Code review comment for lp:~jml/pkgme-service/lzma-support

Hi,

In execing tar there are a few things we have to be careful of to prevent
attacks.

--force-local will mean that if someone uploads a tarball with a colon in the name
it won't try and connect to a remote machine to find the file.

We want --no-same-owner and --no-same-permissions, but they are default for
non-root users, so I don't know if we want to be explicit or not.

In addition, I think this will fix some issues we see in scoreboard with
e.g. unable to process tarfiles, or trying to extract to absolute paths.

Rather than fixing those, we could just replace the existing tarfile extractor
with this one. You are right that it is more expensive though, so maybe we
don't want to.

Thanks,

James