New submission from rep <m...@mwcollect.org>:

Opening (and thus extracting) zip files with appended junk data is not possible 
with the way the current zipfile implementation checks validity. Basically the 
problem comes down to the comment size in the end-of-central-directory record 
being different from the size of the data following that record.

Unix unzip and similar utilities handle that case by looking at the eocd-record 
and taking that as the correct value. Zip files with data appended to them will 
be extracted just fine with these tools.

In python's zipfile the _EndRecData function will return None if the comment 
size does not match the record's value.

The patch modifies this behaviour and takes only the portion of trailing data 
that the record specifies and due to that it does not raise BadZipfile 
exceptions if there's any junk data appended to a zip file.

----------
components: Library (Lib)
files: zipfile_recover_commentsize.patch
keywords: patch
messages: 120326
nosy: rep
priority: normal
severity: normal
status: open
title: zipfile: incorrect comment size will prevent extracting
type: behavior
versions: Python 2.7
Added file: http://bugs.python.org/file19477/zipfile_recover_commentsize.patch

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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue10298>
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