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zipfile: incorrect comment size will prevent extracting #54507

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rep mannequin opened this issue Nov 3, 2010 · 2 comments
Closed

zipfile: incorrect comment size will prevent extracting #54507

rep mannequin opened this issue Nov 3, 2010 · 2 comments
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stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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Mannequin

rep mannequin commented Nov 3, 2010

BPO 10298
Files
  • zipfile_recover_commentsize.patch
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = <Date 2011-02-10.10:27:14.428>
created_at = <Date 2010-11-03.14:00:37.713>
labels = ['type-bug', 'library']
title = 'zipfile: incorrect comment size will prevent extracting'
updated_at = <Date 2011-02-10.10:27:14.427>
user = 'https://bugs.python.org/rep'

    bugs.python.org fields:

    activity = <Date 2011-02-10.10:27:14.427>
actor = 'rep'
assignee = 'none'
closed = True
closed_date = <Date 2011-02-10.10:27:14.428>
closer = 'rep'
components = ['Library (Lib)']
creation = <Date 2010-11-03.14:00:37.713>
creator = 'rep'
dependencies = []
files = ['19477']
hgrepos = []
issue_num = 10298
keywords = ['patch', 'needs review']
message_count = 2.0
messages = ['120326', '128278']
nosy_count = 2.0
nosy_names = ['alanmcintyre', 'rep']
pr_nums = []
priority = 'normal'
resolution = 'accepted'
stage = 'patch review'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue10298'
versions = ['Python 3.1', 'Python 2.7', 'Python 3.2']
    @rep
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    Mannequin Author

    rep mannequin commented Nov 3, 2010

    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.

    @rep rep mannequin added stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error labels Nov 3, 2010
    @rep rep mannequin added stale Stale PR or inactive for long period of time. and removed stale Stale PR or inactive for long period of time. labels Feb 10, 2011
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    rep mannequin commented Feb 10, 2011

    superseded by bpo-10694

    @rep rep mannequin closed this as completed Feb 10, 2011
    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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