gh-78997: AttributeError if loading fails in LibraryLoader.__getattr__

Co-authored-by: Zachary Ware <zachary.ware@gmail.com>
Co-authored-by: Filipe Laíns <filipe.lains@gmail.com>
Co-authored-by: Eric Wieser <wieser.eric@gmail.com>

Lib/ctypes/__init__.py

@@ -444,7 +444,10 @@ def __init__(self, dlltype):
  def __getattr__(self, name):
  if name[0] == '_':
  raise AttributeError(name)
- dll = self._dlltype(name)
+ try:
+ dll = self._dlltype(name)
+ except OSError:
+ raise AttributeError(name)
  setattr(self, name, dll)
  return dll
 

Lib/ctypes/test/test_loading.py

@@ -0,0 +1,188 @@
+from ctypes import *
+import os
+import shutil
+import subprocess
+import sys
+import unittest
+import test.support
+from test.support import import_helper
+from test.support import os_helper
+from ctypes.util import find_library
+
+libc_name = None
+
+def setUpModule():
+ global libc_name
+ if os.name == "nt":
+ libc_name = find_library("c")
+ elif sys.platform == "cygwin":
+ libc_name = "cygwin1.dll"
+ else:
+ libc_name = find_library("c")
+
+ if test.support.verbose:
+ print("libc_name is", libc_name)
+
+class LoaderTest(unittest.TestCase):
+
+ unknowndll = "xxrandomnamexx"
+
+ def test_load(self):
+ if libc_name is None:
+ self.skipTest('could not find libc')
+ CDLL(libc_name)
+ CDLL(os.path.basename(libc_name))
+ self.assertRaises(OSError, CDLL, self.unknowndll)
+
+ def test_load_version(self):
+ if libc_name is None:
+ self.skipTest('could not find libc')
+ if os.path.basename(libc_name) != 'libc.so.6':
+ self.skipTest('wrong libc path for test')
+ cdll.LoadLibrary("libc.so.6")
+ # linux uses version, libc 9 should not exist
+ self.assertRaises(OSError, cdll.LoadLibrary, "libc.so.9")
+ self.assertRaises(OSError, cdll.LoadLibrary, self.unknowndll)
+
+ def test_find(self):
+ for name in ("c", "m"):
+ lib = find_library(name)
+ if lib:
+ cdll.LoadLibrary(lib)
+ CDLL(lib)
+
+ @unittest.skipUnless(os.name == "nt",
+ 'test specific to Windows')
+ def test_load_library(self):
+ # CRT is no longer directly loadable. See issue23606 for the
+ # discussion about alternative approaches.
+ #self.assertIsNotNone(libc_name)
+ if test.support.verbose:
+ print(find_library("kernel32"))
+ print(find_library("user32"))
+
+ if os.name == "nt":
+ windll.kernel32.GetModuleHandleW
+ windll["kernel32"].GetModuleHandleW
+ windll.LoadLibrary("kernel32").GetModuleHandleW
+ WinDLL("kernel32").GetModuleHandleW
+ # embedded null character
+ self.assertRaises(ValueError, windll.LoadLibrary, "kernel32\0")
+
+ @unittest.skipUnless(os.name == "nt",
+ 'test specific to Windows')
+ def test_load_ordinal_functions(self):
+ import _ctypes_test
+ dll = WinDLL(_ctypes_test.__file__)
+ # We load the same function both via ordinal and name
+ func_ord = dll[2]
+ func_name = dll.GetString
+ # addressof gets the address where the function pointer is stored
+ a_ord = addressof(func_ord)
+ a_name = addressof(func_name)
+ f_ord_addr = c_void_p.from_address(a_ord).value
+ f_name_addr = c_void_p.from_address(a_name).value
+ self.assertEqual(hex(f_ord_addr), hex(f_name_addr))
+
+ self.assertRaises(AttributeError, dll.__getitem__, 1234)
+
+ @unittest.skipUnless(os.name == "nt", 'Windows-specific test')
+ def test_1703286_A(self):
+ from _ctypes import LoadLibrary, FreeLibrary
+ # On winXP 64-bit, advapi32 loads at an address that does
+ # NOT fit into a 32-bit integer. FreeLibrary must be able
+ # to accept this address.
+
+ # These are tests for https://www.python.org/sf/1703286
+ handle = LoadLibrary("advapi32")
+ FreeLibrary(handle)
+
+ @unittest.skipUnless(os.name == "nt", 'Windows-specific test')
+ def test_1703286_B(self):
+ # Since on winXP 64-bit advapi32 loads like described
+ # above, the (arbitrarily selected) CloseEventLog function
+ # also has a high address. 'call_function' should accept
+ # addresses so large.
+ from _ctypes import call_function
+ advapi32 = windll.advapi32
+ # Calling CloseEventLog with a NULL argument should fail,
+ # but the call should not segfault or so.
+ self.assertEqual(0, advapi32.CloseEventLog(None))
+ windll.kernel32.GetProcAddress.argtypes = c_void_p, c_char_p
+ windll.kernel32.GetProcAddress.restype = c_void_p
+ proc = windll.kernel32.GetProcAddress(advapi32._handle,
+ b"CloseEventLog")
+ self.assertTrue(proc)
+ # This is the real test: call the function via 'call_function'
+ self.assertEqual(0, call_function(proc, (None,)))
+
+ @unittest.skipUnless(os.name == "nt",
+ 'test specific to Windows')
+ def test_load_hasattr(self):
+ # bpo-34816: shouldn't raise OSError
+ self.assertFalse(hasattr(windll, 'test'))
+
+ @unittest.skipUnless(os.name == "nt",
+ 'test specific to Windows')
+ def test_load_dll_with_flags(self):
+ _sqlite3 = import_helper.import_module("_sqlite3")
+ src = _sqlite3.__file__
+ if src.lower().endswith("_d.pyd"):
+ ext = "_d.dll"
+ else:
+ ext = ".dll"
+
+ with os_helper.temp_dir() as tmp:
+ # We copy two files and load _sqlite3.dll (formerly .pyd),
+ # which has a dependency on sqlite3.dll. Then we test
+ # loading it in subprocesses to avoid it starting in memory
+ # for each test.
+ target = os.path.join(tmp, "_sqlite3.dll")
+ shutil.copy(src, target)
+ shutil.copy(os.path.join(os.path.dirname(src), "sqlite3" + ext),
+ os.path.join(tmp, "sqlite3" + ext))
+
+ def should_pass(command):
+ with self.subTest(command):
+ subprocess.check_output(
+ [sys.executable, "-c",
+ "from ctypes import *; import nt;" + command],
+ cwd=tmp
+ )
+
+ def should_fail(command):
+ with self.subTest(command):
+ with self.assertRaises(subprocess.CalledProcessError):
+ subprocess.check_output(
+ [sys.executable, "-c",
+ "from ctypes import *; import nt;" + command],
+ cwd=tmp, stderr=subprocess.STDOUT,
+ )
+
+ # Default load should not find this in CWD
+ should_fail("WinDLL('_sqlite3.dll')")
+
+ # Relative path (but not just filename) should succeed
+ should_pass("WinDLL('./_sqlite3.dll')")
+
+ # Insecure load flags should succeed
+ # Clear the DLL directory to avoid safe search settings propagating
+ should_pass("windll.kernel32.SetDllDirectoryW(None); WinDLL('_sqlite3.dll', winmode=0)")
+
+ # Full path load without DLL_LOAD_DIR shouldn't find dependency
+ should_fail("WinDLL(nt._getfullpathname('_sqlite3.dll'), " +
+ "winmode=nt._LOAD_LIBRARY_SEARCH_SYSTEM32)")
+
+ # Full path load with DLL_LOAD_DIR should succeed
+ should_pass("WinDLL(nt._getfullpathname('_sqlite3.dll'), " +
+ "winmode=nt._LOAD_LIBRARY_SEARCH_SYSTEM32|" +
+ "nt._LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR)")
+
+ # User-specified directory should succeed
+ should_pass("import os; p = os.add_dll_directory(os.getcwd());" +
+ "WinDLL('_sqlite3.dll'); p.close()")
+
+
+
+if __name__ == "__main__":
+ unittest.main()

Misc/NEWS.d/next/Windows/2021-04-08-00-36-37.bpo-34816.4Xe0id.rst

@@ -0,0 +1,3 @@
+``hasattr(ctypes.windll, 'nonexistant')`` now returns ``False`` instead of raising :exc:`OSError`.
+
+