Fix CVE-2016-6321:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-6321
https://security-tracker.debian.org/tracker/CVE-2016-6321

Patch adapted from upstream source repository (the changes to 'NEWS'
don't apply to the Tar 1.29 release tarball).

http://git.savannah.gnu.org/cgit/tar.git/commit/?id=7340f67b9860ea0531c1450e5aa261c50f67165d

From 7340f67b9860ea0531c1450e5aa261c50f67165d Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@Penguin.CS.UCLA.EDU>
Date: Sat, 29 Oct 2016 21:04:40 -0700
Subject: [PATCH] When extracting, skip ".." members

* NEWS: Document this.
* src/extract.c (extract_archive): Skip members whose names
contain "..".
---
 NEWS          | 8 +++++++-
 src/extract.c | 8 ++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/extract.c b/src/extract.c
index f982433..7904148 100644
--- a/src/extract.c
+++ b/src/extract.c
@@ -1629,12 +1629,20 @@ extract_archive (void)
 {
   char typeflag;
   tar_extractor_t fun;
+  bool skip_dotdot_name;
 
   fatal_exit_hook = extract_finish;
 
   set_next_block_after (current_header);
 
+  skip_dotdot_name = (!absolute_names_option
+		      && contains_dot_dot (current_stat_info.orig_file_name));
+  if (skip_dotdot_name)
+    ERROR ((0, 0, _("%s: Member name contains '..'"),
+	    quotearg_colon (current_stat_info.orig_file_name)));
+
   if (!current_stat_info.file_name[0]
+      || skip_dotdot_name
       || (interactive_option
 	  && !confirm ("extract", current_stat_info.file_name)))
     {
-- 
2.11.0

