Bugtraq mailing list archives
Re: Shred 1.0 Bug Report
From: Mitchell Blank Jr <mitch () SFGOTH COM>
Date: Thu, 12 Oct 2000 15:20:18 -0700
Alfred Perlstein wrote:
Programs like shred are particularly bad, they offer a false sense of security, this instance shows a complete lack of understanding of how most UNIX filesystems are implemented. Shred won't work reliably on: a) data logging filesystems b) transactional filesystems c) filesystems that perform online defrag (FreeBSD-FFS+reallockblks) d) filesystems that offer snapshot capabilities. e) (well i'm sure there's more) Programs like this offer a false sense of security, the proper way to do it is to implement some sort of 'scrub(2)' syscall
Even a scrub syscall wouldn't work very well. In the case of online defrag or log structured filesystems you could scrub the blocks that currently hold the file but there may be other blocks which are now free that have data from that same file. A better solution is something like ext2's "secure removal" flag that indicates that the data should be scrubbed automatically upon removal or truncation (unfortunately the current implementation of ext2 in linux ignores this flag... more of that false sense of security). Then the filesystem knows to scrub blocks that came from that file any time it makes a copy of the data. Then there's the issue of what happens if some of the data in your super-secret file got wrote out to disk just before a crash, but the metadata never made it to disk (or the journal). Solvable, but a pain. -Mitch
Current thread:
- Shred 1.0 Bug Report Jeff Harlan (Oct 10)
- Re: Shred 1.0 Bug Report Guenther H. Leber (Oct 10)
- Re: Shred 1.0 Bug Report Frank Wiles (Oct 11)
- Re: Shred 1.0 Bug Report M. Leo Cooper (Oct 11)
- Re: Shred 1.0 Bug Report Wietse Venema (Oct 11)
- Re: Shred 1.0 Bug Report Alfred Perlstein (Oct 12)
- Re: Shred 1.0 Bug Report Mitchell Blank Jr (Oct 13)
- Re: File "shredding" Kurt Seifried (Oct 13)
- Re: Shred 1.0 Bug Report Wietse Venema (Oct 11)
- Re: Shred 1.0 Bug Report M. Leo Cooper (Oct 11)
- Re: Shred 1.0 Bug Report Dan Kaminsky (Oct 12)
- Re: Shred 1.0 Bug Report Guenther H. Leber (Oct 10)