Subject: Re: tar ignores filenames that contain `..'
To: Thor Lancelot Simon <>
From: Alistair Crooks <>
List: tech-security
Date: 10/23/2002 18:33:34
On Wed, Oct 23, 2002 at 12:15:21PM -0400, Thor Lancelot Simon wrote:
> On Wed, Oct 23, 2002 at 12:05:39PM -0400, Greg A. Woods wrote:
> > 
> > I would say from my experience in using pax exclusively for well over a
> > year now, and from what I read in that followup discussion, that the bug
> > really must be fixed in pkg_create.
> Okay, I'm going to shock and amaze you all by agreeing with Greg.  The
> fact that binary packages contain tar files with upwards path components
> (and thus require the use of insanely dangerous tar options to extract)
> has always disturbed me greatly.  It also makes creating malicious
> packages much easier -- you don't even have to _run_ the binaries in
> them, just extract them.
> Please don't revert security fixes to tar/pax just to avoid fixing
> pkg_create.

And I will jump in and say that it is really pax's problem.  This is
because (a) a lot of the distfiles that we use in pkgsrc come with
symbolic links with ".." in them, so that we can't even extract the
contents properly now - this has nothing to do with pkg_create - and
(b) because we go to great lengths in pkg_create to make symbolic
links relative to ${PREFIX} for binary packages.  You are now
seriously suggesting that we can't make archives relative to a certain
directory because tar or pax might extract over a file that's above
${PREFIX}?  I'd say that was a bug in pax and tar - they should be
able to calculate the depth of directories, and handle it accordingly.

I realise this has nothing to do with pax itself - we'd be seeing the
same problems right now with GNU tar.