class CookieFactoryCBC():
def __init__(self):
self.oracle = Oracle(None, prefix, postfix)
self.sep_field = Message(b';')
self.sep_key = Message(b'=')
self.default_keys = [
Message(b'comment1'),
Message(b'userdata'),
Message(b'comment2')
]
def newCookie(self, user_input):
user_input_msg = Message(user_input, 'ascii')
return self.oracle.encryptCBC(user_input_msg)
def isAdminCookie(self, msg):
decr_msg = self.oracle.decryptCBC(msg)
try:
token = Token.fromMsg(decr_msg, Message(b';'), Message(b'='))
except IndexError:
raise InvalidToken
try:
return token.data[Message(b'admin')] == Message(b'true')
except KeyError:
return False
def AESOracle(msg, test_mode=False):
""" An oracle which does the following, given a message:
chooses an integer m uniformly from [5, 10] and prepends a
random string of m bytes to a message, then chooses an
integer n uniformly from [5, 10] and appends a random
string of n bytes to the message; generates a random
16-byte key; then flips a fair coin and encrypts the
enlarged message with either AES-ECB or AES-CBC (using
another random 16-byte string as the IV) depending on the
result.
The oracle can be used in a simple model of a chosen-
plaintext attack on an unknown cipher. To verify the
success of such an attack, the function has an optional
"test mode" which exposes the mode of AES used for
each encryption.
Args:
msg (string): the message to be affixed-to and
encrypted.
msg_format (string): the format in which the bytes
of 'filename' are encoded. Options are 'ascii'
(default), 'hex', and 'base64'.
test_mode (bool): if test_mode=True, the function
returns a boolean together with each encryption
which reveals which mode of AES was used. If
test_mode=False, encryption mode is not revealed.
Returns:
(if test_mode=False) string : the encryption using
either AES_ECB or AES_CBC, and a random key (and IV,
if applicable), of the concatenation of 'msg' with
random pre/suffixes of small random length.
(if test_mode=True) tuple (bool, string): string arg
is as described in the case test_mode=False. bool arg
is True if AES-ECB was used, False if AES-CBC was used.
"""
prefix = randMsg(5, 10)
postfix = randMsg(5, 10)
oracle = Oracle(None, prefix, postfix)
coin = randint(0, 1)
if coin:
ciphertext = oracle.encryptECB(msg)
else:
ciphertext = oracle.encryptCBC(msg)
if test_mode:
return (coin, ciphertext)
else:
return ciphertext