def break_block(block, previous_block, oracle, blocksize):
"""Decrypts a block encrypted with CBC using a padding oracle. written to use check_padding.
"""
right_bytes = b'' # invariant: rightbytes is the rightmost known bytes of plaintext.
l = 0
def leftpad(_bytes):
return b'\x00' * (blocksize - len(_bytes)) + _bytes
all_bytes = [int.to_bytes(x, 1, 'big') for x in range(256)]
while l < blocksize:
padmask1 = pad(b'\x00' * (blocksize - 1 - l),
blocksize) # both padmasks have correct padding
padmask2 = pad(
b'\xFF' * (blocksize - 1 - l), blocksize
) # therefore, (padmask ^ plaintext ^ (leftpad(right_bytes)) ^ previous_block) has correct padding
for x in all_bytes:
test_bytes = xor(leftpad(x + right_bytes), previous_block) #DUH
if oracle(xor(test_bytes, padmask1), block) and oracle(
xor(test_bytes, padmask2), block):
right_bytes = x + right_bytes
break
l += 1
return right_bytes
def encrypt_one_token():
tokens = [
'MDAwMDAwTm93IHRoYXQgdGhlIHBhcnR5IGlzIGp1bXBpbmc=',
'MDAwMDAxV2l0aCB0aGUgYmFzcyBraWNrZWQgaW4gYW5kIHRoZSBWZWdhJ3MgYXJlIHB1bXBpbic=',
'MDAwMDAyUXVpY2sgdG8gdGhlIHBvaW50LCB0byB0aGUgcG9pbnQsIG5vIGZha2luZw==',
'MDAwMDAzQ29va2luZyBNQydzIGxpa2UgYSBwb3VuZCBvZiBiYWNvbg==',
'MDAwMDA0QnVybmluZyAnZW0sIGlmIHlvdSBhaW4ndCBxdWljayBhbmQgbmltYmxl',
'MDAwMDA1SSBnbyBjcmF6eSB3aGVuIEkgaGVhciBhIGN5bWJhbA==',
'MDAwMDA2QW5kIGEgaGlnaCBoYXQgd2l0aCBhIHNvdXBlZCB1cCB0ZW1wbw==',
'MDAwMDA3SSdtIG9uIGEgcm9sbCwgaXQncyB0aW1lIHRvIGdvIHNvbG8=',
'MDAwMDA4b2xsaW4nIGluIG15IGZpdmUgcG9pbnQgb2g=',
'MDAwMDA5aXRoIG15IHJhZy10b3AgZG93biBzbyBteSBoYWlyIGNhbiBibG93'
]
# token = data(tokens[0]).bytes
token = data(random.sample(tokens, 1)[0], 'b64').bytes
# iv = key[::-1]
iv = int.to_bytes(random.getrandbits(16 * 8), 16, 'big')
return (iv, CBC_encrypt(pad(token, 16), key, iv))
def cyphered_comment(comment):
comment = '"comment1=cooking%20MCs;userdata="'+data(comment).ascii().replace("=","\=").replace(";","\;")+'";comment2=%20like%20a%20pound%20of%20bacon"'
return CBC_encrypt(pad(data(comment).bytes),key)
def cyphered_comment(comment):
comment = '"comment1=cooking%20MCs;userdata="' + data(
comment).ascii().replace("=", "\=").replace(
";", "\;") + '";comment2=%20like%20a%20pound%20of%20bacon"'
return CTR_encrypt(pad(data(comment).bytes),
key) #counterfunction and nonce have default values
def oracle(input_bytes):
unknown_string = data("Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkgaGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBqdXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUgYnkK",'b64').bytes
key = data("sdfKJH432480hnfidjanf430q9fa",'b64').bytes[0:16] # I'm pretending not to know what either of these are
plaintext = input_bytes+unknown_string
plaintext = pad(plaintext,16)
return ECB_encrypt(plaintext,key)
def oracle(input_string):
key = data("sdJH432480hnfidjao2hc",'b64').bytes
return ECB_encrypt(pad(profile_for(input_string).encode(),16),key)
def fake_admin():
key = iv = get_iv()
return CBC_encrypt(pad(b';admin=true;'), key, iv)