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Issue #23529: Limit the size of decompressed data when reading from

Browse source 
GzipFile, BZ2File or LZMAFile.  This defeats denial of service attacks
using compressed bombs (i.e. compressed payloads which decompress to a huge
size).

Patch by Martin Panter and Nikolaus Rath.
This commit is contained in:
Antoine Pitrou 2015-04-11 00:31:01 +02:00
parent 2ce11d296c
commit 2dbc6e6bce
11 changed files with 497 additions and 712 deletions
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25
Lib/test/test_lzma.py
View file

@ -1,4 +1,5 @@
from io import BytesIO, UnsupportedOperation
import _compression
from io import BytesIO, UnsupportedOperation, DEFAULT_BUFFER_SIZE
import os
import pickle
import random
@ -772,13 +773,13 @@ class FileTestCase(unittest.TestCase):
def test_read_multistream_buffer_size_aligned(self):
# Test the case where a stream boundary coincides with the end
# of the raw read buffer.
saved_buffer_size = lzma._BUFFER_SIZE
lzma._BUFFER_SIZE = len(COMPRESSED_XZ)
saved_buffer_size = _compression.BUFFER_SIZE
_compression.BUFFER_SIZE = len(COMPRESSED_XZ)
try:
with LZMAFile(BytesIO(COMPRESSED_XZ * 5)) as f:
self.assertEqual(f.read(), INPUT * 5)
finally:
lzma._BUFFER_SIZE = saved_buffer_size
_compression.BUFFER_SIZE = saved_buffer_size
def test_read_trailing_junk(self):
with LZMAFile(BytesIO(COMPRESSED_XZ + COMPRESSED_BOGUS)) as f:
@ -829,7 +830,7 @@ class FileTestCase(unittest.TestCase):
with LZMAFile(BytesIO(), "w") as f:
self.assertRaises(ValueError, f.read)
with LZMAFile(BytesIO(COMPRESSED_XZ)) as f:
self.assertRaises(TypeError, f.read, None)
self.assertRaises(TypeError, f.read, float())
def test_read_bad_data(self):
with LZMAFile(BytesIO(COMPRESSED_BOGUS)) as f:
@ -925,6 +926,17 @@ class FileTestCase(unittest.TestCase):
with LZMAFile(BytesIO(COMPRESSED_XZ)) as f:
self.assertListEqual(f.readlines(), lines)
def test_decompress_limited(self):
"""Decompressed data buffering should be limited"""
bomb = lzma.compress(bytes(int(2e6)), preset=6)
self.assertLess(len(bomb), _compression.BUFFER_SIZE)
decomp = LZMAFile(BytesIO(bomb))
self.assertEqual(bytes(1), decomp.read(1))
max_decomp = 1 + DEFAULT_BUFFER_SIZE
self.assertLessEqual(decomp._buffer.raw.tell(), max_decomp,
"Excessive amount of data was decompressed")
def test_write(self):
with BytesIO() as dst:
with LZMAFile(dst, "w") as f:
@ -1090,7 +1102,8 @@ class FileTestCase(unittest.TestCase):
self.assertRaises(ValueError, f.seek, 0)
with LZMAFile(BytesIO(COMPRESSED_XZ)) as f:
self.assertRaises(ValueError, f.seek, 0, 3)
self.assertRaises(ValueError, f.seek, 9, ())
# io.BufferedReader raises TypeError instead of ValueError
self.assertRaises((TypeError, ValueError), f.seek, 9, ())
self.assertRaises(TypeError, f.seek, None)
self.assertRaises(TypeError, f.seek, b"derp")