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=INVESTIGATION 1: INSTALLING, CONFIGURING AND MAINTAINING AN SSH SERVER=
So far, you have learned to use the '''ssh''' utility to establish a secure connection to a remote server to perform tasks, administer the server. For these common operations, you have issued the ''ssh'' command, which is actually the '''client''' application for ssh. In order to connect to a remote server (like your VMs, Matrix, etc) they need to be running the SSH service (i.e. the ssh daemon).
'''Answer INVESTIGATION 1 observations / questions in your lab log book.'''
=INVESTIGATION 2: ADDITIONAL METHODS TO SECURE YOUR SSH SERVER =
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=== Part 31: Generating Private and Public Keys (Public Key Infrastructure) ===
As a system administrator, you have the ability to generate or create '''public''' and '''private''' keys to ensure safe and secure ssh connections. This will require a user to prove who they say they are in order to access a Linux server via SSH (i.e. Authentication). The system administer can generate these keys for the first time, or if the system administrator suspects that a hacker has compromised or trying to penetrate the server, they can remove the existing keys and generate new keys.
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=== Part 2: Tunneling to Run Securely Running Graphical Applications on Remote VMs Remotely (via Tunnelling) . ===
You can also use ssh to '''tunnel window and bitmap information''', allowing us to login to a remote desktop host and '''run a Xwindows application''' such as <b>gedit</b> or <b>firefox</b> and the application will run on the remote host but be displayed on the local host.
=INVESTIGATION 3: SECURING THE SSH CONNECTION= To help '''harden''' (i.e. protect a server from attack or "penetration"), system or security administrators have the ability to "trick" or "mislead" a potential hacker in order to prevent system penetration.Just like in the movies, "spying" is not just about collecting information about the adversary, but also to deceive the adversary into making incorrect decisions. [[Image:tunnel-trick.png|thumb|right|550px|You can also use an ssh connection to '''tunnel other types of traffic'''. There could be different reasons for doing this. For example tunneling traffic for an unencrypted application/protocol through ssh can '''increase the security of that application''' (i.e. deceive potential hackers).<br><br>Alternatively you could use it to '''circumvent a firewall that is blocking traffic''' you wish to use but allows ssh traffic to pass through.]]=== Part 1: Deceiving Penetration Testers (Hackers) === In this section, you will learn a common technique that organization use to help harden their servers: Use a combination of '''SSH server configuration''' and''' iptables rules''' in order to trick a hacker into thinking that the SSH port is not working, when in fact, it is running quietly (tunneled) via another port... '''Sneaky, but effective'''...''' >;)''' :'''Perform the following steps:''' # Make certain that your '''c7host''' and '''centos1''' VMs are running.# Switch to your '''c7host''' VM. This will be your web-server.# Make sure that the Apache web server is installed by typing the command:<br /><b><code><span style="color:#3366CC;font-size:1.2em;">rpm -q httpd</span></code></b><br>(If this is not installed, make sure to install '''httpd''').# Issue the following commands to <u>start</u> and <u>enable</u> the '''httpd''' service:<br><b><code><span style="color:#3366CC;font-size:1.2em;">systemctl start httpd</span></code></b><br><b><code><span style="color:#3366CC;font-size:1.2em;">systemctl enable httpd</span></code></b># Issue a command to verify that the '''httpd''' service has been started and has been enabled.# Confirm that httpd is LISTENING to '''tcp''' (port '''80''') using the '''netstat''' command.# Create a small html document called '''/var/www/html/index.html''' that displays a short message. If you do not know how to use HTML markup language, just type a simple <u>text</u> message...# <u>Restart</u> your '''c7host''' VM. # Switch to your '''centos1''' VM and click on the following link to open a web-browser view your html or text message: '''http://localhost'''<br><br># '''IMPORTANT:''' Before proceeding, '''flush the iptables rules''' for '''INPUT''', '''OUTPUT''', and '''FORWARD''' chains for both your '''c7host''' and '''centos1''' VMs.# Issue an iptables command to verify that both the the iptables rules have no rules for those chains for your '''c7host''' and '''centos1''' VM's<br><br># On your '''c7host''' VM, add (append) an iptables rule to '''REJECT''' <u>incoming</u> requests to http ( via TCP, port:80) by issuing the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables -A INPUT -p tcp --dport 80 -j REJECT</span></code></b># Switch to your '''centos1''' VM, and cLick on the following link to launch your message in a web-browser: '''http://localhost'''<br>What happenned? If your message didn't load, why do you think it didn't load?# Return to your c7host VM, and issue the following itables rules to add (append) an exception to view incoming web requests on your local machine (interface card: lo - loopback address): <br><b><code><span style="color:#3366CC;font-size:1.2em;">iptables -A INPUT -i lo -j ACCEPT</span></code></b> # On '''centos1''' confirm that you still cannot connect to c7host web-server by clicking on the following link: '''http://centos1/'''<br><br>The next step is to establish a <u>tunnel</u>. When you establish a tunnel you make an ssh connection to a remote host and open a new port on the local host.<br>That local host port is then connected to a port on the remote host through the established tunnel. When you send requests to the local port it is forwarded through the tunnel to the remote port.<br><br><ol><li value="16">Switch to your '''c7host''' VM, and make certain you are logged in as a regular user (i.e. '''NOT root!'''),</li><li>We are going to establish a tunnel using a <u>local port</u> (port number: '''20808''') on our '''centos1''' VM that will connect to the <u>remote</u> port: 80 on the '''c7host''' VM.<br>Issue the following command (from c7host): <b><code><span style="color:#3366CC;font-size:1.2em;">ssh -L 20808:centos1:80 yourUserID@centos1</span></code></b><br><br> '''Note:'''<br>The '''-L''' option (which means Local port) takes one argument:<br><span style="courier"><local-port>:<connect-to-host>:<connect-to-portMANAGING FIREWALLS FOR PROTECTION >amp;</span><br><br> The command basically connects your local port of 20808 to the remote port of 80 on '''c7host'''.<br>This means all requests to 20808 on the <u>localhost</u> ('''centos1''') are actually tunneled through your ssh connection<br>to port 22 on '''c7host''' and then delivered to port 80 on '''c7host''', bypassing the firewall.<br><br></li><li>Open another terminal in your c7host machine, and verify that the port 20808 is listening on '''centos1''' by issuing the command:<br> <b><code><span style="color:#3366CC;font-size:1.2em;">netstat -aunpt | grep 20808</span></code></b></li><li>Now switch to your '''centos1''' VM and click on the link to see if this tunneling trick works:'''http://localhost:20808'''</li><li>You should see the '''index.html''' page on '''c7host'''.</li><li>Close the ssh connection and verify that the port 20808 is no longer listening.</li></ol> {|width="40%" align="right" cellpadding="10"|- valignTROUBLESHOOTING ="top" |{{Admon/tip |Troubleshooting Tips for SSH|Cannot connect via SSH? To fix issues with the ability to ssh, on both machines:<ul><li>Ensure ssh is '''running'''.</li><li>Disable '''SELinux'''</li><li>'''Flush iptables''' (iptables -F)</li><li>For '''scp''', use the access the option (eg. '''scp -P 2200''' )</li></ul> }} |}
