gh-68164: Set the "regular file" bit in zipfile's writestr

Lib/test/test_zipfile/test_core.py

@@ -496,7 +496,7 @@ def zip_test_writestr_permissions(self, f, compression):
         self.make_test_archive(f, compression)
         with zipfile.ZipFile(f, "r") as zipfp:
             zinfo = zipfp.getinfo('strfile')
-            self.assertEqual(zinfo.external_attr, 0o600 << 16)
+            self.assertEqual(zinfo.external_attr, 0o100600 << 16)
 
             zinfo2 = zipfp.getinfo('written-open-w')
             self.assertEqual(zinfo2.external_attr, 0o600 << 16)
@@ -2271,8 +2271,8 @@ def test_for_archive(self):
             zi = zipfile.ZipInfo(base_filename)._for_archive(zf)
             self.assertEqual(zi.compress_level, 1)
             self.assertEqual(zi.compress_type, zipfile.ZIP_STORED)
-            # ?rw- --- ---
-            filemode = stat.S_IRUSR | stat.S_IWUSR
+            # - rw- --- ---
+            filemode = stat.S_IFREG | stat.S_IRUSR | stat.S_IWUSR
             # filemode is stored as the highest 16 bits of external_attr
             self.assertEqual(zi.external_attr >> 16, filemode)
             self.assertEqual(zi.external_attr & 0xFF, 0)  # no MS-DOS flag

Lib/zipfile/__init__.py

@@ -630,10 +630,10 @@ def _for_archive(self, archive):
         self.compress_type = archive.compression
         self.compress_level = archive.compresslevel
         if self.filename.endswith('/'):  # pragma: no cover
-            self.external_attr = 0o40775 << 16  # drwxrwxr-x
+            self.external_attr = (stat.S_IFDIR | 0o775) << 16  # drwxrwxr-x
             self.external_attr |= 0x10  # MS-DOS directory flag
         else:
-            self.external_attr = 0o600 << 16  # ?rw-------
+            self.external_attr = (stat.S_IFREG | 0o600) << 16  # -rw-------
         return self
 
     def is_dir(self):
@@ -2012,7 +2012,7 @@ def mkdir(self, zinfo_or_directory_name, mode=511):
             zinfo = ZipInfo(directory_name)
             zinfo.compress_size = 0
             zinfo.CRC = 0
-            zinfo.external_attr = ((0o40000 | mode) & 0xFFFF) << 16
+            zinfo.external_attr = ((stat.S_IFDIR | mode) & 0xFFFF) << 16
             zinfo.file_size = 0
             zinfo.external_attr |= 0x10
         else:

Misc/NEWS.d/next/Library/2025-05-19-07-32-51.gh-issue-68164.XhFbJD.rst

@@ -0,0 +1,2 @@
+Fix :func:`zipfile.ZipFile.writestr` so it sets the "regular file" bit by
+default.