[3.8] pythongh-109858: Protect zipfile from "quoted-overlap" zipbomb (pythonGH-110016) (pythonGH-113916)

Raise BadZipFile when try to read an entry that overlaps with other entry or
central directory.
(cherry picked from commit 66363b9)

Author: serhiy-storchaka

Lib/test/test_zipfile.py

@@ -1610,6 +1610,114 @@ def test_open_conflicting_handles(self):
             self.assertEqual(zipf.read('baz'), msg3)
             self.assertEqual(zipf.namelist(), ['foo', 'bar', 'baz'])
 
+    def test_seek_tell(self):
+        # Test seek functionality
+        txt = b"Where's Bruce?"
+        bloc = txt.find(b"Bruce")
+        # Check seek on a file
+        with zipfile.ZipFile(TESTFN, "w") as zipf:
+            zipf.writestr("foo.txt", txt)
+        with zipfile.ZipFile(TESTFN, "r") as zipf:
+            with zipf.open("foo.txt", "r") as fp:
+                fp.seek(bloc, os.SEEK_SET)
+                self.assertEqual(fp.tell(), bloc)
+                fp.seek(-bloc, os.SEEK_CUR)
+                self.assertEqual(fp.tell(), 0)
+                fp.seek(bloc, os.SEEK_CUR)
+                self.assertEqual(fp.tell(), bloc)
+                self.assertEqual(fp.read(5), txt[bloc:bloc+5])
+                fp.seek(0, os.SEEK_END)
+                self.assertEqual(fp.tell(), len(txt))
+                fp.seek(0, os.SEEK_SET)
+                self.assertEqual(fp.tell(), 0)
+        # Check seek on memory file
+        data = io.BytesIO()
+        with zipfile.ZipFile(data, mode="w") as zipf:
+            zipf.writestr("foo.txt", txt)
+        with zipfile.ZipFile(data, mode="r") as zipf:
+            with zipf.open("foo.txt", "r") as fp:
+                fp.seek(bloc, os.SEEK_SET)
+                self.assertEqual(fp.tell(), bloc)
+                fp.seek(-bloc, os.SEEK_CUR)
+                self.assertEqual(fp.tell(), 0)
+                fp.seek(bloc, os.SEEK_CUR)
+                self.assertEqual(fp.tell(), bloc)
+                self.assertEqual(fp.read(5), txt[bloc:bloc+5])
+                fp.seek(0, os.SEEK_END)
+                self.assertEqual(fp.tell(), len(txt))
+                fp.seek(0, os.SEEK_SET)
+                self.assertEqual(fp.tell(), 0)
+
+    @requires_bz2
+    def test_decompress_without_3rd_party_library(self):
+        data = b'PK\x05\x06\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+        zip_file = io.BytesIO(data)
+        with zipfile.ZipFile(zip_file, 'w', compression=zipfile.ZIP_BZIP2) as zf:
+            zf.writestr('a.txt', b'a')
+        with mock.patch('zipfile.bz2', None):
+            with zipfile.ZipFile(zip_file) as zf:
+                self.assertRaises(RuntimeError, zf.extract, 'a.txt')
+
+    @requires_zlib
+    def test_full_overlap(self):
+        data = (
+            b'PK\x03\x04\x14\x00\x00\x00\x08\x00\xa0lH\x05\xe2\x1e'
+            b'8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00\x00\x00a\xed'
+            b'\xc0\x81\x08\x00\x00\x00\xc00\xd6\xfbK\\d\x0b`P'
+            b'K\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0lH\x05\xe2'
+            b'\x1e8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00\x00\x00\x00'
+            b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00aPK'
+            b'\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0lH\x05\xe2\x1e'
+            b'8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00\x00\x00\x00\x00'
+            b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00bPK\x05'
+            b'\x06\x00\x00\x00\x00\x02\x00\x02\x00^\x00\x00\x00/\x00\x00'
+            b'\x00\x00\x00'
+        )
+        with zipfile.ZipFile(io.BytesIO(data), 'r') as zipf:
+            self.assertEqual(zipf.namelist(), ['a', 'b'])
+            zi = zipf.getinfo('a')
+            self.assertEqual(zi.header_offset, 0)
+            self.assertEqual(zi.compress_size, 16)
+            self.assertEqual(zi.file_size, 1033)
+            zi = zipf.getinfo('b')
+            self.assertEqual(zi.header_offset, 0)
+            self.assertEqual(zi.compress_size, 16)
+            self.assertEqual(zi.file_size, 1033)
+            self.assertEqual(len(zipf.read('a')), 1033)
+            with self.assertRaisesRegex(zipfile.BadZipFile, 'File name.*differ'):
+                zipf.read('b')
+
+    @requires_zlib
+    def test_quoted_overlap(self):
+        data = (
+            b'PK\x03\x04\x14\x00\x00\x00\x08\x00\xa0lH\x05Y\xfc'
+            b'8\x044\x00\x00\x00(\x04\x00\x00\x01\x00\x00\x00a\x00'
+            b'\x1f\x00\xe0\xffPK\x03\x04\x14\x00\x00\x00\x08\x00\xa0l'
+            b'H\x05\xe2\x1e8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00'
+            b'\x00\x00b\xed\xc0\x81\x08\x00\x00\x00\xc00\xd6\xfbK\\'
+            b'd\x0b`PK\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0'
+            b'lH\x05Y\xfc8\x044\x00\x00\x00(\x04\x00\x00\x01'
+            b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+            b'\x00aPK\x01\x02\x14\x00\x14\x00\x00\x00\x08\x00\xa0l'
+            b'H\x05\xe2\x1e8\xbb\x10\x00\x00\x00\t\x04\x00\x00\x01\x00'
+            b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00$\x00\x00\x00'
+            b'bPK\x05\x06\x00\x00\x00\x00\x02\x00\x02\x00^\x00\x00'
+            b'\x00S\x00\x00\x00\x00\x00'
+        )
+        with zipfile.ZipFile(io.BytesIO(data), 'r') as zipf:
+            self.assertEqual(zipf.namelist(), ['a', 'b'])
+            zi = zipf.getinfo('a')
+            self.assertEqual(zi.header_offset, 0)
+            self.assertEqual(zi.compress_size, 52)
+            self.assertEqual(zi.file_size, 1064)
+            zi = zipf.getinfo('b')
+            self.assertEqual(zi.header_offset, 36)
+            self.assertEqual(zi.compress_size, 16)
+            self.assertEqual(zi.file_size, 1033)
+            with self.assertRaisesRegex(zipfile.BadZipFile, 'Overlapped entries'):
+                zipf.read('a')
+            self.assertEqual(len(zipf.read('b')), 1033)
+
     def tearDown(self):
         unlink(TESTFN)
         unlink(TESTFN2)

Lib/zipfile.py

@@ -338,6 +338,7 @@ class ZipInfo (object):
         'compress_size',
         'file_size',
         '_raw_time',
+        '_end_offset',
     )
 
     def __init__(self, filename="NoName", date_time=(1980,1,1,0,0,0)):
@@ -376,6 +377,7 @@ def __init__(self, filename="NoName", date_time=(1980,1,1,0,0,0)):
         self.volume = 0                 # Volume number of file header
         self.internal_attr = 0          # Internal attributes
         self.external_attr = 0          # External file attributes
+        self._end_offset = None         # Start of the next local header or central directory
         # Other attributes are set by class ZipFile:
         # header_offset         Byte offset to the file header
         # CRC                   CRC-32 of the uncompressed file
@@ -1264,6 +1266,12 @@ def _RealGetContents(self):
             if self.debug > 2:
                 print("total", total)
 
+        end_offset = self.start_dir
+        for zinfo in sorted(self.filelist,
+                            key=lambda zinfo: zinfo.header_offset,
+                            reverse=True):
+            zinfo._end_offset = end_offset
+            end_offset = zinfo.header_offset
 
     def namelist(self):
         """Return a list of file names in the archive."""
@@ -1418,6 +1426,10 @@ def open(self, name, mode="r", pwd=None, *, force_zip64=False):
                     'File name in directory %r and header %r differ.'
                     % (zinfo.orig_filename, fname))
 
+            if (zinfo._end_offset is not None and
+                zef_file.tell() + zinfo.compress_size > zinfo._end_offset):
+                raise BadZipFile(f"Overlapped entries: {zinfo.orig_filename!r} (possible zip bomb)")
+
             # check for encrypted flag & handle password
             is_encrypted = zinfo.flag_bits & 0x1
             zd = None

Misc/NEWS.d/next/Library/2023-09-28-13-15-51.gh-issue-109858.43e2dg.rst

@@ -0,0 +1,3 @@
+Protect :mod:`zipfile` from "quoted-overlap" zipbomb. It now raises
+BadZipFile when try to read an entry that overlaps with other entry or
+central directory.