ASIS CTF 2015 Quals - grids

asisctf_grids.py

from scipy.spatial import ConvexHull
import numpy as np
import ast
import telnetlib
import re

class Telnet(telnetlib.Telnet):
    # inherit from Telnetlib and add new method
    def __init__(self,host,port):
        telnetlib.Telnet.__init__(self,host,port)
    # make easier when you want to send raw data to server
    def writeRawData(self,data):
        return self.get_socket().send(data)

    def recvRawData(self,size):
        return self.get_socket().recv(size)

# Calculate algebraic area of a polygon using shoelace formula
def area(vertices):
    n = len(vertices)
    area = 0.0
    for i in range(n):
        j = (i + 1) % n
        area += vertices[i][0] * vertices[j][1]
        area -= vertices[j][0] * vertices[i][1]
    area /= 2.0
    return area

host = '217.218.48.84'
port = 12432

# connect
tel = Telnet(host, port)
s = tel.read_until('Are you ready for this challenge?\n')
print s,
# reply
print 'yes'
tel.writeRawData('yes\n')
s = tel.read_until('OK, OK, lets start\n')
print s,
# solve
for i in range(99):
    print '[*] %d-th round' % i
    s = tel.read_until("What's the area?")
    print s,
    l = np.array(ast.literal_eval(re.findall(r'\n(\[.*\])\n', s)[0]))
    hull = ConvexHull(l)
    vertices = l[hull.vertices]
    res = abs(area(vertices))
    print res
    tel.writeRawData(str(res)+'\n')
# get flag
tel.interact()