SSH Wrapper with Pre/Post Connection Scripts

An SSH wrapper that allows you to run custom bash scripts before and after establishing an SSH connection, which is not available by default

Table of Contents

• Installation
• Usage
• Configuration
• Scripts
  • Pre Connection Script
  • Post Connection Script
• Contributing

Installation

To install the SSH wrapper, run the provided install.sh script with root or sudo privileges:

sudo ./install.sh

This script will:

1. Copy the wrapper script to /usr/local/bin as ossh.
2. Copy the pre and post connection scripts to the ~/.ssh/scripts directory.
3. Set the necessary execution permissions for the scripts.

Usage

To use the SSH wrapper, simply call ossh followed by the hostname and any additional ssh arguments:

ossh <hostname> [ssh_args...]

For example:

ossh myserver -p 2222

The wrapper script will automatically execute the pre and post connection scripts.

Configuration

The SSH wrapper relies on your existing ~/.ssh/config file for configuration details such as User, Port, and IdentityFile. Ensure you have the necessary entries in your ~/.ssh/config file for each SSH host you want to use with the wrapper.

Example ~/.ssh/config entry:

Host myserver
  User myuser
  HostName myserver.example.com
  Port 22
  IdentityFile ~/.ssh/id_rsa

Scripts

Pre Connection Script

The pre-connection script is located at ~/.ssh/scripts/before_established.sh. This script will run before establishing the SSH connection.

#!/bin/bash

# Set ssh connection hostname
Hostname=$1

# Parse .ssh/config Hostname params
User=$(get_ssh_option "$Hostname" "User")
Port=$(get_ssh_option "$Hostname" "Port")
IdentityFile=$(get_ssh_option "$Hostname" "IdentityFile")

echo "Do some stuff before ssh connection established..."

# Your code here (e.g., open a port on another server)

echo "Done!"

Post Connection Script

The post-connection script is located at ~/.ssh/scripts/after_established.sh. This script will run after the SSH connection has been established.

#!/bin/bash

# Set ssh connection hostname
Hostname=$1

# Parse .ssh/config Hostname params
User=$(get_ssh_option "$Hostname" "User")
Port=$(get_ssh_option "$Hostname" "Port")
IdentityFile=$(get_ssh_option "$Hostname" "IdentityFile")

echo "Do some stuff after ssh connection established..."

# Your code here (e.g., close a port on another server)

echo "Done!"

Built-in functions

You can specify code for some hostnames using built-in bash function is_hostname(). Example with ~/.ssh/scripts/before_established.sh:

#!/bin/bash

# Set ssh connection hostname
Hostname=$1
Port=$(get_ssh_option "$Hostname" "Port")

echo "Do some staff before ssh connection established..."

if [ $(is_hostname "hostname1 hostname2") == 1 ]; then
    echo "Have to open port on public_vps" before ssh connection established
    ssh public_vps "echo $Port > /tmp/ports_to_open.list"
    sleep 1.1
fi

echo "Done!"

Contributing

Contributions are welcome! Feel free to submit a pull request or open an issue if you have any suggestions or bug reports.