Send ABORT over iSCSI

iscsi_abort.py

#!/usr/bin/env python3
# -*- coding: UTF-8 -*-
# Author : tintinweb@oststrom.com <github.com/tintinweb>
'''
A simple TCP three-way handshake example

#> python scapy_tcp_handshake.py
DEBUG:__main__:init: ('oststrom.com', 80)
DEBUG:__main__:start
DEBUG:__main__:SND: SYN
DEBUG:__main__:RCV: SYN+ACK
DEBUG:__main__:SND: SYN+ACK -> ACK
DEBUG:__main__:RCV: None
DEBUG:__main__:RCV: None
None
DEBUG:__main__:SND: FIN
DEBUG:__main__:RCV: None

Note: linux might send an RST for forged SYN packets. Disable it by executing:
#> iptables -A OUTPUT -p tcp --tcp-flags RST RST -s <src_ip> -j DROP
'''
from scapy.all import *
import time
import sys
import logging
logger = logging.getLogger(__name__)

login_header = [ 0x43, 0x87, 0x00, 0x00, 0x00, 0x00, 0x01, 0xb8,
  0x80, 0x25, 0x18, 0xf4, 0x00, 0x00, 0x00, 0x00,
  0x42, 0xdd, 0x1b, 0x50, 0x00, 0x00, 0x00, 0x00,
  0x64, 0x6d, 0x06, 0x51, 0x00, 0x00, 0x00, 0x01,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  ]
login_text  = "SessionType=Normal\0HeaderDigest=None,CRC32C\0DataDigest=None\0InitialR2T=No\0ImmediateData=Yes\0MaxBurstLength=262144\0FirstBurstLength=262144\0DefaultTime2Wait=2\0DefaultTime2Retain=0\0MaxOutstandingR2T=1\0ErrorRecoveryLevel=0\0IFMarker=No\0OFMarker=No\0MaxConnections=1\0MaxRecvDataSegmentLength=262144\0DataPDUInOrder=Yes\0DataSequenceInOrder=Yes\0"

abort_bytes = [
  0x42, 0x81, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x42, 0xdd, 0x1b, 0x53, 0x42, 0xdd, 0x1b, 0x51,
  0x64, 0x6d, 0x06, 0x53, 0x00, 0x00, 0x00, 0x01,
  0x64, 0x6d, 0x06, 0x51, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
]

test_lun_bytes = [
  0x01, 0x81, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x42, 0xdd, 0x1b, 0x51, 0x00, 0x00, 0x00, 0x00,
  0x64, 0x6d, 0x06, 0x51, 0x00, 0x00, 0x00, 0x01,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
]

def change_u32_at(cmd, value, offset):
    cmd[offset + 3] = value & 0xff
    value = value >> 8
    cmd[offset + 2] = value & 0xff
    value = value >> 8
    cmd[offset + 1] = value & 0xff
    value = value >> 8
    cmd[offset + 0] = value & 0xff
    return cmd

def get_u32_at(cmd,  offset):
    value = cmd[offset + 0] << 24
    value |= cmd[offset + 1] << 16
    value |= cmd[offset + 2] << 8
    value |= cmd[offset + 3]
    
    return value
    
def abort_cmd(statsn):
    cmd = abort_bytes.copy()
    change_u32_at(cmd, statsn, 28)
    return bytes(cmd)

def test_lun_cmd(statsn):
    cmd = test_lun_bytes.copy()
    change_u32_at(cmd, statsn, 28)
    return bytes(cmd)

def login_cmd(initiator, target):
    cmd = login_header.copy()
    cmd += [ord(v) for v in list("InitiatorName=%s\0"% initiator)]
    cmd += [ord(v) for v in list("TargetName=%s\0"% target) ]
    cmd += [ord(v) for v in login_text]
    return bytes(cmd)

class TcpHandshake(object):

    def __init__(self, target):
        self.seq = 0
        self.seq_next = 0
        self.target = target
        self.dst = target[0]
        self.dport = target[1]
        self.sport = random.randrange(0,2**16)
        self.l4 = IP(dst=target[0])/TCP(sport=self.sport, dport=self.dport, flags=0,
                                        seq=random.randrange(0,2**32))
        self.src = self.l4.src
        self.swin = self.l4[TCP].window
        self.dwin= 1 
        self.acked = 0
        self.iscsi_statsn = 0
        logger.debug("init: %s"%repr(target))

    def start(self):
        logger.debug("start")
        return self.send_syn()

    def match_packet(self, pkt):
        if pkt.haslayer(IP) and pkt[IP].dst == self.l4[IP].src \
           and pkt.haslayer(TCP) and pkt[TCP].dport == self.sport \
           and pkt[TCP].ack == self.seq_next:
           return True
        return False

    def _sr1(self, pkt):
        send(pkt)
        ans = sniff(filter="tcp port %s"%self.target[1],lfilter=self.match_packet,count=1,timeout=1)
        return ans[0] if ans else None

    def r1(self):
        ans = sniff(filter="tcp port %s"%self.target[1],lfilter=self.match_packet,count=2,timeout=1)
        return ans[0] if ans else None

    def handle_recv(self, pkt):
        if pkt and pkt.haslayer(IP) and pkt.haslayer(TCP):
            if pkt[TCP].flags & 0x3f == 0x12:   # SYN+ACK
                logger.debug("RCV: SYN+ACK")
                return self.send_synack_ack(pkt)
            elif  pkt[TCP].flags & 4 != 0:      # RST
                logger.debug("RCV: RST")
                raise Exception("RST")
            elif pkt[TCP].flags & 0x1 == 1:     # FIN
                logger.debug("RCV: FIN")
                return self.send_finack(pkt)
            elif pkt[TCP].flags & 0x3f == 0x10: # ACK
                logger.debug("RCV: ACK")
                return None
            elif pkt[TCP].flags & 0x8 == 0x8: # PUSH
                self.acked = len(pkt[TCP]) - 20 # tcp header len
                if (len(pkt[TCP]) - 20 > 24):
                    self.iscsi_statsn = get_u32_at(pkt[TCP].payload.load, 24)
                logger.debug("RCV: PUSH (%d) statsn 0x%x" % (self.acked, self.iscsi_statsn))
                return self.send_ack(pkt)

        logger.debug("RCV: %s"%repr(pkt))
        return None

    def recv1(self):
        return self.handle_recv(self.r1())

    def send_syn(self):
        logger.debug("SND: SYN")
        self.l4[TCP].flags = "S"
        self.seq_next = self.l4[TCP].seq + 1
        response = self._sr1(self.l4)
        self.l4[TCP].seq += 1
        return self.handle_recv(response)

    def send_synack_ack(self, pkt):
        logger.debug("SND: SYN+ACK -> ACK")
        self.l4[TCP].ack = pkt[TCP].seq+1
        self.l4[TCP].flags = "A"
        self.seq_next = self.l4[TCP].seq
        response = self._sr1(self.l4)
        return self.handle_recv(response)

    def send_data(self, d):
        logger.debug("SND: DATA")
        self.l4[TCP].flags = "PA"
        response = self._sr1(self.l4/d)
        self.seq_next = self.l4[TCP].seq + len(d)
        self.l4[TCP].seq += len(d)
        return self.handle_recv(response)

    def send_fin(self):
        logger.debug("SND: FIN")
        self.l4[TCP].flags = "F"
        self.seq_next = self.l4[TCP].seq + 1
        response = self._sr1(self.l4)
        self.l4[TCP].seq += 1
        return self.handle_recv(response)

    def send_finack(self, pkt):
        logger.debug("SND: FIN+ACK")
        self.l4[TCP].flags = "FA"
        self.l4[TCP].ack = pkt[TCP].seq+1
        self.seq_next = self.l4[TCP].seq + 1
        response = send(self.l4)
        self.l4[TCP].seq += 1
        raise Exception("FIN+ACK")

    def send_ack(self, pkt):
        logger.debug("SND: ACK")
        self.l4[TCP].flags = "A"
        self.l4[TCP].ack = pkt[TCP].seq + self.acked
        self.seq_next = self.l4[TCP].seq + self.acked
        response = self._sr1(self.l4)
        #self.l4[TCP].seq += 1

    def send_test_lun(self):
        self.send_data(test_lun_cmd(self.iscsi_statsn + 1))

    def send_abort(self):
        self.send_data(abort_cmd(self.iscsi_statsn + 1))

if __name__=='__main__':
    logging.basicConfig(level=logging.DEBUG)
    logger.setLevel(logging.DEBUG)
    if (len(sys.argv) < 4):
        print("%s IP iqn.target iqn.initiator" % sys.argv[0])
        exit(1)
    else:
        sp_host = sys.argv[1]
        target = sys.argv[2]
        initiator = sys.argv[3]

    conf.verb = 0
    tcp_hs = TcpHandshake((sp_host, 3260))
    tcp_hs.start()
    tcp_hs.send_data(login_cmd(initiator, target))
    tcp_hs.recv1() # receive login response
    tcp_hs.send_test_lun()
    tcp_hs.recv1() # receive test_lun response
    tcp_hs.send_abort()
    print("go remove the backend device\n")
    time.sleep(10) # Sleep for  10 seconds
    tcp_hs.recv1() # receive abort response
    tcp_hs.send_abort() # send some cmd to release previous abort
    tcp_hs.recv1() # receive abort response
    tcp_hs.send_fin()