Hackers Chronicle - Online Cyber Security News: SSH

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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwxd-1vZHDmrS8t6yvlLzxN8LzHFUCjJ3rM0hmYxSGxw9uWY13LUiB43mO4UZVla0__DXTYTBpTZ3O92vSGdAsECR5WVqAvsd9fyua0sSfQMWZVQ7v56bkxTpqHu5T0BTJj3LD5YckE0aa/s1600/ssh-cheatsheet.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="224" data-original-width="360" height="398" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwxd-1vZHDmrS8t6yvlLzxN8LzHFUCjJ3rM0hmYxSGxw9uWY13LUiB43mO4UZVla0__DXTYTBpTZ3O92vSGdAsECR5WVqAvsd9fyua0sSfQMWZVQ7v56bkxTpqHu5T0BTJj3LD5YckE0aa/s640/ssh-cheatsheet.png" width="640" /></a></div>
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This page designed to help beginners starting out with SSH by providing a usable “SSH cheat sheet” full of common commands.</div>
<h2>
    1.1 SSH general</h2>
<table>
          <tbody>
<tr><th>Name</th><th>Summary</th></tr>
<tr><td>ssh without input password</td><td><code>sshpass -p '<your-passwd>' ssh <username>@<ssh_host></code>, <code>brew install sshpass</code></td></tr>
<tr><td>Install sshd server</td><td><code>apt-get install openssh</code>, <code>apt-get install openssh-server</code></td></tr>
<tr><td>Restart sshd server</td><td><code>service sshd restart</code>, <code>systemctl reload sshd.service</code></td></tr>
<tr><td>Run ssh command</td><td><code>ssh -o StrictHostKeyChecking=no -p 2702 root@172.17.0.8 date</code></td></tr>
<tr><td>SSH with verbose ouptut</td><td><code>ssh -vvv -p 2702 root@45.33.87.74 date 2>&1</code></td></tr>
<tr><td>Setup ssh tunnel for your web browsing</td><td><code>sshuttle -r kubo@10.92.21.17 30.0.0.0/16 192.168.150.0/24 -e ...</code></td></tr>
<tr><td>SSH passwordless login</td><td><code>ssh-copy-id <username>@<ssh_host></code>, Or manually update <code>~/.ssh/authorized_keys</code></td></tr>
<tr><td>Remove an entry from <code>known_hosts file</code></td><td><code>ssh-keygen -f ~/.ssh/known_hosts -R github.com</code></td></tr>
<tr><td>Diff local file with remote one</td><td><code>diff local_file.txt <(ssh <username>@<ssh_host> 'cat remote_file.txt')</code></td></tr>
<tr><td>Diff two remote ssh files</td><td><code>diff <(ssh user@remote_host 'cat file1.txt') <(ssh user2@remote_host2 'cat file2.txt')</code></td></tr>
<tr><td>Upload with timestamps/permissions kept</td><td><code>scp -rp /tmp/abc/ ec2-user@<ssh-host>:/root/</code></td></tr>
<tr><td>SSH agent load key</td><td><code>exec ssh-agent bash && ssh-add /tmp/id_rsa</code>, <code>ssh-add</code></td></tr>
<tr><td>SSH list all loaded key</td><td><code>ssh-add -l</code></td></tr>
<tr><td>SSH agent create and load key</td><td><code>exec ssh-agent bash && ssh-keygen</code>, <code>ssh-add</code></td></tr>
<tr><td>Emacs read remote file with tramp</td><td><code>emacs /ssh:<username>@<ssh_host>:/path/to/file</code></td></tr>
</tbody></table>
<h2>
        1.2 SSH tunnel & ssh proxy</h2>
<table>
          <tbody>
<tr><th>Name</th><th>Summary</th></tr>
<tr><td>SSH port forward to a local port</td><td><code>ssh -N -i <ssh-keyfile> -f root@54.179.178.214 -L *:18085:localhost:8085 -n /bin/bash</code></td></tr>
<tr><td>Reverse port forward to remote server</td><td><code>ssh -R *:40099:localhost:22 root@54.179.178.214</code>, <code>ssh -p 40099 root@54.179.178.214</code></td></tr>
<tr><td>Setup ssh tunnel for your web browsing</td><td><code>sshuttle -r kubo@10.92.21.17 30.0.0.0/16 192.168.111.0/24 192.168.150.0/24 192.167.0.0/24</code></td></tr>
</tbody></table>
<h2>
        <a aria-hidden="true" class="anchor" href="https://github.com/DennyZhang/cheatsheet-ssh-A4#13-scp" id="user-content-13-scp"><svg aria-hidden="true" class="octicon octicon-link" height="16" viewbox="0 0 16 16" width="16"></svg></a></h2>
<h2>
        1.3 SCP</h2>
<table>
          <tbody>
<tr><th>Name</th><th>Summary</th></tr>
<tr><td>Download a remote folder</td><td><code>scp -r ec2-user@<ssh-host>:/home/letsencrypt-20180825 ./</code></td></tr>
<tr><td>Upload a file</td><td><code>scp -i <ssh-keyfile> /tmp/hosts ec2-user@<ssh-host>:/root/</code></td></tr>
<tr><td>Upload a folder</td><td><code>scp -r /tmp/abc/ ec2-user@<ssh-host>:/root/</code></td></tr>
<tr><td>Upload with timestamps/permissions kept</td><td><code>scp -rp /tmp/abc/ ec2-user@<ssh-host>:/root/</code></td></tr>
<tr><td>Mount remote directory as local folder</td><td><code>sshfs name@server:/path/remote_folder /path/local_folder</code></td></tr>
</tbody></table>
<h2>
        1.4 SSH security</h2>
<table>
          <tbody>
<tr><th>Name</th><th>Summary</th></tr>
<tr><td>Disable ssh by password</td><td><code>sed -i 's/PasswordAuthentication yes/PasswordAuthentication no/g' /etc/ssh/sshd_config</code></td></tr>
<tr><td>Disable root login</td><td><code>sed -i 's/^PermitRootLogin yes/#PermitRootLogin yes/' /etc/ssh/sshd_config</code></td></tr>
<tr><td>Enable/Disable SSH Host Key Checking</td><td><code>StrictHostKeyChecking yes</code> change <code>~/.ssh/config</code></td></tr>
<tr><td>Protect SSH server from brute force attacks</td><td><a href="https://www.digitalocean.com/community/tutorials/how-to-protect-ssh-with-fail2ban-on-ubuntu-14-04" rel="nofollow">fail2ban command line tool</a></td></tr>
</tbody></table>
<h2>
        1.5 SSH files</h2>
<table>
          <tbody>
<tr><th>Name</th><th>Summary</th></tr>
<tr><td>Generate a new key pair</td><td><code>ssh-keygen</code>, <code>ssh-keygen -C "your_email@example.com" -t rsa</code></td></tr>
<tr><td>Generate key pair without interaction</td><td><code>ssh-keygen -t rsa -f /tmp/sshkey -N "" -q</code></td></tr>
<tr><td>Add passphrase protection to ssh keyfile</td><td><code>ssh-keygen -p -f id_rsa</code> </td></tr>
<tr><td>Convert OpenSSL format to SSH-RSA format</td><td><code>ssh-keygen -f my_ssh.pub -i</code></td></tr>
<tr><td>Critical ssh files/folders</td><td><code>~/.ssh/authorized_keys</code>, <code>~/.ssh/config</code>, <code>~/.ssh/known_hosts</code></td></tr>
<tr><td>SSH config file</td><td><code>/etc/ssh/ssh_config</code>, <code>/etc/ssh/sshd_config</code></td></tr>
<tr><td>SSH key file permission</td><td><code>chmod 600 ~/.ssh/id_rsa</code></td></tr>
<tr><td>SSH folder permission</td><td><code>chmod 700 ~/.ssh</code>, <code>chown -R $USER:$USER ~/.ssh</code></td></tr>
<tr><td>Authorized_keys file permission</td><td><code>chmod 644 ~/.ssh/authorized_keys</code></td></tr>
</tbody></table>
<h2>
        1.6 Parse ssh log file</h2>
<table>
          <tbody>
<tr><th>Name</th><th>Command</th></tr>
<tr><td>Events of ssh down</td><td><code>grep -R "ssh.*Received signal 15" /var/log/auth.log</code></td></tr>
<tr><td>Events of ssh up</td><td><code>grep -R "sshd.*Server listening" /var/log/auth.log</code></td></tr>
<tr><td>Events of ssh failed login</td><td><code>grep -R "sshd.*Failed password for invalid user" /var/log/auth.log</code></td></tr>
<tr><td>Events of ssh break-in attemp</td><td><code>grep -R "sshd.*POSSIBLE BREAK-IN ATTEMPT!" /var/log/auth.log</code></td></tr>
<tr><td>Events of ssh port scap</td><td><code>grep -R "sshd.*Bad protocol version identification" /var/log/auth.log</code></td></tr>
<tr><td>Events of ssh login by public key</td><td><code>grep -R "sshd.*Accepted publickey for" /var/log/auth.log</code></td></tr>
<tr><td>Events of ssh login by password</td><td><code>grep -R "sshd.*Accepted password for" /var/log/auth.log</code></td></tr>
<tr><td>Events of ssh logout event</td><td><code>grep -R "sshd.*pam_unix(sshd:session): session closed for" /var/log/auth.log</code></td></tr>
</tbody></table>
<h2>
        1.7 SSH tools</h2>
<table>
          <tbody>
<tr><th>Name</th><th>Summary</th><th><br /></th></tr>
<tr><td>Export local env to Internet</td><td><a href="https://ngrok.com/" rel="nofollow">ngrok.com</a></td><td><br /></td></tr>
<tr><td>Reverse ssh proxy</td><td><a href="https://github.com/sshuttle/sshuttle">sshuttle</a></td><td><br /></td></tr>
<tr><td>SSH by auto input password</td><td><a href="https://www.cyberciti.biz/faq/noninteractive-shell-script-ssh-password-provider/" rel="nofollow">sshpass</a> sshpass -p “$PASSWORD” ssh -o StrictHostKeyChecking=no $username@$ssh_ip=</td><td><br /></td></tr>
</tbody></table>
<h2>
        1.8 Scripts</h2>
<ul>
<li>Inject local key to remote ssh server server</li>
</ul>
<div class="command wobble-horizontal">
<pre>cat <span class="pl-k">~</span>/.ssh/id_rsa.pub <span class="pl-k">|</span> ssh <span class="pl-smi">$username</span>@<span class="pl-smi">$ssh_hostk</span> <span class="pl-s"><span class="pl-pds">"</span>cat - >> ~/.ssh/authorized_keys<span class="pl-pds">"</span></span>
        
        ssh <span class="pl-smi">$username</span>@<span class="pl-smi">$ssh_hostk</span> <span class="pl-s"><span class="pl-pds">"</span>cat ~/.ssh/authorized_keys<span class="pl-pds">"</span></span></pre>
</div>
<ul>
<li>SSH Config file</li>
</ul>
<div class="content shadow-radial">
<pre>Host sandbox
             HostName 192.168.50.10
             StrictHostKeyChecking no
             User root
        </pre>
<pre>Host 192.168.1.*
           StrictHostKeyChecking no
           Port 32882
           UserKnownHostsFile=/dev/null
           IdentityFile ~/.ssh/id_rsa
        </pre>
</div>
<ul>
<li>Use expect to run ssh command with credential auto input</li>
</ul>
<div class="content shadow-radial">
<pre>    #!/usr/bin/expect
    set timeout 20
    set command "cat /etc/hosts"
    set user "vagrant"
    set password "vagrant"
    set ip "192.168.50.10"
    spawn ssh -o stricthostkeychecking=no $user@$ip "$command"
    expect "*password:*"
    send "$password\r"
    expect eof;</pre>
</div>
<ul>
<li>ssh reverse tunnel</li>
</ul>
<div class="content shadow-radial">
<pre>    # https://www.howtoforge.com/reverse-ssh-tunneling
    autossh -M 40000 -p 2702 -i /home/denny/al -fN \
        -o "PubkeyAuthentication=yes" \
        -o "StrictHostKeyChecking=false" -o "PasswordAuthentication=no" \
        -o "ServerAliveInterval 60" -o "ServerAliveCountMax 3" \
        -R 123.57.240.189:29995:localhost:22 root@123.57.240.189
    </pre>
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This page designed to help beginners starting out with SSH by providing a usable “SSH cheat sheet” full of common commands...

SSH Cheat Sheet

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