Add utility to replace crypt.crypt

The crypt module was removed in Python 3.13. Add the utility function
to replace crypt.crypt which is used by a few projects. Note that
the function internally calls libcrypt library, so that we don't have
to re-implement its algorithm in python layer.

Change-Id: Ibe6748068b8145fdc7ece384c94a923d1032de5f

bindep.txt

@@ -9,3 +9,7 @@ python3-devel [platform:rpm]
 qemu-img [platform:redhat test]
 qemu-tools [platform:suse test]
 qemu-utils [platform:dpkg test]
+
+libxcrypt-compat [platform:redhat crypt]
+libcrypt1 [platform:suse crypt]
+libcrypt1 [platform:dpkg crypt]

oslo_utils/secretutils.py

@@ -18,6 +18,8 @@ Secret utilities.
 .. versionadded:: 3.5
 """
 
+import ctypes
+import ctypes.util
 import hashlib
 import hmac
 
@@ -40,3 +42,25 @@ def md5(string=b'', usedforsecurity=True):
     See https://bugs.python.org/issue9216
     """
     return hashlib.md5(string, usedforsecurity=usedforsecurity)  # nosec
+
+
+if ctypes.util.find_library("crypt"):
+    _libcrypt = ctypes.CDLL(ctypes.util.find_library("crypt"), use_errno=True)
+    _crypt = _libcrypt.crypt
+    _crypt.argtypes = (ctypes.c_char_p, ctypes.c_char_p)
+    _crypt.restype = ctypes.c_char_p
+else:
+    _crypt = None
+
+
+def crypt_password(key, salt):
+    """Encrtpt password string and generate the value in /etc/shadow format
+
+    This is provided as a replacement of crypt.crypt method because crypt
+    module was removed in Python 3.13.
+
+    .. versionadded:: 7.5
+    """
+    if _crypt is None:
+        raise RuntimeError('libcrypt is not available')
+    return _crypt(key.encode('utf-8'), salt.encode('utf-8')).decode('utf-8')

oslo_utils/tests/test_secretutils.py

@@ -77,3 +77,12 @@ class SecretUtilsTest(testscenarios.TestWithScenarios,
             TypeError, secretutils.md5, None, usedforsecurity=True)
         self.assertRaises(
             TypeError, secretutils.md5, None, usedforsecurity=False)
+
+    def test_password_crypt(self):
+        self.assertEqual(
+            '$5$mysalt$fcnMdhaFpUmeWtGOgVuImueZGL1v0Q1kUVbV2NbFOX4',
+            secretutils.crypt_password('mytopsecret', '$5$mysalt$'))
+        self.assertEqual(
+            '$6$mysalt$jTEJ24XtvcWmav/sTQb1tYqmk1kBQD/sxcMIxEPUcie'
+            'J8L9AuCTWxYlxGz.XtIQYWspWkUXQz9zPIFTSKubP6.',
+            secretutils.crypt_password('mytopsecret', '$6$mysalt$'))