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Avoid defining Python's AES class if libssl's is available

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Lonami Exo 2017-08-20 01:23:57 +02:00
parent c296459d0a
commit 274e16ac66
1 changed files with 72 additions and 70 deletions
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142
telethon/crypto/aes.py
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@ -2,76 +2,78 @@ import os
import pyaes
from . import libssl
class AES:
@staticmethod
def decrypt_ige(cipher_text, key, iv):
"""Decrypts the given text in 16-bytes blocks by using the
given key and 32-bytes initialization vector
"""
iv1 = iv[:len(iv) // 2]
iv2 = iv[len(iv) // 2:]
aes = pyaes.AES(key)
plain_text = []
blocks_count = len(cipher_text) // 16
cipher_text_block = [0] * 16
for block_index in range(blocks_count):
for i in range(16):
cipher_text_block[i] = \
cipher_text[block_index * 16 + i] ^ iv2[i]
plain_text_block = aes.decrypt(cipher_text_block)
for i in range(16):
plain_text_block[i] ^= iv1[i]
iv1 = cipher_text[block_index * 16:block_index * 16 + 16]
iv2 = plain_text_block
plain_text.extend(plain_text_block)
return bytes(plain_text)
@staticmethod
def encrypt_ige(plain_text, key, iv):
"""Encrypts the given text in 16-bytes blocks by using the
given key and 32-bytes initialization vector
"""
# Add random padding iff it's not evenly divisible by 16 already
if len(plain_text) % 16 != 0:
padding_count = 16 - len(plain_text) % 16
plain_text += os.urandom(padding_count)
iv1 = iv[:len(iv) // 2]
iv2 = iv[len(iv) // 2:]
aes = pyaes.AES(key)
cipher_text = []
blocks_count = len(plain_text) // 16
for block_index in range(blocks_count):
plain_text_block = list(
plain_text[block_index * 16:block_index * 16 + 16]
)
for i in range(16):
plain_text_block[i] ^= iv1[i]
cipher_text_block = aes.encrypt(plain_text_block)
for i in range(16):
cipher_text_block[i] ^= iv2[i]
iv1 = cipher_text_block
iv2 = plain_text[block_index * 16:block_index * 16 + 16]
cipher_text.extend(cipher_text_block)
return bytes(cipher_text)
# use libssl if available
if libssl.libssl:
# Use libssl if available, since it will be faster
AES = libssl.AES
else:
# Fallback to a pure Python implementation
class AES:
@staticmethod
def decrypt_ige(cipher_text, key, iv):
"""Decrypts the given text in 16-bytes blocks by using the
given key and 32-bytes initialization vector
"""
iv1 = iv[:len(iv) // 2]
iv2 = iv[len(iv) // 2:]
aes = pyaes.AES(key)
plain_text = []
blocks_count = len(cipher_text) // 16
cipher_text_block = [0] * 16
for block_index in range(blocks_count):
for i in range(16):
cipher_text_block[i] = \
cipher_text[block_index * 16 + i] ^ iv2[i]
plain_text_block = aes.decrypt(cipher_text_block)
for i in range(16):
plain_text_block[i] ^= iv1[i]
iv1 = cipher_text[block_index * 16:block_index * 16 + 16]
iv2 = plain_text_block
plain_text.extend(plain_text_block)
return bytes(plain_text)
@staticmethod
def encrypt_ige(plain_text, key, iv):
"""Encrypts the given text in 16-bytes blocks by using the
given key and 32-bytes initialization vector
"""
# Add random padding iff it's not evenly divisible by 16 already
if len(plain_text) % 16 != 0:
padding_count = 16 - len(plain_text) % 16
plain_text += os.urandom(padding_count)
iv1 = iv[:len(iv) // 2]
iv2 = iv[len(iv) // 2:]
aes = pyaes.AES(key)
cipher_text = []
blocks_count = len(plain_text) // 16
for block_index in range(blocks_count):
plain_text_block = list(
plain_text[block_index * 16:block_index * 16 + 16]
)
for i in range(16):
plain_text_block[i] ^= iv1[i]
cipher_text_block = aes.encrypt(plain_text_block)
for i in range(16):
cipher_text_block[i] ^= iv2[i]
iv1 = cipher_text_block
iv2 = plain_text[block_index * 16:block_index * 16 + 16]
cipher_text.extend(cipher_text_block)
return bytes(cipher_text)