bpo-33001: Prevent buffer overrun in os.symlink (GH-5989)
(cherry picked from commit 6921e73e33edc3c61bc2d78ed558eaa22a89a564)
Co-authored-by: Steve Dower <steve.dower@microsoft.com>
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 4f8a2a7..e509188 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -2164,6 +2164,40 @@
target = os.readlink(r'C:\Users\All Users')
self.assertTrue(os.path.samefile(target, r'C:\ProgramData'))
+ def test_buffer_overflow(self):
+ # Older versions would have a buffer overflow when detecting
+ # whether a link source was a directory. This test ensures we
+ # no longer crash, but does not otherwise validate the behavior
+ segment = 'X' * 27
+ path = os.path.join(*[segment] * 10)
+ test_cases = [
+ # overflow with absolute src
+ ('\\' + path, segment),
+ # overflow dest with relative src
+ (segment, path),
+ # overflow when joining src
+ (path[:180], path[:180]),
+ ]
+ for src, dest in test_cases:
+ try:
+ os.symlink(src, dest)
+ except FileNotFoundError:
+ pass
+ else:
+ try:
+ os.remove(dest)
+ except OSError:
+ pass
+ # Also test with bytes, since that is a separate code path.
+ try:
+ os.symlink(os.fsencode(src), os.fsencode(dest))
+ except FileNotFoundError:
+ pass
+ else:
+ try:
+ os.remove(dest)
+ except OSError:
+ pass
@unittest.skipUnless(sys.platform == "win32", "Win32 specific tests")
class Win32JunctionTests(unittest.TestCase):