gh-108948: tarfile should handle sticky bit in FreeBSD

Lib/tarfile.py

@@ -37,6 +37,7 @@
 # Imports
 #---------
 from builtins import open as bltn_open
+import errno
 import sys
 import os
 import io
@@ -2569,7 +2570,15 @@ def chmod(self, tarinfo, targetpath):
         try:
             os.chmod(targetpath, tarinfo.mode)
         except OSError as e:
-            raise ExtractError("could not change mode") from e
+            if hasattr(errno, "EFTYPE") and e.errno == errno.EFTYPE:
+                # On FreeBSD, chmod fails when trying to set the sticky bit on
+                # a file as a normal user. It's a noop in most other platforms.
+                try:
+                    os.chmod(targetpath, tarinfo.mode & ~stat.S_ISVTX)
+                except OSError as e:
+                    raise ExtractError("could not change mode") from e
+            else:
+                raise ExtractError("could not change mode") from e
 
     def utime(self, tarinfo, targetpath):
         """Set modification time of targetpath according to tarinfo.

Lib/test/test_tarfile.py

@@ -9,6 +9,7 @@
 import re
 import warnings
 import stat
+import errno
 
 import unittest
 import unittest.mock
@@ -3818,7 +3819,15 @@ def test_modes(self):
             pass
         new_mode = (os.stat(tmp_filename).st_mode
                     | stat.S_ISVTX | stat.S_ISGID | stat.S_ISUID)
-        os.chmod(tmp_filename, new_mode)
+        try:
+            os.chmod(tmp_filename, new_mode)
+        except OSError as err:
+            # FreeBSD fails with EFTYPE if sticky bit cannot be set, instead
+            # of ignoring it.
+            if hasattr(errno, "EFTYPE") and err.errno == errno.EFTYPE:
+                os.chmod(tmp_filename, new_mode & ~stat.S_ISVTX)
+            else:
+                raise
         got_mode = os.stat(tmp_filename).st_mode
         _t_file = 't' if (got_mode & stat.S_ISVTX) else 'x'
         _suid_file = 's' if (got_mode & stat.S_ISUID) else 'x'

Misc/NEWS.d/next/Library/2023-09-05-17-11-17.gh-issue-108948.HL1Ttw.rst

@@ -0,0 +1 @@
+On FreeBSD, :mod:`tarfile` will not attempt to set the sticky bit on extracted files when it's not possible, matching the behavior of other platforms.