How to check if a zip file is encrypted using python's standard library zipfile?

Question

I am using python's standard library, zipfile, to test an archive:

zf = zipfile.ZipFile(archive_name)
if zf.testzip()==None: checksum_OK=True

And I am getting this Runtime exception:

File "./packaging.py", line 36, in test_wgt
    if zf.testzip()==None: checksum_OK=True
  File "/usr/lib/python2.7/zipfile.py", line 844, in testzip
    f = self.open(zinfo.filename, "r")
  File "/usr/lib/python2.7/zipfile.py", line 915, in open
    "password required for extraction" % name
RuntimeError: File xxxxx/xxxxxxxx.xxx is encrypted, password required for extraction

How can I test, before I run testzip(), if the zip is encrypted? I didn't found an exception to catch that would make this job simpler.

Zachary Hamm · Accepted Answer · 2012-08-20T13:45:56.740

17

A quick glance at the zipfile.py library code shows that you can check the ZipInfo class's flag_bits property to see if the file is encrypted, like so:

zf = zipfile.ZipFile(archive_name)
for zinfo in zf.infolist():
    is_encrypted = zinfo.flag_bits & 0x1 
    if is_encrypted:
        print '%s is encrypted!' % zinfo.filename

Checking to see if the 0x1 bit is set is how the zipfile.py source sees if the file is encrypted (could be better documented!) One thing you could do is catch the RuntimeError from testzip() then loop over the infolist() and see if there are encrypted files in the zip.

You could also just do something like this:

try:
    zf.testzip()
except RuntimeError as e:
    if 'encrypted' in str(e):
        print 'Golly, this zip has encrypted files! Try again with a password!'
    else:
        # RuntimeError for other reasons....

edited Aug 20 '12 at 13:45

answered Aug 20 '12 at 13:36

Zachary Hamm

629
3
16

2

** `except` **, not `catch`. (+1) for looking into the source though. – mgilson Aug 20 '12 at 13:37
Oops. Every time I switch from Java to Python or Python to Java I have to catch my catch's and except's. Sorry. – Zachary Hamm Aug 20 '12 at 13:42
4

The other thing that I would advise is change `# RuntimeError for other reasons ...` to `raise e #Unknown RuntimeError` -- Just to demonstrate that you can re-raise an exception that you've caught. – mgilson Aug 20 '12 at 13:44
It works like this, I think the catch is `except RuntimeError, e:` – Eduard Florinescu Aug 20 '12 at 13:44

score 0 · Answer 2 · answered Aug 20 '12 at 13:29

0

If you want to catch an exception, you can write this:

zf = zipfile.ZipFile(archive_name)
try:
    if zf.testzip() == None:
        checksum_OK = True
except RuntimeError:
    pass

answered Aug 20 '12 at 13:29

Noctis Skytower

21,433
16
79
117

2

Yes, but could not RuntimeError be also trigered by other type of error? – Eduard Florinescu Aug 20 '12 at 13:31

How to check if a zip file is encrypted using python's standard library zipfile?

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