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<body class="article toc2 toc-right">
<div id="header">
<h1>SSH Tunneling!</h1>
<div class="details">
<span id="author" class="author">Apostolos rootApostolos@swarmlab.io</span><br>
</div>
<div id="toc" class="toc2">
<div id="toctitle">Πίνακας περιεχομένων</div>
<ul class="sectlevel1">
4 years ago
<li><a href="#cheat-Docker">1. Install docker (Home PC)</a></li>
4 years ago
<li><a href="#_ssh_tunneling">2. SSH Tunneling</a></li>
<li><a href="#_local_port_forwarding">3. Local Port Forwarding</a></li>
<li><a href="#_remote_port_forwarding">4. Remote Port Forwarding</a></li>
<li><a href="#_ssh_command">5. SSH Command</a>
<ul class="sectlevel2">
<li><a href="#_connect_to_server">5.1. Connect to server</a></li>
<li><a href="#_executing_remote_commands_on_the_server">5.2. Executing remote commands on the server</a></li>
</ul>
</li>
<li><a href="#_sshd_config_ssh_server_configuration">6. sshd_config - SSH Server Configuration</a>
<ul class="sectlevel2">
<li><a href="#_cryptographic_policy">6.1. Cryptographic policy</a></li>
<li><a href="#_verbose_logging">6.2. Verbose logging</a></li>
<li><a href="#_root_login">6.3. Root login</a></li>
<li><a href="#_port_forwarding">6.4. Port forwarding</a></li>
<li><a href="#_generate_a_key_pair">6.5. Generate a key pair</a></li>
<li><a href="#_install_your_public_key">6.6. Install your public key</a></li>
</ul>
</li>
<li><a href="#_run_graphics_applications_remotely">7. run graphics applications remotely</a></li>
<li><a href="#_copy_files_and_directories_between_two_systems">8. Copy Files and Directories Between Two Systems</a>
<ul class="sectlevel2">
<li><a href="#_copy_a_file_from_a_local_to_a_remote_system">8.1. Copy a file from a local to a remote system</a></li>
<li><a href="#_copy_a_remote_file_to_a_local_system_using_the_scp_ommand">8.2. Copy a Remote File to a Local System using the scp ommand</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p><br></p>
</div>
</div>
</div>
<div class="sect1">
4 years ago
<h2 id="cheat-Docker">1. Install docker (Home PC)</h2>
4 years ago
<div class="sectionbody">
<div class="paragraph">
4 years ago
<p>HowTo: See <a href="http://docs.swarmlab.io/SwarmLab-HowTos/labs/Howtos/docker/install.adoc.html" target="_blank" rel="noopener">How to</a></p>
4 years ago
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="title">NOTE</div>
<div class="paragraph">
<p>Assuming you&#8217;re already logged in</p>
</div>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_ssh_tunneling">2. SSH Tunneling</h2>
<div class="sectionbody">
<div class="paragraph">
<p><strong><strong>SSH Tunneling</strong></strong>, is the ability to use ssh to create a bi-directional encrypted network connection between machines over which data can be exchanged, typically TCP/IP.</p>
</div>
<div class="imageblock">
<div class="content">
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<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="title">NOTE</div>
<div class="paragraph">
<p>SSH is a standard for secure remote logins and file transfers over untrusted networks. It also provides a way to secure the data traffic of any given application using port forwarding, basically tunneling any TCP/IP port over SSH. This means that the application data traffic is directed to flow inside an encrypted SSH connection so that it cannot be eavesdropped or intercepted while it is in transit. SSH tunneling enables adding network security to legacy applications that do not natively support encryption.</p>
</div>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_local_port_forwarding">3. Local Port Forwarding</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="title">local port forwarding</div>
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">ssh -nNT -L 8000:localhost:3306 user@192.168.89.5</code></pre>
</div>
</div>
<div class="paragraph">
<p>The above command sets up an ssh tunnel between your machine and the server, and forwards all traffic from localhost:3306 to localhost:8000 (on your machine).</p>
</div>
<div class="paragraph">
<p>So now you could connect to MySQL running on your server via localhost on port 8000 on your machine.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_remote_port_forwarding">4. Remote Port Forwarding</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="title">remote port forwarding</div>
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">ssh -nNT -R 4000:localhost:3000 user@192.168.89.5</code></pre>
</div>
</div>
<div class="paragraph">
<p>The above command sets up an ssh tunnel between your machine and the server, and forwards all traffic from localhost:3000 (on your machine) to localhost:4000 (in the context of the server).</p>
</div>
<div class="paragraph">
<p>So now you can connect to the locally running service on port 3000 on the server on port 4000</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_ssh_command">5. SSH Command</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Practically every Linux system includes the ssh command. This command is used to start the SSH client program that enables secure connection to the SSH server on a remote machine. The ssh command is used from logging into the remote machine, transferring files between the two machines, and for executing commands on the remote machine.</p>
</div>
<div class="sect2">
<h3 id="_connect_to_server">5.1. Connect to server</h3>
<div class="listingblock">
<div class="title">connect</div>
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">ssh user@192.168.89.5
The authenticity of host '192.168.89.5' cannot be established.
DSA key fingerprint is 04:48:30:31:b0:f3:5a:9b:01:9d:b3:a7:38:e2:b1:0c.
Are you sure you want to continue connecting (yes/no)?</code></pre>
</div>
</div>
<div class="paragraph">
<p>Type yes to continue. This will add the server to your list of known hosts (~/.ssh/known_hosts) as seen in the following message:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">Warning: Permanently added '192.168.89.5' (DSA) to the list of known hosts.</code></pre>
</div>
</div>
<div class="paragraph">
<p>Each server has a host key, and the above question related to verifying and saving the host key, so that next time you connect to the server, it can verify that it actually is the same server.</p>
</div>
</div>
<div class="sect2">
<h3 id="_executing_remote_commands_on_the_server">5.2. Executing remote commands on the server</h3>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">ssh user@192.168.89.5 /bin/bash -c "ls -al"</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_sshd_config_ssh_server_configuration">6. sshd_config - SSH Server Configuration</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The OpenSSH server reads a configuration file when it is started. Usually this file is /etc/ssh/sshd_config, but the location can be changed using the -f command line option when starting sshd.</p>
</div>
<div class="sect2">
<h3 id="_cryptographic_policy">6.1. Cryptographic policy</h3>
<div class="ulist">
<ul>
<li>
<p>Symmetric algorithms for encrypting the bulk of transferred data are configured using the Ciphers option. A good value is aes128-ctr,aes192-ctr,aes256-ctr.</p>
</li>
<li>
<p>Host key algorithms are selected by the HostKeyAlgorithms option. A good value is ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss.</p>
</li>
<li>
<p>Key exchange algorithms are selected by the KexAlgorithms option. recommend ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha256.</p>
</li>
</ul>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="paragraph">
<p>not recommend allowing diffie-hellman-group1-sha1, unless needed for compatibility. It uses a 768 bit prime number, which is too small by today&#8217;s standards and may be breakable by intelligence agencies in real time. Using it could expose connections to man-in-the-middle attacks when faced with such adversaries.</p>
</div>
</td>
</tr>
</table>
</div>
</div>
<div class="sect2">
<h3 id="_verbose_logging">6.2. Verbose logging</h3>
<div class="paragraph">
<p>It is strongly recommended that LogLevel be set to VERBOSE. This way, the key fingerprint for any SSH key used for login is logged. This information is important for SSH key management, especially in legacy environments.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">LogLevel VERBOSE</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_root_login">6.3. Root login</h3>
<div class="paragraph">
<p>root access should generally go through a privileged access management system</p>
</div>
<div class="paragraph">
<p>To disable passwords for root, but still allow key-based access without forced command, use:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">PermitRootLogin prohibit-password</code></pre>
</div>
</div>
<div class="paragraph">
<p>To disable passwords and only allow key-based access with a forced command, use:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">PermitRootLogin forced-commands-only</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_port_forwarding">6.4. Port forwarding</h3>
<div class="paragraph">
<p>Generally prevent port forwarding on servers, unless expressly needed for tunneling legacy applications.
There is substantial risk that users will use SSH tunneling to open backdoors into the organization through the firewall to get access to work machines from home.</p>
</div>
</div>
<div class="sect2">
<h3 id="_generate_a_key_pair">6.5. Generate a key pair</h3>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">ssh-keygen</code></pre>
</div>
</div>
<div class="paragraph">
<p>Output:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa):
Created directory '/home/user/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/user/.ssh/id_rsa.
Your public key has been saved in /home/user/.ssh/id_rsa.pub.
The key fingerprint is:
8c:2a:ed:82:98:6d:12:0a:3a:ba:b2:1c:c0:25:be:5b</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_install_your_public_key">6.6. Install your public key</h3>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">sh-copy-id -i ~/.ssh/id_rsa.pub UserName@RemoteServer</code></pre>
</div>
</div>
<div class="paragraph">
<p>Output:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">UserName@RemoteServer's password: ********</code></pre>
</div>
</div>
<div class="paragraph">
<p>Now try logging into the machine, with "ssh 'username@remoteserver'", and check in:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">~/.ssh/authorized_keys</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_run_graphics_applications_remotely">7. run graphics applications remotely</h2>
<div class="sectionbody">
<div class="paragraph">
<p>X11 forwarding needs to be enabled on both the client side and the server side.</p>
</div>
<div class="ulist">
<ul>
<li>
<p>On the client side, the -X (capital X) option to ssh enables X11 forwarding</p>
</li>
<li>
<p>On the server side, X11Forwarding yes must specified in /etc/ssh/sshd_config.</p>
</li>
<li>
<p>The xauth program must be installed on the server side.</p>
</li>
</ul>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">ssh -X user@192.168.89.5 gimp</code></pre>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_copy_files_and_directories_between_two_systems">8. Copy Files and Directories Between Two Systems</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_copy_a_file_from_a_local_to_a_remote_system">8.1. Copy a file from a local to a remote system</h3>
<div class="paragraph">
<p>To copy a file from a local to a remote system run the following command:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">scp file.txt user@192.168.89.5:/remote/directory</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_copy_a_remote_file_to_a_local_system_using_the_scp_ommand">8.2. Copy a Remote File to a Local System using the scp ommand</h3>
<div class="paragraph">
<p>To copy a file named file.txt from a remote server with IP 192.168.89.5 run the following command:</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="highlight"><code class="language-bash" data-lang="bash">scp user@192.168.89.5:/remote/file.txt /local/directory</code></pre>
</div>
</div>
<div class="paragraph">
<p><br>
<br>
</p>
</div>
<hr>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="title">Reminder</div>
<div class="paragraph">
<p>Caminante, no hay camino,<br>
se hace camino al andar.</p>
</div>
<div class="paragraph">
<p>Wanderer, there is no path,<br>
the path is made by walking.</p>
</div>
<div class="paragraph">
<p><strong>Antonio Machado</strong> Campos de Castilla</p>
</div>
</td>
</tr>
</table>
</div>
</div>
</div>
</div>
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<div id="footer-text">
4 years ago
Last updated 2020-10-21 10:04:26 UTC
4 years ago
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