Commit 93b061bc authored by Georg Brandl's avatar Georg Brandl

Issue #1159051: Back out a fix for handling corrupted gzip files that

broke backwards compatibility.
parent a9217a42
......@@ -33,6 +33,9 @@ def write32u(output, value):
# 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).
......@@ -256,32 +259,27 @@ class GzipFile(io.BufferedIOBase):
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'':
return False
raise EOFError("Reached EOF")
if magic != b'\037\213':
raise IOError('Not a gzipped file')
method, flag, self.mtime = struct.unpack("<BBIxx", self._read_exact(8))
method = ord( self.fileobj.read(1) )
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
extra_len, = struct.unpack("<H", self._read_exact(2))
self._read_exact(extra_len)
xlen = ord(self.fileobj.read(1))
xlen = xlen + 256*ord(self.fileobj.read(1))
self.fileobj.read(xlen)
if flag & FNAME:
# Read and discard a null-terminated string containing the filename
while True:
......@@ -295,13 +293,12 @@ class GzipFile(io.BufferedIOBase):
if not s or s==b'\000':
break
if flag & FHCRC:
self._read_exact(2) # Read & discard the 16-bit header CRC
self.fileobj.read(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()
......@@ -335,16 +332,20 @@ class GzipFile(io.BufferedIOBase):
readsize = 1024
if size < 0: # get the whole thing
while self._read(readsize):
readsize = min(self.max_read_chunk, readsize * 2)
size = self.extrasize
try:
while True:
self._read(readsize)
readsize = min(self.max_read_chunk, readsize * 2)
except EOFError:
size = self.extrasize
else: # just get some more of it
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)
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
offset = self.offset - self.extrastart
chunk = self.extrabuf[offset: offset + size]
......@@ -365,9 +366,12 @@ class GzipFile(io.BufferedIOBase):
if self.extrasize == 0:
if self.fileobj is None:
return b''
# 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)):
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:
pass
offset = self.offset - self.extrastart
remaining = self.extrasize
......@@ -380,14 +384,13 @@ class GzipFile(io.BufferedIOBase):
def _read(self, size=1024):
if self.fileobj is None:
return False
raise EOFError("Reached EOF")
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()
if not self._read_gzip_header():
return False
self._read_gzip_header()
self.decompress = zlib.decompressobj(-zlib.MAX_WBITS)
self._new_member = False
......@@ -404,7 +407,7 @@ class GzipFile(io.BufferedIOBase):
self.fileobj.prepend(self.decompress.unused_data, True)
self._read_eof()
self._add_read_data( uncompress )
return False
raise EOFError('Reached EOF')
uncompress = self.decompress.decompress(buf)
self._add_read_data( uncompress )
......@@ -420,7 +423,6 @@ class GzipFile(io.BufferedIOBase):
# 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
......@@ -435,7 +437,8 @@ class GzipFile(io.BufferedIOBase):
# 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, isize = struct.unpack("<II", self._read_exact(8))
crc32 = read32(self.fileobj)
isize = read32(self.fileobj) # may exceed 2GB
if crc32 != self.crc:
raise IOError("CRC check failed %s != %s" % (hex(crc32),
hex(self.crc)))
......
......@@ -292,24 +292,6 @@ class BZ2FileTest(BaseTest):
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()"
......
......@@ -365,19 +365,6 @@ class TestGzip(unittest.TestCase):
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_read_with_extra(self):
# Gzip data with an extra field
......
......@@ -14,11 +14,12 @@ Library
which were omitted in 3.2.4 when updating the bundled version of
libffi used by ctypes.
- Issue #17666: Fix reading gzip files with an extra field.
- Issue #15535: Fix namedtuple pickles which were picking up the OrderedDict
instead of just the underlying tuple.
- Issue #1159051: Back out a fix for handling corrupted gzip files that
broke backwards compatibility.
Build
-----
......
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