Patch #698833: Support file decryption in zipfile.
This commit is contained in:
Martin v. Löwis
parent
07aa3ed372
commit
c6d626ed9f
|
|
@ -17,8 +17,10 @@ understanding of the format, as defined in
|
|||
{PKZIP Application Note}.
|
||||
|
||||
This module does not currently handle ZIP files which have appended
|
||||
comments, or multi-disk ZIP files. It can handle ZIP files that use the
|
||||
ZIP64 extensions (that is ZIP files that are more than 4 GByte in size).
|
||||
comments, or multi-disk ZIP files. It can handle ZIP files that use
|
||||
the ZIP64 extensions (that is ZIP files that are more than 4 GByte in
|
||||
size). It supports decryption of encrypted files in ZIP archives, but
|
||||
it cannot currently create an encrypted file.
|
||||
|
||||
The available attributes of this module are:
|
||||
|
||||
|
|
@ -138,9 +140,18 @@ cat myzip.zip >> python.exe
|
|||
Print a table of contents for the archive to \code{sys.stdout}.
|
||||
\end{methoddesc}
|
||||
|
||||
\begin{methoddesc}{read}{name}
|
||||
\begin{methoddesc}{setpassword}{pwd}
|
||||
Set \var{pwd} as default password to extract encrypted files.
|
||||
\versionadded{2.6}
|
||||
\end{methoddesc}
|
||||
|
||||
\begin{methoddesc}{read}{name\optional{, pwd}}
|
||||
Return the bytes of the file in the archive. The archive must be
|
||||
open for read or append.
|
||||
open for read or append. \var{pwd} is the password used for encrypted
|
||||
files and, if specified, it will override the default password set with
|
||||
\method{setpassword()}.
|
||||
|
||||
\versionchanged[\var{pwd} was added]{2.6}
|
||||
\end{methoddesc}
|
||||
|
||||
\begin{methoddesc}{testzip}{}
|
||||
|
|
|
|||
|
|
@ -349,8 +349,49 @@ class OtherTests(unittest.TestCase):
|
|||
# and report that the first file in the archive was corrupt.
|
||||
self.assertRaises(RuntimeError, zipf.testzip)
|
||||
|
||||
|
||||
class DecryptionTests(unittest.TestCase):
|
||||
# This test checks that ZIP decryption works. Since the library does not
|
||||
# support encryption at the moment, we use a pre-generated encrypted
|
||||
# ZIP file
|
||||
|
||||
data = (
|
||||
'PK\x03\x04\x14\x00\x01\x00\x00\x00n\x92i.#y\xef?&\x00\x00\x00\x1a\x00'
|
||||
'\x00\x00\x08\x00\x00\x00test.txt\xfa\x10\xa0gly|\xfa-\xc5\xc0=\xf9y'
|
||||
'\x18\xe0\xa8r\xb3Z}Lg\xbc\xae\xf9|\x9b\x19\xe4\x8b\xba\xbb)\x8c\xb0\xdbl'
|
||||
'PK\x01\x02\x14\x00\x14\x00\x01\x00\x00\x00n\x92i.#y\xef?&\x00\x00\x00'
|
||||
'\x1a\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x01\x00 \x00\xb6\x81'
|
||||
'\x00\x00\x00\x00test.txtPK\x05\x06\x00\x00\x00\x00\x01\x00\x01\x006\x00'
|
||||
'\x00\x00L\x00\x00\x00\x00\x00' )
|
||||
|
||||
plain = 'zipfile.py encryption test'
|
||||
|
||||
def setUp(self):
|
||||
fp = open(TESTFN, "wb")
|
||||
fp.write(self.data)
|
||||
fp.close()
|
||||
self.zip = zipfile.ZipFile(TESTFN, "r")
|
||||
|
||||
def tearDown(self):
|
||||
self.zip.close()
|
||||
os.unlink(TESTFN)
|
||||
|
||||
def testNoPassword(self):
|
||||
# Reading the encrypted file without password
|
||||
# must generate a RunTime exception
|
||||
self.assertRaises(RuntimeError, self.zip.read, "test.txt")
|
||||
|
||||
def testBadPassword(self):
|
||||
self.zip.setpassword("perl")
|
||||
self.assertRaises(RuntimeError, self.zip.read, "test.txt")
|
||||
|
||||
def testGoodPassword(self):
|
||||
self.zip.setpassword("python")
|
||||
self.assertEquals(self.zip.read("test.txt"), self.plain)
|
||||
|
||||
def test_main():
|
||||
run_unittest(TestsWithSourceFile, TestZip64InSmallFiles, OtherTests, PyZipFileTests)
|
||||
run_unittest(TestsWithSourceFile, TestZip64InSmallFiles, OtherTests,
|
||||
PyZipFileTests, DecryptionTests)
|
||||
#run_unittest(TestZip64InSmallFiles)
|
||||
|
||||
if __name__ == "__main__":
|
||||
|
|
|
|||
|
|
@ -296,6 +296,65 @@ class ZipInfo (object):
|
|||
extra = extra[ln+4:]
|
||||
|
||||
|
||||
class _ZipDecrypter:
|
||||
"""Class to handle decryption of files stored within a ZIP archive.
|
||||
|
||||
ZIP supports a password-based form of encryption. Even though known
|
||||
plaintext attacks have been found against it, it is still useful
|
||||
for low-level securicy.
|
||||
|
||||
Usage:
|
||||
zd = _ZipDecrypter(mypwd)
|
||||
plain_char = zd(cypher_char)
|
||||
plain_text = map(zd, cypher_text)
|
||||
"""
|
||||
|
||||
def _GenerateCRCTable():
|
||||
"""Generate a CRC-32 table.
|
||||
|
||||
ZIP encryption uses the CRC32 one-byte primitive for scrambling some
|
||||
internal keys. We noticed that a direct implementation is faster than
|
||||
relying on binascii.crc32().
|
||||
"""
|
||||
poly = 0xedb88320
|
||||
table = [0] * 256
|
||||
for i in range(256):
|
||||
crc = i
|
||||
for j in range(8):
|
||||
if crc & 1:
|
||||
crc = ((crc >> 1) & 0x7FFFFFFF) ^ poly
|
||||
else:
|
||||
crc = ((crc >> 1) & 0x7FFFFFFF)
|
||||
table[i] = crc
|
||||
return table
|
||||
crctable = _GenerateCRCTable()
|
||||
|
||||
def _crc32(self, ch, crc):
|
||||
"""Compute the CRC32 primitive on one byte."""
|
||||
return ((crc >> 8) & 0xffffff) ^ self.crctable[(crc ^ ord(ch)) & 0xff]
|
||||
|
||||
def __init__(self, pwd):
|
||||
self.key0 = 305419896
|
||||
self.key1 = 591751049
|
||||
self.key2 = 878082192
|
||||
for p in pwd:
|
||||
self._UpdateKeys(p)
|
||||
|
||||
def _UpdateKeys(self, c):
|
||||
self.key0 = self._crc32(c, self.key0)
|
||||
self.key1 = (self.key1 + (self.key0 & 255)) & 4294967295
|
||||
self.key1 = (self.key1 * 134775813 + 1) & 4294967295
|
||||
self.key2 = self._crc32(chr((self.key1 >> 24) & 255), self.key2)
|
||||
|
||||
def __call__(self, c):
|
||||
"""Decrypt a single character."""
|
||||
c = ord(c)
|
||||
k = self.key2 | 2
|
||||
c = c ^ (((k * (k^1)) >> 8) & 255)
|
||||
c = chr(c)
|
||||
self._UpdateKeys(c)
|
||||
return c
|
||||
|
||||
class ZipFile:
|
||||
""" Class with methods to open, read, write, close, list zip files.
|
||||
|
||||
|
|
@ -330,6 +389,7 @@ class ZipFile:
|
|||
self.filelist = [] # List of ZipInfo instances for archive
|
||||
self.compression = compression # Method of compression
|
||||
self.mode = key = mode.replace('b', '')[0]
|
||||
self.pwd = None
|
||||
|
||||
# Check if we were passed a file-like object
|
||||
if isinstance(file, basestring):
|
||||
|
|
@ -461,7 +521,11 @@ class ZipFile:
|
|||
"""Return the instance of ZipInfo given 'name'."""
|
||||
return self.NameToInfo[name]
|
||||
|
||||
def read(self, name):
|
||||
def setpassword(self, pwd):
|
||||
"""Set default password for encrypted files."""
|
||||
self.pwd = pwd
|
||||
|
||||
def read(self, name, pwd=None):
|
||||
"""Return file bytes (as a string) for name."""
|
||||
if self.mode not in ("r", "a"):
|
||||
raise RuntimeError, 'read() requires mode "r" or "a"'
|
||||
|
|
@ -469,6 +533,13 @@ class ZipFile:
|
|||
raise RuntimeError, \
|
||||
"Attempt to read ZIP archive that was already closed"
|
||||
zinfo = self.getinfo(name)
|
||||
is_encrypted = zinfo.flag_bits & 0x1
|
||||
if is_encrypted:
|
||||
if not pwd:
|
||||
pwd = self.pwd
|
||||
if not pwd:
|
||||
raise RuntimeError, "File %s is encrypted, " \
|
||||
"password required for extraction" % name
|
||||
filepos = self.fp.tell()
|
||||
|
||||
self.fp.seek(zinfo.header_offset, 0)
|
||||
|
|
@ -489,6 +560,18 @@ class ZipFile:
|
|||
zinfo.orig_filename, fname)
|
||||
|
||||
bytes = self.fp.read(zinfo.compress_size)
|
||||
# Go with decryption
|
||||
if is_encrypted:
|
||||
zd = _ZipDecrypter(pwd)
|
||||
# The first 12 bytes in the cypher stream is an encryption header
|
||||
# used to strengthen the algorithm. The first 11 bytes are
|
||||
# completely random, while the 12th contains the MSB of the CRC,
|
||||
# and is used to check the correctness of the password.
|
||||
h = map(zd, bytes[0:12])
|
||||
if ord(h[11]) != ((zinfo.CRC>>24)&255):
|
||||
raise RuntimeError, "Bad password for file %s" % name
|
||||
bytes = "".join(map(zd, bytes[12:]))
|
||||
# Go with decompression
|
||||
self.fp.seek(filepos, 0)
|
||||
if zinfo.compress_type == ZIP_STORED:
|
||||
pass
|
||||
|
|
|
|||
Loading…
Reference in New Issue