python中的Zipfile文件权限

Question

我使用zipfile lib从zip中提取文件，现在将目录解压缩后，我发现我的文件的权限已损坏，

import zipfile
fh = open('sample.zip', 'rb')
z = zipfile.ZipFile(fh)
print z.namelist()
for name in z.namelist():
    z.extract(name, '/tmp/')
fh.close()

但是当我使用linux解压缩工具时，不会发生此问题，我尝试使用

os.system('unzip sample.zip')

但是我仍然想用zipfile做到这一点

Answer 1

相关的Python问题提供了关于为什么首先存在该问题的一些见解： https ： //bugs.python.org/issue18262和https://bugs.python.org/issue15795

此外，原始的Zip规范可以在以下位置找到： https : //pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT

重要的部分是：

4.4.2 version made by (2 bytes)

        4.4.2.1 The upper byte indicates the compatibility of the file
        attribute information.  If the external file attributes 
        are compatible with MS-DOS and can be read by PKZIP for 
        DOS version 2.04g then this value will be zero.  If these 
        attributes are not compatible, then this value will 
        identify the host system on which the attributes are 
        compatible.  Software can use this information to determine
        the line record format for text files etc.  

        4.4.2.2 The current mappings are:

         0 - MS-DOS and OS/2 (FAT / VFAT / FAT32 file systems)
         1 - Amiga                     2 - OpenVMS
         3 - UNIX                      4 - VM/CMS
         5 - Atari ST                  6 - OS/2 H.P.F.S.
         7 - Macintosh                 8 - Z-System
         9 - CP/M                     10 - Windows NTFS
        11 - MVS (OS/390 - Z/OS)      12 - VSE
        13 - Acorn Risc               14 - VFAT
        15 - alternate MVS            16 - BeOS
        17 - Tandem                   18 - OS/400
        19 - OS X (Darwin)            20 thru 255 - unused
...
4.4.15 external file attributes: (4 bytes)

       The mapping of the external attributes is
       host-system dependent (see 'version made by').  For
       MS-DOS, the low order byte is the MS-DOS directory
       attribute byte.  If input came from standard input, this
       field is set to zero.

这意味着外部文件属性是系统特定的。 解释其他系统的外部文件属性可能会使情况更糟。 如果仅关心UNIX，则可以检查ZipInfo.created_system并将其与3 （对于UNIX）进行比较。 不幸的是，该规范在解释外部属性方面并没有进一步帮助我们。

该Wiki中有一些内容http://forensicswiki.org/wiki/Zip#External_file_attributes

The external attributes UNIX (3) is 4 bytes of size and consists of:

╔═════════╦══════════╦════════╦═══════════════════════════════════════════════════════╗
║ Offset  ║  Size    ║ Value  ║                      Description                      ║
╠═════════╬══════════╬════════╬═══════════════════════════════════════════════════════╣
║      0  ║ 1        ║        ║ FAT (MS-DOS) file attributes.                         ║
║      1  ║ 1        ║        ║ Unknown                                               ║
║      2  ║ 16 bits  ║        ║ The UNIX mode (or permission).                        ║
║         ║          ║        ║ The value seems to be similar to stat.st_mode value.  ║
╚═════════╩══════════╩════════╩═══════════════════════════════════════════════════════╝

虽然这是观察性的，但似乎是共识。

放在一起：

from zipfile import ZipFile

ZIP_UNIX_SYSTEM = 3

def extract_all_with_permission(zf, target_dir):
  for info in zf.infolist():
    extracted_path = zf.extract(info, target_dir)

    if info.create_system == ZIP_UNIX_SYSTEM:
      unix_attributes = info.external_attr >> 16
      if unix_attributes:
        os.chmod(extracted_path, unix_attributes)

with ZipFile('sample.zip', 'r') as zf:
  extract_all_with_permission(zf, '/tmp')

可能会有一个问题，为什么我们要首先保留权限。 有人可能敢说我们只想保留可执行标志。 在这种情况下，较为安全的选择是仅针对文件还原可执行标志。

from zipfile import ZipFile
from stat import S_IXUSR

ZIP_UNIX_SYSTEM = 3

def extract_all_with_executable_permission(zf, target_dir):
  for info in zf.infolist():
    extracted_path = zf.extract(info, target_dir)

    if info.create_system == ZIP_UNIX_SYSTEM and os.path.isfile(extracted_path):
      unix_attributes = info.external_attr >> 16
      if unix_attributes & S_IXUSR:
        os.chmod(extracted_path, os.stat(extracted_path).st_mode | S_IXUSR)

with ZipFile('sample.zip', 'r') as zf:
  extract_all_with_executable_permission(zf, '/tmp')

Answer 2

import zipfile
import os

unZipFile = zipfile.ZipFile("sample.zip", "r")

tmp_dir = "/tmp"
try:
    for info in unZipFile.infolist():
        real_path = unZipFile.extract(info, tmp_dir)

        # permission
        unix_attributes = info.external_attr >> 16
        target = os.path.join(tmp_dir, info.filename)
        if unix_attributes:
            os.chmod(target, unix_attributes)

        if not real_path:
            print "Extract failed: " + info.filename
finally:
    unZipFile.close()