Python文件权限中的Zipfile

i used zipfilelib 从 zip 中提取文件，现在解压目录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解压工具就不会出现这个问题 我尝试使用

os.system('unzip sample.zip')

但我仍然想这样做zipfile

相关的 Python 问题提供了一些关于该问题最初存在的原因的见解：https://bugs.python.org/issue18262 and https://bugs.python.org/issue15795

此外，原始 Zip 规范可以在这里找到：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。解释不同系统的外部文件属性可能会使情况变得更糟。如果我们只关心 UNIX，我们可以检查ZipInfo.created_system并将其与3（对于 UNIX）。不幸的是，该规范并不能帮助我们进一步解释如何解释外部属性。

这个维基里有一些东西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.  ║
╚═════════╩══════════╩════════╩═══════════════════════════════════════════════════════╝
  

虽然这是相当观察性的，但这似乎是共识。

将其放在一起：

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')

可能会出现一个问题，为什么我们首先要保留权限。有些人可能敢说我们只想保留可执行标志。在这种情况下，一个稍微安全的选择可能是仅恢复文件的可执行标志。

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')