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Title: zipfile: incorrect comment size will prevent extracting
Type: behavior Stage: patch review
Components: Library (Lib) Versions: Python 3.1, Python 3.2, Python 2.7
Status: closed Resolution: accepted
Dependencies: Superseder:
Assigned To: Nosy List: alanmcintyre, rep
Priority: normal Keywords: needs review, patch

Created on 2010-11-03 14:00 by rep, last changed 2022-04-11 14:57 by admin. This issue is now closed.

File name Uploaded Description Edit
zipfile_recover_commentsize.patch rep, 2010-11-03 14:00 review
Messages (2)
msg120326 - (view) Author: (rep) Date: 2010-11-03 14:00
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.
msg128278 - (view) Author: (rep) Date: 2011-02-10 10:27
superseded by issue 10694
Date User Action Args
2022-04-11 14:57:08adminsetgithub: 54507
2011-02-10 10:27:14repsetstatus: pending -> closed

messages: + msg128278
resolution: accepted
2011-02-10 10:26:34repsetstatus: languishing -> pending
2011-02-10 10:26:28repsetstatus: open -> languishing
2010-11-04 17:55:09eric.araujosetkeywords: + needs review
nosy: + alanmcintyre
stage: patch review

versions: + Python 3.1, Python 3.2
2010-11-03 14:00:37repcreate