Generate SSH key file pair, copy to remote server, and add entry to .ssh/config

ssh_key_config.sh

#!/usr/bin/env bash

# TODO: Allow specifying the key type and size as optional arguments
# TODO: Validate the IP address, port number, and hostname
# TODO: Add a check for the existence of the .ssh directory/config file
# TODO: Better handling of existing SSH config entries, offer to update/append
# TODO: Check that external commands are available before using them

# This script generates SSH key file pairs, copies the key file to a remote server, and adds an entry in the local .ssh/config

# Check for terminal color support
if [ -t 1 ]; then
    RED='\033[0;31m'
    NO_COLOR='\033[0m'
else
    RED=''
    NO_COLOR=''
fi

display_help() {
    echo "Usage: $0 -k <key_name> -u <remote_username> -i <remote_ip> -p <remote_port> -n <host_name>"
    echo "Arguments:"
    echo "  -k key_name        - The name of the SSH key file."
    echo "  -u remote_username - The username for the remote system."
    echo "  -i remote_ip       - The IP address of the remote system."
    echo "  -p remote_port     - The port number of the remote system."
    echo "  -n host_name       - The host name to use in the .ssh/config file."
    exit 0
}

check_preconditions() {
    local key_name=$1
    local host_name=$2
    local found_issues=0
    # Check if the SSH key file pairs already exist
    if [ -f "$HOME/.ssh/${key_name}" ] || [ -f "$HOME/.ssh/${key_name}.pub" ]; then
        echo -e "${RED}Key file name ${key_name} already exists.${NO_COLOR}"
        found_issues=1
    fi
    # Check for duplication in .ssh/config
    if grep -q "^Host ${host_name}$" "$HOME/.ssh/config"; then
        echo -e "${RED}An entry for ${host_name} already exists in .ssh/config.${NO_COLOR}"
        found_issues=1
    fi
    # Exit if any issues were found
    if [ "$found_issues" -ne 0 ]; then
        echo "Resolve the issues and try again."
        exit 1
    fi
}

generate_ssh_key() {
    local key_name=$1
    ssh-keygen -f "$HOME/.ssh/${key_name}" -t ecdsa -b 521
    chmod 600 "$HOME/.ssh/${key_name}"
    chmod 644 "$HOME/.ssh/${key_name}.pub"
}

copy_ssh_key() {
    local username=$1
    local ip_address=$2
    local key_name=$3
    local remote_port=$4
    ssh-copy-id -i "$HOME/.ssh/${key_name}.pub" -p "${remote_port}" "${username}@${ip_address}"
}

add_ssh_config() {
    local host_name=$1
    local ip_address=$2
    local user_name=$3
    local remote_port=$4
    local key_name=$5
    echo -e "\nHost ${host_name}
HostName ${ip_address}
User ${user_name}
Port ${remote_port}
IdentityFile $HOME/.ssh/${key_name}" >> "$HOME/.ssh/config"
    chmod 644 "$HOME/.ssh/config"
}

# main()
while getopts ":hk:u:i:p:n:" opt; do
    case ${opt} in
        h )
            display_help
            ;;
        k )
            key_name=$OPTARG
            ;;
        u )
            remote_username=$OPTARG
            ;;
        i )
            remote_ip=$OPTARG
            ;;
        p )
            remote_port=$OPTARG
            ;;
        n )
            host_name=$OPTARG
            ;;
        \? )
            echo -e "${RED}Invalid Option: -$OPTARG${NO_COLOR}" 1>&2
            display_help
            ;;
        : )
            echo -e "${RED}Option -$OPTARG requires an argument.${NO_COLOR}" 1>&2
            exit 1
            ;;
    esac
done
shift $((OPTIND -1))

# Check for unexpected arguments
if [ $# -gt 0 ]; then
    echo -e "${RED}Unexpected arguments provided.${NO_COLOR}"
    display_help
    exit 1
fi

# Ensure all required arguments were provided
if [ -z "${key_name}" ] || [ -z "${remote_username}" ] || [ -z "${remote_ip}" ] || [ -z "${remote_port}" ] || [ -z "${host_name}" ]; then
    echo -e "${RED}All arguments are required.${NO_COLOR}"
    display_help
    exit 1
fi

check_preconditions "${key_name}" "${host_name}"
generate_ssh_key "${key_name}"
copy_ssh_key "${remote_username}" "${remote_ip}" "${key_name}" "${remote_port}"
add_ssh_config "${host_name}" "${remote_ip}" "${remote_username}" "${remote_port}" "${key_name}"
echo "SSH setup completed."