PythonWorkshop2

PythonWorkshop2 Sat 24 Oct 2009 14:00 till Sat 24 Oct 2009 20:00 What: Python workshop continued Tagline: Follow up of the first python workshop Where: HSB Brussels,Belgium Cost: 5 EUR (for non-members) Who: User:Fs111 URL:

[[People::User:Fs111| ]]

What is this?

This is a follow up session on the first Python_Workshop. More to come, watch this space.

Homework

Your home work is the following:

• Build a TCP portscanner that scans a host given on the commandline on all 2^16 TCP ports and prints out all open ports on the given host
• extension: instead of printing the port number, print the name of the service if it exists in /etc/services

Tips

• modules you need: sys and socket

Example session

This is what I would expect from the scanner:

$ python scan.py 192.168.1.1
open ports on 192.168.1.1
   22: ssh
   23: telnet
   80: http
 1863: msnp
 1864: paradym-31port
 4443: pharos
 5190: aol
 5431: park-agent
 5566: Unknown service

Participants

Put your name here if you are coming:

Who	Comment	Present
fs111	for great justice!	yes
erik	loved part 1	yes
ptr_	missed part 1	yes
Antonio	missed the hackerspace
tazo	back for more	yes
tvlooy	have you got anything without spam in it?	no
nicodache	space blank left is intentionally This
Koert	This space is still left intentionally blank	yes
Sandb	This intentionally blank space is left	yes
Xflame		yes

Nifty Tips&tricks

• serves your local current working directory

python -m SimpleHTTPServer [port]

• testing for values in dictionaries

>>> d = {}
>>> 1 in d
False
>>> d.get(1,"not found")
'not found'
>>> d[1] = "test"
>>> d.get(1,"not found")
'test'
>>> 1 in d
True
>>> 

• string replacement, using a dictionary

>>> d = {'name':'pieter', 'age':32}
>>> print "%(name)s %(age)d" % d
pieter 32
>>>

• specify the encoding of the python source file

 #!/usr/bin/env python
 # -*- coding: utf-8 -*-

• play with sets - they are cool (union, intersection, etc)

• you can use frozenset as index of a dictionary -- (sets are 'unhashable' -- the index value should be 'unchangeable')

 f = frozenset(set([0, 'blah', 'foo', 'bar']))
 d = { f:'some value'}

• varargs :

def f(*arguments):
  print arguments

def g(**arguments):
  print arguments

• list comprehension

 l = range(20)
 l2 = [ item for item in l if item %2==0]

or without lists (generator objects)

 l2 = ( item for item in l if item %2==0 )

parsing /etc/services

i found a nice online utility for creating regex wizardry http://txt2re.com/