When extracting, skip ".." members

* NEWS: Document this.
* src/extract.c (extract_archive): Skip members whose names
contain "..".

NEWS

@@ -1,9 +1,15 @@
-GNU tar NEWS - User visible changes. 2016-05-27
+GNU tar NEWS - User visible changes. 2016-10-29
 Please send GNU tar bug reports to <[email protected]>
 
 
 version 1.29.90 (Git)
 
+* Member names containing '..' components are now skipped when extracting.
+
+This fixes tar's behavior to match its documentation, and is a bit
+safer when extracting untrusted archives over old files (an unsafe
+practice that the tar manual has long recommended against).
+
 * Report erroneous use of positional options.
 
 During archive creation or update, tar keeps track of positional

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)))
     {