hacktracking: June 2015

# PicoCTF 2k14 - Web Interception

# cat web_interception.py
import socket

host = 'vuln2014.picoctf.com'
port = 65414

def print_recvdata(data):
 for i in range(0, len(data), kl * 2):
  print '<<< ' + data[i:i + (kl * 2)]

def sendrecv(msg):
 s = socket.socket()
 s.connect((host, port))
 s.recv(1024)
 s.send(msg)
 data = s.recv(1024)
 s.close()
 return data

kl = 16  # key length
cdl = 80 # current data length

for i in range(1, 30):
 msg = 'aa' * i
 data = sendrecv(msg)[:-1]
 dl = len(data)/2 # data length
 if cdl < dl:
  print_recvdata(data)
  print 'Data    = ', dl
  print 'Get     = ', gl
  print 'Message = ', ml
  print 'Secret  = ', sl
  break
 else:
  gl = len('GET /')
  ml = len(msg)/2
  sl = dl - ml - gl # secret length
 print i

pad = sl + kl - gl

found = ''

for i in range(pad - 1, kl - gl, -1):
 msg = 'aa' * i
 print '>>> ' + msg + '..' * (pad - len(msg)/2)
 data = sendrecv(msg)[:-1]
 f = 0 # from block1
 t = (kl * 2) * (sl/kl + 1) # to block1 + #blocks(sl)
 key = data[f:t]
 #print_recvdata(data)
 for j in range(0, 256):
  h = format(j, '02x')
  nh = msg + found + h
  data = sendrecv(nh)[:-1]
  if data[f:t] == key:
   print '>>> ' + nh
   #print_recvdata(data)
   print 'found = \'' + chr(j) + '\''
   found += h
   break

print 'secret_data = \'' + found.decode('hex') + '\''

# python web_interception.py
1
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9
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11
<<< c2ede3651650defcac13ecd82b7b9e7b
<<< 7a7bc20c2692db821734385bfa01f1db
<<< 7bb2c562649b06c08ae178a597ba85d2
<<< c87adffd4197a50cdc4d47384db2b219
<<< 8e930fb9cdf30c3a2c914731545f9fb3
<<< 695e6035c5752aa0d133f436a7d4475f
Data    =  96
Get     =  5
Message =  11
Secret  =  64
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20
found = ' '
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa2048
found = 'H'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa204854
found = 'T'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454
found = 'T'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..........
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa2048545450
found = 'P'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa............
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f
found = '/'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..............
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f31
found = '1'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e
found = '.'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e31
found = '1'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d
'ound = '
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a
found = '
'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a43
found = 'C'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..........................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f
found = 'o'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa............................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f
found = 'o'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..............................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b
found = 'k'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69
found = 'i'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b6965
found = 'e'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a
found = ':'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20
found = ' '
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a2066
found = 'f'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..........................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c
found = 'l'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa............................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61
found = 'a'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..............................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c6167
found = 'g'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d
found = '='
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d63
found = 'c'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f
found = 'o'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e
found = 'n'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67
found = 'g'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..........................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e6772
found = 'r'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa............................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e677261
found = 'a'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..............................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174
found = 't'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e6772617473
found = 's'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f
found = '_'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f
found = 'o'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e
found = 'n'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f
found = '_'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..........................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f79
found = 'y'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa............................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f
found = 'o'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..............................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75
found = 'u'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f7572
found = 'r'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f
found = '_'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66
found = 'f'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f6669
found = 'i'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f666972
found = 'r'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..........................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273
found = 's'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa............................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f6669727374
found = 't'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..............................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f
found = '_'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f65
found = 'e'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563
found = 'c'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f656362
found = 'b'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f
found = '_'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f64
found = 'd'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..........................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f6465
found = 'e'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa............................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f646563
found = 'c'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..............................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f64656372
found = 'r'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f6465637279
found = 'y'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa..................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f646563727970
found = 'p'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa....................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f64656372797074
found = 't'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa......................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f6465637279707469
found = 'i'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa........................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f64656372797074696f
found = 'o'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaa..........................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f64656372797074696f6e
found = 'n'
>>> aaaaaaaaaaaaaaaaaaaaaaaaaa............................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f64656372797074696f6e0d
'ound = '
>>> aaaaaaaaaaaaaaaaaaaaaaaa..............................................................................................................................
>>> aaaaaaaaaaaaaaaaaaaaaaaa20485454502f312e310d0a436f6f6b69653a20666c61673d636f6e67726174735f6f6e5f796f75725f66697273745f6563625f64656372797074696f6e0d0a
found = '
'
secret_data = ' HTTP/1.1
Cookie: flag=congrats_on_your_first_ecb_decryption
'

Reference

https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation

# PicoCTF 2k14 - Block

# cat block.py
#!/usr/bin/python2
from sys import argv, exit
import struct

SBoxes = [[15, 1, 7, 0, 9, 6, 2, 14, 11, 8, 5, 3, 12, 13, 4, 10], [3, 7, 8, 9, 11, 0, 15, 13, 4, 1, 10, 2, 14, 6, 12, 5], [4, 12, 9, 8, 5, 13, 11, 7, 6, 3, 10, 14, 15, 1, 2, 0], [2, 4, 10, 5, 7, 13, 1, 15, 0, 11, 3, 12, 14, 9, 8, 6], [3, 8, 0, 2, 13, 14, 5, 11, 9, 1, 7, 12, 4, 6, 10, 15], [14, 12, 7, 0, 11, 4, 13, 15, 10, 3, 8, 9, 2, 6, 1, 5]]

SInvBoxes = [[3, 1, 6, 11, 14, 10, 5, 2, 9, 4, 15, 8, 12, 13, 7, 0], [5, 9, 11, 0, 8, 15, 13, 1, 2, 3, 10, 4, 14, 7, 12, 6], [15, 13, 14, 9, 0, 4, 8, 7, 3, 2, 10, 6, 1, 5, 11, 12], [8, 6, 0, 10, 1, 3, 15, 4, 14, 13, 2, 9, 11, 5, 12, 7], [2, 9, 3, 0, 12, 6, 13, 10, 1, 8, 14, 7, 11, 4, 5, 15], [3, 14, 12, 9, 5, 15, 13, 2, 10, 11, 8, 4, 1, 6, 0, 7]]

def S(block, SBoxes):
    output = 0
    for i in xrange(0, len(SBoxes)):
        output |= SBoxes[i][(block >> 4*i) & 0b1111] << 4*i

    return output


PBox = [13, 3, 15, 23, 6, 5, 22, 21, 19, 1, 18, 17, 20, 10, 7, 8, 12, 2, 16, 9, 14, 0, 11, 4]
PInvBox = [21, 9, 17, 1, 23, 5, 4, 14, 15, 19, 13, 22, 16, 0, 20, 2, 18, 11, 10, 8, 12, 7, 6, 3]
def permute(block, pbox):
    output = 0
    for i in xrange(24):
        bit = (block >> pbox[i]) & 1
        output |= (bit << i)
    return output

def encrypt_data(data, key):
    enc = ""
    for i in xrange(0, len(data), 3):
        block = int(data[i:i+3].encode('hex'), 16)

        for j in xrange(0, 3):
            block ^= key
            block = S(block, SBoxes)
            block = permute(block, PBox)

        block ^= key

        enc += ("%06x" % block).decode('hex')

    return enc

def decrypt_data(data, key):
    dec = ""
    for i in xrange(0, len(data), 3):
        block = int(data[i:i+3].encode('hex'), 16)

        block ^= key
        for j in xrange(0, 3):
            block = permute(block, PInvBox)
            block = S(block, SInvBoxes)
            block ^= key

        dec += ("%06x" % block).decode('hex')

    return dec

def encrypt(data, key1, key2):
    encrypted = encrypt_data(data, key1)
    encrypted = encrypt_data(encrypted, key2)
    return encrypted

def decrypt(data, key1, key2):
    decrypted = decrypt_data(data, key2)
    decrypted = decrypt_data(decrypted, key1)
    return decrypted

def usage():
    print "Usage: %s [encrypt/decrypt] [key1] [key2] [in_file] [out_file]" % argv[0]
    exit(1)

def main():
    if len(argv) != 6:
        usage()

    if len(argv[2]) > 6:
        print "key1 is too large"
    elif len(argv[3]) > 6:
        print "key2 is too large"

    key1 = int(argv[2], 16)
    key2 = int(argv[3], 16)

    in_file = open(argv[4], "r")

    data = ""
    while True:
        read = in_file.read(1024)
        if len(read) == 0:
            break

        data += read

    in_file.close()

    if argv[1] == "encrypt":
        data = "message: " + data
        if len(data) % 3 != 0: #pad
            data += ("\x00" * (3 - (len(data) % 3)))

        output = encrypt(data, key1, key2)
    elif argv[1] == "decrypt":
        output = decrypt(data, key1, key2)
    else:
        usage()


    out_file = open(argv[5], "w")
    out_file.write(output)
    out_file.close()

if __name__ == "__main__":
    main()

# cat meet_in_the_middle.py
from block import encrypt_data, decrypt, decrypt_data

f = open('encrypted', 'r')
data = f.read()
f.close()

enc = []
print '+ enc'
for i in range(0, 0xffffff + 1):
        enc.append(encrypt_data('message: ', i).encode('hex'))

dec = []
print '+ dec'
for i in range(0, 0xffffff + 1):
        dec.append(decrypt_data(data[:9], i).encode('hex'))

print '+ check'
match = list(set(enc) & set(dec))[0]
key1 = enc.index(match)
key2 = dec.index(match)
print match, hex(key1)[2:], hex(key2)[2:]

print decrypt(data, key1, key2)

# pypy meet_in_the_middle.py
+ enc
+ dec
+ check
e06e0453ea35d9beb6 a6bffa 6fa0d
message: c57d156f9cbcdb526b8544df95d9cb

Reference

https://en.wikipedia.org/wiki/Meet-in-the-middle_attack

# PicoCTF 2k14 - Bit Puzzle

# cat bitpuzzle.py 
from z3 import *

v1 = BitVec('v1', 32)
v2 = BitVec('v2', 32)
v3 = BitVec('v3', 32)
v4 = BitVec('v4', 32)
v5 = BitVec('v5', 32)
v6 = BitVec('v6', 32)
v7 = BitVec('v7', 32)
v8 = BitVec('v8', 32)

s = Solver()

s.add(v3 + v2 == 0xc0dcdfce)
s.add(v1 + v2 == 0xd5d3dddc)
s.add((5 * v2) + (3 * v1) == 0x404a7666)
s.add(v1 ^ v4 == 0x18030607)
s.add(v4 & v1 == 0x666c6970)
s.add(v5 * v2 == 0xb180902b)
s.add(v3 * v5 == 0x3e436b5f)
s.add(v5 + (2 * v6) == 0x5c483831)
s.add(v6 & 0x70000000 == 0x70000000)
s.add(v6 / v7 == 1)
s.add(v6 % v7 == 0xe000cec)
s.add((3 * v5) + (2 * v8) == 0x3726eb17)
s.add((7 * v8) + (4 * v3) == 0x8b0b922d)
s.add(v4 + (3 * v8) == 0xb9cf9c91)

import struct

d = {}

if s.check() == sat:
 m = s.model()
 print m
 for v in m:
  d[str(v)] = struct.pack('<I', int(str(m[v])))

flag = ''

for k in sorted(d):
 flag += d[k]

print flag

# python bitpuzzle.py 
[v6 = 1953459295,
 v7 = 1718574963,
 v2 = 1600613993,
 v4 = 1852795252,
 v8 = 1853187679,
 v3 = 1635086693,
 v1 = 1986817907,
 v5 = 1936285555]
solving_equations_is_lots_of_fun

# PicoCTF 2k14 - Low Entropy

# cat low_entropy.py
import Crypt
import gmpy
import Socket

publickey = 0xc20a1d8b3903e1864d14a4d1f32ce57e4665fc5683960d2f7c0f30d5d247f5fa264fa66b49e801943ab68be3d9a4b393ae22963888bf145f07101616e62e0db2b04644524516c966d8923acf12af049a1d9d6fe3e786763613ee9b8f541291dcf8f0ac9dccc5d47565ef332d466bc80dc5763f1b1139f14d3c0bae072725815f
ciphertext = 0x49f573321bdb3ad0a78f0e0c7cd4f4aa2a6d5911c90540ddbbaf067c6aabaccde78c8ff70c5a4abe7d4efa19074a5249b2e6525a0168c0c49535bc993efb7e2c221f4f349a014477d4134f03413fd7241303e634499313034dbb4ac96606faed5de01e784f2706e85bf3e814f5f88027b8aeccf18c928821c9d2d830b5050a1e

cont = True

while cont:
 s = Socket.Socket(Socket.TCP)
 s.connect('vuln2014.picoctf.com', 51818)
 s.read()
 recv = s.read()
 if recv != '':
  n = int('0x' + recv, 16)
  p = Crypt.egcd(publickey, n)[0]
  if p != 1:
   cont = False
 s.close()

q = publickey / p
n = p * q
totien = (p - 1) * (q - 1)
e = 65537
d =  gmpy.invert(e, totien)
cleartext = pow(ciphertext, d, n)

print hex(cleartext)[2:].decode('hex')

# python low_entropy.py
[i] Sock: Connecting...
[i] Sock: Connecting...
[i] Sock: Connecting...
[i] Sock: Connecting...
Good thing no one can read this! I'd hate for them to know that the flag is make_sure_your_rng_generates_lotsa_primes.

# PicoCTF 2k14 - ECC

Problem

String Encoding: ASCII

def STR(a):
    a = str(a)
    # Yes, this is a little bit silly :-)
    for i in range(0, len(a) - 1, 2):
            print(chr(int(a[i:i+2]))),

e.g. STR(7269767679) = "HELLO"

Cryptosystem:
Elliptic Curve: y^2 = x^3 + ax + b mod n
a = 0
b = ?
n = 928669833265826932708591

Encryption: C = e * M mod n
Decryption: M = d * C mod n
e = 141597355687225811174313
d = 87441340171043308346177
C = (236857987845294655469221, 12418605208975891779391)
STR(M.x) + STR(M.y) = ?

Solution

# apt-add-repository -y ppa:aims/sagemath
# apt-get update
# apt-get install sagemath-upstream-binary
# sage

sage: y = 12418605208975891779391
sage: x = 236857987845294655469221
sage: a = 0
sage: n = 928669833265826932708591
sage: b = (y**2 - x**3 - a*x) % n
sage: b
268892790095131465246420

sage: F = FiniteField(n)
sage: E = EllipticCurve(F, [a, b])
sage: G = E.point((x, y))
sage: d = 87441340171043308346177
sage: M = G * d
sage: M
(6976767380847367326785 : 828669833265826932708578 : 1)

In [1]: print STR(6976767380847367326785), STR(828669833265826932708578)
ELLIPTIC CURVES ARE FUN

References

https://www.youtube.com/watch?v=vnpZXJL6QCQ