[SOLVED] Network Scanner build using Scapy only scans itself

Issue

Below is the code of NetworkScanner that I tried to build as my first Python project. #!/usr/bin/env python

import scapy.all as scapy
import optparse


def scan(ip):
    packet1 = scapy.ARP(pdst=ip)
    etherpacket = scapy.Ether(dst='ff:ff:ff:ff:ff:ff')
    broadcast_packet = etherpacket / packet1
    ans = scapy.srp(broadcast_packet, timeout=60, verbose=False)[0]
    ret_list = list()

    for item in ans:
        dic = {}
        dic['ip'] = item[1].pdst
        dic['mac'] = item[1].hwdst
        ret_list.append(dic)
    print(ret_list)
    return ret_list


def printfun(returnlist):
    print("IP\t\t\tMAC Address\n----------------------------------------------")
    for elem in returnlist:
        print(elem["ip"] + "\t\t" + elem["mac"])


def getip():

    parser = optparse.OptionParser()
    parser.add_option('-i', "--ip", dest = 'received_ip', help="Please enter the ip you want to scan")
    (option, arguments) = parser.parse_args()
    return option.received_ip


ip = getip()
if ip:
    result = scan(ip)
    printfun(result)
else:
    print("no ip given")

Now I did follow some tutorials and learned to build parallelly and it seems right to me but I am not good. but when I execute the program, it only scans the IP of virtual Host itself on which it is executed.

/PycharmProjects/Networkscanner$ sudo python networkscanner.py -i 192.168.1.1/24
[{'ip': '192.168.1.205', 'mac': '08:00:27:1f:30:76'}, {'ip': '192.168.1.205', 'mac': '08:00:27:1f:30:76'}]
IP          MAC Address
----------------------------------------------
192.168.1.205       08:00:27:1f:30:76
192.168.1.205       08:00:27:1f:30:76

when I use the inbuild network scanner of python it gives these results.

 Currently scanning: Finished!   |   Screen View: Unique Hosts                 

 5 Captured ARP Req/Rep packets, from 4 hosts.   Total size: 300               
 _____________________________________________________________________________
   IP            At MAC Address     Count     Len  MAC Vendor / Hostname      
 -----------------------------------------------------------------------------
 192.168.1.1     a0:47:d7:36:2a:c0      2     120  Best IT World (India) Pvt Lt
 192.168.1.203   e4:42:a6:30:93:64      1      60  Intel Corporate             
 192.168.1.205   30:b5:c2:10:05:3b      1      60  TP-LINK TECHNOLOGIES CO.,LTD
 192.168.1.207   30:b5:c2:10:05:3b      1      60  TP-LINK TECHNOLOGIES CO.,LTD

Edit: I tried the Monitor mode, but that does not help. I also tried to run it on main windows with also an external WiFi adaptor, still same issue

can someone please assist what is wrong in my code?

Solution

Determining the problem

If we name variables more appropriately, it becomes apparent what the problem is:

for sent_recv in ans:
    dic = {}
    return_packet = sent_recv[1]
    dic['ip'] = return_packet.pdst
    dic['mac'] = return_packet.hwdst
    ret_list.append(dic)

• Each item is a tuple of a sent packet and a received packet. Naming it as such helps to identify it.
• The 2nd element of sent_recv is the returned packet. Let's name it as such.
• The destination IP and MAC address of the returning packet are going to be that of our machine. This makes sense in the context of your output: You get your own IP/MAC for every response.

So if we change it to the src IP/MAC of the returning packet, we'll get the information we're after:

for sent_recv in ans:
    dic = {}
    return_packet = sent_recv[1]
    # Difference is dst => src here
    dic['ip'] = return_packet.psrc
    dic['mac'] = return_packet.hwsrc
    ret_list.append(dic)

Note: An ARP packet should not take 60s to return - it's more on the scale of 10-100ms depending on network size. A timeout of 2s is more appropriate here.

Testing the fix

Running this with modified code, we get the desired result:

$ python script.py -i "192.168.1.0/24"
[{'ip': '192.168.1.48', 'mac': '00:1b:78:20:ee:40'}, 
 {'ip': '192.168.1.67', 'mac': '6c:33:a9:42:6a:18'}, 
...

IP          MAC Address
----------------------------------------------
192.168.1.48        00:1b:78:20:ee:40
192.168.1.67        6c:33:a9:42:6a:18
...

Answered By - Ross Jacobs