known last state extension attack test works
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GPG Key ID:
25B4ACF7D88186CC
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@ -0,0 +1,46 @@
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current buffer: 5441
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loading buffer
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current in_byte: K
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current buffer: 544143
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loading buffer
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internal state after the bytes were read: c2b50599
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buffer pre last fill: 5441434b
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buffer after last fill: 5441434b
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last internal state: 1b516b3a
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Hacked MIC: cd255d98
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current in_byte:
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current buffer: 4e
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current in_byte: A
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current buffer: 4e20
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current in_byte: T
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current buffer: 4e2041
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current in_byte: T
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current buffer: 4e204154
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current in_byte: A
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current buffer: 54
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current in_byte: C
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current buffer: 5441
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current in_byte: K
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current buffer: 544143
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internal state after the bytes were read: 0e986369
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buffer pre last fill: 5441434b
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buffer after last fill: 5441434b
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last internal state: 1a9d9590
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Hacked MIC: 31bda0ab
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=========
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working extension attack against a basic mic:
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=========
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>>> authur1.authur1(bytearray(4), False, bytearray(0x33a9cfff.to_bytes(4))).hex()
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'fd0ef003'
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>>> authur1.keyed_hash(bytearray(8), bytearray(16), False).hex()
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'fd0ef003'
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>>>
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@ -41,11 +41,15 @@ def inner_authur1(input: int) -> int:
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return output
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def authur1(input: bytearray, verbose: bool = False) -> bytearray:
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if verbose:
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print("input: %s" % input)
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def authur1(input: bytearray,
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verbose: bool = False,
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first_state: bytearray = DEFINED_INITIAL,
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return_last_state: bool = False) -> bytearray:
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internal_buffer: bytearray = bytearray()
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accumulator: bytearray = DEFINED_INITIAL
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accumulator: bytearray = first_state
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if verbose:
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print("input: %s" % input.hex())
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print("first internal state: %s" % accumulator.hex())
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for in_byte in input:
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if verbose:
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print("current in_byte: %s" % chr(in_byte))
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@ -85,38 +89,17 @@ def authur1(input: bytearray, verbose: bool = False) -> bytearray:
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print("last internal state: %s" % accumulator.hex())
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# now Q the accumulator and return
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# if input = "" this step breaks things, just remove it.
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if len(input) != 0:
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if len(input) != 0 and not return_last_state:
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accuint: int = int.from_bytes(accumulator)
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accuint: int = inner_authur1(accuint)
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accumulator: bytearray = bytearray(accuint.to_bytes(4))
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return accumulator
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def keyed_hash(message: bytearray, key: bytearray) -> bytearray:
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def keyed_hash(message: bytearray, key: bytearray, verbose: bool = False, return_last_state: bool = False) -> bytearray:
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assert len(key) == 16, "key is not 16 Byte long: %s" % len(key)
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# prepend only
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input: bytearray = key + message
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mic: bytearray = authur1(input)
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return mic
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def reverse_inner_authur1(output: int) -> int:
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assert output.bit_length() <= 32, "output length is <= 32: %d" % output.bit_length()
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# plexcryptool.binary uses u32 for shifting
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#output: int = input ^ (binary.rotl32(input, SHIFT_LENGTH))
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# -> output ^ input = binary.rotl32(input, SHIFT_LENGTH)
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# -> input = binary.rotl32(input, SHIFT_LENGTH) ^ output
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input: int = output ^ (binary.rotr32(output, SHIFT_LENGTH))
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assert False, "inner_authur1 can not be reversed!"
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assert input.bit_length() <= 32, "input length is <= 32: %d" % input.bit_length()
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return input
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def find_last_internal_state(mic: bytearray) -> bytearray:
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# reverse the mic to get the last internal state
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# TODO
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raise NotImplementedError("find last internal state is still TODO")
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mic: bytearray = authur1(input, verbose, return_last_state=return_last_state)
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return mic
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def extension_attack(valid_pairs: list):
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@ -175,8 +158,37 @@ def extension_attack(valid_pairs: list):
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print("The given originals were not sufficient to perform an extension attack.\n"+
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"We need a message, which has a length that is a multiple of 16 (Bytes).")
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return
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last_internal: bytearray = find_last_internal_state(target_pair[1])
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print("Found a fitting target pair: (%s,%s)" % target_pair)
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# now find the last internal state.
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# inner_authur1 cannot be reversed, so we need to brute force it
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# the key space is only 2**32, so it should be possible
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# we need to check everyone of these 2**32 against the valid hashes to find a working one
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found_the_state = False
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KEY_SPACE = 2**32
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extension_msg = bytearray("ef".encode())
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# given mic for "abcdef" 0f6b8802
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looking_for = bytearray(0x0f6b8802.to_bytes(4))
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last_internal_state = None
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print("=" * 120)
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print("Bruteforcing the internal state, this might take a while")
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print("=" * 120)
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for i in range(0, KEY_SPACE):
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mic = authur1(extension_msg, False, bytearray(i.to_bytes(4)))
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if found_the_state:
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break
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if not mic is None and mic == looking_for:
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print("=" * 120)
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print("FOUND THE THING")
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found_the_state = True
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last_internal_state = i
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print("IT IS %s" % hex(last_internal_state))
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extension_text = "EXTENSION ATTACK"
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hacked_mic = authur1(bytearray(extension_text.encode()), True, bytearray(last_internal_state.to_bytes(4)))
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print("Hacked MIC: %s" % hacked_mic.hex())
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def test():
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init: int = int.from_bytes(DEFINED_INITIAL)
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@ -204,25 +216,28 @@ def test():
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print("H aka authur1 passed the test")
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test_reverse_inner_authur1()
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#test_reverse_inner_authur1()
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test_extension_attack()
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print("All tests passed!")
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def test_extension_attack():
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"""
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Test the attack against a known key
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Test the attack against a known last state
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"""
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# TODO
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raise(NotImplementedError("Extension attack is still TODO"))
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key = bytearray(0x13377331.to_bytes(16))
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message = bytearray("1234".encode())
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ext_message = bytearray("EXT".encode())
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# we need to bruteforce this, skip for the test
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mic = keyed_hash(message, key)
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last_internal_state = keyed_hash(message, key, return_last_state=True)
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forged_mic = authur1(ext_message, False, last_internal_state)
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message.extend(ext_message)
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validated_mic = keyed_hash(message, key)
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assert validated_mic == forged_mic, "forged mic\n%sis not valid\n%s" % ( forged_mic.hex(), validated_mic.hex() )
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print("Manual extension attack with known last internal state works\n(%s == %s)" % (forged_mic.hex(), validated_mic.hex()))
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def test_reverse_inner_authur1():
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a = 0x1337
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aq = inner_authur1(a)
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assert reverse_inner_authur1(aq) == a, "reverse_inner_authur1 does not work:\n%s\nis not\n%s" % (
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bin(a),
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bin(reverse_inner_authur1(a))
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)
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def main():
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parser = argparse.ArgumentParser(prog="authur1", description='Implementation and attack for the custom authur1 hash. Don\'t actually use this hash!')
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