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OPS235 Lab 7

412 bytes removed, 08:53, 28 June 2016

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:We can use the '''netstat''' utility as a trouble-shooting / confirmation tool to view the SSH service and determine which STATE the SSH service is performing: '''LISTENING''', '''ESTABLISHED''', '''CLOSED''' , or '''WAITING'''

<ol><li value="2">Run the '''netstat -atunp''' command (pipe to "grep sshd") to check the state of a possible ''ssh connection''. What is the state (i.e. LISTENING or ESTABLISHED)?</li>

<li>~~Open another terminal and establish an ssh connection to~~ While in your '''centos3''' VM ~~using~~ , issue the following commandto connect to the same VM via ssh: <code>ssh ops235@centos3</code></li><li>~~You~~ Enter yes at the prompt, and enter your OPS235 password. The output should ~~receive a message~~ appear similar ~~to the following~~as what is shown below:

:The authenticity of host 'centos3 (192.168.235.13)' can't be established.

:RSA key fingerprint is 53:b4:ad:c8:51:17:99:4b:c9:08:ac:c1:b6:05:71:9b.

:Are you sure you want to continue connecting (yes/no)? yes

:Warning: Permanently added 'centos3' (RSA) to the list of known hosts. </li>

~~<li>Answer '''yes''' to add to the list of known hosts.</li>~~

<li>Issue the following command to confirm that you connected to your centos3 VM: <code>hostname</code></li></ol>

[[Image:spoof.png|thumb|right|485px|If you receive a message like the one displayed above, you should investigate why it is happening as it could indicate a '''serious security issue''', or it could just mean that something on '''the host has changed'''(i.e. the OS was reinstalled)]]

<ol><li value="7">~~Switch back to your '''centos3''' VM and re~~Re-run that same '''netstat pipeline command'''. Any change to the connection status?</li><li>~~Return to the second terminal, and log~~Log-out of your ssh connection by typing <code>exit</code>.<li>Run that same '''netstat''' command ~~in the original terminal and check the state of the connection after logging out~~again. Wait a few minutes and then check again. Record your observations.~~</li>~~<li>Make certain to exit all connections, and remain in your '''centos2''' VM. When using ssh to connect to other servers, it is very easy to forget which server you are currently using. Verify that you are in your '''centos2''' VM by entering the command: <code>hostname</code>~~<li>Use the Internet to search for '''TCP 3 way handshake''' to see how TCP connections are established and closed. ~~</li>

</ol>

So far, we have learned to establish an ssh connection to another host using a password to establish your identity. But '''passwords are not the only or even the best way of authenticating your identit'''y. We can also use '''Public/Private key encryption'''.

<ol>

<li value="12">Switch to your '''centos2''' VM.</li><li>Confirm you are in your centos2 VM by entering the command: <code>hostname</code> Make certain that you are in your centos you are NOT logged in as root!''' (you have been warned!)</li>

<li>To generate a keypair (public/private keys), issue the following command: <code>ssh-keygen</code></li>

<li>That should generate output similar to the following:</li>

Msaul

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OPS235 Lab 7

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