[3.13] gh-132710: only use stable _uuid.generate_time_safe() to deduce MAC address (GH-132901) (#134704)

This commit includes the original commit and the NEWS entry that was added separately.

(cherry picked from commit 3bffada)
(cherry picked from commit 9eb84d8)

Author: picnixz

Lib/test/test_uuid.py

@@ -1,6 +1,7 @@
 import unittest
 from test import support
 from test.support import import_helper
+from test.support.script_helper import assert_python_ok
 import builtins
 import contextlib
 import copy
@@ -773,10 +774,37 @@ def test_cli_uuid5_ouputted_with_valid_namespace_and_name(self):
 class TestUUIDWithoutExtModule(BaseTestUUID, unittest.TestCase):
     uuid = py_uuid
 
+
 @unittest.skipUnless(c_uuid, 'requires the C _uuid module')
 class TestUUIDWithExtModule(BaseTestUUID, unittest.TestCase):
     uuid = c_uuid
 
+    def check_has_stable_libuuid_extractable_node(self):
+        if not self.uuid._has_stable_extractable_node:
+            self.skipTest("libuuid cannot deduce MAC address")
+
+    @unittest.skipUnless(os.name == 'posix', 'POSIX only')
+    def test_unix_getnode_from_libuuid(self):
+        self.check_has_stable_libuuid_extractable_node()
+        script = 'import uuid; print(uuid._unix_getnode())'
+        _, n_a, _ = assert_python_ok('-c', script)
+        _, n_b, _ = assert_python_ok('-c', script)
+        n_a, n_b = n_a.decode().strip(), n_b.decode().strip()
+        self.assertTrue(n_a.isdigit())
+        self.assertTrue(n_b.isdigit())
+        self.assertEqual(n_a, n_b)
+
+    @unittest.skipUnless(os.name == 'nt', 'Windows only')
+    def test_windows_getnode_from_libuuid(self):
+        self.check_has_stable_libuuid_extractable_node()
+        script = 'import uuid; print(uuid._windll_getnode())'
+        _, n_a, _ = assert_python_ok('-c', script)
+        _, n_b, _ = assert_python_ok('-c', script)
+        n_a, n_b = n_a.decode().strip(), n_b.decode().strip()
+        self.assertTrue(n_a.isdigit())
+        self.assertTrue(n_b.isdigit())
+        self.assertEqual(n_a, n_b)
+
 
 class BaseTestInternals:
     _uuid = py_uuid

Lib/uuid.py

@@ -572,22 +572,24 @@ def _netstat_getnode():
 try:
     import _uuid
     _generate_time_safe = getattr(_uuid, "generate_time_safe", None)
+    _has_stable_extractable_node = getattr(_uuid, "has_stable_extractable_node", False)
     _UuidCreate = getattr(_uuid, "UuidCreate", None)
 except ImportError:
     _uuid = None
     _generate_time_safe = None
+    _has_stable_extractable_node = False
     _UuidCreate = None
 
 
 def _unix_getnode():
     """Get the hardware address on Unix using the _uuid extension module."""
-    if _generate_time_safe:
+    if _generate_time_safe and _has_stable_extractable_node:
         uuid_time, _ = _generate_time_safe()
         return UUID(bytes=uuid_time).node
 
 def _windll_getnode():
     """Get the hardware address on Windows using the _uuid extension module."""
-    if _UuidCreate:
+    if _UuidCreate and _has_stable_extractable_node:
         uuid_bytes = _UuidCreate()
         return UUID(bytes_le=uuid_bytes).node
 

Misc/NEWS.d/next/Library/2025-08-05-09-32-00.gh-issue-132710.ApU3TZ.rst

@@ -0,0 +1,3 @@
+If possible, ensure that :func:`uuid.getnode` returns the same result even
+across different processes. Previously, the result was constant only within
+the same process. Patch by Bénédikt Tran.

Modules/_uuidmodule.c

@@ -78,23 +78,47 @@ py_UuidCreate(PyObject *Py_UNUSED(context),
     return NULL;
 }
 
+static int
+py_windows_has_stable_node(void)
+{
+    UUID uuid;
+    RPC_STATUS res;
+    Py_BEGIN_ALLOW_THREADS
+    res = UuidCreateSequential(&uuid);
+    Py_END_ALLOW_THREADS
+    return res == RPC_S_OK;
+}
 #endif /* MS_WINDOWS */
 
 
 static int
-uuid_exec(PyObject *module) {
+uuid_exec(PyObject *module)
+{
+#define ADD_INT(NAME, VALUE)                                        \
+    do {                                                            \
+        if (PyModule_AddIntConstant(module, (NAME), (VALUE)) < 0) { \
+           return -1;                                               \
+        }                                                           \
+    } while (0)
+
     assert(sizeof(uuid_t) == 16);
 #if defined(MS_WINDOWS)
-    int has_uuid_generate_time_safe = 0;
+    ADD_INT("has_uuid_generate_time_safe", 0);
 #elif defined(HAVE_UUID_GENERATE_TIME_SAFE)
-    int has_uuid_generate_time_safe = 1;
+    ADD_INT("has_uuid_generate_time_safe", 1);
 #else
-    int has_uuid_generate_time_safe = 0;
+    ADD_INT("has_uuid_generate_time_safe", 0);
 #endif
-    if (PyModule_AddIntConstant(module, "has_uuid_generate_time_safe",
-                                has_uuid_generate_time_safe) < 0) {
-        return -1;
-    }
+
+#if defined(MS_WINDOWS)
+    ADD_INT("has_stable_extractable_node", py_windows_has_stable_node());
+#elif defined(HAVE_UUID_GENERATE_TIME_SAFE_STABLE_MAC)
+    ADD_INT("has_stable_extractable_node", 1);
+#else
+    ADD_INT("has_stable_extractable_node", 0);
+#endif
+
+#undef ADD_INT
     return 0;
 }