From 8281fc11b47064f9a4908358befa9db6829f8b88 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 10 Jan 2024 15:55:36 +0200
Subject: [PATCH] gh-109858: Protect zipfile from "quoted-overlap" zipbomb
 (GH-110016)

Raise BadZipFile when try to read an entry that overlaps with other entry or
central directory.
(cherry picked from commit 66363b9a7b9fe7c99eba3a185b74c5fdbf842eba)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
---
 Lib/test/test_zipfile.py                                                |   60 ++++++++++
 Lib/zipfile.py                                                          |   10 +
 Misc/NEWS.d/next/Library/2023-09-28-13-15-51.gh-issue-109858.43e2dg.rst |    3 
 3 files changed, 73 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2023-09-28-13-15-51.gh-issue-109858.43e2dg.rst

--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -2304,6 +2304,66 @@ class OtherTests(unittest.TestCase):
                 zipf.read('a')
             self.assertEqual(len(zipf.read('b')), 1033)
 
+    @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)
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -1217,6 +1217,12 @@ class _ZipWriteFile(io.BufferedIOBase):
             self._zipfile._writing = False
 
 
+        end_offset = self._zipfile.start_dir
+        for zinfo in sorted(self._zipfile.filelist,
+                            key=lambda zinfo: zinfo.header_offset,
+                            reverse=True):
+            zinfo._end_offset = end_offset
+            end_offset = zinfo.header_offset
 
 class ZipFile:
     """ Class with methods to open, read, write, close, list zip files.
@@ -1600,6 +1606,10 @@ class ZipFile:
 
             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)")
+
+            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
--- /dev/null
+++ b/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.