[Python-checkins] cpython (3.2): Issue #1159051: GzipFile now raises EOFError when reading a corrupted file
serhiy.storchaka
python-checkins at python.org
Tue Jan 22 16:17:02 CET 2013
http://hg.python.org/cpython/rev/174332b89a0d
changeset: 81656:174332b89a0d
branch: 3.2
parent: 81651:0f25119ceee8
user: Serhiy Storchaka <storchaka at gmail.com>
date: Tue Jan 22 17:01:59 2013 +0200
summary:
Issue #1159051: GzipFile now raises EOFError when reading a corrupted file
with truncated header or footer.
Added tests for reading truncated gzip and bzip2 files.
files:
Lib/gzip.py | 72 ++++++++++++++----------------
Lib/test/test_bz2.py | 18 +++++++
Lib/test/test_gzip.py | 15 ++++++
Misc/NEWS | 3 +
4 files changed, 70 insertions(+), 38 deletions(-)
diff --git a/Lib/gzip.py b/Lib/gzip.py
--- a/Lib/gzip.py
+++ b/Lib/gzip.py
@@ -33,9 +33,6 @@
# or unsigned.
output.write(struct.pack("<L", value))
-def read32(input):
- return struct.unpack("<I", input.read(4))[0]
-
def open(filename, mode="rb", compresslevel=9):
"""Shorthand for GzipFile(filename, mode, compresslevel).
@@ -259,27 +256,31 @@
self.crc = zlib.crc32(b"") & 0xffffffff
self.size = 0
+ def _read_exact(self, n):
+ data = self.fileobj.read(n)
+ while len(data) < n:
+ b = self.fileobj.read(n - len(data))
+ if not b:
+ raise EOFError("Compressed file ended before the "
+ "end-of-stream marker was reached")
+ data += b
+ return data
+
def _read_gzip_header(self):
magic = self.fileobj.read(2)
if magic == b'':
- raise EOFError("Reached EOF")
+ return False
if magic != b'\037\213':
raise IOError('Not a gzipped file')
- method = ord( self.fileobj.read(1) )
+
+ method, flag, self.mtime = struct.unpack("<BBIxx", self._read_exact(8))
if method != 8:
raise IOError('Unknown compression method')
- flag = ord( self.fileobj.read(1) )
- self.mtime = read32(self.fileobj)
- # extraflag = self.fileobj.read(1)
- # os = self.fileobj.read(1)
- self.fileobj.read(2)
if flag & FEXTRA:
# Read & discard the extra field, if present
- xlen = ord(self.fileobj.read(1))
- xlen = xlen + 256*ord(self.fileobj.read(1))
- self.fileobj.read(xlen)
+ self._read_exact(struct.unpack("<H", self._read_exact(2)))
if flag & FNAME:
# Read and discard a null-terminated string containing the filename
while True:
@@ -293,12 +294,13 @@
if not s or s==b'\000':
break
if flag & FHCRC:
- self.fileobj.read(2) # Read & discard the 16-bit header CRC
+ self._read_exact(2) # Read & discard the 16-bit header CRC
unused = self.fileobj.unused()
if unused:
uncompress = self.decompress.decompress(unused)
self._add_read_data(uncompress)
+ return True
def write(self,data):
self._check_closed()
@@ -332,20 +334,16 @@
readsize = 1024
if size < 0: # get the whole thing
- try:
- while True:
- self._read(readsize)
- readsize = min(self.max_read_chunk, readsize * 2)
- except EOFError:
- size = self.extrasize
+ while self._read(readsize):
+ readsize = min(self.max_read_chunk, readsize * 2)
+ size = self.extrasize
else: # just get some more of it
- try:
- while size > self.extrasize:
- self._read(readsize)
- readsize = min(self.max_read_chunk, readsize * 2)
- except EOFError:
- if size > self.extrasize:
- size = self.extrasize
+ while size > self.extrasize:
+ if not self._read(readsize):
+ if size > self.extrasize:
+ size = self.extrasize
+ break
+ readsize = min(self.max_read_chunk, readsize * 2)
offset = self.offset - self.extrastart
chunk = self.extrabuf[offset: offset + size]
@@ -366,12 +364,9 @@
if self.extrasize == 0:
if self.fileobj is None:
return b''
- try:
- # Ensure that we don't return b"" if we haven't reached EOF.
- while self.extrasize == 0:
- # 1024 is the same buffering heuristic used in read()
- self._read(max(n, 1024))
- except EOFError:
+ # Ensure that we don't return b"" if we haven't reached EOF.
+ # 1024 is the same buffering heuristic used in read()
+ while self.extrasize == 0 and self._read(max(n, 1024)):
pass
offset = self.offset - self.extrastart
remaining = self.extrasize
@@ -384,13 +379,14 @@
def _read(self, size=1024):
if self.fileobj is None:
- raise EOFError("Reached EOF")
+ return False
if self._new_member:
# If the _new_member flag is set, we have to
# jump to the next member, if there is one.
self._init_read()
- self._read_gzip_header()
+ if not self._read_gzip_header():
+ return False
self.decompress = zlib.decompressobj(-zlib.MAX_WBITS)
self._new_member = False
@@ -407,7 +403,7 @@
self.fileobj.prepend(self.decompress.unused_data, True)
self._read_eof()
self._add_read_data( uncompress )
- raise EOFError('Reached EOF')
+ return False
uncompress = self.decompress.decompress(buf)
self._add_read_data( uncompress )
@@ -423,6 +419,7 @@
# a new member on the next call
self._read_eof()
self._new_member = True
+ return True
def _add_read_data(self, data):
self.crc = zlib.crc32(data, self.crc) & 0xffffffff
@@ -437,8 +434,7 @@
# We check the that the computed CRC and size of the
# uncompressed data matches the stored values. Note that the size
# stored is the true file size mod 2**32.
- crc32 = read32(self.fileobj)
- isize = read32(self.fileobj) # may exceed 2GB
+ crc32, isize = struct.unpack("<II", self._read_exact(8))
if crc32 != self.crc:
raise IOError("CRC check failed %s != %s" % (hex(crc32),
hex(self.crc)))
diff --git a/Lib/test/test_bz2.py b/Lib/test/test_bz2.py
--- a/Lib/test/test_bz2.py
+++ b/Lib/test/test_bz2.py
@@ -295,6 +295,24 @@
self.assertRaises(ValueError, f.readline)
self.assertRaises(ValueError, f.readlines)
+ def test_read_truncated(self):
+ # Drop the eos_magic field (6 bytes) and CRC (4 bytes).
+ truncated = self.DATA[:-10]
+ with open(self.filename, 'wb') as f:
+ f.write(truncated)
+ with BZ2File(self.filename) as f:
+ self.assertRaises(EOFError, f.read)
+ with BZ2File(self.filename) as f:
+ self.assertEqual(f.read(len(self.TEXT)), self.TEXT)
+ self.assertRaises(EOFError, f.read, 1)
+ # Incomplete 4-byte file header, and block header of at least 146 bits.
+ for i in range(22):
+ with open(self.filename, 'wb') as f:
+ f.write(truncated[:i])
+ with BZ2File(self.filename) as f:
+ self.assertRaises(EOFError, f.read, 1)
+
+
class BZ2CompressorTest(BaseTest):
def testCompress(self):
# "Test BZ2Compressor.compress()/flush()"
diff --git a/Lib/test/test_gzip.py b/Lib/test/test_gzip.py
--- a/Lib/test/test_gzip.py
+++ b/Lib/test/test_gzip.py
@@ -365,6 +365,21 @@
datac = gzip.compress(data)
self.assertEqual(gzip.decompress(datac), data)
+ def test_read_truncated(self):
+ data = data1*50
+ # Drop the CRC (4 bytes) and file size (4 bytes).
+ truncated = gzip.compress(data)[:-8]
+ with gzip.GzipFile(fileobj=io.BytesIO(truncated)) as f:
+ self.assertRaises(EOFError, f.read)
+ with gzip.GzipFile(fileobj=io.BytesIO(truncated)) as f:
+ self.assertEqual(f.read(len(data)), data)
+ self.assertRaises(EOFError, f.read, 1)
+ # Incomplete 10-byte header.
+ for i in range(2, 10):
+ with gzip.GzipFile(fileobj=io.BytesIO(truncated[:i])) as f:
+ self.assertRaises(EOFError, f.read, 1)
+
+
def test_main(verbose=None):
support.run_unittest(TestGzip)
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -202,6 +202,9 @@
Library
-------
+- Issue #1159051: GzipFile now raises EOFError when reading a corrupted file
+ with truncated header or footer.
+
- Issue #15861: tkinter now correctly works with lists and tuples containing
strings with whitespaces, backslashes or unbalanced braces.
--
Repository URL: http://hg.python.org/cpython
More information about the Python-checkins
mailing list