Re: [Bug-tar] xattr support on Linux

[Pavel Raiskup]

On Wed, 2012-10-10 at 12:30 +0200, Joerg Schilling wrote:
> Paul Eggert <address@hidden> wrote:
> 
> > On 10/08/2012 08:52 AM, Pavel Raiskup wrote:
> > > we are not able to store/restore extended attributes containing '='
> > > character in the keyword properly - same situation in star as our patch
> > > uses the same approach.
> >
> > Can't we fix this by URL-encoding '=' and '%' when creating the tar file
> > and URL-decoding when extracting?  It sounds easy, but it's not done
> > by that patch, so what am I missing?
> 
> What is the problem?

Jörg, the problem is here:

  $ touch FILE
  $ setfattr -n 'user.=N=A=M=E=' -v VALUE FILE
  $ star H=exustar -xattr -c -f example.star FILE
  star: 1 blocks + 0 bytes (total of 10240 bytes = 10.00k).
  $ cat example.star 
  [snip]
  70 SCHILY.xattr.security.selinux=unconfined_u:object_r:user_tmp_t:s0
  37 SCHILY.xattr.user.=N=A=M=E==VALUE
  [/snip]              ^ this is the problem

During extraction, the very first occurrence of '=' is interpreted like
pax header KEY/VALUE splitter - both in star/patched GNU tar.

> Given that these xattrs are just name=value tags, shouldn't '=' be foibidden
> in xattrs?

As Tim said, xattr keyword may contain anything except '\0' character.

> -     Are there really such tags?
> 
> -     The original implementaion was developed together with SuSE, so why was
>       there no such problem for SuSE?

Nobody complained problems even in our implementation.

Pavel