tar/libarchive gzip problem [was: portsnap corrupted]

Hey Tim,

I think one of the recent changes to tar or libarchive broke gzip
handling in some cases.  See more below.

[portsnap extract fails with gzip error]

I'm not sure why I didn't run into it in my tests, but I think the
problem is in tar / libarchive's handling of gzip files.  Taking one
random "broken" file [1] it fails with tar's build in decompression,
but works using external zcat.

[1] http://portsnap1.freebsd.org/f/19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz
http://people.freebsd.org/~simon/tmp/19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz


Broken system:

[simon_at_eddie:/tmp] tar --version
bsdtar 2.5.903a - libarchive 2.5.903a
[simon_at_eddie:/tmp] uname -a
FreeBSD eddie.nitro.dk 8.0-CURRENT FreeBSD 8.0-CURRENT #1: Tue Dec 30 22:28:33 CET 2008     simon_at_eddie.nitro.dk:/FreeBSD/obj/FreeBSD/system-CURRENT/sys/EDDIE  i386
[simon_at_eddie:/tmp] tar tvf 19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz > /dev/null
tar: Error opening archive: Invalid GZip header (saw 99 at offset 1)
[simon_at_eddie:/tmp] zcat 19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz | tar tf - > /dev/null 
[simon_at_eddie:/tmp] zcat 19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz | sha256 
19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d


OK system:

[simon_at_benji:/tmp] tar --version
bsdtar 2.5.5 - libarchive 2.5.5
[simon_at_benji:/tmp] uname -a
FreeBSD benji.s 7.1-RC2 FreeBSD 7.1-RC2 #0: Tue Dec 23 15:18:30 UTC 2008     root_at_logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386
[simon_at_benji:/tmp] tar tvf 19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz > /dev/null 
[simon_at_benji:/tmp] zcat 19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz | sha256 
19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d


Another OK system:

[simon_at_ref8-amd64:files] tar --version
bsdtar 2.5.5 - libarchive 2.5.5
[simon_at_ref8-amd64:files] uname -a
FreeBSD ref8-amd64.freebsd.org 8.0-CURRENT FreeBSD 8.0-CURRENT #2 r184542:185402: Fri Nov 28 19:14:40 UTC 2008     peter_at_ref8-amd64.freebsd.org:/scratch/src/sys/amd64/compile/REF8-AMD64  amd64
[simon_at_ref8-amd64:files] tar tvf 19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz > /dev/null
[simon_at_ref8-amd64:files] zcat 19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d.gz | sha256
19faa3b8bd15bb8f4cd9f665a7623887729f3bd834d780e8b069df979f228e8d

-- 
Simon L. Nielsen