Create Linux User Login Monitor on Paid Monitor

The output should look similar to this:

{"status":"ok","data":305}

This is showing us that the monitor was successfully created and that the id of the resulting monitor is 305.  If you go to your Paid Monitor account now, you will be able to access this monitor.  From the top level menu, go to Monitors then Manage Monitors and then Custom Monitors.  Here you should find the Login Monitor.  Click the check box next to the title and then click Add to Window.  A window will pop up below the Custom Monitors dialog box.  Close the Custom Monitors dialog box and you will see your new monitor there.  But no data has been sent to it, so it is not that interesting.

Save this file to paid-monitor_add_result.sh and make executable.  You can run it with no parameters to get a help menu, that should be self-explanatory.  You can either provide the API Key and Secret Key on the command-line or fill in the script to contain it.  The script will provide you with the monitorId if you forget yours, but you will have to know the tag name you gave to your Custom Monitor when you created it.  Therefore, either your tag or your monitorId is required to run this script.

Capturing Information on Login

Now that we have a script to send data to the Custom Monitor, we need to have data to send.  This script could easily be run from .bashrc or /etc/bashrc – and that would work fine, if we knew that no user would be deleting their .bashrc.  Since we cannot guarantee that, we will use PAM (Pluggable Authentication Module) to control how and when we send information to the Custom Monitor.  Since no user without root access will be able to alter PAM, this is a secure way to guarantee login information.  Also since sshd, sftp, ftp, and most other programs utilize PAM for authentication, this will monitor all logins to the server, not just shell logins.

PAM offers many options and modules, we will be utilizing a module called pam_script.  pam_script allows you to execute a script on session open, session close, and/or on auth.  You must download and install pam_script first:

wget 'https://freshmeat.net/urls/47ddad89e38001dbe0dc50424e36987b' -O libpam-script.tar.gz
tar -xzvf libpam-script.tar.gz
cd libpam-script-x.x.x #x.x.x is the version that you just download, apparent from tar output
make
sudo cp pam_script.so /lib/security/
sudo chown root:root /lib/security/pam_script.so
sudo chmod 755 /lib/security/pam_script.so

pam_script is now installed, but not configured.  There are three files associated with pam_script, /etc/security/onsessionopen /etc/security/onsessionclose /etc/security/onauth  The first two files will work on a session and the last will work for a successful auth.  Since we want to monitor successful auths, we will create the onauth file:

#!/bin/sh
# onauth for Paid Monitor Custom Login Monitor
USER=$1
SERVICE=$2
HOST=$PAM_RHOST

/etc/security/paid-monitor_add_data.sh -m loginMonitor -r "user_login:$USER;host:$HOST;srv:$SERVICE"


This script will require that you move the paid-monitor_add_data.sh script to /etc/security and make it and the onauth script executable by root and owned by root:

sudo mv paid-monitor_add_data.sh /etc/security
sudo chmod 700 /etc/security/paid-monitor_add_data.sh
sudo chown root:root /etc/security/paid-monitor_add_data.sh
sudo chmod 700 /etc/security/onauth
sudo chown root:root /etc/security/onauth

Now we need to set PAM to utilize the pam_script module.  Depending on your system this will vary, but you need to edit the /etc/pam.d/common-auth file or something similar on your system.  You should add the following line:

# require the scripts to run at auth
auth required   pam_script.so  runas=root expose=rhost

Here we are telling module to run as root and to expose the rhost variable, which will contain the remote host information that we utilize in the above script with the $PAM_RHOST variable

Testing the Monitor

Now we have a setup that will log all usernames, remote hosts, and service that they logged in from to our Custom Monitor.  Give it a try, ssh to your machine several times.  You will see the values appear in your account’s Custom Monitor.