#!/bin/bash
# blotout.sh: ÆÄÀÏÀÇ ¸ðµç ±â·Ï Áö¿ì±â.

#  ÀÌ ½ºÅ©¸³Æ®´Â ´ë»ó ÆÄÀÏÀ» Áö¿ì±â Àü¿¡ 
#+ ÀÓÀÇÀÇ ¹ÙÀÌÆ®µé·Î µ¤¾î¾²°í, 0À¸·Î µ¤¾î¾²±â¸¦ ¹Ýº¹ÇÕ´Ï´Ù.
#  ÀÌ·¸°Ô ÇÏ°í ³ª¸é, µð½ºÅ© ¼½Å͸¦ ¹°¸®ÀûÀ¸·Î °Ë»çÇصµ
#+ ¿ø·¡ÀÇ ÆÄÀÏ µ¥ÀÌŸ¸¦ ã¾Æ ³¾ ¼ö ¾ø½À´Ï´Ù.

PASSES=7         # ÆÄÀÏ Á¶°¢(file-shredding) ´Ü°è.
BLOCKSIZE=1      #  /dev/urandom À¸·Î I/O ¸¦ ÇÒ ¶§ ÇÊ¿äÇÑ À¯´Ö ºí·° Å©±â.
                 #+ ÀÌ Å©±â°¡ ÁöÁ¤µÇÁö ¾ÊÀ¸¸é ÀÌ»óÇÑ °á°ú°¡ ³ª¿É´Ï´Ù.
E_BADARGS=70
E_NOT_FOUND=71
E_CHANGED_MIND=72

if [ -z "$1" ]   # ÆÄÀÏÀÌ ÁöÁ¤µÇÁö ¾Ê¾ÒÀ½.
then
  echo "»ç¿ë¹ý: `basename $0` filename"
  exit $E_BADARGS
fi

file=$1

if [ ! -e "$file" ]
then
  echo "\"$file\" ÆÄÀÏÀ» ãÀ» ¼ö ¾øÀ½."
  exit $E_NOT_FOUND
fi  

echo; echo -n "\"$file\" ÆÄÀÏÀ» Á¤¸»·Î ¿ÏÀüÈ÷ Áö¿ö ¹ö¸®°Ú½À´Ï±î(y/n)? "
read answer
case "$answer" in
[nN]) echo "Çϱ⠽ȴٱ¸¿ä?"
      exit $E_CHANGED_MIND
      ;;
*)    echo "\"$file\" ÆÄÀÏÀ» ¿ÏÀüÈ÷ Áö¿ì´Â Áß.";;
esac


flength=$(ls -l "$file" | awk '{print $5}')  # 5 ¹ø° Çʵ尡 ÆÄÀÏ ±æÀÌ.

pass_count=1

echo

while [ "$pass_count" -le "$PASSES" ]
do
  echo "$pass_count ¹ø° ´Ü°è"
  sync         # ¹öÆÛ Ç÷¯½¬.
  dd if=/dev/urandom of=$file bs=$BLOCKSIZE count=$flength
               # ÆÄÀÏÀ» ÀÓÀÇÀÇ ¹ÙÀÌÆ®µé·Î µ¤¾î¾¸.
  sync         # ´Ù½Ã ¹öÆÛ Ç÷¯½¬.
  dd if=/dev/zero of=$file bs=$BLOCKSIZE count=$flength
               # ÆÄÀÏÀ» 0À¸·Î µ¤¾î¾¸.
  sync         # ¶Ç ´Ù½Ã ¹öÆÛ Ç÷¯½¬.
  let "pass_count += 1"
  echo
done  


rm -f $file    # ¸¶Áö¸·À¸·Î, ¿ÂÅë µÚ¼¯ÀÌ°í Á¶°¢³ª ¹ö¸° ÆÄÀÏÀ» »èÁ¦.
sync           # ¸¶Áö¸· ¹öÆÛ Ç÷¯½¬.

echo "\"$file\" ÆÄÀÏÀÌ ¿ÏÀüÈ÷ »èÁ¦µÇ¾ú½À´Ï´Ù."; echo


#  ÀÌ ½ºÅ©¸³Æ®´Â ÆÄÀÏÀ» ¿ÏÀüÈ÷ "Á¶°¢³»´Âµ¥"(shredding) ºñÈ¿À²ÀûÀÌ°í ´À¸° ¹æ¹ýÀ» 
#+ ¾´ °Í¸¸ »©¸é Á¤¸» ¾ÈÀüÇÕ´Ï´Ù. GNU "fileutils" ÆÐÅ°ÁöÁßÀÇ ÇϳªÀÎ
#+ "shred" ¸í·É¾îµµ ¶È°°Àº ÀÏÀ» ÇÏÁö¸¸ Á» ´õ È¿À²ÀûÀÔ´Ï´Ù.

#  ÀÌ ½ºÅ©¸³Æ®·Î Áö¿öÁø ÆÄÀÏÀº ÀϹÝÀûÀÎ ¹æ¹ýÀ¸·Î´Â "undelete"µÇ°Å³ª
#+ º¹±¸ÇØ ³¾ ¼ö ¾ø½À´Ï´Ù.
#  ÇÏÁö¸¸...
#+ ÀÌ·± °£´ÜÇÑ ¹æ¹ýÀº °úÇÐÀûÀÎ ºÐ¼®(forensic analysis)±îÁö ¸·¾Æ³»Áö´Â ¸øÇÕ´Ï´Ù.


#  Tom VierÀÇ "wipe" ÆÄÀÏ »èÁ¦ ÆÐÅ°Áö´Â ÀÌ °£´ÜÇÑ ½ºÅ©¸³Æ®º¸´Ù Á» ´õ 
#+ ¿ÏÀüÇÏ°Ô ÆÄÀÏÀ» Áö¿ö ÁÝ´Ï´Ù.
#     http://www.ibiblio.org/pub/Linux/utils/file/wipe-2.0.0.tar.bz2

#  ÆÄÀÏ »èÁ¦¿Í º¸¾È¿¡ ´ëÇؼ­ Á» ´õ ÀÚ¼¼ÇÏ°Ô ¾Ë°í ½Í´Ù¸é,
#+ Peter GutmannÀÇ ³í¹®À» Âü°íÇϱ⠹ٶø´Ï´Ù.
#+     "Secure Deletion of Data From Magnetic and Solid-State Memory".
#           http://www.cs.auckland.ac.nz/~pgut001/secure_del.html


exit 0