New submission from Thomas Waldmann: zipfile.is_zipfile has false positives way too easily.
I just have seen it in practive when a MoinMoin wiki site with a lot of pdf attachments crashed with 500. This was caused by a valid PDF that just happened to contain PK\005\006 somewhere in the middle - this was enough to satisfy is_zipfile() and triggered further processing as a zipfile, which then crashed with IOError (which was not catched in our code, yet). I have looked into zipfile code: if the usual EOCD structure (with empty comment) is not at EOF, it is suspected that there might be a non-empty comment and ~64K before EOF are searched for the PK\005\006 magic. If it is somewhere there, it is assumed that the file is a zip, without any further validity check. Attached is a failure demo that works with at least 2.7 and 3.5. https://en.wikipedia.org/wiki/Zip_(file_format) ---------- components: Library (Lib) files: isz_fail.py messages: 279084 nosy: Thomas.Waldmann priority: normal severity: normal status: open title: is_zipfile false positives type: behavior versions: Python 2.7, Python 3.5 Added file: http://bugs.python.org/file45162/isz_fail.py _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue28494> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
