def test_unapply_whole_block_padding(self):
padded = b"YELLOW\x03\x03\x03"
expected_bytes = b"YELLOW"
actual_bytes = PKCS7Padding.unapply(padded)
self.assertEqual(expected_bytes, actual_bytes)
def test_unapply_cryptopals_case(self):
padded = b"YELLOW SUBMARINE\x04\x04\x04\x04"
expected_bytes = b"YELLOW SUBMARINE"
actual_bytes = PKCS7Padding.unapply(padded)
self.assertEqual(expected_bytes, actual_bytes)
def test_unapply_all_padding_returns_empty(self):
padded = b"\x04\x04\x04\x04"
expected_bytes = b""
actual_bytes = PKCS7Padding.unapply(padded)
self.assertEqual(expected_bytes, actual_bytes)
def main():
"""
Already implemented `PKCS7Padding.unapply()` in set2.challenge09
Display that it solves the challenge
"""
b = b"ICE ICE BABY\x04\x04\x04\x04"
print("PKCS7Padding.unapply(%s):" % b)
print(PKCS7Padding.unapply(b))
b = b"ICE ICE BABY\x05\x05\x05\x05"
print("PKCS7Padding.unapply(%s):" % b)
try:
PKCS7Padding.unapply(b)
except (InvalidPaddingException):
print("Exception raised")
b = b"ICE ICE BABY\x01\x02\x03\x04"
print("PKCS7Padding.unapply(%s):" % b)
try:
PKCS7Padding.unapply(b)
except (InvalidPaddingException):
print("Exception raised")
def decrypt_profile(encrypted: bytes) -> str:
"""
params:
encrypted: profile encrypted using `encrypted_profile()`
returns:
encoded profile
"""
cipher = AES.new(CONSISTENT_KEY, AES.MODE_ECB)
ecb = ECBMode(16, cipher.encrypt, cipher.decrypt)
padded = ecb.decrypt(encrypted)
return PKCS7Padding.unapply(padded).decode()
def valid_padding(encrypted: bytes, iv: bytes) -> bool:
"""
params:
encrypted: encrypted message
iv: IV used to encrypt `encrypted`
returns:
True if decryption of `encrypted` has valid padding
False otherwise
"""
blksize = len(CONSISTENT_KEY)
cipher = AES.new(CONSISTENT_KEY, AES.MODE_ECB)
cbc = CBCMode(blksize=blksize,
encrypt_blk=cipher.encrypt,
decrypt_blk=cipher.decrypt,
iv=iv)
decrypted = cbc.decrypt(encrypted)
try:
PKCS7Padding.unapply(decrypted)
return True
except InvalidPaddingException:
return False
def is_admin(encrypted: bytes, blksize: int = 16) -> bool:
"""
params:
encrypted: message encrypted using `encryption_oracle()`
blksize: blocksize used by `encryption_oracle()`
returns:
True if decrypted message contains ";admin=true;", False otherwise
"""
cipher = AES.new(CONSISTENT_KEY, AES.MODE_ECB)
cbc = CBCMode(blksize=blksize,
encrypt_blk=cipher.encrypt,
decrypt_blk=cipher.decrypt,
iv=CONSISTENT_IV)
padded = cbc.decrypt(encrypted)
decrypted = PKCS7Padding.unapply(padded)
return b";admin=true;" in decrypted
def break_cbc(encrypted: bytes, iv: bytes, padding_oracle: Callable[[bytes, bytes], bool]) \
-> bytes:
"""
params:
encrypted: encrypted message from `encryption_oracle()`
iv: IV used for encryption from `encryption_oracle()`
padding_oracle: `valid_padding()`
returns:
decrypted bytes for `encrypted`
"""
decrypted = b''
prev_blk = iv
for curr_blk in blocks(encrypted, 16):
decrypted += break_cbc_single_blk(prev_blk, curr_blk, padding_oracle)
prev_blk = curr_blk
return PKCS7Padding.unapply(decrypted)
def validate_ascii(encrypted: bytes) -> bytes:
"""
params:
encrypted: message encrypted using `aes_cbc()`
returns:
decrypted bytes if they contain extended ascii characters,
None otherwise
"""
cipher = AES.new(key, AES.MODE_ECB)
cbc = CBCMode(blksize=blksize,
encrypt_blk=cipher.encrypt,
decrypt_blk=cipher.decrypt,
iv=key)
padded = cbc.decrypt(encrypted)
decrypted = PKCS7Padding.unapply(padded)
for c in decrypted:
if c >= 128:
return decrypted
return None
def test_unapply_padding_value_does_not_match_number_of_pads(self):
padded = b"ICE ICE BABY\x05\x05\x05\x05"
with self.assertRaises(InvalidPaddingException):
PKCS7Padding.unapply(padded)
def test_unapply_padding_value_incosistent(self):
padded = b"ICE ICE BABY\x01\x02\x03\x04"
with self.assertRaises(InvalidPaddingException):
PKCS7Padding.unapply(padded)
def test_unapply_padding_value_larger_than_valid_raises(self):
padded = b"YELLOW\x16\x16\x16"
with self.assertRaises(InvalidPaddingException):
PKCS7Padding.unapply(padded)
def test_unapply_padding_ending_with_zero_raises(self):
padded = b"YELLOW\x00"
with self.assertRaises(InvalidPaddingException):
PKCS7Padding.unapply(padded)
