Avoid Archive::Tar directory traversal

Addresses CVE-2018-12015
From Silamael <silamael () coronamundi ! de>

Original bug reports:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=900834
https://rt.cpan.org/Public/Bug/Display.html?id=125523

Original commit with the fix:
https://github.com/jib/archive-tar-new/commit/ae65651eab053fc6dc4590dbb863a268215c1fc5

OK bluhm@, they should already be committed! deraadt@

1 files changed, 14 insertions, 0 deletions

diff --git a/gnu/usr.bin/perl/cpan/Archive-Tar/lib/Archive/Tar.pm b/gnu/usr.bin/perl/cpan/Archive-Tar/lib/Archive/Tar.pm
index 6a047a32d6c..d110bd7bd8f 100644
--- a/gnu/usr.bin/perl/cpan/Archive-Tar/lib/Archive/Tar.pm
+++ b/gnu/usr.bin/perl/cpan/Archive-Tar/lib/Archive/Tar.pm
@@ -845,6 +845,20 @@ sub _extract_file {
         return;
     }
 
+    ### If a file system already contains a block device with the same name as
+    ### the being extracted regular file, we would write the file's content
+    ### to the block device. So remove the existing file (block device) now.
+    ### If an archive contains multiple same-named entries, the last one
+    ### should replace the previous ones. So remove the old file now.
+    ### If the old entry is a symlink to a file outside of the CWD, the new
+    ### entry would create a file there. This is CVE-2018-12015
+    ### <https://rt.cpan.org/Ticket/Display.html?id=125523>.
+    if (-l $full || -e _) {
+	if (!unlink $full) {
+	    $self->_error( qq[Could not remove old file '$full': $!] );
+	    return;
+	}
+    }
     if( length $entry->type && $entry->is_file ) {
         my $fh = IO::File->new;
         $fh->open( '>' . $full ) or (