bpo-40501: Replace ctypes code in uuid with native module (GH-19948)

Author: zooba

Lib/test/test_uuid.py

@@ -852,17 +852,6 @@ def test_netstat_getnode(self):
         node = self.uuid._netstat_getnode()
         self.check_node(node, 'netstat')
 
-    @unittest.skipUnless(os.name == 'nt', 'requires Windows')
-    def test_ipconfig_getnode(self):
-        node = self.uuid._ipconfig_getnode()
-        self.check_node(node, 'ipconfig')
-
-    @unittest.skipUnless(importable('win32wnet'), 'requires win32wnet')
-    @unittest.skipUnless(importable('netbios'), 'requires netbios')
-    def test_netbios_getnode(self):
-        node = self.uuid._netbios_getnode()
-        self.check_node(node)
-
     def test_random_getnode(self):
         node = self.uuid._random_getnode()
         # The multicast bit, i.e. the least significant bit of first octet,
@@ -874,6 +863,13 @@ def test_random_getnode(self):
         node2 = self.uuid._random_getnode()
         self.assertNotEqual(node2, node, '%012x' % node)
 
+class TestInternalsWithoutExtModule(BaseTestInternals, unittest.TestCase):
+    uuid = py_uuid
+
+@unittest.skipUnless(c_uuid, 'requires the C _uuid module')
+class TestInternalsWithExtModule(BaseTestInternals, unittest.TestCase):
+    uuid = c_uuid
+
     @unittest.skipUnless(os.name == 'posix', 'requires Posix')
     def test_unix_getnode(self):
         if not importable('_uuid') and not importable('ctypes'):
@@ -885,19 +881,10 @@ def test_unix_getnode(self):
         self.check_node(node, 'unix')
 
     @unittest.skipUnless(os.name == 'nt', 'requires Windows')
-    @unittest.skipUnless(importable('ctypes'), 'requires ctypes')
     def test_windll_getnode(self):
         node = self.uuid._windll_getnode()
         self.check_node(node)
 
 
-class TestInternalsWithoutExtModule(BaseTestInternals, unittest.TestCase):
-    uuid = py_uuid
-
-@unittest.skipUnless(c_uuid, 'requires the C _uuid module')
-class TestInternalsWithExtModule(BaseTestInternals, unittest.TestCase):
-    uuid = c_uuid
-
-
 if __name__ == '__main__':
     unittest.main()

Lib/uuid.py

@@ -555,178 +555,44 @@ def _netstat_getnode():
     return _find_mac_under_heading('netstat', '-ian', b'Address')
 
 def _ipconfig_getnode():
-    """Get the hardware address on Windows by running ipconfig.exe."""
-    import os, re, subprocess
-    first_local_mac = None
-    dirs = ['', r'c:\windows\system32', r'c:\winnt\system32']
-    try:
-        import ctypes
-        buffer = ctypes.create_string_buffer(300)
-        ctypes.windll.kernel32.GetSystemDirectoryA(buffer, 300)
-        dirs.insert(0, buffer.value.decode('mbcs'))
-    except:
-        pass
-    for dir in dirs:
-        try:
-            proc = subprocess.Popen([os.path.join(dir, 'ipconfig'), '/all'],
-                                    stdout=subprocess.PIPE,
-                                    encoding="oem")
-        except OSError:
-            continue
-        with proc:
-            for line in proc.stdout:
-                value = line.split(':')[-1].strip().lower()
-                if re.fullmatch('(?:[0-9a-f][0-9a-f]-){5}[0-9a-f][0-9a-f]', value):
-                    mac = int(value.replace('-', ''), 16)
-                    if _is_universal(mac):
-                        return mac
-                    first_local_mac = first_local_mac or mac
-    return first_local_mac or None
+    """[DEPRECATED] Get the hardware address on Windows."""
+    # bpo-40501: UuidCreateSequential() is now the only supported approach
+    return _windll_getnode()
 
 def _netbios_getnode():
-    """Get the hardware address on Windows using NetBIOS calls.
-    See http://support.microsoft.com/kb/118623 for details."""
-    import win32wnet, netbios
-    first_local_mac = None
-    ncb = netbios.NCB()
-    ncb.Command = netbios.NCBENUM
-    ncb.Buffer = adapters = netbios.LANA_ENUM()
-    adapters._pack()
-    if win32wnet.Netbios(ncb) != 0:
-        return None
-    adapters._unpack()
-    for i in range(adapters.length):
-        ncb.Reset()
-        ncb.Command = netbios.NCBRESET
-        ncb.Lana_num = ord(adapters.lana[i])
-        if win32wnet.Netbios(ncb) != 0:
-            continue
-        ncb.Reset()
-        ncb.Command = netbios.NCBASTAT
-        ncb.Lana_num = ord(adapters.lana[i])
-        ncb.Callname = '*'.ljust(16)
-        ncb.Buffer = status = netbios.ADAPTER_STATUS()
-        if win32wnet.Netbios(ncb) != 0:
-            continue
-        status._unpack()
-        bytes = status.adapter_address[:6]
-        if len(bytes) != 6:
-            continue
-        mac = int.from_bytes(bytes, 'big')
-        if _is_universal(mac):
-            return mac
-        first_local_mac = first_local_mac or mac
-    return first_local_mac or None
+    """[DEPRECATED] Get the hardware address on Windows."""
+    # bpo-40501: UuidCreateSequential() is now the only supported approach
+    return _windll_getnode()
 
 
-_generate_time_safe = _UuidCreate = None
-_has_uuid_generate_time_safe = None
-
 # Import optional C extension at toplevel, to help disabling it when testing
 try:
     import _uuid
+    _generate_time_safe = getattr(_uuid, "generate_time_safe", None)
+    _UuidCreate = getattr(_uuid, "UuidCreate", None)
+    _has_uuid_generate_time_safe = _uuid.has_uuid_generate_time_safe
 except ImportError:
     _uuid = None
+    _generate_time_safe = None
+    _UuidCreate = None
+    _has_uuid_generate_time_safe = None
 
 
 def _load_system_functions():
-    """
-    Try to load platform-specific functions for generating uuids.
-    """
-    global _generate_time_safe, _UuidCreate, _has_uuid_generate_time_safe
-
-    if _has_uuid_generate_time_safe is not None:
-        return
-
-    _has_uuid_generate_time_safe = False
-
-    if sys.platform == "darwin" and int(os.uname().release.split('.')[0]) < 9:
-        # The uuid_generate_* functions are broken on MacOS X 10.5, as noted
-        # in issue #8621 the function generates the same sequence of values
-        # in the parent process and all children created using fork (unless
-        # those children use exec as well).
-        #
-        # Assume that the uuid_generate functions are broken from 10.5 onward,
-        # the test can be adjusted when a later version is fixed.
-        pass
-    elif _uuid is not None:
-        _generate_time_safe = _uuid.generate_time_safe
-        _has_uuid_generate_time_safe = _uuid.has_uuid_generate_time_safe
-        return
-
-    try:
-        # If we couldn't find an extension module, try ctypes to find
-        # system routines for UUID generation.
-        # Thanks to Thomas Heller for ctypes and for his help with its use here.
-        import ctypes
-        import ctypes.util
-
-        # The uuid_generate_* routines are provided by libuuid on at least
-        # Linux and FreeBSD, and provided by libc on Mac OS X.
-        _libnames = ['uuid']
-        if not sys.platform.startswith('win'):
-            _libnames.append('c')
-        for libname in _libnames:
-            try:
-                lib = ctypes.CDLL(ctypes.util.find_library(libname))
-            except Exception:                           # pragma: nocover
-                continue
-            # Try to find the safe variety first.
-            if hasattr(lib, 'uuid_generate_time_safe'):
-                _uuid_generate_time_safe = lib.uuid_generate_time_safe
-                # int uuid_generate_time_safe(uuid_t out);
-                def _generate_time_safe():
-                    _buffer = ctypes.create_string_buffer(16)
-                    res = _uuid_generate_time_safe(_buffer)
-                    return bytes(_buffer.raw), res
-                _has_uuid_generate_time_safe = True
-                break
-
-            elif hasattr(lib, 'uuid_generate_time'):    # pragma: nocover
-                _uuid_generate_time = lib.uuid_generate_time
-                # void uuid_generate_time(uuid_t out);
-                _uuid_generate_time.restype = None
-                def _generate_time_safe():
-                    _buffer = ctypes.create_string_buffer(16)
-                    _uuid_generate_time(_buffer)
-                    return bytes(_buffer.raw), None
-                break
-
-        # On Windows prior to 2000, UuidCreate gives a UUID containing the
-        # hardware address.  On Windows 2000 and later, UuidCreate makes a
-        # random UUID and UuidCreateSequential gives a UUID containing the
-        # hardware address.  These routines are provided by the RPC runtime.
-        # NOTE:  at least on Tim's WinXP Pro SP2 desktop box, while the last
-        # 6 bytes returned by UuidCreateSequential are fixed, they don't appear
-        # to bear any relationship to the MAC address of any network device
-        # on the box.
-        try:
-            lib = ctypes.windll.rpcrt4
-        except:
-            lib = None
-        _UuidCreate = getattr(lib, 'UuidCreateSequential',
-                              getattr(lib, 'UuidCreate', None))
-
-    except Exception as exc:
-        import warnings
-        warnings.warn(f"Could not find fallback ctypes uuid functions: {exc}",
-                      ImportWarning)
+    """[DEPRECATED] Platform-specific functions loaded at import time"""
 
 
 def _unix_getnode():
-    """Get the hardware address on Unix using the _uuid extension module
-    or ctypes."""
-    _load_system_functions()
-    uuid_time, _ = _generate_time_safe()
-    return UUID(bytes=uuid_time).node
+    """Get the hardware address on Unix using the _uuid extension module."""
+    if _generate_time_safe:
+        uuid_time, _ = _generate_time_safe()
+        return UUID(bytes=uuid_time).node
 
 def _windll_getnode():
-    """Get the hardware address on Windows using ctypes."""
-    import ctypes
-    _load_system_functions()
-    _buffer = ctypes.create_string_buffer(16)
-    if _UuidCreate(_buffer) == 0:
-        return UUID(bytes=bytes_(_buffer.raw)).node
+    """Get the hardware address on Windows using the _uuid extension module."""
+    if _UuidCreate:
+        uuid_bytes = _UuidCreate()
+        return UUID(bytes_le=uuid_bytes).node
 
 def _random_getnode():
     """Get a random node ID."""
@@ -755,7 +621,8 @@ def _random_getnode():
 elif _DARWIN:
     _OS_GETTERS = [_ifconfig_getnode, _arp_getnode, _netstat_getnode]
 elif _WINDOWS:
-    _OS_GETTERS = [_netbios_getnode, _ipconfig_getnode]
+    # bpo-40201: _windll_getnode will always succeed, so these are not needed
+    _OS_GETTERS = []
 elif _AIX:
     _OS_GETTERS = [_netstat_getnode]
 else:
@@ -802,7 +669,6 @@ def uuid1(node=None, clock_seq=None):
 
     # When the system provides a version-1 UUID generator, use it (but don't
     # use UuidCreate here because its UUIDs don't conform to RFC 4122).
-    _load_system_functions()
     if _generate_time_safe is not None and node is clock_seq is None:
         uuid_time, safely_generated = _generate_time_safe()
         try:

Misc/NEWS.d/next/Security/2020-05-06-00-41-11.bpo-40501._61wv_.rst

@@ -0,0 +1,2 @@
+:mod:`uuid` no longer uses :mod:`ctypes` to load :file:`libuuid` or
+:file:`rpcrt4.dll` at runtime.

Modules/_uuidmodule.c

@@ -1,5 +1,5 @@
 /*
- * Python UUID module that wraps libuuid -
+ * Python UUID module that wraps libuuid or Windows rpcrt4.dll.
  * DCE compatible Universally Unique Identifier library.
  */
 
@@ -12,6 +12,12 @@
 #include <uuid.h>
 #endif
 
+#ifdef MS_WINDOWS
+#include <rpc.h>
+#endif
+
+#ifndef MS_WINDOWS
+
 static PyObject *
 py_uuid_generate_time_safe(PyObject *Py_UNUSED(context),
                            PyObject *Py_UNUSED(ignored))
@@ -31,17 +37,50 @@ py_uuid_generate_time_safe(PyObject *Py_UNUSED(context),
     return Py_BuildValue("y#i", buf, sizeof(uuid), (int) status);
 # else
     return Py_BuildValue("y#i", (const char *) &uuid, sizeof(uuid), (int) status);
-# endif
-#else
+# endif /* HAVE_UUID_CREATE */
+#else /* HAVE_UUID_GENERATE_TIME_SAFE */
     uuid_generate_time(uuid);
     return Py_BuildValue("y#O", (const char *) uuid, sizeof(uuid), Py_None);
-#endif
+#endif /* HAVE_UUID_GENERATE_TIME_SAFE */
 }
 
+#else /* MS_WINDOWS */
+
+static PyObject *
+py_UuidCreate(PyObject *Py_UNUSED(context),
+              PyObject *Py_UNUSED(ignored))
+{
+    UUID uuid;
+    RPC_STATUS res;
+
+    Py_BEGIN_ALLOW_THREADS
+    res = UuidCreateSequential(&uuid);
+    Py_END_ALLOW_THREADS
+
+    switch (res) {
+    case RPC_S_OK:
+    case RPC_S_UUID_LOCAL_ONLY:
+    case RPC_S_UUID_NO_ADDRESS:
+        /*
+        All success codes, but the latter two indicate that the UUID is random
+        rather than based on the MAC address. If the OS can't figure this out,
+        neither can we, so we'll take it anyway.
+        */
+        return Py_BuildValue("y#", (const char *)&uuid, sizeof(uuid));
+    }
+    PyErr_SetFromWindowsErr(res);
+    return NULL;
+}
+
+#endif /* MS_WINDOWS */
+
+
 static int
 uuid_exec(PyObject *module) {
     assert(sizeof(uuid_t) == 16);
-#ifdef HAVE_UUID_GENERATE_TIME_SAFE
+#if defined(MS_WINDOWS)
+    int has_uuid_generate_time_safe = 0;
+#elif defined(HAVE_UUID_GENERATE_TIME_SAFE)
     int has_uuid_generate_time_safe = 1;
 #else
     int has_uuid_generate_time_safe = 0;
@@ -54,7 +93,12 @@ uuid_exec(PyObject *module) {
 }
 
 static PyMethodDef uuid_methods[] = {
+#if defined(HAVE_UUID_UUID_H) || defined(HAVE_UUID_H)
     {"generate_time_safe", py_uuid_generate_time_safe, METH_NOARGS, NULL},
+#endif
+#if defined(MS_WINDOWS)
+    {"UuidCreate", py_UuidCreate, METH_NOARGS, NULL},
+#endif
     {NULL, NULL, 0, NULL}           /* sentinel */
 };