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{{Admon/caution|Draft LabTHIS IS AN OLD VERSION OF THE LAB|'''This lab has NOT been released for regular distributionis an archived version. When the lab is ready to be released, Do not use this caution banner will disappearin your OPS235 course.'''}}
= Setup and Configure Secure Shell Services (ssh) Using Virtual Machines =
@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
The RSA host key for fedora3 centos3 has changed,
and the key for the according IP address 192.168.235.13
is unchanged. This could either mean that
Add correct host key in /home/user1/.ssh/known_hosts to get rid of this message.
Offending key in /home/user1/.ssh/known_hosts:53
RSA host key for fedora3 centos3 has changed and you have requested strict
checking.
Host key verification failed.
<ol><li value="4">When prompted enter your password for your ops235 account on centos3.</li>
<li>Establish an ssh connection using your learn account from fedora3 centos3 to fedora2centos2.</li></ol>{{Admon/note |Proof of Established SSH Connection | When you have both ssh connections established between fedora2 centos2 and fedora3 centos3 check your network connections using the netstat command. You should now see at least 2 TCP connections with a state of ESTABLISHED. One connection represents the connection from fedora2 centos2 to fedora3 centos3 and the other represents the connection from centos3 to centos2. You should also see that you still have ssh listening to TCP port 22. Notice that the client side of each connection uses a random port number in the upper ranges. This common behaviour for client side applications.}}
<ol><li value="6">Logout of your ssh connection by typing <code>exit</code>.
<li>Check the state of the connection after logging out. Wait a few minutes and then check again. Record your observations.</li>
=== Investigation 4: How do you use scp and sftp. ===
{{Admon/note | Use your fedora2 centos2 VM | Complete this investigation on your fedora2 centos2 VM.}}
{{Admon/note | | There are 2 common command line tools for transferring files between hosts over an encrypted ssh connection, <code>scp</code> and <code>sftp</code>.<br /> <code>sftp</code> is an interactive file transfer program that functions much like an ftp client. }}
# To connect to a remote host type the command:<br /><code>sftp ops235@fedora3centos3</code>
# This will establish an interactive session after authentication.
# Type <code>help</code> to see the list of sftp commands at any time.
# Try using <code>sftp</code> to transfer files back and forth between hosts.
# As you did previously you can also use the <code>scp</code> command to copy files to and from remote hosts and even from one remote host to another.
# Use <code>scp</code> to copy your services file to the fedora3 centos3 host into the /tmp directory. (The path on a remote host follows the ''':''') using the command: <br /><code>scp /etc/services ops235@fedora3centos3:/tmp</code># Experiment with <code>scp</code> to copy a file from fedora3 centos3 directly to fedora1centos1.{{Admon/tip| SELinux | SELinux may prevent ssh from accessing your home directories on Fedora 1 centos1 because you created a new filesystem there. You can reset the security context of the /home directory with this command: <code>restorecon -Rv /home</code>}}
=== Investigation 5: How do you use ssh to tunnel X. ===
{{Admon/note | Use your fedora2 centos2 and fedora1 centos1 VMs | Complete this investigation on your fedora2 centos2 and fedora1 VM'scentos1 VMs.}}
{{Admon/tip | fedora1 centos1 VM iptables and ssh service | You may need to adjust the firewall on your fedora1 centos1 host to complete this section, and verify that the sshd service is running on that VM.}}
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 <code>gedit</code> or <code>firefox</code> and the application will run on the remote host but be displayed on the local host.
# Once connected run the <code>gedit</code> application. (Gnome Text Editor)
# The gedit window will display on fedora2 centos2 but it is running fedora1centos1.
# Enter some text and save a file with <code>gedit</code>.
# Exit <code>gedit</code>.
# Where was the file saved?
# Experiment with running other GUI applications through <code>ssh</code>.
'''Answer the Investigation 5 observations / questions in your lab log book.'''
== Further Securing your Secure Shell Connection ==
=== Investigation 6: How do you use ssh to tunnel other traffic. ===
{{Admon/note | Use your fedora2 centos2 and fedora1 centos1 VMs | Complete this investigation on your fedora2 centos2 and fedora1 VM'scentos1 VMs.}}
{{Admon/note | | 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. Alternatively you could use it to circumvent a firewall that is blocking traffic you wish to use but allows ssh traffic to pass through.}}
# You will be working with the 2nd scenario of bypassing a firewall that blocks http traffic.
# In this investigation fedora1 centos1 will be your http server and fedora2 centos2 will be your client.# On the HTTP server (fedora1), make sure the Apache web server is installed by typing the command:<br /><code>rpm -q httpd</code># If it is installed check the configuration of the service to see if it is automatically started at any runlevels by issuing using the command:<br /><code>systemctl status httpd.servicechkconfig h</code>command.# If it has not been started automatically start the service using the service command:<br /><code>systemctl start httpd.service</code># Confirm that httpd is listening to TCP/80 using the netstat command:<br /><code>netstat -atnp</code>.
# Create a small html document called <code>/var/www/html/index.html</code> that displays a short message.*
# On the fedora1 centos1 (the http server) confirm everything is working locally by using a browser to connect to http://localhost# The Set the default firewall configuration on fedora1 is centos1 to REJECT incoming requests to http (TCP/80)# Confirm that you can't connect by using firefox on fedora2 centos to connect to fedora1 centos1 http://fedora1centos1/# On fedora2 centos2 confirm that the httpd service is stopped so it cannot interfere with your observations.
# The next step is to establish a tunnel. When you establish a tunnel you make an ssh connection to a remote host and open a new port on the local host. 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.
:::: [[Image:Tunnel.png]]
<ol><li value="13">Establish a tunnel using a local port on fedora2 centos2 of 20808, that connects to the remote port on fedora1 centos1 of 80, using the following command on fedora2centos2:<br /><code>ssh -L 20808:fedora1centos1:80 user@fedora1centos1</code></li></ol>{{Admon/note | Note! | The -L (which means Local port) takes one argument of <pre><local-port>:<connect-to-host>:<connect-to-port></pre> The command basically connects your local port of 20808 to the remote port of 80 on fedora1centos1. This means all requests to 20808 on the localhost (fedora2centos2) are actually tunnelled through your ssh connection to port 22 on fedora1 centos1 and then delivered to port 80 on fedora1centos1, bypassing the firewall. }}<ol><li value="14">Once the tunnel is established use netstat to verify the port 20808 is listening on fedora2centos2</li><li>Now using the browser on fedora2 centos2 connect to http://localhost:20808</li><li>You should see the index.html page on fedora1centos1.</li>
<li>Close the ssh connection and verify that the port 20808 is no longer listening.</li>
</ol>
=== Investigation 7: How do you make sshd more secure ===
{{Admon/note | Note! | Complete this investigation on your fedora2 centos2 and fedora1 centos1 VM's.}}
{{Admon/note | | Anytime you configure your computer to allow logins from the network you are leaving yourself vulnerable to potential unauthorized access by so called "hackers". Running the sshd service is a fairly common practice but care must be taken to make things more difficult for those hackers that attempt to use "brute force" attacks to gain access to your system. Hackers use their knowledge of your system and many password guesses to gain access. They know which port is likely open to attack (TCP:22), the administrative account name (root), all they need to do is to "guess" the password.}}
# Confirm the new port is being used with a <code>netstat</code> command.
# Before we can use this new port we must change our firewall to allow traffic through the new port number and block access to port 22:<br /><code>iptables -I INPUT -p tcp -s0/0 --dport 22 -j DROP</code><br /><code>iptables -I INPUT -p tcp -s0/0 --dport 2200 -j ACCEPT</code>
# To test the new port connect to fedora1 centos1 from fedora2 centos2 using the following command:<br /><code>ssh -p 2200 user@fedora1centos1</code>
{{Admon/important|Cannot connect via SSH?|To fix issues with the ability to ssh, on both machines:<ul><li>Ensure ssh is running. Systemctl status sshd.service.</li><li>Disable selinux by going into /etc/selinux/config and change "enforcing" to "disabled"; "targeted" to "minimum".</li><li>If your are still encountering problems flush iptables.</li></ul>}}
{{Admon/tip | Tip! | For scp access the option to be used is: <code>scp -P 2200</code>}}
{{Admon/tip | Tip! | For more ideas on making sshd more secure consult the HOW-TO link above.}}
<ol><li value="14">Finally as a system administrator you should periodically monitor your system logs for unauthorized login attempts.</li>
<li>On Fedora CentOS systems the log file that is used is <code>/var/log/secure</code> </li>
<li>It also logs all uses of the <code>su</code> and <code>sudo</code> commands.</li>
<li>Attempt to connect to all of your VM's as root and other users using both public key and password authentication. Use some su and sudo commands also. </li>
'''Answer the Investigation 7 observations / questions in your lab log book.'''
== Completing the lab ==
