Get rid of int_to_bytes() function

We know the exact length, so use int.to_bytes() directly.

Thanks to mesonium for the suggestion in #48.

Author: mitya57

secretstorage/dhcrypto.py

@@ -8,7 +8,6 @@
 algorithm.'''
 
 import hmac
-import math
 import os
 from hashlib import sha256
 
@@ -27,12 +26,6 @@
 )
 
 
-def int_to_bytes(number: int, length: int) -> bytes:
-    result = number.to_bytes(math.ceil(number.bit_length() / 8), 'big')
-    # Pad with zero bytes if needed.
-    return b'\x00' * (length - len(result)) + result
-
-
 DH_PRIME_1024 = int.from_bytes(DH_PRIME_1024_BYTES, 'big')
 
 
@@ -48,7 +41,7 @@ def __init__(self) -> None:
     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, 128)
+        common_secret = common_secret_int.to_bytes(128, 'big')
         # HKDF with null salt, empty info and SHA-256 hash
         salt = b'\x00' * 0x20
         pseudo_random_key = hmac.new(salt, common_secret, sha256).digest()

secretstorage/util.py

@@ -35,7 +35,7 @@
     SS_PATH,
     SS_PREFIX,
 )
-from secretstorage.dhcrypto import Session, int_to_bytes
+from secretstorage.dhcrypto import Session
 from secretstorage.exceptions import (
     ItemNotFoundException,
     SecretServiceNotAvailableException,
@@ -102,7 +102,7 @@ def open_session(connection: DBusConnection) -> Session:
         output, result = service.call(
             'OpenSession', 'sv',
             ALGORITHM_DH,
-            ('ay', int_to_bytes(session.my_public_key, 128)))
+            ('ay', session.my_public_key.to_bytes(128, 'big')))
     except DBusErrorResponse as resp:
         if resp.name != DBUS_NOT_SUPPORTED:
             raise