More descriptive error msg when laf_crypto fails to import, py2 compat, pytest for crypto

laf_crypto.py

@@ -1,11 +1,16 @@
-from Crypto.Cipher import AES
+import struct
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+from cryptography.hazmat.backends import default_backend
 from lglaf import int_as_byte
 
 
 def key_transform(old_key):
     new_key = b''
     for x in range(32, 0, -1):
-        new_key += int_as_byte(old_key[x-1] - (x % 0x0C))
+        c = old_key[x-1]
+        if not isinstance(c, int):
+            c = ord(c)
+        new_key += int_as_byte(c - (x % 0x0C))
     return new_key
 
 
@@ -13,11 +18,10 @@ def xor_key(key, kilo_challenge):
     # Reserve key
     key_xor = b''
     pos = 0
+    challenge = struct.unpack('>I', kilo_challenge)[0]
     for i in range(8):
-        key_xor += int_as_byte(key[pos] ^ kilo_challenge[3])
-        key_xor += int_as_byte(key[pos + 1] ^ kilo_challenge[2])
-        key_xor += int_as_byte(key[pos + 2] ^ kilo_challenge[1])
-        key_xor += int_as_byte(key[pos + 3] ^ kilo_challenge[0])
+        k = struct.unpack('<I', key[pos:pos + 4])[0]
+        key_xor += struct.pack('<I', k ^ challenge)
         pos += 4
     return key_xor
 
@@ -29,5 +33,6 @@ def encrypt_kilo_challenge(encryption_key, kilo_challenge):
         plaintext += int_as_byte(k)
     encryption_key = key_transform(encryption_key)
     xored_key = xor_key(encryption_key, kilo_challenge)
-    obj = AES.new(xored_key, AES.MODE_ECB)
-    return obj.encrypt(plaintext)
+    obj = Cipher(algorithms.AES(xored_key), modes.ECB(),
+                 backend=default_backend()).encryptor()
+    return obj.update(plaintext) + obj.finalize()

lglaf.py

@@ -24,16 +24,21 @@ except ImportError:
 _logger = logging.getLogger("LGLAF.py")
 
 # Python 2/3 compat
-try: input = raw_input
-except: pass
-if '\0' == b'\0': int_as_byte = chr
-else: int_as_byte = lambda x: bytes([x])
+try:
+    input = raw_input
+except:
+    pass
+
+if '\0' == b'\0':
+    int_as_byte = chr
+else:
+    int_as_byte = lambda x: bytes([x])
 
 # laf crypto for KILO challenge/response
 try:
     import laf_crypto
-except ImportError:
-    _logger.warning("LAF Crypto failed to import!")
+except ImportError as e:
+    _logger.warning("LAF Crypto failed to import! Error: %s" % e)
     pass
 
 # Use Manufacturer key for KILO challenge/response

tests/conftest.py

@@ -0,0 +1,5 @@
+import pytest
+
+@pytest.fixture(scope='session')
+def laf_key():
+    return b'qndiakxxuiemdklseqid~a~niq,zjuxl'

tests/test_crypto.py

@@ -0,0 +1,17 @@
+from binascii import unhexlify
+import laf_crypto
+
+
+def test_transform(laf_key):
+    transformed = laf_crypto.key_transform(laf_key)
+    assert transformed == b'dqoev)ohnsWu\\bk`oiicmZ_lpqe\\ealp'
+
+def test_xor_key(laf_key):
+    transformed_key = b'dqoev)ohnsWu\\bk`oiicmZ_lpqe\\ealp'
+    challenge = unhexlify(b'f29ae130')
+    xored_key = laf_crypto.xor_key(transformed_key, challenge)
+    assert xored_key == b'T\x90\xf5\x97F\xc8\xf5\x9a^\x92\xcd\x87l\x83\xf1\x92_\x88\xf3\x91]\xbb\xc5\x9e@\x90\xff\xaeU\x80\xf6\x82'
+
+def test_challenge(laf_key):
+    resp = laf_crypto.encrypt_kilo_challenge(laf_key, unhexlify(b'f29ae130'))
+    assert resp == unhexlify(b'2f47ca81ebeee6f414263c0542c8d132')