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env/lib/python3.10/site-packages/secretstorage/dhcrypto.py

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+# SecretStorage module for Python
+# Access passwords using the SecretService DBus API
+# Author: Dmitry Shachnev, 2014-2018
+# License: 3-clause BSD, see LICENSE file
+
+'''This module contains needed classes, functions and constants
+to implement dh-ietf1024-sha256-aes128-cbc-pkcs7 secret encryption
+algorithm.'''
+
+import hmac
+import math
+import os
+
+from hashlib import sha256
+from typing import Optional  # Needed for mypy
+
+# A standard 1024 bits (128 bytes) prime number for use in Diffie-Hellman exchange
+DH_PRIME_1024_BYTES = (
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, 0x21, 0x68,
+    0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, 0x29, 0x02, 0x4E, 0x08,
+    0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A,
+    0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B,
+    0x30, 0x2B, 0x0A, 0x6D, 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51,
+    0xC2, 0x45, 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,
+    0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, 0xEE, 0x38,
+    0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, 0x7C, 0x4B, 0x1F, 0xE6,
+    0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF
+)
+
+
+def int_to_bytes(number: int) -> bytes:
+    return number.to_bytes(math.ceil(number.bit_length() / 8), 'big')
+
+
+DH_PRIME_1024 = int.from_bytes(DH_PRIME_1024_BYTES, 'big')
+
+
+class Session:
+    def __init__(self) -> None:
+        self.object_path = None  # type: Optional[str]
+        self.aes_key = None  # type: Optional[bytes]
+        self.encrypted = True
+        # 128-bytes-long strong random number
+        self.my_private_key = int.from_bytes(os.urandom(0x80), 'big')
+        self.my_public_key = pow(2, self.my_private_key, DH_PRIME_1024)
+
+    def set_server_public_key(self, server_public_key: int) -> None:
+        common_secret_int = pow(server_public_key, self.my_private_key,
+                                DH_PRIME_1024)
+        common_secret = int_to_bytes(common_secret_int)
+        # Prepend NULL bytes if needed
+        common_secret = b'\x00' * (0x80 - len(common_secret)) + common_secret
+        # HKDF with null salt, empty info and SHA-256 hash
+        salt = b'\x00' * 0x20
+        pseudo_random_key = hmac.new(salt, common_secret, sha256).digest()
+        output_block = hmac.new(pseudo_random_key, b'\x01', sha256).digest()
+        # Resulting AES key should be 128-bit
+        self.aes_key = output_block[:0x10]