clear-swap-corrupt.sh

#!/bin/bash
#
###########################
# Clear Swap Application  #
# Patrick L. Francis      #
# Last Updated 1/30/2011  #
###########################
#
#############################################################################
# Modified by IRQ42                                                         #
# Added feature to corrupt remnant data on swap partitions/files before     #
# turning swap back on as well as bug fixes.    Work in progress ...        #
# Dec. 2015                                                                 #
#############################################################################



## make sure user is root before running app

if [[ $EUID -ne 0 ]]; then
    clear
    echo
    echo
    echo -e "..............................................."
    echo -e ".. You must be \033[1mroot\033[0m to do this .."
    echo -e "..............................................."
    echo
    echo
    echo
    sleep 5 # why waste 5 seconds of my time?
    clear
    exit 1
fi



# Wipe out remnant data
corrupt_data() {
    for f in $1
    do
    # regex accepts UUID versions 1 through 5
    regex_uuid='[a-f0-9]{8}-[a-f0-9]{4}-[1-5][a-f0-9]{3}-[89aAbB][a-f0-9]{3}-[a-f0-9]{12}'

        echo "..............................................."
        echo "..Corrupting remnant swap data on $f ..        "
        echo "..Do not interrupt until complete!!............"
        echo "..............................................."

        # see if we are dealing with a block device
        if [[ $(stat $f | egrep -c 'block') -eq 1 ]]
        then
            # get UUID of swap fs .. swap must be on before doing so
            uuid=$(blkid -c /dev/null -o list | grep "$f" | egrep -o $regex_uuid)

            # get size of block device
            fsize=$(blockdev --getsize64 $f)

            # swapoff before writing
            echo -e "swapoff UUID: $uuid\t$f"
            swapoff -U $uuid
            sync

            # write FSIZE bytes of garbage to device
            head -c $fsize $garbage_stream > $f
            sync

            # mkswap and restore original UUID
            mkswap --uuid $uuid $f

        # have to swapon devices in loop for some reason
        echo -e "swapon UUID: $uuid\t$f"
            swapon -U $uuid

        # see if we are dealing with a regular file
        elif [[ $(stat $f | egrep -c 'regular') -eq 1 ]]
        then
            # get size of regular file
            fsize=$(stat $f | grep 'Size:' | awk '{print $2}')

            # swapoff before writing
            echo -e "swapoff swap file: $f"
            swapoff $f
            sync

            #write FSIZE bytes of garbage to file
            head -c $fsize $garbage_stream> $f
            sync

            # turn swap file back on
            echo -e "swapon swap file $f"
            swapon $f

        # anything else we print an error message
        else
            echo "E: $f is unrecognized file type, can't write (not safe)"
        fi

    done
}

do_corrupt=1

# check for too many arguments
if [[ $# -gt 1 ]]
then
    echo "$0: too many arguments. $0 -h for info"

    exit 1
# check for empty first arg
elif [[ $# -eq 0 || -z $1 ]] # || $(egrep -c '\s' $1) -gt 0 ]]
then
    do_corrupt=0

    ## do to bugs, this option is not currently supported
    echo "Sorry, this option is not yet supported"
    echo -e "Try \x1b[35m$0 /dev/zero\x1b[0m for speed"

    exit 0
# show help
elif [[ $(echo $1 | egrep -c '\s?-h$') -eq 1 ]]
then
    echo "SYNOPSIS:"
    echo "$0 [specialfile]"
    echo
    echo "Specify a character device to read data from to corrupt remnant data."
    echo "e.g. $0 /dev/urandom"
    echo
    echo "If no character device to read from is specified, swap will be cleared but"
    echo "media will not be overwritten."

    exit 0
elif [[ $(stat $1 | egrep -c 'character special file') -ne 1 ]]
then
    echo "E: $1 is not a character special file. Quitting!"

    exit 1
fi

garbage_stream=$1

echo -e "..............................................."
echo -e ".. How do things look before we do anything? .."
echo -e "..............................................."
free
echo -e "........................................."
echo -e ".. Let's sync up before we get started .."
echo -e "........................................."
echo -e "."
sync
echo -e "."
echo -e "......................................................"
echo -e ".. Let's dump our drop_caches and see how that does .."
echo -e "......................................................"
echo -e "."
echo 3 > /proc/sys/vm/drop_caches
#echo 0 > /proc/sys/vm/drop_caches ## not needed due to above, causes issues.
free
echo -e "."
echo -e "...................................................."
echo -e "..Let's compare free physical memory to swap size .."
echo -e "...................................................."

## How much free memory do we have?

physical=`free|grep Mem:|awk '{print $4}'`

## How large is swap?

swap=`free|grep Swap:|awk '{print $3}'`

## Is the amount of free physical memory less than size of swap
## If so, push it to phyiscal memory... if it is not, then exit.

## I avoid any type of math in bash and use awk for comparison operators

compare=`echo "$physical $swap good bad" | awk '{if ($1 > $2) print $3; else print $4}'`

if [ "$compare" == "good" ]; then

    # get path(s) for swaps
    swaps=$(cat /proc/swaps | egrep '\/' | awk '{print $1}')

    echo -e "."
    echo -e "..................................................."
    echo -e ".. sufficient physical memory, clearing swap now .."
    echo -e "..................................................."
    ## turn swaps off, then back on
    echo -e "."
    echo -e "......................"
    echo -e ".. turning swaps off .."
    echo -e "......................"
    echo -e "."


    # after swapoff, corrupt remnant data on disk
    if [[ $do_corrupt -eq 1 ]]
    then
        corrupt_data $swaps
    else
        swapoff -a # this needs to be fixed proper .. wtf were you thinking when you wrote this?
    fi

    echo -e "."
    echo -e "....................."
    echo -e ".. turning swap on .."
    echo -e "....................."
    echo -e "."
    swapon -a  # this doesn't work in all cases, you need to do them explicitly!!
    echo -e "."
    echo -e "..................................................."
    echo -e ".. swap has been freed, here is how it looks now .."
    echo -e "..................................................."
    echo
    echo
    free
else
    echo
    echo
    echo -e ".............................................."
    echo -e ".. kill the app, not enough physical memory .."
    echo -e ".............................................."
    echo
    echo
    exit 1
fi

exit 0