Changes

= Setup and Configure Secure Shell Services (ssh) Using Virtual Machines =

==Overview==

==Required Materials (Bring to All Labs)==

==Prerequisites==

Each Link below displays online manpages for each command (via [http://linuxmanpages.com/ http://linuxmanpages.com]):

|- valign="top"

|

*[http://linuxmanpages.com/man1/ssh.1.php ssh]

*[http://linuxmanpages.com/man1/ssh-keygen.1.php ssh-keygen]

*[http://linuxmanpages.com/man1/scp.1.php scp]

*[http://linuxmanpages.com/man1/sftp.1.php sftp]

*[http://linuxmanpages.com/man8/ping.8.php ping]

*[http://linuxmanpages.com/man8/arp.8.php arp]

|}

{{Admon/important | Update your systems | It is advisable to perform a <code>yum update</code> on your Fedora host and all 3 VM's.}}

{{Admon/important | Backup your VMs before proceeding | If you did not do it at the end of Lab 6, stop all of your VMs and backup your VM disk images.}}

=== Investigation 1: How do you enable the sshd service. ===

# OpenSSH should have been installed by default. Lets confirm this by issuing the command:<br /> <code>rpm -qa | grep ssh</code>

# You should see a number of packages installed including <code>openssh-clients</code> and <code>openssh-server</code>

# Now that you know the service is running investigate what port number and protocol sshd uses by issuing the command:<br /><code>netstat -atunp</code>

# What protocol and port is the sshd process using?

'''Answer the Investigation 1 observations / questions in your lab log book.'''

=== Investigation 2: How do you establish an ssh connection. ===

{{Admon/note | | '''Public Key authentication''' is a method of establishing identity using a pair of encryption keys that are designed to work together. One key is known as your private key (which as the name suggests should remain private and protected) and the other is known as the public key. (which as the name suggests can be freely distributed) The keys are designed to work together to encrypt data asymmetrically, that is to say that when we encrypt data with one of the keys it can only be decrypted with the other key from the pair. This means that when we connect, ssh can use the private key that only exists on my system in my account, to encrypt a message. That message can be decrypted by anybody with the corresponding public key. While it doesn't mean the message is secure as anybody could decrypt it with the public key, it does establish my identity, if the host can successfully decrypt the message then it must have come from the one person in possession of the private key. This basic method of authentication is used extensively in many network communications protocols that require the ability to authenticate identity.}}

# That should generate output similar to the following:

<pre>

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

The key fingerprint is:

93:58:20:56:72:d7:bd:14:86:9f:42:aa:82:3d:f8:e5 user1@fedora2

</pre>

{{Admon/tip | Lengthy Passphrases | You will then be prompted for a passphrase. The passphrase must be entered in order to use your private key. Passphrases are more secure than passwords and should be lengthy, hard to guess and easy to remember. For example one passphrase that meets this criteria might be "seneca students like fish at 4:00am". Avoid famous phrases such as "to be or not to be" as they are easy to guess. It is possible to leave the passphrase blank but this is dangerous. It means that if a hacker were able to get into your account they could then use your private key to access other systems you use.}}

<ol><li value="4"> Once your keys have been saved you should check to make sure the permissions of the <code>.ssh</code> directory and your key files are secure. </li>

<li>The next step is to copy your public key to fedora3 (the remote host). You can use the scp command to do it.</li>

<li><code>scp</code> (secure copy) is used to copy files between hosts over the ssh protocol. The files are sent over an encrypted channel as is all ssh traffic. </li>

<li>This will copy your public key to your ops235 home directory on fedora3.</li>

<li>The ''':''' is important as it separates the hostname from the path where it is copied to. </li>

<li>Now ssh to fedora3 using a password to authenticate.</li>

<li>Once logged in to fedora3 we need to add the public key to your list of authorized_keys</li>

{{Admon/important | Note! | You don't want to overwrite the file as it may contain multiple public keys. Make sure you are using the append redirection '''>>''' and not '''>'''.}}

<ol><li value="16"> Once again you should secure the <code>.ssh</code> directory and the <code>authorized_keys</code> file using the following commands:<br /><code>chmod 700 ~/.ssh</code><br /><code>chmod 600 ~/.ssh/authorized_keys</code></li>

-->

=== Investigation 4: How do you use scp and sftp. ===

# To connect to a remote host type the command:<br /><code>sftp ops235@fedora3</code>

# Experiment with <code>scp</code> to copy a file from fedora3 directly to fedora1.

{{Admon/tip| SELinux | SELinux may prevent ssh from accessing your home directories on Fedora 1 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/tip | fedora1 VM iptables and ssh service | You may need to adjust the firewall on your fedora1 host to complete this section, and verify that the sshd service is running on that VM.}}

# Where was the file saved?

# Experiment with running other GUI applications through <code>ssh</code>.

=== Investigation 6: How do you use ssh to tunnel other traffic. ===

{{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.}}

# In this investigation fedora1 will be your http server and fedora2 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>

# Confirm that httpd is listening to TCP/80 using the command:<br /><code>netstat -atnp</code>

# Create a small html document called <code>/var/www/html/index.html</code> that displays a short message.*

<li>You should see the index.html page on fedora1.</li>

<li>Close the ssh connection and verify that the port 20808 is no longer listening.</li>

{{Admon/note | Note! | Complete this investigation on your fedora2 and fedora1 VM's.}}

# 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 from fedora2 using the following command:<br /><code>ssh -p 2200 user@fedora1</code>

{{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.}}

<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>

<li>Inspect the log to see what kind of information is logged.</li>

== Completing the lab ==

# have secured ssh against root access

# What port does sshd use by defaults?