remove CBC padding (#269)

Author: saimonation

cterasdk/direct/crypto.py

@@ -28,7 +28,8 @@ def decrypt_block(block, encryption_key):
         encrypted_data = block[17:]
         logging.getLogger('cterasdk.direct').debug('Decrypting Block.')
         decryptor = Cipher(algorithms.AES(encryption_key), modes.CBC(initialization_vector)).decryptor()
-        return decryptor.update(encrypted_data)
+        decrypted_data = decryptor.update(encrypted_data)
+        return decrypted_data[:-decrypted_data[-1]]  # Remove CBC Padding
     except ValueError as error:
         logging.getLogger('cterasdk.direct').error('Failed to decrypt block. Key error. %s', error)
     except UnsupportedAlgorithm as error:

cterasdk/direct/decompressor.py

@@ -7,45 +7,34 @@ def decompress(compressed_block):
     """
     Decompress a Block.
 
-    :param bytes block: Compressed Block
-    :returns: Decompressed Block
-    :rtype: bytes
-    """
-    return decompress_with_magic_header(compressed_block) \
-        if compressed_block.startswith(b'\x82SNAPPY\x00') else decompress_without_magic_header(compressed_block)
-
-
-def decompress_with_magic_header(compressed_block):
-    """
-    Decompress a Block.
-
     :param bytes block: Compressed Block
     :returns: Decompressed Block
     :rtype: bytes
     """
     try:
-        logging.getLogger('cterasdk.direct').debug('Decompressing Block.')
-        decompressed_block = bytearray()
-        size_of_data = len(compressed_block)
-        chunk_size, chunk_start = 4, 16
-        while chunk_start < size_of_data:
-            chunk_end = chunk_start + chunk_size + int.from_bytes(compressed_block[chunk_start:chunk_start + chunk_size])
-            chunk_start = chunk_start + chunk_size
-            if chunk_end > size_of_data:
-                break
-            decompressed_block.extend(snappy.decompress(compressed_block[chunk_start:chunk_end]))
-            chunk_start = chunk_end
-        return decompressed_block
+        return decompress_with_magic_header(compressed_block) \
+            if compressed_block.startswith(b'\x82SNAPPY\x00') else snappy.uncompress(compressed_block)
     except snappy.UncompressError:
         raise DirectIOError()
 
 
-def decompress_without_magic_header(compressed_block):
+def decompress_with_magic_header(compressed_block):
     """
     Decompress a Block.
 
-    :param bytes compressed_block: Compressed Block
+    :param bytes block: Compressed Block
     :returns: Decompressed Block
     :rtype: bytes
     """
-    return snappy.uncompress(compressed_block[:compressed_block.rfind(b'EOF') + 3])
+    logging.getLogger('cterasdk.direct').debug('Decompressing Block.')
+    decompressed_block = bytearray()
+    size_of_data = len(compressed_block)
+    chunk_size, chunk_start = 4, 16
+    while chunk_start < size_of_data:
+        chunk_end = chunk_start + chunk_size + int.from_bytes(compressed_block[chunk_start:chunk_start + chunk_size])
+        chunk_start = chunk_start + chunk_size
+        if chunk_end > size_of_data:
+            break
+        decompressed_block.extend(snappy.decompress(compressed_block[chunk_start:chunk_end]))
+        chunk_start = chunk_end
+    return decompressed_block