[3.13] gh-141907: Better handle support for SHA3 for test_hashlib (GH-141908) (#141919)

gh-141907: Better handle support for SHA3 for test_hashlib (GH-141908)

* test_hashlib: better handle support for SHA3

It's possible that the SSL library supports only SHA3 algo and doesn't
have SHAKE one.

The current test wrongly detect this and set both HASH and HASHXOF to
None expecting to have the extra SHA3 attributes present but this should
only be true for SHAKE algo.

To better handle this, move the HASH condition to a dedicated try-expect
condition and check if HASHXOF is None in the relevant code effectively
checking if SHA3 is supported by the SSL library but SHAKE algo needs to
use the sha3module one.

---------
(cherry picked from commit fee7782650)

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Co-authored-by: Christian Marangi <ansuelsmth@gmail.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>

Lib/test/test_hashlib.py

@@ -40,12 +40,15 @@ else:
 openssl_hashlib = import_fresh_module('hashlib', fresh=['_hashlib'])
 
 try:
-    from _hashlib import HASH, HASHXOF, openssl_md_meth_names, get_fips_mode
+    import _hashlib
 except ImportError:
-    HASH = None
-    HASHXOF = None
-    openssl_md_meth_names = frozenset()
-
+    _hashlib = None
+# The extension module may exist but only define some of these. gh-141907
+HASH = getattr(_hashlib, 'HASH', None)
+HASHXOF = getattr(_hashlib, 'HASHXOF', None)
+openssl_md_meth_names = getattr(_hashlib, 'openssl_md_meth_names', frozenset())
+get_fips_mode = getattr(_hashlib, 'get_fips_mode', None)
+if not get_fips_mode:
     def get_fips_mode():
         return 0
 
@@ -558,9 +561,14 @@ class HashLibTestCase(unittest.TestCase):
         constructors = self.constructors_to_test[name]
         for hash_object_constructor in constructors:
             m = hash_object_constructor()
-            if HASH is not None and isinstance(m, HASH):
-                # _hashopenssl's variant does not have extra SHA3 attributes
-                continue
+            if name.startswith('shake_'):
+                if HASHXOF is not None and isinstance(m, HASHXOF):
+                    # _hashopenssl's variant does not have extra SHA3 attributes
+                    continue
+            else:
+                if HASH is not None and isinstance(m, HASH):
+                    # _hashopenssl's variant does not have extra SHA3 attributes
+                    continue
             self.assertEqual(capacity + rate, 1600)
             self.assertEqual(m._capacity_bits, capacity)
             self.assertEqual(m._rate_bits, rate)
@@ -1057,7 +1065,8 @@ class HashLibTestCase(unittest.TestCase):
     def test_hash_disallow_instantiation(self):
         # internal types like _hashlib.HASH are not constructable
         support.check_disallow_instantiation(self, HASH)
-        support.check_disallow_instantiation(self, HASHXOF)
+        if HASHXOF is not None:
+            support.check_disallow_instantiation(self, HASHXOF)
 
     def test_readonly_types(self):
         for algorithm, constructors in self.constructors_to_test.items():