#!/bin/sh

# This method is based on the information provided by Peter Gutmann from the
# Sixth (6th) Annual USENIX Security Symposium in a paper entitled:
# "Secure Deletion of Data from Magnetic and Solid-State Memory"

# Securely overwrite regular disks
# Partitions are overwritten 35 times; rounds 1-4 use /dev/arandom, rounds
# 5-31 use Guttman's deterministic patterns, and rounds 32-35 use
# /dev/arandom. This option implements the method described by Peter
# Gutmann in his whitepaper, Secure Deletion of Data from Magnetic and
# Solid-State Memory, presented at the 6th USENIX Security Symposium.

usage() {
	echo "$0 rawdiskdevtowipe" 
	echo "example: $0 /dev/rwd0c"
	exit
}
if ! [ "$1" ]; then
	usage
fi
if ! [ -c /dev/arandom ]; then
	cd /dev
	sh ./MAKEDEV random
	if ! [ -c /dev/arandom ]; then
		echo "/dev/arandom does not exist and cannot make it, bailing!"
		exit 1
	fi
fi


parsedd() {
	while read line; do
		case "$line" in
		*transferred*) echo "$line";;
		esac
	done
}
	

disk="$1"

set -A gpat \
	55 55 55 \
	aa aa aa \
	92 49 24 \
	49 24 92 \
	24 92 49 \
	00 00 00 \
	11 11 11 \
	22 22 22 \
	33 33 33 \
	44 44 44 \
	55 55 55 \
	66 66 66 \
	77 77 77 \
	88 88 88 \
	99 99 99 \
	aa aa aa \
	bb bb bb \
	cc cc cc \
	dd dd dd \
	ee ee ee \
	ff ff ff \
	92 49 24 \
	49 24 92 \
	24 92 49 \
	6d b6 db \
	b6 db 6d \
	db 6d b6


typeset -i8 o1 o2 o3

f=0
cd /tmp

count=0
pass=0
while [ count -lt 4 ]; do
	let pass=pass+1
	echo "Pass $pass: /dev/arandom"
	time dd if=/dev/arandom of=$disk bs=1m 2>&1 | parsedd
	let count=count+1
done

g=0
while [ "${gpat[$g]}" ]; do
	g1=$g
	g2=$((g+1))
	g3=$((g+2))
	let g=g+3

	let pass=pass+1
	if [ "${gpat[$g1]}" = "00" ]; then
		echo "Pass $pass: /dev/zero"
		time dd if=/dev/zero of=$disk bs=1m 2>&1 | parsedd
		continue
	fi
	echo -n "Pass $pass: 0x${gpat[$g1]}${gpat[$g2]}${gpat[$g3]}"


	# yes, should use mktemp, but not present on ramdisks
	runfile=/tmp/continue.$$.$RANDOM.$RANDOM
	rm -f $runfile
	: > $runfile
	(
		o1=$((16#${gpat[$g1]}))
		o2=$((16#${gpat[$g2]}))
		o3=$((16#${gpat[$g3]}))
		s="$(echo -n "\\0${o1#*#}\\0${o2#*#}\\0${o3#*#}")"
		echo -n "(" > /dev/stderr
		count=0
		while [ count -lt 16 ]
		do
			echo -n "."
			s="$s$s"
			let count=count+1
		done
		echo " ${#s} byte buffer)" > /dev/stderr
		while [ -f $runfile ]; do echo -n "$s"; done
	) | {
		time dd of=$disk ibs=3m obs=1m 2>&1 | parsedd 
		rm -f $runfile
	}
done

count=0
while [ count -lt 4 ]; do
	let pass=pass+1
	echo "Pass $pass: /dev/arandom"
	time dd if=/dev/arandom of=$disk bs=1m 2>&1 | parsedd
	let count=count+1
done