[issue6196] tarfile.extractall(readaccess=True)

[Sridhar Ratnakumar]

Sridhar Ratnakumar <sridharr at activestate.com> added the comment:

[Lars] (...) We talk about a very small number of cases here and the
generator_tools-0.3.5.tar.gz is really broken beyond repair. It is the
only thing that should be fixed here IMO ;-)

Sure, that is what the pyopenssl folks did - fix their tarball. However,
it is reasonable expect certain tarballs to be 'broken beyond repair'
when you are running tarfile.extracall over a huge number of tarballs
such as the ones in PyPI.

Indeed, the tarfile module already has several fixes for such 'broken'
cases, Viz:

[quote]'If ignore_zeros is False, treat an empty block as the end of the
archive. If it is True, skip empty (and invalid) blocks and try to get
as many members as possible. This is only useful for reading
concatenated or **damaged** archives.'[endquote] [emphasis added]

[quote]'(...)Directory information like owner, modification time and
permissions are set after all members have been extracted. This is done
to work around two problems: A directory’s modification time is reset
each time a file is created in it. And, if a directory’s **permissions
do not allow writing**, extracting files to it will fail'[endquote]
[emphasis added]

[Lars] I agree with David here. It is easy to manipulate the tarfile in
advance, as you have shown yourself. The performance argument does not
convince me either.

Ok. Can you comment on this argument?

[quote]'(...)the very reason to write a program to extract tarball
(instead of doing it manually) is to automate it .. which automation is
*more effective and simple* if ``extractall`` had a flag such as
readaccess=True'[endquote] (emphasis added)

[quote]'I just think it is not simple (as in, keeping the code off from
such hacks that are tangential to the problem being solved) and
effective (as in, not having to deal with potential unintended side
effects like bugs in the post-fix chmoding or in the pre-fix tarinfo
mode modifications).'[endquote]

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue6196>
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