🗓 May 7, 2022 11:01:10 AM

✨ xor_key_from_file extra function

chepy/extras/crypto_extras.py

@@ -1,3 +1,4 @@
+import binascii
 import json
 from typing import Iterator, Dict, List, Union
 from binascii import hexlify, unhexlify
@@ -82,6 +83,38 @@ def xor_two_files(file1: str, file2: str) -> bytes:  # pragma: no cover
     pass
 
 
+def xor_key_from_files(
+    f1_path: str, f2_path: str, min: int = 1, max: int = 257
+) -> Union[bytes, None]:  # pragma: no cover
+    """XOR two files and get the key.
+
+    Args:
+        f1_path (str): File 1 path
+        f2_path (str): File 2 path
+        min (int, optional): Min chars to test. Defaults to 1.
+        max (int, optional): Max chars to test. Defaults to 257.
+
+    Returns:
+        Union[bytes, None]: Key as hex bytes or None if no key found
+    """
+
+    def find_same(s: bytes):
+        i = (s + s).find(s, 1, -1)
+        return None if i == -1 else s[:i]
+
+    for i in range(min, max):
+        with open(f1_path, "rb") as f:
+            d1 = f.read(i)
+
+        with open(f2_path, "rb") as f:
+            d2 = f.read(i)
+
+        x = bytes(a ^ b for a, b in zip(d1, d2))
+        o = find_same(x)
+        if o is not None:
+            return binascii.hexlify(o)
+
+
 def xor(data: bytes, key: bytes) -> bytes:  # pragma: no cover
     """XOR data with a hex key
 

chepy/extras/crypto_extras.pyi

@@ -1,5 +1,6 @@
-from typing import Dict, Iterator
+from typing import Dict, Iterator, Union
 
 def factordb(n: int) -> dict: ...
 def construct_private_key(n: int, e: int, d: int, format: str=..., passphrase: str=...) -> str: ...
 def xor_bruteforce_multi(data: str, min: int=..., max: int=..., errors: str=...) -> Iterator[Dict[str, str]]: ...
+def xor_key_from_files(f1_path:str, f2_path: str, min: int =..., max: int = ...) -> Union[bytes, None]: ...