, log_level, port, queue_num)
self.forbidden = forbidden
self.tcb = 0
self.drop_all_from = None
def check_censor(self, packet):
"""
Check if the censor should run against this packet. Returns true or false.
"""
try:
self.logger.debug("Inbound packet to censor: %s", layers.packet.Packet._str_packet(packet))
# Only censor TCP packets for now
if "TCP" not in packet:
return False
if packet["TCP"].sprintf('%TCP.flags%') == "S":
self.tcb = packet["TCP"].seq + 1
self.logger.debug("Synchronizing TCB on packet: %s", layers.packet.Packet._str_packet(packet))
return False
if packet["TCP"].seq == self.tcb:
self.tcb += len(self.get_payload(packet))
else:
self.logger.debug("Ignoring packet: %s", layers.packet.Packet._str_packet(packet))
return False
for keyword in self.forbidden:
if keyword in self.get_payload(packet):
self.logger.debug("Packet triggered censor: %s", layers.packet.Packet._str_packet(packet))
return True
return False
except Exception:
self.logger.exception("Censor 2 exception caught.")
return False
def censor(self, scapy_packet):
"""
Send 5 resets to the client.
"""
rst = IP(src=scapy_packet[IP].dst, dst=scapy_packet[IP].src)/TCP(dport=scapy_packet[TCP].sport, sport=scapy_packet[TCP].dport, ack=scapy_packet[TCP].seq+len(str(scapy_packet[TCP].payload)), seq=scapy_packet[TCP].ack, flags="R")
for i in range(0, 5):
self.mysend(rst)