From 202ed2506c84cd98e9e35621b5b2929ceb717864 Mon Sep 17 00:00:00 2001
From: Sam Ezeh <sam.z.ezeh@gmail.com>
Date: Mon, 23 May 2022 18:59:21 +0100
Subject: [PATCH] gh-83245: Raise BadZipFile instead of ValueError when reading
a corrupt ZIP file (GH-32291)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
---
Lib/test/test_zipfile.py | 11 +++++++++++
Lib/zipfile.py | 2 ++
.../Library/2022-04-03-19-40-09.bpo-39064.76PbIz.rst | 2 ++
3 files changed, 15 insertions(+)
create mode 100644 Misc/NEWS.d/next/Library/2022-04-03-19-40-09.bpo-39064.76PbIz.rst
diff --git a/Lib/test/test_zipfile.py b/Lib/test/test_zipfile.py
index 848bf4f76d4..f4c11d88c8a 100644
--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -1740,6 +1740,17 @@ def test_empty_file_raises_BadZipFile(self):
fp.write("short file")
self.assertRaises(zipfile.BadZipFile, zipfile.ZipFile, TESTFN)
+ def test_negative_central_directory_offset_raises_BadZipFile(self):
+ # Zip file containing an empty EOCD record
+ buffer = bytearray(b'PK\x05\x06' + b'\0'*18)
+
+ # Set the size of the central directory bytes to become 1,
+ # causing the central directory offset to become negative
+ for dirsize in 1, 2**32-1:
+ buffer[12:16] = struct.pack('<L', dirsize)
+ f = io.BytesIO(buffer)
+ self.assertRaises(zipfile.BadZipFile, zipfile.ZipFile, f)
+
def test_closed_zip_raises_ValueError(self):
"""Verify that testzip() doesn't swallow inappropriate exceptions."""
data = io.BytesIO()
diff --git a/Lib/zipfile.py b/Lib/zipfile.py
index 9f4437526c9..fc6ca65e5ed 100644
--- a/Lib/zipfile.py
+++ b/Lib/zipfile.py
@@ -1381,6 +1381,8 @@ def _RealGetContents(self):
print("given, inferred, offset", offset_cd, inferred, concat)
# self.start_dir: Position of start of central directory
self.start_dir = offset_cd + concat
+ if self.start_dir < 0:
+ raise BadZipFile("Bad offset for central directory")
fp.seek(self.start_dir, 0)
data = fp.read(size_cd)
fp = io.BytesIO(data)
diff --git a/Misc/NEWS.d/next/Library/2022-04-03-19-40-09.bpo-39064.76PbIz.rst b/Misc/NEWS.d/next/Library/2022-04-03-19-40-09.bpo-39064.76PbIz.rst
new file mode 100644
index 00000000000..34d31527e33
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-04-03-19-40-09.bpo-39064.76PbIz.rst
@@ -0,0 +1,2 @@
+:class:`zipfile.ZipFile` now raises :exc:`zipfile.BadZipFile` instead of ``ValueError`` when reading a
+corrupt zip file in which the central directory offset is negative.
--
GitLab