CODEWITHSUNDEEP
pythonscapy
Ethan Schlegel
Ethan Schlegel

Reputation: 11

Problems with python scapy portscanner

I programmed a port scanner to learn more about networking
but for some reason it only returns port n is closed for every port scanned.

import sys 
from scapy.all import *

 target = str(sys.argv[1])
 beg = int(sys.argv[2])
 ran = int(sys.argv[3])
 ptable = []
 print "beginning port scan on target: " + target
 for x in range(beg,ran):
    pkt = IP(dst=target)/TCP(dport=x,flags="S")
    ans,uans = sr(pkt,timeout=0.5)
    if TCP in ans:      
            if ans[TCP].flags == "SA":
                ptable.append(1)

            else:
                ptable.append(0)


print "======================== port scan summary ==========================="
print " "

for i in range(beg,ran):

    if ptable[i-1] == 1:

        print "port " + str(i) + " is open"
    else:
        print "port " + str(i) + " is closed"

Upvotes: 1

Views: 214

Answers (1)

Pierre
Pierre

Reputation: 6237

This is because ans[TCP].flags returns the numerical value (rather than a string that would moreover be ambiguous):

>>> TCP(flags='SA').flags == 'SA'
False
>>> TCP(flags='SA').flags
18

You should use if ans[TCP].flags == 18: instead of == "SA", or better yet, if ans[TCP].flags & 18 == 18:.

Upvotes: 2

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