wipe Properly overwrite filenames

This patch is based on the source of shred from coreutils by Colin Plumb. While shred is now licensed under GPLv3, the parts of this patch that were derived from shred could easily be changed to a version of shred (git commit cad884a) that was licensed under GPLv2 or later.

Note that this patch only keeps the filename from being readable in the filesystem structure. For journaling fileystems, such as ext{3,4}, the filename is still retained in the journal.

Testcase: $ dd if=/dev/zero bs=1M count=256 of=wipeimagefile-ext2.bin; $ losetup /dev/loop2 wipeimagefile-ext2.bin; $ mkfs.ext2 /dev/loop2; $ mkdir /mnt/wipetest; $ mount /dev/loop2 /mnt/wipetest; $ echo "very secret data that should be deleted after use" > /mnt/wipetest/secretfile.txt; $ wipe -fc /mnt/wipetest/secretfile.txt; $ umount /mnt/wipetest; $ losetup -d /dev/loop2; $ rmdir /mnt/wipetest; $ fls wipeimagefile-ext2.bin wipeimagefile-ext2.bin d/d 11: lost+found r/- * 0: secretfile.txt r/- * 0: 4hv06IB9SyTgVt d/d 2561: $OrphanFiles

This change is

Oct 15 '13 09:10 tyll

ping?

Oct 22 '13 16:10 tyll

Should we assume that wipe is dead from the PoV of upstream? (Having my Debian package maintainer hat on.)

Oct 31 '13 08:10 mika