212 lines
4.3 KiB
Markdown
212 lines
4.3 KiB
Markdown
# SSH Notes
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## SSH Tunneling
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### Local Forwarding
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#### Examples
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NOTE: these use autossh to prevent the tunnel from dying
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Plex
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```shell
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autossh -f -nNT -p3141 -N -L 8080:192.168.0.209:32400 chawley@aristotle.planethawleywood.com
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```
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ESXi
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```shell
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autossh -f -nNT -p3141 -N -L 8090:192.168.0.208:443 chawley@aristotle.planethawleywood.com
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```
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Both ESXi and AWX
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```shell
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autossh -f -nNT -p3141 -N -L 8090:192.168.0.208:443 -L 8091:192.168.0.25:80 chawley@aristotle.planethawleywood.com
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```
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Both Plex and Derry OD
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```shell
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autossh -f -nNT -p3141 -N -L 8080:192.168.0.209:32400 -L 8070:192.168.0.209:80 chawley@aristotle.planethawleywood.com
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```
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---
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<table>
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<tr>
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<td><strong>Protocol</strong>
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</td>
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<td>SSH
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</td>
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</tr>
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<tr>
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<td><strong>From</strong>
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</td>
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<td>my office workstation
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</td>
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</tr>
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<tr>
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<td><strong>To</strong>
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</td>
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<td>RRD Jumpbox (54.84.9.50)
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</td>
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</tr>
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<tr>
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<td><strong>Via</strong>
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</td>
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<td>chawley2@ladmin2
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</td>
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</tr>
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<tr>
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<td><strong>Notes</strong>
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</td>
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<td> I have the jumpbox host configured in.ssh/config on both machines
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</td>
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</tr>
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<tr>
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<td colspan="2" ><strong><code>ssh -N -L 8090:54.184.92.50:22 chawley2@ladmin2.precisiondm.com</code></strong>
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</td>
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</tr>
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</table>
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<table>
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<tr>
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<td><strong>Protocol</strong>
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</td>
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<td>web
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</td>
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</tr>
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<tr>
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<td><strong>From</strong>
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</td>
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<td>my office workstation
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</td>
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</tr>
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<tr>
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<td><strong>To</strong>
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</td>
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<td>Plex (derry)
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</td>
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</tr>
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<tr>
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<td><strong>Via</strong>
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</td>
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<td>chawley@aristotle
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</td>
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</tr>
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<tr>
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<td colspan="2" ><strong><code>ssh -p3141 -N -L 8080:192.168.0.209:32400 chawley@aristotle.planethawleywood.com</code></strong>
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</td>
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</tr>
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</table>
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### Remote Forwarding
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NOTE: By default, OpenSSH only allows connecting to remote forwarded ports from the server host. However, the GatewayPorts option in the server configuration file sshd_config can be used to control this.
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The following alternatives are possible:
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```shell
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GatewayPorts no
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```
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This prevents connecting to forwarded ports from outside the server computer.
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```shell
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GatewayPorts yes
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```
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This allows anyone to connect to the forwarded ports. If the server is on the public Internet, anyone on the Internet can connect to the port.
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#### Examples
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<table>
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<tr>
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<td><strong>Protocol</strong>
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</td>
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<td>web
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</td>
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</tr>
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<tr>
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<td><strong>From</strong>
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</td>
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<td>derry
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</td>
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</tr>
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<tr>
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<td><strong>To</strong>
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</td>
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<td>overlook
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</td>
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</tr>
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<tr>
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<td><strong>Notes</strong>
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</td>
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<td>This allows you to access apache web pages on derry by visiting <code>http://overlook.planethawleywood.com:8888</code> as long as <code>GatewayPorts yes</code> is present in <code>/etc/ssh/sshd_config</code> (as explained above) and port 8888 is open on Overlook
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</td>
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</tr>
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<tr>
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<td colspan="2" ><strong><code>ssh -R 8888:localhost:80 root@overlook</code></strong>
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</td>
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</tr>
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</table>
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### Reference
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* [How To Use SSH Tunneling](https://www.howtogeek.com/168145/how-to-use-ssh-tunneling/)
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* [SSH Port Forwarding Example](https://www.ssh.com/ssh/tunneling/example)
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## Kill Unresponsive SSH
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### Summary
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Let’s say you’re happily typing in your remote shell when all of a sudden, the crappy Wi-Fi network you’re using goes down. You end up with a perfectly unusable frozen shell, ugh!
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To do that, assuming you lost connectivity, press in that order:
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```shell
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[Enter]
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~
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.
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```
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That is, <return key> then tilde then period
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This will send an escape sequence to your local SSH client and terminate the connection.—So this will always work even without a network connection.
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Here’s the list of escape sequences:
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### Supported escape sequences:
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`~.` - terminate connection (and any multiplexed sessions) \
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`~B` - send a BREAK to the remote system \
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`~C` - open a command line \
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`~R` - Request rekey (SSH protocol 2 only) \
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`~^Z `- suspend ssh \
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<code>~<em>#</em></code> - list forwarded connections \
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<code>~&</code> - background ssh (when waiting for connections to terminate) \
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<code>~?</code> - this message \
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<code>~~</code> - send the escape character by typing it twice \
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\
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(Note that escapes are only recognized immediately after newline.)
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## SSH Keygen
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### Generate an SSH Key with a comment
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```shell
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ssh-keygen -C "comment" -f <file>
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```
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