Bug#900593: diffoscope: GNU tar xattrs result in: libarchive: Ignoring malformed pax extended attribute

[Tianon Gravi]

Package: diffoscope
Version: 95
Severity: normal

First, thanks for diffoscope; it's the best. :)

The context for this bug is in [1].  The basic gist is that I need to
preserve extended attributes to get the proper capabilities on
"/bin/ping" inside a rootfs tarball, so I updated my GNU tar invocation
to include "--xattrs", "--acls", and "--selinux" (just for good
measure).

[1]: https://github.com/debuerreotype/debuerreotype/pull/38

After doing so, I did a quick "diffoscope" of the before/after (which
normally is indispensibly helpful in ensuring that my PR does exactly
what I expect it to and not a single thing more).  I was expecting to
see something showing me that I've got some new extended attributes on
at least "/bin/ping" (and possibly other files), but instead got the
following:

| $ diffoscope travis/20170101/amd64/jessie/rootfs.tar.xz
output/20170101/amd64/jessie/rootfs.tar.xz
| 2018-06-01 17:22:24 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:24 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:24 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:25 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:25 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:26 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:26 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:26 W: libarchive: Ignoring malformed pax extended attribute
| 2018-06-01 17:22:26 W: libarchive: Ignoring malformed pax extended attribute
|  |############################|  100%
Time: 0:00:10
| --- travis/20170101/amd64/jessie/rootfs.tar.xz
| +++ output/20170101/amd64/jessie/rootfs.tar.xz
| ├── rootfs.tar
| │ ├── filetype from file(1)
| │ │ @@ -1 +1 @@
| │ │ -POSIX tar archive (GNU)
| │ │ +POSIX tar archive

I've uploaded the two .tar.xz files in question to [2] in case you'd
like to reproduce. :)

[2]: https://people.debian.org/~tianon/diffoscope-gnu-tar-xattrs/

If there's something obvious I've missed, I apologize!  I searched the
bugs and the list as much as I could, and couldn't find anything similar
(which was surprising -- I would've thought someone else would've run
into this long before me). O:>


♥,
- Tianon
  4096R / B42F 6819 007F 00F8 8E36  4FD4 036A 9C25 BF35 7DD4


-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.15.0-2-amd64 (SMP w/12 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8),
LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages diffoscope depends on:
ii  libpython3.6-stdlib    3.6.5-9
ii  python3                3.6.5-3
ii  python3-distro         1.0.1-2
ii  python3-distutils      3.6.5-3
ii  python3-libarchive-c   2.1-3.1
ii  python3-magic          2:0.4.15-1
ii  python3-pkg-resources  39.1.0-1

Versions of packages diffoscope recommends:
ii  abootimg                         0.6-1+b2
ii  acl                              2.2.52-3+b1
ii  apktool                          2.3.3-1
ii  binutils-multiarch               2.30-20
ii  bzip2                            1.0.6-8.1
ii  caca-utils                       0.99.beta19-2+b3
ii  colord                           1.3.3-2
ii  db-util                          5.3.1
ii  default-jdk-headless             2:1.10-65
ii  device-tree-compiler             1.4.6-1
ii  docx2txt                         1.4-1
ii  e2fsprogs                        1.44.2-1
ii  enjarify                         1:1.0.3-4
ii  fontforge-extras                 0.3-4
ii  fp-utils                         3.0.4+dfsg-19
ii  fp-utils-3.0.4 [fp-utils]        3.0.4+dfsg-19
ii  genisoimage                      9:1.1.11-3+b2
ii  gettext                          0.19.8.1-6+b1
ii  ghc                              8.0.2-11
ii  ghostscript                      9.22~dfsg-2.1
ii  giflib-tools                     5.1.4-2
ii  gnumeric                         1.12.39-1
ii  gnupg                            2.2.5-1
ii  imagemagick                      8:6.9.9.34+dfsg-3+b1
ii  imagemagick-6.q16 [imagemagick]  8:6.9.9.34+dfsg-3+b1
ii  jsbeautifier                     1.6.4-7
ii  libarchive-tools                 3.2.2-3.1
ii  llvm                             1:4.0-40
ii  mono-utils                       4.6.2.7+dfsg-1
ii  odt2txt                          0.5-1+b2
ii  oggvideotools                    0.9.1-4
ii  openssh-client                   1:7.7p1-2
ii  pdftk                            2.02-4+b2
ii  pgpdump                          0.31-0.2
ii  poppler-utils                    0.63.0-2
ii  procyon-decompiler               0.5.32-4
ii  python3-argcomplete              1.8.1-1
ii  python3-binwalk                  2.1.1-16
ii  python3-debian                   0.1.32
ii  python3-defusedxml               0.5.0-1
ii  python3-guestfs                  1:1.38.1-1
ii  python3-jsondiff                 1.1.1-2
ii  python3-progressbar              2.3-4
ii  python3-pyxattr                  0.6.0-2+b1
ii  python3-tlsh                     3.4.4+20151206-1+b3
ii  r-base-core                      3.4.4-1+b2
ii  rpm2cpio                         4.14.1+dfsg1-2
ii  sng                              1.1.0-1+b1
ii  sqlite3                          3.23.1-1
ii  squashfs-tools                   1:4.3-6
ii  tcpdump                          4.9.2-3
ii  unzip                            6.0-21
ii  vim-common                       2:8.0.1766-1
pn  xmlutils                         <none>
ii  xxd                              2:8.0.1766-1
ii  xz-utils                         5.2.2-1.3

Versions of packages diffoscope suggests:
ii  libjs-jquery  3.2.1-1

-- no debconf information