Issue #13158: Fix decoding and encoding of base-256 number fields in tarfile.
The nti() function that converts a number field from a tar header to a number failed to decode GNU tar specific base-256 fields. I also added support for decoding and encoding negative base-256 number fields.
This commit is contained in:
parent
82ac9bcdb3
commit
ac3d137a30
|
@ -196,16 +196,18 @@ def nti(s):
|
|||
"""
|
||||
# There are two possible encodings for a number field, see
|
||||
# itn() below.
|
||||
if s[0] != chr(0o200):
|
||||
if s[0] in (0o200, 0o377):
|
||||
n = 0
|
||||
for i in range(len(s) - 1):
|
||||
n <<= 8
|
||||
n += s[i + 1]
|
||||
if s[0] == 0o377:
|
||||
n = -(256 ** (len(s) - 1) - n)
|
||||
else:
|
||||
try:
|
||||
n = int(nts(s, "ascii", "strict") or "0", 8)
|
||||
except ValueError:
|
||||
raise InvalidHeaderError("invalid header")
|
||||
else:
|
||||
n = 0
|
||||
for i in range(len(s) - 1):
|
||||
n <<= 8
|
||||
n += ord(s[i + 1])
|
||||
return n
|
||||
|
||||
def itn(n, digits=8, format=DEFAULT_FORMAT):
|
||||
|
@ -214,25 +216,26 @@ def itn(n, digits=8, format=DEFAULT_FORMAT):
|
|||
# POSIX 1003.1-1988 requires numbers to be encoded as a string of
|
||||
# octal digits followed by a null-byte, this allows values up to
|
||||
# (8**(digits-1))-1. GNU tar allows storing numbers greater than
|
||||
# that if necessary. A leading 0o200 byte indicates this particular
|
||||
# encoding, the following digits-1 bytes are a big-endian
|
||||
# representation. This allows values up to (256**(digits-1))-1.
|
||||
# that if necessary. A leading 0o200 or 0o377 byte indicate this
|
||||
# particular encoding, the following digits-1 bytes are a big-endian
|
||||
# base-256 representation. This allows values up to (256**(digits-1))-1.
|
||||
# A 0o200 byte indicates a positive number, a 0o377 byte a negative
|
||||
# number.
|
||||
if 0 <= n < 8 ** (digits - 1):
|
||||
s = bytes("%0*o" % (digits - 1, n), "ascii") + NUL
|
||||
else:
|
||||
if format != GNU_FORMAT or n >= 256 ** (digits - 1):
|
||||
raise ValueError("overflow in number field")
|
||||
elif format == GNU_FORMAT and -256 ** (digits - 1) <= n < 256 ** (digits - 1):
|
||||
if n >= 0:
|
||||
s = bytearray([0o200])
|
||||
else:
|
||||
s = bytearray([0o377])
|
||||
n = 256 ** digits + n
|
||||
|
||||
if n < 0:
|
||||
# XXX We mimic GNU tar's behaviour with negative numbers,
|
||||
# this could raise OverflowError.
|
||||
n = struct.unpack("L", struct.pack("l", n))[0]
|
||||
|
||||
s = bytearray()
|
||||
for i in range(digits - 1):
|
||||
s.insert(0, n & 0o377)
|
||||
s.insert(1, n & 0o377)
|
||||
n >>= 8
|
||||
s.insert(0, 0o200)
|
||||
else:
|
||||
raise ValueError("overflow in number field")
|
||||
|
||||
return s
|
||||
|
||||
def calc_chksums(buf):
|
||||
|
|
|
@ -1582,9 +1582,31 @@ class MiscTest(unittest.TestCase):
|
|||
self.assertEqual(tarfile.nts(b"foo\0\0\0\0\0", "ascii", "strict"), "foo")
|
||||
self.assertEqual(tarfile.nts(b"foo\0bar\0", "ascii", "strict"), "foo")
|
||||
|
||||
def test_number_fields(self):
|
||||
def test_read_number_fields(self):
|
||||
# Issue 13158: Test if GNU tar specific base-256 number fields
|
||||
# are decoded correctly.
|
||||
self.assertEqual(tarfile.nti(b"0000001\x00"), 1)
|
||||
self.assertEqual(tarfile.nti(b"7777777\x00"), 0o7777777)
|
||||
self.assertEqual(tarfile.nti(b"\x80\x00\x00\x00\x00\x20\x00\x00"), 0o10000000)
|
||||
self.assertEqual(tarfile.nti(b"\x80\x00\x00\x00\xff\xff\xff\xff"), 0xffffffff)
|
||||
self.assertEqual(tarfile.nti(b"\xff\xff\xff\xff\xff\xff\xff\xff"), -1)
|
||||
self.assertEqual(tarfile.nti(b"\xff\xff\xff\xff\xff\xff\xff\x9c"), -100)
|
||||
self.assertEqual(tarfile.nti(b"\xff\x00\x00\x00\x00\x00\x00\x00"), -0x100000000000000)
|
||||
|
||||
def test_write_number_fields(self):
|
||||
self.assertEqual(tarfile.itn(1), b"0000001\x00")
|
||||
self.assertEqual(tarfile.itn(0o7777777), b"7777777\x00")
|
||||
self.assertEqual(tarfile.itn(0o10000000), b"\x80\x00\x00\x00\x00\x20\x00\x00")
|
||||
self.assertEqual(tarfile.itn(0xffffffff), b"\x80\x00\x00\x00\xff\xff\xff\xff")
|
||||
self.assertEqual(tarfile.itn(-1), b"\xff\xff\xff\xff\xff\xff\xff\xff")
|
||||
self.assertEqual(tarfile.itn(-100), b"\xff\xff\xff\xff\xff\xff\xff\x9c")
|
||||
self.assertEqual(tarfile.itn(-0x100000000000000), b"\xff\x00\x00\x00\x00\x00\x00\x00")
|
||||
|
||||
def test_number_field_limits(self):
|
||||
self.assertRaises(ValueError, tarfile.itn, -1, 8, tarfile.USTAR_FORMAT)
|
||||
self.assertRaises(ValueError, tarfile.itn, 0o10000000, 8, tarfile.USTAR_FORMAT)
|
||||
self.assertRaises(ValueError, tarfile.itn, -0x10000000001, 6, tarfile.GNU_FORMAT)
|
||||
self.assertRaises(ValueError, tarfile.itn, 0x10000000000, 6, tarfile.GNU_FORMAT)
|
||||
|
||||
|
||||
class ContextManagerTest(unittest.TestCase):
|
||||
|
|
Loading…
Reference in New Issue