[issue40301] zipfile module: new feature (two lines of code), useful for test, security and forensics

[Daniel Hillier]

Daniel Hillier <daniel.hillier at gmail.com> added the comment:

Hi Massimo,

Unless I'm missing something about your requirements, the advantage is that
it already works in python 2.7 so there is no need to patch Python. Just
bundle the above function with your analysis tool and you're good to go.

Cheers,
Dan

On Sat, Apr 18, 2020 at 11:36 PM Massimo Sala <report at bugs.python.org>
wrote:

>
> Massimo Sala <massimo.sala.71 at gmail.com> added the comment:
>
> Hi Daniel
>
> Could you please elaborate the advantages of your loop versus my two lines
> of code?
> I don't grasp...
>
> Thanks, Massimo
>
> On Sat, 18 Apr 2020 at 03:26, Daniel Hillier <report at bugs.python.org>
> wrote:
>
> >
> > Daniel Hillier <daniel.hillier at gmail.com> added the comment:
> >
> > Could something similar be achieved by looking for the earliest file
> > header offset?
> >
> > def find_earliest_header_offset(zf):
> >     earliest_offset = None
> >     for zinfo in zf.infolist():
> >         if earliest_offset is None:
> >             earliest_offset = zinfo.header_offset
> >         else:
> >             earliest_offset = min(zinfo.header_offset, earliest_offset)
> >     return earliest_offset
> >
> >
> > You could also adapt this using
> >
> >     zinfo.compress_size + len(zinfo.FileHeader())
> >
> > to see if there were any sections inside the archive which were not
> > referenced from the central directory. Not sure if zip files with
> arbitrary
> > bytes inside the archive would be valid everywhere, but I think they are
> > using zipfile.
> >
> > You can also have zipped content inside an archive which has a valid
> > fileheader but no reference from the central directory. Those entries are
> > discoverable by implementations which process content serially from the
> > start of the file but not implementations which rely on the central
> > directory.
> >
> > ----------
> > nosy: +dhillier
> >
> > _______________________________________
> > Python tracker <report at bugs.python.org>
> > <https://bugs.python.org/issue40301>
> > _______________________________________
> >
>
> ----------
>
> _______________________________________
> Python tracker <report at bugs.python.org>
> <https://bugs.python.org/issue40301>
> _______________________________________
>

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