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Improved IV handling code for Title Keys in crypto.py

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This commit is contained in:
Campbell 2024-05-03 17:27:52 -04:00
parent 9890a6dbac
commit ba320a29de
1 changed files with 34 additions and 10 deletions
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44
src/libWiiPy/crypto.py
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@ -8,7 +8,7 @@ from .commonkeys import get_common_key
from Crypto.Cipher import AES
def decrypt_title_key(title_key_enc, common_key_index, title_id) -> bytes:
def decrypt_title_key(title_key_enc: bytes, common_key_index: int, title_id: bytes | str) -> bytes:
"""
Gets the decrypted version of the encrypted Title Key provided.
@ -20,8 +20,8 @@ def decrypt_title_key(title_key_enc, common_key_index, title_id) -> bytes:
The encrypted Title Key.
common_key_index : int
The index of the common key used to encrypt the Title Key.
title_id : bytes
The title ID of the title that the key is for.
title_id : bytes, str
The Title ID of the title that the key is for.
Returns
-------
@ -30,8 +30,20 @@ def decrypt_title_key(title_key_enc, common_key_index, title_id) -> bytes:
"""
# Load the correct common key for the title.
common_key = get_common_key(common_key_index)
# Calculate the IV by adding 8 bytes to the end of the Title ID.
title_key_iv = binascii.unhexlify(title_id)
# Convert the IV into the correct format based on the type provided.
title_key_iv = b''
if type(title_id) is bytes:
if len(title_id) == 16:
title_key_iv = binascii.unhexlify(title_id)
elif len(title_id) == 8:
pass
else:
raise ValueError("Title ID is not valid!")
elif type(title_id) is str:
title_key_iv = binascii.unhexlify(title_id)
else:
raise TypeError("Title ID is not valid! It must be either type str or bytes.")
# The IV will always be in the same format by this point, so add the last 8 bytes.
title_key_iv = title_key_iv + (b'\x00' * 8)
# Create a new AES object with the values provided.
aes = AES.new(common_key, AES.MODE_CBC, title_key_iv)
@ -40,7 +52,7 @@ def decrypt_title_key(title_key_enc, common_key_index, title_id) -> bytes:
return title_key
def encrypt_title_key(title_key_dec, common_key_index, title_id) -> bytes:
def encrypt_title_key(title_key_dec: bytes, common_key_index: int, title_id: bytes | str) -> bytes:
"""
Encrypts the provided Title Key with the selected common key.
@ -52,8 +64,8 @@ def encrypt_title_key(title_key_dec, common_key_index, title_id) -> bytes:
The decrypted Title Key.
common_key_index : int
The index of the common key used to encrypt the Title Key.
title_id : bytes
The title ID of the title that the key is for.
title_id : bytes, str
The Title ID of the title that the key is for.
Returns
-------
@ -62,8 +74,20 @@ def encrypt_title_key(title_key_dec, common_key_index, title_id) -> bytes:
"""
# Load the correct common key for the title.
common_key = get_common_key(common_key_index)
# Calculate the IV by adding 8 bytes to the end of the Title ID.
title_key_iv = binascii.unhexlify(title_id)
# Convert the IV into the correct format based on the type provided.
title_key_iv = b''
if type(title_id) is bytes:
if len(title_id) == 16:
title_key_iv = binascii.unhexlify(title_id)
elif len(title_id) == 8:
pass
else:
raise ValueError("Title ID is not valid!")
elif type(title_id) is str:
title_key_iv = binascii.unhexlify(title_id)
else:
raise TypeError("Title ID is not valid! It must be either type str or bytes.")
# The IV will always be in the same format by this point, so add the last 8 bytes.
title_key_iv = title_key_iv + (b'\x00' * 8)
# Create a new AES object with the values provided.
aes = AES.new(common_key, AES.MODE_CBC, title_key_iv)