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test.py
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test.py
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#! /usr/bin/python
'''
Padding Oracle Attack implementation without remote server
Check the readme for a full cryptographic explanation
Author: mpgn <martial.puygrenier@gmail.com>
Date: 2016
'''
import argparse
import re
import binascii
import sys
import time
from binascii import unhexlify, hexlify
from itertools import cycle, izip
from Crypto.Cipher import AES
from Crypto import Random
"""
AES-CBC
function encrypt, decrypt, pad, unpad)
"""
def pad(s):
return s + (16 - len(s) % 16) * chr(16 - len(s) % 16)
def unpad(s):
t = s.encode("hex")
exe = re.findall('..',t)
padding = int(exe[-1], 16)
exe = exe[::-1]
if padding == 0 or padding > 16:
return 0
for i in range(padding):
if int(exe[i],16) != padding:
return 0
return s[:-ord(s[len(s)-1:])]
def encrypt( msg, iv):
raw = pad(msg)
key = Random.new().read( AES.block_size )
cipher = AES.new('V38lKILOJmtpQMHp', AES.MODE_CBC, iv )
return cipher.encrypt( raw ), iv
def decrypt( enc, iv ):
decipher = AES.new('V38lKILOJmtpQMHp', AES.MODE_CBC, iv )
return unpad(decipher.decrypt( enc ))
''' the function you want change to adapte the result to your problem '''
def test_validity(error):
if error != 404:
return 1
return 0
def call_oracle(up_cipher, iv):
if decrypt( up_cipher, iv ) == 0:
return 404
return 200
''' create custom block for the byte we search'''
def block_search_byte(size_block, i, pos, l):
hex_char = hex(pos).split('0x')[1]
return "00"*(size_block-(i+1)) + ("0" if len(hex_char)%2 != 0 else '') + hex_char + ''.join(l)
''' create custom block for the padding'''
def block_padding(size_block, i):
l = []
for t in range(0,i+1):
l.append(("0" if len(hex(i+1).split('0x')[1])%2 != 0 else '') + (hex(i+1).split('0x')[1]))
return "00"*(size_block-(i+1)) + ''.join(l)
# the exploit don't need to touch this part
# split the cipher in len of size_block
def split_len(seq, length):
return [seq[i:i+length] for i in range(0, len(seq), length)]
def hex_xor(s1,s2):
return hexlify(''.join(chr(ord(c1) ^ ord(c2)) for c1, c2 in zip(unhexlify(s1), cycle(unhexlify(s2)))))
def run(cipher,size_block):
cipher = cipher.upper()
found = False
valide_value = []
result = []
len_block = size_block*2
cipher_block = split_len(cipher, len_block)
if len(cipher_block) == 1:
print "[-] Abort there is only one block, i can't influence the IV. Tried a longer message"
sys.exit()
#for each cipher_block
for block in reversed(range(1,len(cipher_block))):
if len(cipher_block[block]) != len_block:
print "[-] Abort length block doesn't match the size_block"
break
print "[+] Search value block : ", block, "\n"
#for each byte of the block
for i in range(0,size_block):
# test each byte max 255
for ct_pos in range(0,256):
# 1 xor 1 = 0 or valide padding need to be checked
if ct_pos != i+1 or (len(valide_value) > 0 and int(valide_value[-1],16) == ct_pos):
bk = block_search_byte(size_block, i, ct_pos, valide_value)
bp = cipher_block[block-1]
bc = block_padding(size_block, i)
tmp = hex_xor(bk,bp)
cb = hex_xor(tmp,bc).upper()
up_cipher = cb + cipher_block[block]
#time.sleep(0.5)
# we call the oracle, our god
error = call_oracle(up_cipher.decode('hex'),iv)
if args.verbose == True:
exe = re.findall('..',cb)
discover = ('').join(exe[size_block-i:size_block])
current = ('').join(exe[size_block-i-1:size_block-i])
find_me = ('').join(exe[:-i-1])
sys.stdout.write("\r[+] Test [Byte %03i/256 - Block %d ]: \033[31m%s\033[33m%s\033[36m%s\033[0m" % (ct_pos, block, find_me, current, discover))
sys.stdout.flush()
if test_validity(error):
found = True
# data analyse and insert in rigth order
value = re.findall('..',bk)
valide_value.insert(0,value[size_block-(i+1)])
if args.verbose == True:
print ''
print "[+] Block M_Byte : %s"% bk
print "[+] Block C_{i-1}: %s"% bp
print "[+] Block Padding: %s"% bc
print ''
bytes_found = ''.join(valide_value)
if i == 0 and bytes_found.decode("hex") > hex(size_block) and block == len(cipher_block)-1:
print "[-] Error decryption failed the padding is > "+str(size_block)
sys.exit()
print '\033[36m' + '\033[1m' + "[+]" + '\033[0m' + " Found", i+1, "bytes :", bytes_found
print ''
break
if found == False:
# lets say padding is 01 for the last block (the padding block)
if len(cipher_block)-1 == block and i == 0:
value = re.findall('..',bk)
valide_value.insert(0,"01")
if args.verbose == True:
print ''
print '[-] No padding found, but maybe the padding is length 01 :)'
print "[+] Block M_Byte : %s"% bk
print "[+] Block C_{i-1}: %s"% bp
print "[+] Block Padding: %s"% bc
print ''
bytes_found = ''.join(valide_value)
else:
print "\n[-] Error decryption failed"
result.insert(0, ''.join(valide_value))
hex_r = ''.join(result)
if len(hex_r) > 0:
print "[+] Partial Decrypted value (HEX):", hex_r.upper()
padding = int(hex_r[len(hex_r)-2:len(hex_r)],16)
print "[+] Partial Decrypted value (ASCII):", hex_r[0:-(padding*2)].decode("hex")
sys.exit()
found = False
result.insert(0, ''.join(valide_value))
valide_value = []
print ''
hex_r = ''.join(result)
print "[+] Decrypted value (HEX):", hex_r.upper()
padding = int(hex_r[len(hex_r)-2:len(hex_r)],16)
print "[+] Decrypted value (ASCII):", hex_r[0:-(padding*2)].decode("hex")
return hex_r[0:-(padding*2)].decode("hex")
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='Exploit of Padding Oracle Attack')
parser.add_argument('-m', "--message", required=True, help='message to pown')
parser.add_argument('-v', "--verbose", help='debug mode, you need a large screen', action="store_true")
args = parser.parse_args()
print "[+] Encrypt", args.message
cipher, iv = encrypt(args.message, "1234567812345678")
cipher_intercepted = cipher.encode("hex")
print "[+] %s ---> %s" % (args.message, cipher_intercepted)
plaintext = decrypt(cipher, iv)
run(cipher_intercepted,16)