141 lines
3.3 KiB
Groff
141 lines
3.3 KiB
Groff
.\" This definition swiped from the gcc(1) man page
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.de Sp
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.if n .sp
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.if t .sp 0.4
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..
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.TH SRM 1
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.SH NAME
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srm \- secure remove (secure_deletion toolkit)
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.SH SYNOPSIS
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.B srm [-d] [-f] [-l] [-l] [-r] [-v] [-z] files
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.SH DESCRIPTION
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.I srm
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is designed to delete data on mediums in a secure manner which can not be
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recovered by thiefs, law enforcement or other threats.
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The wipe algorythm is based on the paper "Secure Deletion of Data from
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Magnetic and Solid-State Memory" presented at the 6th Usenix Security
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Symposium by Peter Gutmann, one of the leading civilian cryptographers.
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.PP
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The
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.I secure data deletion
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process of srm goes like this:
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.PP
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.TP
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.B *
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1 pass with 0xff
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.TP
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.B *
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5 random passes. /dev/urandom is used for a secure RNG if available.
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.TP
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.B *
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27 passes with special values defined by Peter Gutmann.
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.TP
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.B *
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5 random passes. /dev/urandom is used for a secure RNG if available.
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.TP
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.B *
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Rename the file to a random value
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.TP
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.B *
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Truncate the file
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.PP
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.PP
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As an additional measure of security, the file is opened in O_SYNC mode
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and after each pass an fsync() call is done.
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.I srm
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writes 32k blocks for the purpose of speed, filling buffers of disk caches
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to force them to flush and overwriting old data which belonged to the file.
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.PP
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.SH COMMANDLINE OPTIONS
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.PP
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.TP
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.B \-d
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ignore the two special dot files . and .. on the commandline. (so you can
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execute it like "srm -d .* *")
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.TP
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.B \-f
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fast (and insecure mode): no /dev/urandom, no synchronize mode.
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.TP
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.B \-l
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lessens the security. Only two passes are written: one mode with 0xff
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and a final mode random values.
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.TP
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.B \-l
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-l for a second time lessons the security even more: only one random pass
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is written.
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.TP
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.B \-r
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recursive mode, deletes all subdirectories.
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.TP
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.B \-v
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verbose mode
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.TP
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.B \-z
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wipes the last write with zeros instead of random data
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.PP
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.SH LIMITATIONS
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.TP
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.B NFS
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Beware of NFS. You can't ensure you really completely wiped your data
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from the remote disks.
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.TP
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.B Raid
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Raid Systems use stripped disks and have got large caches. It's hard to wipe
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them.
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.TP
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.B swap, /tmp, etc.
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Some of your data might have a temporary (deleted) copy somewhere on the
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disk. You should use
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.I sfill
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which comes with the
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.I secure_deletion package
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to ensure to wipe also the free diskspace. However, If already a small
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file aquired a block with your precious data, no tool known to me can help
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you here. For a secure deletion of the swap space
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.I sswap
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is available.
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.PP
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.SH BUGS
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No bugs. There was never a bug in the secure_deletion package (in contrast
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to my other tools, whew, good luck ;-)
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Send me any that you find. Patches are nice too :)
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.SH AUTHOR
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.Sp
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van Hauser / THC
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.I <vh@thc.org>
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.SH DISTRIBUTION
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The newest version of the
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.I secure_deletion package
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can be obtained from
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.I http://www.thc.org
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.Sp
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.I srm
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and the
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.I secure_deletion package
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is (C) 1997-2003 by van Hauser / THC (vh@thc.org)
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.Sp
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; Version 2.
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.Sp
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This program is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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.SH SEE ALSO
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.I sfill
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(1),
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.I sswap
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(1),
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.I smem
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(1)
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