main2.py

from packets import *
import socket
import time
from packetExtraction import *
import sys
from timeit import default_timer as timer

def extract_packet_from_IP(packet):
    # gets a TCP packet that starts from IP layer (Ether headers seperated) and returns headers of tcp and ip layer
    headers = dict()
    head, data = ip(packet)
    if head['Protocol number'] != tcp_prot:  # it's not a tcp packet
        return
    headers['IP'] = head
    head, data = tcp(data)
    headers['TCP'] = head

    return headers

def calculate_ports(ports):
    # ports can be a tuple or a list
    # if ports parameter is a tuple it is a range of ports. e.g -> (70, 90) => ports 70, 71, ..., 90
    # otherwise it consits of single ports. e.g -> [70, 90] => ports 70, 90
    if type(ports) == tuple:
        ports = [i for i in range(min(ports[0], ports[1]), max(ports[0], ports[1]))]
    return ports

def send_tcp_packets(dst, ports, delay, iface, flags, sport=20):
    # dst is the dst address, a string, can be a name like google.com or an ip
    # ports can be a tuple for a range or a list for single ports
    # delay is an int. the time to wait for an appropriate for a response
    # flags is a string of tcp flags. like "S" for SYN or "FA" for ACK/FIN
    # sport is an int, source port

    ports = calculate_ports(ports)
    dst = socket.gethostbyname(dst)

    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)
    packets_recieved = list()

    for port in ports:
        status = True
        packet_to_send = TCPpacket(dst, port, iface, sport, flags).make()
        s.sendto(packet_to_send, (dst, 0))

        # in order to keep track of how much to wait for an appropriate answer, start and end is used 
        # between sending a packet and recieving an answer. if time interval got bigger than delay parameter
        # then stops waiting for the answer and sends the next packet
        start = time.time() 
        end = time.time()

        while end - start < delay + 0.1:  # 0.1 is added because of additional calculations (of course 0.1 is also too much for calculations!)
            s.settimeout(delay - (end - start))
            try:
                packet, addr = s.recvfrom(1024)
            except socket.timeout:
                break
            headers = extract_packet_from_IP(packet)
            end = time.time()
            if headers is None:
                continue
            packets_recieved.append((headers, addr))

        print('.', end='', flush=True)

    print('\n')
    return packets_recieved


def connect_scan(dst, ports, delay, iface, sport=20):
    print('*' * 30)
    print('Starting Connect scan'.center(30))
    ports = calculate_ports(ports)
    open_ports = list()

    for port in ports:
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        s.settimeout(delay)
        try:
            s.connect((dst, port))
        except:
            print('.', end='', flush=True)
            continue
        print('.', end='', flush=True)
        open_ports.append(port)
        s.close()
    
    print()

    print('Connection with ports {', *open_ports, '} could establish!\n\n')
    print('*' * 30)


def syn_scan(dst, ports, delay, iface, sport=20):

    print('*' * 30)
    print('Starting SYN scan'.center(30))

    dst = socket.gethostbyname(dst)

    answers = send_tcp_packets(dst, ports, delay, iface, 'S')
    # returns a list of tuples. each contains header of rececieved packet and source address of packet.
    
    open_ports = list()

    for answer in answers:
        if answer[1][0] != dst:
            continue
        header = answer[0]['TCP']
        if header['SYN'] and header['ACK']:
            open_ports.append(header['Source port number'])

    print()

    print('Port numbers {', *open_ports, '} sent back SYN/ACK tcp packets!\n\n')
    print('*' * 30)
                

def ack_scan(dst, ports, delay, iface, sport=20):
    print('*' * 30)
    print('Starting ACK scan'.center(30))

    answers = send_tcp_packets(dst, ports, delay, iface, 'A')

    unfiltered_ports = list()

    for answer in answers:
        if answer[1][0] != dst:
            continue
        header = answer[0]['TCP']
        if header['RST']:
            unfiltered_ports.append(header['Source port number'])
    
    print()
    print('Port numbers {', *unfiltered_ports, '} may be unfiltered!\n\n')
    print('*' * 30)

def fin_scan(dst, ports, delay, iface, sport=20):
    print('*' * 30)
    print('Starting FIN scan'.center(30))

    # if an answer with rst flag has been recieved that port may be closed!
    # if there was no answer, that port may be either open or filtered

    answers = send_tcp_packets(dst, ports, delay, iface, 'F')

    open_ports = set(calculate_ports(ports))  # becaus we want to delete some closed ports, it is easier to use set instead of list

    for answer in answers:
        if answer[1][0] != dst:
            continue
        header = answer[0]['TCP']
        if header['RST']:  # closed ports sometimes send RST packets in answer of FIN packets
            open_ports.discard(header['Source port number'])

    print()
    print('Port numbers {', *open_ports, '} may be opened or maybe filtered!\n\n')
    print('*' * 30)

def win_scan(dst, ports, delay, iface, sport=20):
    # it's like ack scan. in some cases when a port is open and unfiltered the rst packet has a psitive window size
    # in unfiltered closed ports sometimes in rst packet window size is zero
    print('*' * 30)
    print('Starting FIN scan'.center(30))

    answers = send_tcp_packets(dst, ports, delay, iface, 'A')

    open_ports = list()

    for answer in answers:
        if answer[1][0] != dst:
            continue
        header = answer[0]['TCP']
        if header['RST'] and header['Window size']:  # window size is not zero and rst flag is on
            open_ports.append(header['Source port number'])
    
    print()
    print('Port numbers {', *open_ports, '} may be open!\n\n')
    print('*' * 30)



options = sys.argv[1:]

# dst is a string, scan is a function, ports is a tuple for range of ports and a list for single ports, delay is an int
# iface is a string

# default values
dst = '127.0.0.1'
scan = connect_scan
ports = (1, 100)
delay = 1
iface = None


for option in options:  # expected option format: "<sth>=<sth>"
    option = option.strip().split('=')
    option[0] = option[0].lower()
    if len(option) != 2 or option[0] not in ('mode', 'dst', 'ports', 'delay', 'iface'):
        # there is no value. e.g -> mode , mode=
        # Or more than one values. e.g -> mode=cports=100 , ports=1-100=150
        # unknown arguments -> tcpport=80
        print(f'Unknown "{"=".join(option)}"')
        continue

    option[1] = option[1].lower()

    if option[0] == 'mode':
        if option[1] == 'c':
            scan = connect_scan
            print('---Connect scan---')
        elif option[1] == 's':
            scan = syn_scan
            print('---SYN scan---')
        elif option[1] == 'f':
            scan = fin_scan
            print('---FIN scan---')
        elif option[1] == 'w':
            scan = win_scan
            print('---Window scan---')
        elif option[1] == 'a':
            scan = ack_scan
            print('---ACK scan---')
        else:
            print(f'Scan mode not found: {option[1]}')
    elif option[0] == 'ports':
        if re.match(r'^(\d+,)*\d*$', option[1]):  # single port. e.g "15,17,10,4"
            # in single ports -> ports are in a list
            ports = list(map(int, option[1].split(',')))
            print('---Ports:', ports, '---')
        elif re.match(r'^\d+\-\d+$', option[1]):  # a range of ports. e.g "100-150" or maybe "30-10"
            # range of ports -> start and end port are first and second item of a tuple
            first, second = tuple(map(int, option[1].split('-')))
            ports = (min(first, second), max(first, second))
            print('---Range of ports:', ports, '---')
        else:
            print(f'Wrong ports input: "{option[1]}"')
    elif option[0] == 'delay':
        if re.match(r'^\d+\.?\d*$', option[1]):
            delay = float(option[1])
            print(f'---Delay: {delay}---')
        else:
            print(f'Wrong delay input: {option[1]}')
    elif option[0] == 'dst':
        dst = option[1]
        print(f'---Target: {dst}---')
    elif option[0] == 'iface':
        iface = option[1]
        print(f'---interface set to {iface}---')

if iface is None:
    raise AttributeError('Interface name must be specified')


scan(dst, ports, delay, iface)