From 468e01d16472b3442551849199edacb711f3e0ba Mon Sep 17 00:00:00 2001
From: Michael Weghorn <m.weghorn@posteo.de>
Date: Mon, 29 Aug 2022 22:29:19 +0200
Subject: [PATCH] Correct hmac import from Python stdlib

Commit 82c0c4fdd2d99150ed11c188fbc0586512b13edb
("Fallback to hashlib instead of deprecated libs")
had changed the hmac import to try the import from
the hashlib module, but there appears to be 'hmac'
underneath hashlib in neither Python 2 nor Python 3, but
it's a separate module.

Test on Debian testing with Python 2.7.18:

    $ python2
    Python 2.7.18 (default, Aug  1 2022, 06:23:55)
    [GCC 12.1.0] on linux2
    Type "help", "copyright", "credits" or "license" for more information.
    Jedi is not installed, falling back to readline
    >>> from hashlib import hmac as HMAC
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ImportError: cannot import name hmac
    >>> import hmac as HMAC
    >>>

The same with Python 3.10.6:

    $ python3
    Python 3.10.6 (main, Aug 10 2022, 11:19:32) [GCC 12.1.0] on linux
    Type "help", "copyright", "credits" or "license" for more information.
    Using Jedi for tab completion.
    >>> from hashlib import hmac as HMAC
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ImportError: cannot import name 'hmac' from 'hashlib' (/usr/lib/python3.10/hashlib.py)
    >>> import hmac as HMAC
    >>>

Even the official Python 3.10.6 documentation for the hashlib
module use plain hmac import [1] in its example:

    >>> import hmac, hashlib
    >>> m = hmac.new(b'secret key', digestmod=hashlib.blake2s)
    >>> m.update(b'message')
    >>> m.hexdigest()
    'e3c8102868d28b5ff85fc35dda07329970d1a01e273c37481326fe0c861c8142'

Therefore, revert that change to the import and use the direct hmac
import again to make the case where PyCrypto is not installed work
again.

[1] https://docs.python.org/3/library/hashlib.html

Fixes: #223
---
 virtualsmartcard/src/vpicc/virtualsmartcard/CryptoUtils.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virtualsmartcard/src/vpicc/virtualsmartcard/CryptoUtils.py b/virtualsmartcard/src/vpicc/virtualsmartcard/CryptoUtils.py
index 23a6cc7..07a095f 100644
--- a/virtualsmartcard/src/vpicc/virtualsmartcard/CryptoUtils.py
+++ b/virtualsmartcard/src/vpicc/virtualsmartcard/CryptoUtils.py
@@ -31,7 +31,7 @@ try:
 
 except ImportError:
     # PyCrypto not available.  Use the Python standard library.
-    from hashlib import hmac as HMAC
+    import hmac as HMAC
 
 CYBERFLEX_IV = b'\x00' * 8