Re: git archive generates tar with malformed pax extended attribute

From: Jeff King <peff@peff.net>
Date: May 28, 2019, 05:58 UTC
Message-ID: <20190528055805.GB7946@sigill.intra.peff.net>
In-Reply-To: <b4aaff4b-eaf7-9eaf-063f-42c073078060@web.de>

On Sat, May 25, 2019 at 03:26:53PM +0200, René Scharfe wrote:

> We could truncate symlink targets at the first NUL as well in git
> archive -- but that would be a bit sad, as the archive formats allow
> storing the "real" target from the repo, with NUL and all.  We could
> make git fsck report such symlinks.

This is a little tricky, because fsck generally looks at individual objects, and the bad pattern is a combination of a tree and a blob together. I think you could make it work by reusing some of the code and patterns from 9e84a6d758 (Merge branch 'jk/submodule-fsck-loose' into maint, 2018-05-22).

> Can Unicode symlink targets contain NULs?  We wouldn't want to damage
> them even if we decide to truncate.

On Windows, I suppose, where pathnames can be UTF-16? I don't know how any of that works with Git. I guess we'd always have to assume the filenames in Git are UTF-8 or at least some ASCII-superset, since we cannot encode NULs; and presumably that would extend to link destinations, too. So I doubt it's a problem in practice. Personally, I'd wait until somebody with such a system cares enough to suggest a new behavior, rather than trying to guess. :)

Likewise, I think at this point with Keegan's original report that Git is doing something reasonable with a lousy input. Unless something interesting comes out of the golang/go bug report discussion (thank you for opening that!), it's probably not worth chasing hypotheticals.

-Peff