Shell scripting

[#686578]

I don't have any immediate questions, but I wanted to post this as an open discussion for thoughts and ideas. More simple or maybe even more complex ways of what I'm doing would be appreciated to see how things work.

I'm trying to create a script thats purpose is to create a series of daily logs of failed login attempts so that you can see on any single day how many failed login attempts any user has had. This should be useful for seeing trends in failed login attempts and if you might have any hacking attempts, or some bullshit reason like that.

I wrote this pseudocode to sort of help actualize my idea:

 Check if last two lines of /etc/pam.d/system-auth
                  If last two lines are right then proceed
                  If last two lines are not right then write appropriately
  Check if logs folder exists
                If no then – create
                If yes then proceed
  Get date 12/31/2009
  Check if day exists already
                  If no then – create
                  If yes then proceed
  Append faillog –a to file
  Faillog –r to reset the faillog

[#686578]

So I'm trying to complete the first section at the moment, check if the last two lines of the file matches a certain string to verify that failloging is enabled.

I'm testing this with the following enviroment; I have a file named test with four lines:

line 1
line 2
line 3
line 4

After a lot of playing around I got this bit of code to work:

if [ "`tail -2 test`" != "`echo -e "line 3\nline 4"`" ] 
then
     echo -e "Requirements not found\nAppending..."
     echo -e "line 3\nline 4" >> test
     echo "Next Step"
else
     echo -e "Requirements found\nNext Step"
fi

It tests to see if the last two lines of file test are NOT "line 3\nline 4", if it is does NOT match then it adds "line 3\nline 4" as well as some other stuff just so I can see what the script is doing. If it DOES match then it moves onto the next step, which I think I'll start on tomorrow.

[#686578]

This probably looks very very basic to some of you out there, but it's been a few years since I've programmed in any language and not only am I learning a new one (sort of, it's pretty much just C, as far as I know) I'm relearning all thought processes of how to program.

[#686578]

Step 2, check if logs directory exists:

if [ -e /var/log/fla ]
then
    echo -e "Logs directory found.\nNext Step"
else
    echo -e "Logs directory not found\nCreating directory."
    mkdir /var/log/fla
    echo "Next Step"
fi

[#686578]

Third step, check if the log for that day exists already:

if [ -e "/var/log/fla/`date +%m-%d-%Y`" ]
then
    echo -e "Log for this day exists\nNext Step"
else
    echo -e "Log for this day does not exist\nCreating..."
    touch "/var/log/fla/`date +%m-%d-%Y`"
    echo "Next Step"
fi

[#686578]

Fourth final step:

echo "Writing to log..."
faillog -a >> /var/log/fla/`date +%m-%d-%Y`
echo "Resetting failed login attempts"
faillog -r

[#686578]

Finished product, completely tested, no bugs:

if [ "`tail -2 /etc/pam.d/system-auth`" != "`echo -e "auth required pam_tally.so no_magic_root\naccount required pam_tally.so deny=3 no_magic_root lock_time=180"`" ]
then
    echo -e "Requirements not found\nAppending..."
    echo -e "auth required pam_tally.so no_magic_root\naccount required pam_tally.so deny=3 no_magic_root lock_time=180" >> /etc/pam.d/system-auth
    echo -e "Next Step"
else
    echo -e "Requirements found\nNext Step"
fi
if [ -e /var/log/fla ]
then
    echo -e "Log directory found.\nNext Step"
else
    echo -e "Log directory not found\nCreating directory."
    mkdir /var/log/fla
    echo "Next Step"
fi
if [ -e "/var/log/fla/`date +%m-%d-%Y`" ]
then
    echo -e "Log for this day exists\nNext step"
else
    echo -e "Log for this day does not exist\nCreating..."
    touch "/var/log/fla/`date  +%m-%d-%y`"
    echo "Next Step"
fi
echo "Writing to log..."
faillog -a >> /var/log/fla`date +%m-%d-%Y`
echo "Rresetting failed login attempts"
faillog -r
echo "Script complete"

[#686578]

If anyone has any comments on how I could've done this better, easier, or even more complex please leave them.