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What is this script for?

One of the typical scenarios where ssht is helpful is depicted in the figure below. User may need to connect a port of a remote database (i.e. 3306) where only SSH port (usually port 22) is reachable.

    ----------------------------------------------------------------------

                                |
    -------------+              |    +------------+
        LOCAL    |              |    |  REMOTE    | :22 SSH
        CLIENT   | <== SSH ========> |  DATABASE  | :3306 database
    -------------+              |    +------------+
                                |
                             FIREWALL (only port 22 is open)

    ----------------------------------------------------------------------

Fig1: How to connect to a service blocked by a firewall through SSH tunnel.

If allowed by the SSH server, it is also possible to reach a private database (from the perspective of REMOTE SERVER) not directly visible from the outside (LOCAL CLIENT's perspective).


    ----------------------------------------------------------------------

                                |
    -------------+              |    +----------+               +-----------+
        LOCAL    |              |    |  REMOTE  | :22 SSH       | PRIVATE   |
        CLIENT   | <== SSH ========> |  SERVER  | <== local ==> | DATABASE  | :3306 database
    -------------+              |    +----------+               +-----------+
                                |
                             FIREWALL (only port 22 is open)

    ----------------------------------------------------------------------

Fig2: How to connect to PRIVATE DATABASE through SSH tunnel.

Credits on this section to pahaz/sshtunnel

Installation

Dependencies

  • yq (YAML Query)
  • openssh: The ssh command (Should be available in most Linux distributions).

Install

sudo wget https://github.com/MarkelCA/ssh-tunnels/releases/download/latest/ssht -O /usr/bin/ssht \
    && sudo chmod +x /usr/bin/ssht

Configuration

The default configuration file is read from ~/.config/ssht/ssht.yml. However, you can specify other files using the -f flag for every command.

To create your configuration copy the example yaml:

mkdir -p ~/.config/ssht/
cp ./ssht.example.yml ~/.config/ssht/ssht.yml

Now modify the file to add your own tunnel configurations.

Example

Let's break down the example from ssht.example.yml.

tunnels:
  remote_database:
    host_destination: 127.0.0.1
    port_destination: 3306
    port_forward: 3333
    host_server: remote-server.com
    user_server: myuser
    ssh_key_path:  ~/.ssh/remote_server_key

  private_database:
    host_destination: private-database.com
    port_destination: 3306
    port_forward: 3335
    host_server: remote-server.com
    user_server: myuser
    # (missing ssh_key_path) -> In this case it will pick the ssh key from the ~/.ssh/config file

This example config file complements the first section's explanation. The remote_database would represent the first picture, where the host_destination and the host_server is the same, while the private_database example does likewise with the second picture, where the database lies in the same network but not the same machine as the host_server.

If you're familiar with the openssh's tunnel management the params from the yaml file will be transformed to this command: ssh -N -L <port_forward>:<host_destination>:<port_destination> <user_server>@<host_server> -f -i <ssh_key_path>

Examples: ssh -N -L 3333:127.0.0.1:3306 myuser@remote-server.com -f -i ~/.ssh/remote_server_key ssh -N -L 3335:private-database.com:3306 myuser@remote-server.com -f

If no ssh_key_path if provided the ssh's command -f option will be ommited and the command will be tried with the default key specified at the ~/.ssh/config file.

Run

You can type the help command to learn the usage.

➜  ~ ssht help
Manages SSH tunnels from a YAML configuration.

Usage:
ssht <command> [-f|--file <file>]

Commands:
    - open [query]    Opens ssh tunnels
    - close [query]   Closes ssh tunnels
    - status [query]  Tells if a tunnel is opened or closed.
    - show [query]    Shows an ssht.yml configuration
    - list            Lists the available tunnels in the configuration
    - help [command]  Shows the help description for a command

Options:
    - -f|--file   The configuration file. Default if none is
                  provided: ~/.config/ssht/ssht.yml

Help with specific command:
ssht help <command>

Example:
ssht help open
ssht help help

For more info visit: https://github.com/markelca/ssh-tunnels#example

Examples

These are some of the most usual commands you'll run with this script:

ssht open remote_database
ssht open remote_database -f ./other-ssht-config.yml # Passing another config file
ssht open ".*_database" # Allows regex expressions too
ssht close ".*_database" # Same for closing