Firewall Check Script

Shell Programming and Scripting
1

Hello,

I made a following script that check every 5 minutes to check firewall is running or not, if firewall down that raise an alert only once, but following script generate an alert every 5 minutes according to cronjob:

FILE="/var/log/fwstatus" 
CHK="/tmp/fwstatus" 
 
service iptables status | if grep ESTABLISHED 1> /dev/null 2> /dev/null 
 
then 
rm -f $CHK 
echo "Firewall Running on Server" 
 
if test -f $CHK 
then 
echo "Not Sending an Email" 
exit 
fi 
 
 
else 
 
echo `date` | tee $FILE 
echo | tee -a $FILE 
 
echo "Firewall not Running" | tee -a $FILE 
echo | tee -a $FILE 
echo "Starting a Firewall Service" | tee -a $FILE 
echo | tee -a $FILE 
 
/scripts/fw-scripts/fw | tee -a $FILE (This is IPTABLES Script) 
 
if test $? = 0 
then 
echo "FW Run" | tee -a $FILE 
else 
echo "FW Stop" | tee -a $FILE 
fi 
 
echo "Now sending mail" 
$MAILPROG -s "$SUBJECT" "$EMAIL" < $FILE 
 
echo "Creating Tmp File" 
touch $CHK 
 
fi
2

If I am understanding your issue correctly, you are getting an email alert that the firewall is down each time cron runs the job (every five minutes).

This reason you are getting an email each time is due to 2 factors:

  1. Firewall is still down, even though your script is suppose to start it
  2. You never check to see if $CHK, your /tmp/fwstatus file, exist before sending the email.

Change this:

        echo "Now sending mail"
        $MAILPROG -s "$SUBJECT" "$EMAIL" < $FILE
        echo "Creating Tmp File"
        touch $CHK
fi

To this:

    if test -f $CHK
                then
                # do nothing - it's existence means you sent an email already
                #   and hopefully that email made it to you :)
             else
                echo "Now sending mail"
                $MAILPROG -s "$SUBJECT" "$EMAIL" < $FILE
                echo "Creating Tmp File"
                touch $CHK
fi

Also, I noticed this and don't believe these lines are required - you remove $CHK, and then do a test to see if it's there.

service iptables status | if grep ESTABLISHED 1> /dev/null 2> /dev/null
        then
        rm -f $CHK
        echo "Firewall Running on Server"
line not needed ---->   if test -f $CHK
line not needed ---->           then
                        echo "Not Sending an Email"
                        exit
line not needed ---->   fi