Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[3.8] gh-109858: Protect zipfile from "quoted-overlap" zipbomb (GH-110016) #113916

Merged
merged 1 commit into from
Jan 17, 2024
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
60 changes: 60 additions & 0 deletions Lib/test/test_zipfile.py
Original file line number Diff line number Diff line change
Expand Up @@ -1998,6 +1998,66 @@ def test_decompress_without_3rd_party_library(self):
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)
Expand Down
12 changes: 12 additions & 0 deletions Lib/zipfile.py
Original file line number Diff line number Diff line change
Expand Up @@ -339,6 +339,7 @@ class ZipInfo (object):
'compress_size',
'file_size',
'_raw_time',
'_end_offset',
)

def __init__(self, filename="NoName", date_time=(1980,1,1,0,0,0)):
Expand Down Expand Up @@ -378,6 +379,7 @@ 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
Expand Down Expand Up @@ -1402,6 +1404,12 @@ 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."""
Expand Down Expand Up @@ -1557,6 +1565,10 @@ 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
if is_encrypted:
Expand Down
Original file line number Diff line number Diff line change
@@ -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.
Loading