the_keymaker.sh

#!/bin/bash

#               The Keymaker v2.6.2
#                   o——m
#
# Generates ssh keys per remote host, creates good configs, and optionally pushes to the host.
#
# NOTE: When using Github.com set your user to git and do not set a shortname
# 
# Setup: make executable via `chmod u+x the_keymaker.sh`
#        Optional: OS-dependant. These have been tested on Ubuntu.
#                  1) Place in /usr/local/bin/ and rename so it is available in your path; or
#                  2) Create an alias to reference this file.
# Run: `./the_keymaker.sh` and enter information based on prompts.
#
# This tool was created to help developers maintain a 
# succinct and relatively safe ssh config file.


################
#   Variables  #
################

#Generic variables
ssh_folder="$HOME/.ssh"
ssh_config_path="$ssh_folder/config"
quiet=false
verbose=false
first_key=false

#config file variables
hostname=""
shortname=""
remoteuser=""
email=""
port=""

################
#   Function   #
################

#Exits the program if an error status code is returned. Otherwise prints OK
catch() {
  if [[ "$@" =~ ^-?[0-9]+$ ]]; then
    local STATUS="$@";
  else
    "$@"
    local STATUS=$?;
  fi
  if [ $STATUS -ne 0 ]; then
    echo -e "[\e[31mFAILED\e[39m]";
    exit $STATUS;
  else
    echo -e "[\e[32mOK\e[39m]";
  fi
  return $STATUS;
}

################
#   Setup      #
################
#Grab command line arguments
while [[ $# > 0 ]]; do
	key="$1"
	case $key in
		-q|--quiet)
			quiet=true
			shift # past argument
			;;

		-v|--verbose)
			verbose=true
			shift
			;;

		*)
			# unknown option
			echo "Error: Unknown flag: '$key'"
			exit 1;
			;;
	esac
done

#Mutually exclusive flags, make sure they're all good
if [[ $verbose == true && $quiet == true ]]; then
	echo "Cannot be both verbose and quiet. Please choose one option or the other.";
	exit 1;
fi


# Create missing folder if necessary
if [ ! -d "$ssh_folder" ]; then
	if [[ $quiet == false ]]; then
		echo -n "Missing folder $ssh_folder creating..."
	fi
	catch mkdir -p "$ssh_folder"
fi


# Create config file if necessary
if [ -f $ssh_config_path ]; then

	#Check if keymaker has made on before, if not make a backup and inform user
	# What's going on.
	if grep -q "^#Generated by the_keymaker o——m" "$ssh_config_path"; then
		if [[ $verbose == true ]]; then
			echo "Config file previously created by the keymaker. Will append key."
		fi
	else 
		backup_path="$ssh_config_path.BACKUP"
		echo "========================================================"
		echo "                  WARNING"
		echo "  You appear to already have a config file located at:"
		echo "         $ssh_config_path"
		echo " Therefore the keymaker will backup your config file at:"
		echo "         $backup_path"
		echo "========================================================="
		echo -n "Creating backup... "
		catch mv $ssh_config_path $backup_path
		echo -n "Creating new config file..."
		catch touch $ssh_config_path
		first_key=true
	fi
else 
	echo -n "Missing config file, creating..."
	catch touch "$ssh_config_path"
	first_key=true
fi
	
#If this is the first key keymaker has made we want to throw some safe defaults into the config file.
if [[ $first_key == true ]]; then
	echo "First SSH Key generated by keymaker, creating safe default values."

	echo "#Generated by the_keymaker o——m v2.6.1" > $ssh_config_path
	echo "Host *" >> $ssh_config_path
	echo "	VisualHostKey yes" >> $ssh_config_path
	echo "	ServerAliveInterval 30" >> $ssh_config_path
	echo "	ServerAliveCountMax 120" >> $ssh_config_path
	echo "	IdentitiesOnly yes" >> $ssh_config_path
	echo "	ForwardAgent no" >> $ssh_config_path
	echo "	ForwardX11 no" >> $ssh_config_path
	echo "	UseRoaming no" >> $ssh_config_path
fi


################
#  User Input  #
################

#Get hostname to use in ssh user@hostname
while [ "$hostname" == "" ]; do
	read -r -p "Enter host name you wish to generate keys for: " hostname
	if [ "$hostname" == "" ]; then
		echo -e "[\e[31mError\e[39m] Missing hostname!";
	fi
done

#This is optional and thus does not have a while loop
read -r -p "Enter a shortname for the host. eg 'sn' Allows for ssh sn. Leave blank for none: " shortname
if [ "$shortname" == "" ]; then
	shortname="$hostname"
fi

#Get remote user to use in ssh user@hostname
while [ "$remoteuser" == "" ]; do
	read -r -p "Enter username for remote host: " remoteuser
	if [ "$remoteuser" == "" ]; then
		echo -e "[\e[31mError\e[39m] Missing remote user name!";
	fi
done

#Get email to use in the ssh key
while [ "$email" == "" ]; do
	read -r -p "Enter your email to be associated with this key (or anything it's just a comment): " email
	if [ "$email" == "" ]; then
		echo -e "[\e[31mError\e[39m] Missing email!";
	fi
done

read -r -p "Port (default: 22): " port

#Create variables based on information passed
key_filename="$hostname""_id"
key_filepath="$HOME/.ssh/$key_filename"

#Gather flags for ssh key creation

# defaults
alg_flags="-t ed25519"

# responses
key_pass="n"
rsa="n"

# Passphrase?
read -r -p "Do you want to use a passphrase with this key? y/n (default: n): " key_pass

# What algorithm?
read -r -p "Do you want to use a legacy RSA 4096-bit key? Otherwise a modern ed25519 key will be used. y/n (default: n): " rsa

if [[ "$rsa" == "y" || "$rsa" == "Y" ]]; then
	alg_flags="-t rsa -b 4096"
fi

# using a variable to hold the flag '-N ""' was causing issues
if [[ "$key_pass" == "y" || "$key_pass" == "Y" ]]; then
	ssh-keygen $alg_flags -C "$email" -f "$key_filepath"
else
	ssh-keygen $alg_flags -C "$email" -N "" -f "$key_filepath"
fi
keygen_status=$?

#If the key was created successfully echo the host info to the config file
#Give the user some info and copy to the remote machine.
if [ $keygen_status -eq 0 ]; then

	# TODO: Make this IF more maintainable
	if [[ "$port" != "" ]]; then
		echo "
Host $shortname
	User $remoteuser
	HostName $hostname
	Port $port
	IdentityFile $key_filepath
	VisualHostKey yes" >> $ssh_config_path
	else
		echo "
Host $shortname
	User $remoteuser
	HostName $hostname
	IdentityFile $key_filepath
	VisualHostKey yes" >> $ssh_config_path
	fi

	echo -e "=== Key generation complete! o——m ===";
	echo ""

	auto_copy="n"
	read -r -p "Do you wish to attempt to copy the file over? (Will not work if password logins have been disabled) y/n (default: n) " auto_copy

	if [[ "$auto_copy" == "y" || "$auto_copy" == "Y" ]]; then
		echo "Now attempting to copy key over..."
		ssh-copy-id -i "$key_filepath.pub" $remoteuser@$hostname
		copy_result=$?
		if [ $copy_result -eq 0 ]; then
			echo "SSH key setup complete!";
			exit 0;
		else
			echo "ERROR: An error occurred copying the key to the remote server."
			echo "Try again manually."
			exit $copy_result
		fi
	else
		echo ""
		echo "Key contents for easy copy and paste (see above for file path):"
		cat "$key_filepath.pub"
		exit 0
	fi
else
	echo "Error with key generation, exiting with status code.";
	exit $keygen_status;
fi