openvpn-install/openvpn-install.sh

#!/bin/bash
# shellcheck disable=SC1091,SC2034
# SC1091: Not following /etc/os-release (sourced dynamically)
# SC2034: Variables used indirectly or exported for subprocesses

# Secure OpenVPN server installer for Debian, Ubuntu, CentOS, Amazon Linux 2023, Fedora, Oracle Linux, Arch Linux, Rocky Linux and AlmaLinux.
# https://github.com/angristan/openvpn-install

# Configuration constants
readonly DEFAULT_CERT_VALIDITY_DURATION_DAYS=3650 # 10 years
readonly DEFAULT_CRL_VALIDITY_DURATION_DAYS=5475  # 15 years
readonly EASYRSA_VERSION="3.2.5"
readonly EASYRSA_SHA256="662ee3b453155aeb1dff7096ec052cd83176c460cfa82ac130ef8568ec4df490"

# =============================================================================
# Logging Configuration
# =============================================================================
# Set VERBOSE=1 to see command output, VERBOSE=0 (default) for quiet mode
# Set LOG_FILE to customize log location (default: openvpn-install.log in current dir)
# Set LOG_FILE="" to disable file logging
VERBOSE=${VERBOSE:-0}
LOG_FILE=${LOG_FILE:-openvpn-install.log}
OUTPUT_FORMAT=${OUTPUT_FORMAT:-table} # table or json - json suppresses log output

# Color definitions (disabled if not a terminal, unless FORCE_COLOR=1)
if [[ -t 1 ]] || [[ $FORCE_COLOR == "1" ]]; then
	readonly COLOR_RESET='\033[0m'
	readonly COLOR_RED='\033[0;31m'
	readonly COLOR_GREEN='\033[0;32m'
	readonly COLOR_YELLOW='\033[0;33m'
	readonly COLOR_BLUE='\033[0;34m'
	readonly COLOR_CYAN='\033[0;36m'
	readonly COLOR_DIM='\033[0;90m'
	readonly COLOR_BOLD='\033[1m'
else
	readonly COLOR_RESET=''
	readonly COLOR_RED=''
	readonly COLOR_GREEN=''
	readonly COLOR_YELLOW=''
	readonly COLOR_BLUE=''
	readonly COLOR_CYAN=''
	readonly COLOR_DIM=''
	readonly COLOR_BOLD=''
fi

# Write to log file (no colors, with timestamp)
_log_to_file() {
	if [[ -n "$LOG_FILE" ]]; then
		echo "$(date '+%Y-%m-%d %H:%M:%S') $*" >>"$LOG_FILE"
	fi
}

# Logging functions
log_info() {
	[[ $OUTPUT_FORMAT == "json" ]] && return
	echo -e "${COLOR_BLUE}[INFO]${COLOR_RESET} $*"
	_log_to_file "[INFO] $*"
}

log_warn() {
	[[ $OUTPUT_FORMAT == "json" ]] && return
	echo -e "${COLOR_YELLOW}[WARN]${COLOR_RESET} $*"
	_log_to_file "[WARN] $*"
}

log_error() {
	echo -e "${COLOR_RED}[ERROR]${COLOR_RESET} $*" >&2
	_log_to_file "[ERROR] $*"
	if [[ -n "$LOG_FILE" ]]; then
		echo -e "${COLOR_YELLOW}        Check the log file for details: ${LOG_FILE}${COLOR_RESET}" >&2
	fi
}

log_fatal() {
	echo -e "${COLOR_RED}[ERROR]${COLOR_RESET} $*" >&2
	_log_to_file "[FATAL] $*"
	if [[ -n "$LOG_FILE" ]]; then
		echo -e "${COLOR_YELLOW}        Check the log file for details: ${LOG_FILE}${COLOR_RESET}" >&2
		_log_to_file "Script exited with error"
	fi
	exit 1
}

log_success() {
	[[ $OUTPUT_FORMAT == "json" ]] && return
	echo -e "${COLOR_GREEN}[OK]${COLOR_RESET} $*"
	_log_to_file "[OK] $*"
}

log_debug() {
	if [[ $VERBOSE -eq 1 && $OUTPUT_FORMAT != "json" ]]; then
		echo -e "${COLOR_DIM}[DEBUG]${COLOR_RESET} $*"
	fi
	_log_to_file "[DEBUG] $*"
}

log_prompt() {
	# For user-facing prompts/questions (no prefix, just cyan)
	# Skip display in non-interactive mode
	if [[ $NON_INTERACTIVE_INSTALL != "y" ]]; then
		echo -e "${COLOR_CYAN}$*${COLOR_RESET}"
	fi
	_log_to_file "[PROMPT] $*"
}

log_header() {
	# For section headers
	# Skip display in non-interactive mode
	if [[ $NON_INTERACTIVE_INSTALL != "y" ]]; then
		echo ""
		echo -e "${COLOR_BOLD}${COLOR_BLUE}=== $* ===${COLOR_RESET}"
		echo ""
	fi
	_log_to_file "=== $* ==="
}

log_menu() {
	# For menu options - only show in interactive mode
	if [[ $NON_INTERACTIVE_INSTALL != "y" ]]; then
		echo "$@"
	fi
}

# Run a command with optional output suppression
# Usage: run_cmd "description" command [args...]
run_cmd() {
	local desc="$1"
	shift
	# Display the command being run
	echo -e "${COLOR_DIM}> $*${COLOR_RESET}"
	_log_to_file "[CMD] $*"
	if [[ $VERBOSE -eq 1 ]]; then
		if [[ -n "$LOG_FILE" ]]; then
			"$@" 2>&1 | tee -a "$LOG_FILE"
		else
			"$@"
		fi
	else
		if [[ -n "$LOG_FILE" ]]; then
			"$@" >>"$LOG_FILE" 2>&1
		else
			"$@" >/dev/null 2>&1
		fi
	fi
	local ret=$?
	if [[ $ret -eq 0 ]]; then
		log_debug "$desc completed successfully"
	else
		log_error "$desc failed with exit code $ret"
	fi
	return $ret
}

# Run a command that must succeed, exit on failure
# Usage: run_cmd_fatal "description" command [args...]
run_cmd_fatal() {
	local desc="$1"
	shift
	if ! run_cmd "$desc" "$@"; then
		log_fatal "$desc failed"
	fi
}

# =============================================================================
# CLI Configuration
# =============================================================================
readonly SCRIPT_NAME="openvpn-install"

# =============================================================================
# Help Text Functions
# =============================================================================
show_help() {
	cat <<-EOF
		OpenVPN installer and manager

		Usage: $SCRIPT_NAME <command> [options]

		Commands:
			install       Install and configure OpenVPN server
			uninstall     Remove OpenVPN server
			client        Manage client certificates
			server        Server management
			interactive   Launch interactive menu

		Global Options:
			--verbose     Show detailed output
			--log <path>  Log file path (default: openvpn-install.log)
			--no-log      Disable file logging
			--no-color    Disable colored output
			-h, --help    Show help

		Run '$SCRIPT_NAME <command> --help' for command-specific help.
	EOF
}

show_install_help() {
	cat <<-EOF
		Install and configure OpenVPN server

		Usage: $SCRIPT_NAME install [options]

		Options:
			-i, --interactive     Run interactive install wizard

		Network Options:
			--endpoint <host>     Public IP or hostname for clients (auto-detected)
			--endpoint-type <4|6> Endpoint IP version: 4 or 6 (default: 4)
			--ip <addr>           Server listening IP (auto-detected)
			--client-ipv4         Enable IPv4 for VPN clients (default: enabled)
			--no-client-ipv4      Disable IPv4 for VPN clients
			--client-ipv6         Enable IPv6 for VPN clients
			--no-client-ipv6      Disable IPv6 for VPN clients (default)
			--subnet-ipv4 <x.x.x.0>  IPv4 VPN subnet (default: 10.8.0.0)
			--subnet-ipv6 <prefix>   IPv6 VPN subnet (default: fd42:42:42:42::)
			--port <num>          OpenVPN port (default: 1194)
			--port-random         Use random port (49152-65535)
			--protocol <proto>    Protocol: udp or tcp (default: udp)
			--mtu <size>          Tunnel MTU (default: 1500)

		DNS Options:
			--dns <provider>      DNS provider (default: cloudflare)
				Providers: system, unbound, cloudflare, quad9, quad9-uncensored,
				fdn, dnswatch, opendns, google, yandex, adguard, nextdns, custom
			--dns-primary <ip>    Custom primary DNS (requires --dns custom)
			--dns-secondary <ip>  Custom secondary DNS (optional)

		Security Options:
			--cipher <cipher>     Data channel cipher (default: AES-128-GCM)
				Ciphers: AES-128-GCM, AES-192-GCM, AES-256-GCM, AES-128-CBC,
				AES-192-CBC, AES-256-CBC, CHACHA20-POLY1305
			--cert-type <type>    Certificate type: ecdsa or rsa (default: ecdsa)
			--cert-curve <curve>  ECDSA curve (default: prime256v1)
				Curves: prime256v1, secp384r1, secp521r1
			--rsa-bits <size>     RSA key size: 2048, 3072, 4096 (default: 2048)
			--cc-cipher <cipher>  Control channel cipher (auto-selected)
			--tls-version-min <ver>  Minimum TLS version: 1.2 or 1.3 (default: 1.2)
			--tls-ciphersuites <list>  TLS 1.3 cipher suites, colon-separated
			--tls-groups <list>   Key exchange groups, colon-separated
				(default: X25519:prime256v1:secp384r1:secp521r1)
			--hmac <alg>          HMAC algorithm: SHA256, SHA384, SHA512 (default: SHA256)
			--tls-sig <mode>      TLS mode: crypt-v2, crypt, auth (default: crypt-v2)
			--server-cert-days <n>  Server cert validity in days (default: 3650)

		Other Options:
			--multi-client        Allow same cert on multiple devices

		Initial Client Options:
			--client <name>       Initial client name (default: client)
			--client-password [p] Password-protect client (prompts if no value given)
			--client-cert-days <n>  Client cert validity in days (default: 3650)
			--no-client           Skip initial client creation

		Examples:
			$SCRIPT_NAME install
			$SCRIPT_NAME install --port 443 --protocol tcp
			$SCRIPT_NAME install --dns quad9 --cipher AES-256-GCM
			$SCRIPT_NAME install -i
	EOF
}

show_uninstall_help() {
	cat <<-EOF
		Remove OpenVPN server

		Usage: $SCRIPT_NAME uninstall [options]

		Options:
			-f, --force   Skip confirmation prompt

		Examples:
			$SCRIPT_NAME uninstall
			$SCRIPT_NAME uninstall --force
	EOF
}

show_client_help() {
	cat <<-EOF
		Manage client certificates

		Usage: $SCRIPT_NAME client <subcommand> [options]

		Subcommands:
			add <name>     Add a new client
			list           List all clients
			revoke <name>  Revoke a client certificate
			renew <name>   Renew a client certificate

		Run '$SCRIPT_NAME client <subcommand> --help' for more info.
	EOF
}

show_client_add_help() {
	cat <<-EOF
		Add a new VPN client

		Usage: $SCRIPT_NAME client add <name> [options]

		Options:
			--password [pass]   Password-protect client (prompts if no value given)
			--cert-days <n>     Certificate validity in days (default: 3650)
			--output <path>     Output path for .ovpn file (default: ~/<name>.ovpn)

		Examples:
			$SCRIPT_NAME client add alice
			$SCRIPT_NAME client add bob --password
			$SCRIPT_NAME client add charlie --cert-days 365 --output /tmp/charlie.ovpn
	EOF
}

show_client_list_help() {
	cat <<-EOF
		List all client certificates

		Usage: $SCRIPT_NAME client list [options]

		Options:
			--format <fmt>  Output format: table or json (default: table)

		Examples:
			$SCRIPT_NAME client list
			$SCRIPT_NAME client list --format json
	EOF
}

show_client_revoke_help() {
	cat <<-EOF
		Revoke a client certificate

		Usage: $SCRIPT_NAME client revoke <name> [options]

		Options:
			-f, --force   Skip confirmation prompt

		Examples:
			$SCRIPT_NAME client revoke alice
			$SCRIPT_NAME client revoke bob --force
	EOF
}

show_client_renew_help() {
	cat <<-EOF
		Renew a client certificate

		Usage: $SCRIPT_NAME client renew <name> [options]

		Options:
			--cert-days <n>   New certificate validity in days (default: 3650)

		Examples:
			$SCRIPT_NAME client renew alice
			$SCRIPT_NAME client renew bob --cert-days 365
	EOF
}

show_server_help() {
	cat <<-EOF
		Server management

		Usage: $SCRIPT_NAME server <subcommand> [options]

		Subcommands:
			status   List currently connected clients
			renew    Renew server certificate

		Run '$SCRIPT_NAME server <subcommand> --help' for more info.
	EOF
}

show_server_status_help() {
	cat <<-EOF
		List currently connected clients

		Note: Client data is updated every 60 seconds by OpenVPN.

		Usage: $SCRIPT_NAME server status [options]

		Options:
			--format <fmt>  Output format: table or json (default: table)

		Examples:
			$SCRIPT_NAME server status
			$SCRIPT_NAME server status --format json
	EOF
}

show_server_renew_help() {
	cat <<-EOF
		Renew server certificate

		Usage: $SCRIPT_NAME server renew [options]

		Options:
			--cert-days <n>   New certificate validity in days (default: 3650)
			-f, --force       Skip confirmation/warning

		Examples:
			$SCRIPT_NAME server renew
			$SCRIPT_NAME server renew --cert-days 1825
	EOF
}

# =============================================================================
# CLI Command Handlers
# =============================================================================

# Check if OpenVPN is installed
isOpenVPNInstalled() {
	[[ -e /etc/openvpn/server/server.conf ]]
}

# Require OpenVPN to be installed
requireOpenVPN() {
	if ! isOpenVPNInstalled; then
		log_fatal "OpenVPN is not installed. Run '$SCRIPT_NAME install' first."
	fi
}

# Require OpenVPN to NOT be installed
requireNoOpenVPN() {
	if isOpenVPNInstalled; then
		log_fatal "OpenVPN is already installed. Use '$SCRIPT_NAME client' to manage clients or '$SCRIPT_NAME uninstall' to remove."
	fi
}

# Parse DNS provider string to DNS number
parse_dns_provider() {
	case "$1" in
	system | unbound | cloudflare | quad9 | quad9-uncensored | fdn | dnswatch | opendns | google | yandex | adguard | nextdns | custom)
		DNS="$1"
		;;
	*) log_fatal "Invalid DNS provider: $1. See '$SCRIPT_NAME install --help' for valid providers." ;;
	esac
}

# Parse cipher string
parse_cipher() {
	case "$1" in
	AES-128-GCM | AES-192-GCM | AES-256-GCM | AES-128-CBC | AES-192-CBC | AES-256-CBC | CHACHA20-POLY1305)
		CIPHER="$1"
		;;
	*) log_fatal "Invalid cipher: $1. See '$SCRIPT_NAME install --help' for valid ciphers." ;;
	esac
}

# Parse curve string
parse_curve() {
	case "$1" in
	prime256v1 | secp384r1 | secp521r1) echo "$1" ;;
	*) log_fatal "Invalid curve: $1. Valid curves: prime256v1, secp384r1, secp521r1" ;;
	esac
}

# =============================================================================
# Configuration Constants
# =============================================================================
# Protocol options
readonly PROTOCOLS=("udp" "tcp")

# DNS providers (use string names)
readonly DNS_PROVIDERS=("system" "unbound" "cloudflare" "quad9" "quad9-uncensored" "fdn" "dnswatch" "opendns" "google" "yandex" "adguard" "nextdns" "custom")

# Cipher options
readonly CIPHERS=("AES-128-GCM" "AES-192-GCM" "AES-256-GCM" "AES-128-CBC" "AES-192-CBC" "AES-256-CBC" "CHACHA20-POLY1305")

# Certificate types (use strings)
readonly CERT_TYPES=("ecdsa" "rsa")

# ECDSA curves
readonly CERT_CURVES=("prime256v1" "secp384r1" "secp521r1")

# RSA key sizes
readonly RSA_KEY_SIZES=("2048" "3072" "4096")

# TLS versions
readonly TLS_VERSIONS=("1.2" "1.3")

# TLS signature modes (use strings)
readonly TLS_SIG_MODES=("crypt-v2" "crypt" "auth")

# HMAC algorithms
readonly HMAC_ALGS=("SHA256" "SHA384" "SHA512")

# TLS 1.3 cipher suite options
readonly TLS13_OPTIONS=("all" "aes-256-only" "aes-128-only" "chacha20-only")

# TLS groups options
readonly TLS_GROUPS_OPTIONS=("all" "x25519-only" "nist-only")

# =============================================================================
# Set Installation Defaults
# =============================================================================
# Centralized function to set all defaults - called before configuration
set_installation_defaults() {
	# Network
	ENDPOINT_TYPE="${ENDPOINT_TYPE:-4}"
	CLIENT_IPV4="${CLIENT_IPV4:-y}"
	CLIENT_IPV6="${CLIENT_IPV6:-n}"
	VPN_SUBNET_IPV4="${VPN_SUBNET_IPV4:-10.8.0.0}"
	VPN_SUBNET_IPV6="${VPN_SUBNET_IPV6:-fd42:42:42:42::}"
	PORT="${PORT:-1194}"
	PROTOCOL="${PROTOCOL:-udp}"

	# DNS (use string name)
	DNS="${DNS:-cloudflare}"

	# Multi-client
	MULTI_CLIENT="${MULTI_CLIENT:-n}"

	# Encryption
	CIPHER="${CIPHER:-AES-128-GCM}"
	CERT_TYPE="${CERT_TYPE:-ecdsa}"
	CERT_CURVE="${CERT_CURVE:-prime256v1}"
	RSA_KEY_SIZE="${RSA_KEY_SIZE:-2048}"
	TLS_VERSION_MIN="${TLS_VERSION_MIN:-1.2}"
	TLS13_CIPHERSUITES="${TLS13_CIPHERSUITES:-TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256}"
	TLS_GROUPS="${TLS_GROUPS:-X25519:prime256v1:secp384r1:secp521r1}"
	HMAC_ALG="${HMAC_ALG:-SHA256}"
	TLS_SIG="${TLS_SIG:-crypt-v2}"

	# Derive CC_CIPHER from CERT_TYPE if not set
	if [[ -z $CC_CIPHER ]]; then
		if [[ $CERT_TYPE == "ecdsa" ]]; then
			CC_CIPHER="TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256"
		else
			CC_CIPHER="TLS-ECDHE-RSA-WITH-AES-128-GCM-SHA256"
		fi
	fi

	# Client
	CLIENT="${CLIENT:-client}"
	PASS="${PASS:-1}"
	CLIENT_CERT_DURATION_DAYS="${CLIENT_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}"
	SERVER_CERT_DURATION_DAYS="${SERVER_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}"

	# Note: Gateway values (VPN_GATEWAY_IPV4, VPN_GATEWAY_IPV6) and IPV6_SUPPORT
	# are computed in prepare_network_config() which is called after validation
}

# Validation functions
validate_port() {
	local port="$1"
	if ! [[ "$port" =~ ^[0-9]+$ ]] || [[ "$port" -lt 1 ]] || [[ "$port" -gt 65535 ]]; then
		log_fatal "Invalid port: $port. Must be a number between 1 and 65535."
	fi
}

validate_subnet_ipv4() {
	local subnet="$1"
	# Check format: x.x.x.0 where x is 0-255
	if ! [[ "$subnet" =~ ^([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})\.0$ ]]; then
		log_fatal "Invalid IPv4 subnet: $subnet. Must be in format x.x.x.0 (e.g., 10.8.0.0)"
	fi
	local octet1="${BASH_REMATCH[1]}"
	local octet2="${BASH_REMATCH[2]}"
	local octet3="${BASH_REMATCH[3]}"
	# Validate each octet is 0-255
	if [[ "$octet1" -gt 255 ]] || [[ "$octet2" -gt 255 ]] || [[ "$octet3" -gt 255 ]]; then
		log_fatal "Invalid IPv4 subnet: $subnet. Octets must be 0-255."
	fi
	# Check for RFC1918 private address ranges
	if ! { [[ "$octet1" -eq 10 ]] ||
		[[ "$octet1" -eq 172 && "$octet2" -ge 16 && "$octet2" -le 31 ]] ||
		[[ "$octet1" -eq 192 && "$octet2" -eq 168 ]]; }; then
		log_fatal "Invalid IPv4 subnet: $subnet. Must be a private network (10.x.x.0, 172.16-31.x.0, or 192.168.x.0)."
	fi
}

validate_subnet_ipv6() {
	local subnet="$1"
	# Accept format: IPv6 address ending with :: (prefix only, no CIDR notation here)
	# We expect formats like: fd42:42:42:42:: or fdxx:xxxx:xxxx:xxxx::
	# The script will append /112 for the server directive

	# IPv6 ULA validation (fd00::/8 range with at least /48 prefix)
	# ULA format: fdxx:xxxx:xxxx:: or fdxx:xxxx:xxxx:xxxx:: where x is hex
	if ! [[ "$subnet" =~ ^fd[0-9a-fA-F]{2}(:[0-9a-fA-F]{1,4}){2,5}::$ ]]; then
		log_fatal "Invalid IPv6 subnet: $subnet. Must be a ULA address with at least a /48 prefix, ending with :: (e.g., fd42:42:42::)"
	fi
}

validate_positive_int() {
	local value="$1"
	local name="$2"
	if ! [[ "$value" =~ ^[0-9]+$ ]] || [[ "$value" -lt 1 ]]; then
		log_fatal "Invalid $name: $value. Must be a positive integer."
	fi
}

validate_mtu() {
	local mtu="$1"
	if ! [[ "$mtu" =~ ^[0-9]+$ ]] || [[ "$mtu" -lt 576 ]] || [[ "$mtu" -gt 65535 ]]; then
		log_fatal "Invalid MTU: $mtu. Must be between 576 and 65535."
	fi
}

# Maximum length for client names (OpenSSL CN limit)
readonly MAX_CLIENT_NAME_LENGTH=64

# Check if client name is valid (non-fatal, returns true/false)
is_valid_client_name() {
	local name="$1"
	[[ "$name" =~ ^[a-zA-Z0-9_-]+$ ]] && [[ ${#name} -le $MAX_CLIENT_NAME_LENGTH ]]
}

# Validate client name and exit with error if invalid
validate_client_name() {
	local name="$1"
	if [[ -z "$name" ]]; then
		log_fatal "Client name cannot be empty."
	fi
	if ! [[ "$name" =~ ^[a-zA-Z0-9_-]+$ ]]; then
		log_fatal "Invalid client name: $name. Only alphanumeric characters, underscores, and hyphens are allowed."
	fi
	if [[ ${#name} -gt $MAX_CLIENT_NAME_LENGTH ]]; then
		log_fatal "Client name too long: ${#name} characters. Maximum is $MAX_CLIENT_NAME_LENGTH characters (OpenSSL CN limit)."
	fi
}

# Validate all configuration values (catches invalid env vars in non-interactive mode)
validate_configuration() {
	# Validate PROTOCOL
	case "$PROTOCOL" in
	udp | tcp) ;;
	*) log_fatal "Invalid protocol: $PROTOCOL. Must be 'udp' or 'tcp'." ;;
	esac

	# Validate DNS
	case "$DNS" in
	system | unbound | cloudflare | quad9 | quad9-uncensored | fdn | dnswatch | opendns | google | yandex | adguard | nextdns | custom) ;;
	*) log_fatal "Invalid DNS provider: $DNS. Valid providers: system, unbound, cloudflare, quad9, quad9-uncensored, fdn, dnswatch, opendns, google, yandex, adguard, nextdns, custom" ;;
	esac

	# Validate CERT_TYPE
	case "$CERT_TYPE" in
	ecdsa | rsa) ;;
	*) log_fatal "Invalid cert type: $CERT_TYPE. Must be 'ecdsa' or 'rsa'." ;;
	esac

	# Validate TLS_SIG
	case "$TLS_SIG" in
	crypt-v2 | crypt | auth) ;;
	*) log_fatal "Invalid TLS signature mode: $TLS_SIG. Must be 'crypt-v2', 'crypt', or 'auth'." ;;
	esac

	# Validate PORT
	if ! [[ "$PORT" =~ ^[0-9]+$ ]] || [[ "$PORT" -lt 1 ]] || [[ "$PORT" -gt 65535 ]]; then
		log_fatal "Invalid port: $PORT. Must be a number between 1 and 65535."
	fi

	# Validate CLIENT_IPV4/CLIENT_IPV6
	if [[ $CLIENT_IPV4 != "y" ]] && [[ $CLIENT_IPV6 != "y" ]]; then
		log_fatal "At least one of CLIENT_IPV4 or CLIENT_IPV6 must be 'y'"
	fi

	# Validate ENDPOINT_TYPE
	case "$ENDPOINT_TYPE" in
	4 | 6) ;;
	*) log_fatal "Invalid endpoint type: $ENDPOINT_TYPE. Must be '4' or '6'." ;;
	esac

	# Validate CIPHER
	case "$CIPHER" in
	AES-128-GCM | AES-192-GCM | AES-256-GCM | AES-128-CBC | AES-192-CBC | AES-256-CBC | CHACHA20-POLY1305) ;;
	*) log_fatal "Invalid cipher: $CIPHER. Valid ciphers: AES-128-GCM, AES-192-GCM, AES-256-GCM, AES-128-CBC, AES-192-CBC, AES-256-CBC, CHACHA20-POLY1305" ;;
	esac

	# Validate CERT_CURVE (only if ECDSA)
	if [[ $CERT_TYPE == "ecdsa" ]]; then
		case "$CERT_CURVE" in
		prime256v1 | secp384r1 | secp521r1) ;;
		*) log_fatal "Invalid cert curve: $CERT_CURVE. Must be 'prime256v1', 'secp384r1', or 'secp521r1'." ;;
		esac
	fi

	# Validate RSA_KEY_SIZE (only if RSA)
	if [[ $CERT_TYPE == "rsa" ]]; then
		case "$RSA_KEY_SIZE" in
		2048 | 3072 | 4096) ;;
		*) log_fatal "Invalid RSA key size: $RSA_KEY_SIZE. Must be 2048, 3072, or 4096." ;;
		esac
	fi

	# Validate TLS_VERSION_MIN
	case "$TLS_VERSION_MIN" in
	1.2 | 1.3) ;;
	*) log_fatal "Invalid TLS version: $TLS_VERSION_MIN. Must be '1.2' or '1.3'." ;;
	esac

	# Validate HMAC_ALG
	case "$HMAC_ALG" in
	SHA256 | SHA384 | SHA512) ;;
	*) log_fatal "Invalid HMAC algorithm: $HMAC_ALG. Must be SHA256, SHA384, or SHA512." ;;
	esac

	# Validate MTU if set
	if [[ -n $MTU ]]; then
		if ! [[ "$MTU" =~ ^[0-9]+$ ]] || [[ "$MTU" -lt 576 ]] || [[ "$MTU" -gt 65535 ]]; then
			log_fatal "Invalid MTU: $MTU. Must be a number between 576 and 65535."
		fi
	fi

	# Validate custom DNS if selected
	if [[ $DNS == "custom" ]] && [[ -z $DNS1 ]]; then
		log_fatal "Custom DNS selected but DNS1 (primary DNS) is not set. Use --dns-primary to specify."
	fi

	# Validate VPN subnets using the dedicated validation functions
	# These check format, octet ranges, and RFC1918/ULA compliance
	if [[ -n $VPN_SUBNET_IPV4 ]]; then
		validate_subnet_ipv4 "$VPN_SUBNET_IPV4"
	fi

	if [[ $CLIENT_IPV6 == "y" ]] && [[ -n $VPN_SUBNET_IPV6 ]]; then
		validate_subnet_ipv6 "$VPN_SUBNET_IPV6"
	fi
}

# =============================================================================
# Interactive Helper Functions
# =============================================================================
# Generic select-from-menu function for arrays
# Usage: select_from_array "prompt" array_name "default_value" result_var
# Note: Uses namerefs (-n) for arrays
select_from_array() {
	local prompt="$1"
	local -n _options_ref="$2"
	local default="$3"
	local -n _result_ref="$4"

	# If already set (non-interactive mode), just return
	if [[ -n $_result_ref ]]; then
		return
	fi

	# Find default index (1-based for display)
	local default_idx=1
	for i in "${!_options_ref[@]}"; do
		if [[ "${_options_ref[$i]}" == "$default" ]]; then
			default_idx=$((i + 1))
			break
		fi
	done

	# Display menu
	local count=${#_options_ref[@]}
	for i in "${!_options_ref[@]}"; do
		log_menu "   $((i + 1))) ${_options_ref[$i]}"
	done

	# Read selection
	local choice
	until [[ $choice =~ ^[0-9]+$ ]] && ((choice >= 1 && choice <= count)); do
		read -rp "$prompt [1-$count]: " -e -i "$default_idx" choice
	done

	_result_ref="${_options_ref[$((choice - 1))]}"
}

# Select with custom labels (for menu items that need different display text)
# Usage: select_with_labels "prompt" labels_array values_array "default_value" result_var
select_with_labels() {
	local prompt="$1"
	local -n _labels_ref="$2"
	local -n _values_ref="$3"
	local default="$4"
	local -n _result_ref="$5"

	# If already set (non-interactive mode), just return
	if [[ -n $_result_ref ]]; then
		return
	fi

	# Find default index
	local default_idx=1
	for i in "${!_values_ref[@]}"; do
		if [[ "${_values_ref[$i]}" == "$default" ]]; then
			default_idx=$((i + 1))
			break
		fi
	done

	# Display menu
	local count=${#_labels_ref[@]}
	for i in "${!_labels_ref[@]}"; do
		log_menu "   $((i + 1))) ${_labels_ref[$i]}"
	done

	# Read selection
	local choice
	until [[ $choice =~ ^[0-9]+$ ]] && ((choice >= 1 && choice <= count)); do
		read -rp "$prompt [1-$count]: " -e -i "$default_idx" choice
	done

	_result_ref="${_values_ref[$((choice - 1))]}"
}

# Prompt for yes/no with default
# Usage: prompt_yes_no "prompt" "default" result_var
prompt_yes_no() {
	local prompt="$1"
	local default="$2"
	local -n _result_ref="$3"

	# If already set, just return
	if [[ $_result_ref =~ ^[yn]$ ]]; then
		return
	fi

	until [[ $_result_ref =~ ^[yn]$ ]]; do
		read -rp "$prompt [y/n]: " -e -i "$default" _result_ref
	done
}

# Prompt for a value with validation function
# Usage: prompt_validated "prompt" "validator_func" "default" result_var
# The validator should return 0 for valid, non-0 for invalid
prompt_validated() {
	local prompt="$1"
	local validator="$2"
	local default="$3"
	local -n _result_ref="$4"

	# If already set and valid, return
	if [[ -n $_result_ref ]] && $validator "$_result_ref" 2>/dev/null; then
		return
	fi

	_result_ref=""
	until [[ -n $_result_ref ]] && $validator "$_result_ref" 2>/dev/null; do
		read -rp "$prompt: " -e -i "$default" _result_ref
	done
}

# Non-fatal port validator (returns 0/1)
is_valid_port() {
	local port="$1"
	[[ "$port" =~ ^[0-9]+$ ]] && ((port >= 1 && port <= 65535))
}

# Non-fatal MTU validator (returns 0/1)
is_valid_mtu() {
	local mtu="$1"
	[[ "$mtu" =~ ^[0-9]+$ ]] && ((mtu >= 576 && mtu <= 65535))
}

# Handle install command
cmd_install() {
	local interactive=false
	local no_client=false
	local client_password_flag=false
	local client_password_value=""

	while [[ $# -gt 0 ]]; do
		case "$1" in
		-i | --interactive)
			interactive=true
			shift
			;;
		--endpoint)
			[[ -z "${2:-}" ]] && log_fatal "--endpoint requires an argument"
			ENDPOINT="$2"
			shift 2
			;;
		--ip)
			[[ -z "${2:-}" ]] && log_fatal "--ip requires an argument"
			IP="$2"
			APPROVE_IP=y
			shift 2
			;;
		--endpoint-type)
			[[ -z "${2:-}" ]] && log_fatal "--endpoint-type requires an argument"
			case "$2" in
			4) ENDPOINT_TYPE="4" ;;
			6) ENDPOINT_TYPE="6" ;;
			*) log_fatal "Invalid endpoint type: $2. Use '4' or '6'." ;;
			esac
			shift 2
			;;
		--client-ipv4)
			CLIENT_IPV4=y
			shift
			;;
		--no-client-ipv4)
			CLIENT_IPV4=n
			shift
			;;
		--client-ipv6)
			CLIENT_IPV6=y
			shift
			;;
		--no-client-ipv6)
			CLIENT_IPV6=n
			shift
			;;
		--ipv6)
			# Legacy flag: enable IPv6 for clients (backward compatibility)
			CLIENT_IPV6=y
			shift
			;;
		--subnet-ipv4)
			[[ -z "${2:-}" ]] && log_fatal "--subnet-ipv4 requires an argument"
			validate_subnet_ipv4 "$2"
			VPN_SUBNET_IPV4="$2"
			shift 2
			;;
		--subnet-ipv6)
			[[ -z "${2:-}" ]] && log_fatal "--subnet-ipv6 requires an argument"
			validate_subnet_ipv6 "$2"
			VPN_SUBNET_IPV6="$2"
			shift 2
			;;
		--subnet)
			# Legacy flag: --subnet now maps to --subnet-ipv4
			[[ -z "${2:-}" ]] && log_fatal "--subnet requires an argument"
			validate_subnet_ipv4 "$2"
			VPN_SUBNET_IPV4="$2"
			shift 2
			;;
		--port)
			[[ -z "${2:-}" ]] && log_fatal "--port requires an argument"
			validate_port "$2"
			PORT="$2"
			shift 2
			;;
		--port-random)
			PORT="random"
			shift
			;;
		--protocol)
			[[ -z "${2:-}" ]] && log_fatal "--protocol requires an argument"
			case "$2" in
			udp | tcp)
				PROTOCOL="$2"
				;;
			*) log_fatal "Invalid protocol: $2. Use 'udp' or 'tcp'." ;;
			esac
			shift 2
			;;
		--mtu)
			[[ -z "${2:-}" ]] && log_fatal "--mtu requires an argument"
			validate_mtu "$2"
			MTU="$2"
			shift 2
			;;
		--dns)
			[[ -z "${2:-}" ]] && log_fatal "--dns requires an argument"
			parse_dns_provider "$2"
			shift 2
			;;
		--dns-primary)
			[[ -z "${2:-}" ]] && log_fatal "--dns-primary requires an argument"
			DNS1="$2"
			shift 2
			;;
		--dns-secondary)
			[[ -z "${2:-}" ]] && log_fatal "--dns-secondary requires an argument"
			DNS2="$2"
			shift 2
			;;
		--multi-client)
			MULTI_CLIENT=y
			shift
			;;
		--cipher)
			[[ -z "${2:-}" ]] && log_fatal "--cipher requires an argument"
			parse_cipher "$2"
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--cert-type)
			[[ -z "${2:-}" ]] && log_fatal "--cert-type requires an argument"
			case "$2" in
			ecdsa | rsa) CERT_TYPE="$2" ;;
			*) log_fatal "Invalid cert-type: $2. Use 'ecdsa' or 'rsa'." ;;
			esac
			shift 2
			;;
		--cert-curve)
			[[ -z "${2:-}" ]] && log_fatal "--cert-curve requires an argument"
			CERT_CURVE=$(parse_curve "$2")
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--rsa-bits)
			[[ -z "${2:-}" ]] && log_fatal "--rsa-bits requires an argument"
			case "$2" in
			2048 | 3072 | 4096) RSA_KEY_SIZE="$2" ;;
			*) log_fatal "Invalid RSA key size: $2. Use 2048, 3072, or 4096." ;;
			esac
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--cc-cipher)
			[[ -z "${2:-}" ]] && log_fatal "--cc-cipher requires an argument"
			CC_CIPHER="$2"
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--tls-ciphersuites)
			[[ -z "${2:-}" ]] && log_fatal "--tls-ciphersuites requires an argument"
			TLS13_CIPHERSUITES="$2"
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--tls-version-min)
			[[ -z "${2:-}" ]] && log_fatal "--tls-version-min requires an argument"
			case "$2" in
			1.2 | 1.3) TLS_VERSION_MIN="$2" ;;
			*) log_fatal "Invalid TLS version: $2. Use '1.2' or '1.3'." ;;
			esac
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--tls-groups)
			[[ -z "${2:-}" ]] && log_fatal "--tls-groups requires an argument"
			TLS_GROUPS="$2"
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--hmac)
			[[ -z "${2:-}" ]] && log_fatal "--hmac requires an argument"
			case "$2" in
			SHA256 | SHA384 | SHA512) HMAC_ALG="$2" ;;
			*) log_fatal "Invalid HMAC algorithm: $2. Use SHA256, SHA384, or SHA512." ;;
			esac
			CUSTOMIZE_ENC=y
			shift 2
			;;
		--tls-sig)
			[[ -z "${2:-}" ]] && log_fatal "--tls-sig requires an argument"
			case "$2" in
			crypt-v2 | crypt | auth) TLS_SIG="$2" ;;
			*) log_fatal "Invalid TLS mode: $2. Use 'crypt-v2', 'crypt', or 'auth'." ;;
			esac
			shift 2
			;;
		--server-cert-days)
			[[ -z "${2:-}" ]] && log_fatal "--server-cert-days requires an argument"
			validate_positive_int "$2" "server-cert-days"
			SERVER_CERT_DURATION_DAYS="$2"
			shift 2
			;;
		--client)
			[[ -z "${2:-}" ]] && log_fatal "--client requires an argument"
			validate_client_name "$2"
			CLIENT="$2"
			shift 2
			;;
		--client-password)
			client_password_flag=true
			# Check if next arg is a value or another flag
			if [[ -n "${2:-}" ]] && [[ ! "$2" =~ ^- ]]; then
				client_password_value="$2"
				shift
			fi
			shift
			;;
		--client-cert-days)
			[[ -z "${2:-}" ]] && log_fatal "--client-cert-days requires an argument"
			validate_positive_int "$2" "client-cert-days"
			CLIENT_CERT_DURATION_DAYS="$2"
			shift 2
			;;
		--no-client)
			no_client=true
			shift
			;;
		-h | --help)
			show_install_help
			exit 0
			;;
		*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME install --help' for usage."
			;;
		esac
	done

	# Validate custom DNS settings
	if [[ -n "${DNS1:-}" || -n "${DNS2:-}" ]] && [[ "${DNS:-}" != "custom" ]]; then
		log_fatal "--dns-primary and --dns-secondary require --dns custom"
	fi

	# Check if already installed
	requireNoOpenVPN

	if [[ $interactive == true ]]; then
		# Run interactive installer
		installQuestions
	else
		# Non-interactive mode - set flags and defaults
		NON_INTERACTIVE_INSTALL=y
		APPROVE_INSTALL=y
		APPROVE_IP=${APPROVE_IP:-y}
		CONTINUE=y

		# Handle random port
		if [[ $PORT == "random" ]]; then
			PORT=$(shuf -i 49152-65535 -n1)
			log_info "Random Port: $PORT"
		fi

		# Client setup
		if [[ $no_client == true ]]; then
			NEW_CLIENT=n
		else
			NEW_CLIENT=y
			if [[ $client_password_flag == true ]]; then
				PASS=2
				if [[ -n "$client_password_value" ]]; then
					PASSPHRASE="$client_password_value"
				fi
			fi
		fi

		# Set all defaults for any unset values
		set_installation_defaults

		# Validate configuration values (catches invalid env vars)
		validate_configuration

		# Detect IPs and set up network config (interactive mode does this in installQuestions)
		detect_server_ips
	fi

	# Prepare derived network configuration (gateways, etc.)
	prepare_network_config

	installOpenVPN
}

# Handle uninstall command
cmd_uninstall() {
	local force=false

	while [[ $# -gt 0 ]]; do
		case "$1" in
		-f | --force)
			force=true
			shift
			;;
		-h | --help)
			show_uninstall_help
			exit 0
			;;
		*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME uninstall --help' for usage."
			;;
		esac
	done

	requireOpenVPN

	if [[ $force == true ]]; then
		REMOVE=y
	fi

	removeOpenVPN
}

# Handle client command
cmd_client() {
	local subcmd="${1:-}"
	shift || true

	case "$subcmd" in
	"" | "-h" | "--help")
		show_client_help
		exit 0
		;;
	add)
		cmd_client_add "$@"
		;;
	list)
		cmd_client_list "$@"
		;;
	revoke)
		cmd_client_revoke "$@"
		;;
	renew)
		cmd_client_renew "$@"
		;;
	*)
		log_fatal "Unknown client subcommand: $subcmd. See '$SCRIPT_NAME client --help' for usage."
		;;
	esac
}

# Handle client add command
cmd_client_add() {
	local client_name=""
	local password_flag=false
	local password_value=""

	# First non-flag argument is the client name
	while [[ $# -gt 0 ]]; do
		case "$1" in
		--password)
			password_flag=true
			# Check if next arg is a value or another flag
			if [[ -n "${2:-}" ]] && [[ ! "$2" =~ ^- ]]; then
				password_value="$2"
				shift
			fi
			shift
			;;
		--cert-days)
			[[ -z "${2:-}" ]] && log_fatal "--cert-days requires an argument"
			validate_positive_int "$2" "cert-days"
			CLIENT_CERT_DURATION_DAYS="$2"
			shift 2
			;;
		--output)
			[[ -z "${2:-}" ]] && log_fatal "--output requires an argument"
			CLIENT_FILEPATH="$2"
			shift 2
			;;
		-h | --help)
			show_client_add_help
			exit 0
			;;
		-*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME client add --help' for usage."
			;;
		*)
			if [[ -z "$client_name" ]]; then
				client_name="$1"
			else
				log_fatal "Unexpected argument: $1"
			fi
			shift
			;;
		esac
	done

	[[ -z "$client_name" ]] && log_fatal "Client name is required. See '$SCRIPT_NAME client add --help' for usage."
	validate_client_name "$client_name"

	requireOpenVPN

	# Set up variables for newClient function
	CLIENT="$client_name"
	CLIENT_CERT_DURATION_DAYS=${CLIENT_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}

	if [[ $password_flag == true ]]; then
		PASS=2
		if [[ -n "$password_value" ]]; then
			PASSPHRASE="$password_value"
		fi
	else
		PASS=1
	fi

	newClient
}

# Handle client list command
cmd_client_list() {
	local format="table"

	while [[ $# -gt 0 ]]; do
		case "$1" in
		--format)
			[[ -z "${2:-}" ]] && log_fatal "--format requires an argument"
			case "$2" in
			table | json) format="$2" ;;
			*) log_fatal "Invalid format: $2. Use 'table' or 'json'." ;;
			esac
			shift 2
			;;
		-h | --help)
			show_client_list_help
			exit 0
			;;
		*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME client list --help' for usage."
			;;
		esac
	done

	requireOpenVPN

	OUTPUT_FORMAT="$format" listClients
}

# Handle client revoke command
cmd_client_revoke() {
	local client_name=""
	local force=false

	while [[ $# -gt 0 ]]; do
		case "$1" in
		-f | --force)
			force=true
			shift
			;;
		-h | --help)
			show_client_revoke_help
			exit 0
			;;
		-*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME client revoke --help' for usage."
			;;
		*)
			if [[ -z "$client_name" ]]; then
				client_name="$1"
			else
				log_fatal "Unexpected argument: $1"
			fi
			shift
			;;
		esac
	done

	[[ -z "$client_name" ]] && log_fatal "Client name is required. See '$SCRIPT_NAME client revoke --help' for usage."

	requireOpenVPN

	CLIENT="$client_name"
	if [[ $force == true ]]; then
		REVOKE_CONFIRM=y
	fi

	revokeClient
}

# Handle client renew command
cmd_client_renew() {
	local client_name=""

	while [[ $# -gt 0 ]]; do
		case "$1" in
		--cert-days)
			[[ -z "${2:-}" ]] && log_fatal "--cert-days requires an argument"
			validate_positive_int "$2" "cert-days"
			CLIENT_CERT_DURATION_DAYS="$2"
			shift 2
			;;
		-h | --help)
			show_client_renew_help
			exit 0
			;;
		-*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME client renew --help' for usage."
			;;
		*)
			if [[ -z "$client_name" ]]; then
				client_name="$1"
			else
				log_fatal "Unexpected argument: $1"
			fi
			shift
			;;
		esac
	done

	[[ -z "$client_name" ]] && log_fatal "Client name is required. See '$SCRIPT_NAME client renew --help' for usage."

	requireOpenVPN

	CLIENT="$client_name"
	CLIENT_CERT_DURATION_DAYS=${CLIENT_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}

	renewClient
}

# Handle server command
cmd_server() {
	local subcmd="${1:-}"
	shift || true

	case "$subcmd" in
	"" | "-h" | "--help")
		show_server_help
		exit 0
		;;
	status)
		cmd_server_status "$@"
		;;
	renew)
		cmd_server_renew "$@"
		;;
	*)
		log_fatal "Unknown server subcommand: $subcmd. See '$SCRIPT_NAME server --help' for usage."
		;;
	esac
}

# Handle server status command
cmd_server_status() {
	local format="table"

	while [[ $# -gt 0 ]]; do
		case "$1" in
		--format)
			[[ -z "${2:-}" ]] && log_fatal "--format requires an argument"
			case "$2" in
			table | json) format="$2" ;;
			*) log_fatal "Invalid format: $2. Use 'table' or 'json'." ;;
			esac
			shift 2
			;;
		-h | --help)
			show_server_status_help
			exit 0
			;;
		*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME server status --help' for usage."
			;;
		esac
	done

	requireOpenVPN

	OUTPUT_FORMAT="$format" listConnectedClients
}

# Handle server renew command
cmd_server_renew() {
	local force=false

	while [[ $# -gt 0 ]]; do
		case "$1" in
		--cert-days)
			[[ -z "${2:-}" ]] && log_fatal "--cert-days requires an argument"
			validate_positive_int "$2" "cert-days"
			SERVER_CERT_DURATION_DAYS="$2"
			shift 2
			;;
		-f | --force)
			force=true
			shift
			;;
		-h | --help)
			show_server_renew_help
			exit 0
			;;
		*)
			log_fatal "Unknown option: $1. See '$SCRIPT_NAME server renew --help' for usage."
			;;
		esac
	done

	requireOpenVPN

	SERVER_CERT_DURATION_DAYS=${SERVER_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}
	if [[ $force == true ]]; then
		CONTINUE=y
	fi

	renewServer
}

# Handle interactive command (legacy menu)
cmd_interactive() {
	while [[ $# -gt 0 ]]; do
		case "$1" in
		-h | --help)
			echo "Launch interactive menu for OpenVPN management"
			echo ""
			echo "Usage: $SCRIPT_NAME interactive"
			exit 0
			;;
		*)
			log_fatal "Unknown option: $1"
			;;
		esac
	done

	if isOpenVPNInstalled; then
		manageMenu
	else
		installQuestions
		installOpenVPN
	fi
}

# Main argument parser
parse_args() {
	# Parse global options first
	while [[ $# -gt 0 ]]; do
		case "$1" in
		--verbose)
			VERBOSE=1
			shift
			;;
		--log)
			[[ -z "${2:-}" ]] && log_fatal "--log requires an argument"
			LOG_FILE="$2"
			shift 2
			;;
		--no-log)
			LOG_FILE=""
			shift
			;;
		--no-color)
			# Colors already set at script start, but we can unset them
			COLOR_RESET=''
			COLOR_RED=''
			COLOR_GREEN=''
			COLOR_YELLOW=''
			COLOR_BLUE=''
			COLOR_CYAN=''
			COLOR_DIM=''
			COLOR_BOLD=''
			shift
			;;
		-h | --help)
			show_help
			exit 0
			;;
		-*)
			# Could be a command-specific option, let command handle it
			break
			;;
		*)
			# First non-option is the command
			break
			;;
		esac
	done

	# Get the command
	local cmd="${1:-}"
	shift || true

	# Check if user just wants help (don't require root for help)
	# Also detect --format json early to suppress log output before initialCheck
	local wants_help=false
	local prev_arg=""
	for arg in "$@"; do
		if [[ "$arg" == "-h" || "$arg" == "--help" ]]; then
			wants_help=true
		fi
		if [[ "$prev_arg" == "--format" && "$arg" == "json" ]]; then
			OUTPUT_FORMAT="json"
		fi
		prev_arg="$arg"
	done

	# Dispatch to command handler
	case "$cmd" in
	"")
		show_help
		exit 0
		;;
	install)
		[[ $wants_help == false ]] && initialCheck
		cmd_install "$@"
		;;
	uninstall)
		[[ $wants_help == false ]] && initialCheck
		cmd_uninstall "$@"
		;;
	client)
		[[ $wants_help == false ]] && initialCheck
		cmd_client "$@"
		;;
	server)
		[[ $wants_help == false ]] && initialCheck
		cmd_server "$@"
		;;
	interactive)
		[[ $wants_help == false ]] && initialCheck
		cmd_interactive "$@"
		;;
	*)
		log_fatal "Unknown command: $cmd. See '$SCRIPT_NAME --help' for usage."
		;;
	esac
}

# =============================================================================
# System Check Functions
# =============================================================================
function isRoot() {
	if [ "$EUID" -ne 0 ]; then
		return 1
	fi
}

function tunAvailable() {
	if [ ! -e /dev/net/tun ]; then
		return 1
	fi
}

function checkOS() {
	if [[ -e /etc/debian_version ]]; then
		OS="debian"
		source /etc/os-release

		if [[ $ID == "debian" || $ID == "raspbian" ]]; then
			if [[ $VERSION_ID -lt 11 ]]; then
				log_warn "Your version of Debian is not supported."
				log_info "However, if you're using Debian >= 11 or unstable/testing, you can continue at your own risk."
				until [[ $CONTINUE =~ (y|n) ]]; do
					read -rp "Continue? [y/n]: " -e CONTINUE
				done
				if [[ $CONTINUE == "n" ]]; then
					exit 1
				fi
			fi
		elif [[ $ID == "ubuntu" ]]; then
			OS="ubuntu"
			MAJOR_UBUNTU_VERSION=$(echo "$VERSION_ID" | cut -d '.' -f1)
			if [[ $MAJOR_UBUNTU_VERSION -lt 18 ]]; then
				log_warn "Your version of Ubuntu is not supported."
				log_info "However, if you're using Ubuntu >= 18.04 or beta, you can continue at your own risk."
				until [[ $CONTINUE =~ (y|n) ]]; do
					read -rp "Continue? [y/n]: " -e CONTINUE
				done
				if [[ $CONTINUE == "n" ]]; then
					exit 1
				fi
			fi
		fi
	elif [[ -e /etc/os-release ]]; then
		source /etc/os-release
		if [[ $ID == "fedora" || $ID_LIKE == "fedora" ]]; then
			OS="fedora"
		fi
		if [[ $ID == "opensuse-tumbleweed" ]]; then
			OS="opensuse"
		fi
		if [[ $ID == "opensuse-leap" ]]; then
			OS="opensuse"
			if [[ ${VERSION_ID%.*} -lt 16 ]]; then
				log_info "The script only supports openSUSE Leap 16+."
				log_fatal "Your version of openSUSE Leap is not supported."
			fi
		fi
		if [[ $ID == "centos" || $ID == "rocky" || $ID == "almalinux" ]]; then
			OS="centos"
		fi
		if [[ $ID == "ol" ]]; then
			OS="oracle"
		fi
		if [[ $OS =~ (centos|oracle) ]] && [[ ${VERSION_ID%.*} -lt 8 ]]; then
			log_info "The script only supports CentOS Stream / Rocky Linux / AlmaLinux / Oracle Linux version 8+."
			log_fatal "Your version is not supported."
		fi
		if [[ $ID == "amzn" ]]; then
			if [[ "$(echo "$PRETTY_NAME" | cut -c 1-18)" == "Amazon Linux 2023." ]] && [[ "$(echo "$PRETTY_NAME" | cut -c 19)" -ge 6 ]]; then
				OS="amzn2023"
			else
				log_info "The script only supports Amazon Linux 2023.6+"
				log_info "Amazon Linux 2 is EOL and no longer supported."
				log_fatal "Your version of Amazon Linux is not supported."
			fi
		fi
		if [[ $ID == "arch" ]]; then
			OS="arch"
		fi
	elif [[ -e /etc/arch-release ]]; then
		OS=arch
	else
		log_fatal "It looks like you aren't running this installer on a Debian, Ubuntu, Fedora, openSUSE, CentOS, Amazon Linux 2023, Oracle Linux, Arch Linux, Rocky Linux or AlmaLinux system."
	fi
}

function checkArchPendingKernelUpgrade() {
	if [[ $OS != "arch" ]]; then
		return 0
	fi

	# Check if running kernel's modules are available
	# (detects if kernel was upgraded but system not rebooted)
	# Skip this check in containers - they share host kernel but have their own /lib/modules
	if [[ -f /.dockerenv ]] || grep -qE '(docker|lxc|containerd)' /proc/1/cgroup 2>/dev/null; then
		log_info "Running in container, skipping kernel modules check"
	else
		local running_kernel
		running_kernel=$(uname -r)
		if [[ ! -d "/lib/modules/${running_kernel}" ]]; then
			log_error "Kernel modules for running kernel ($running_kernel) not found!"
			log_info "This usually means the kernel was upgraded but the system wasn't rebooted."
			log_fatal "Please reboot your system and run this script again."
		fi
	fi

	log_info "Checking for pending kernel upgrades on Arch Linux..."

	# Sync package database to check for updates
	if ! pacman -Sy &>/dev/null; then
		log_warn "Failed to sync package database, skipping kernel upgrade check"
		return 0
	fi

	# Check for pending linux kernel upgrades
	local pending_kernels
	pending_kernels=$(pacman -Qu 2>/dev/null | grep -E '^linux' || true)

	if [[ -n "$pending_kernels" ]]; then
		log_warn "Linux kernel upgrade(s) pending:"
		echo "$pending_kernels" | while read -r line; do
			log_info "  $line"
		done
		echo ""
		log_info "This script uses 'pacman -Syu' which will upgrade your kernel."
		log_info "After a kernel upgrade, the TUN module won't be available until you reboot."
		echo ""
		log_info "Please upgrade your system and reboot first:"
		log_info "  sudo pacman -Syu"
		log_info "  sudo reboot"
		echo ""
		log_fatal "Aborting. Run this script again after upgrading and rebooting."
	fi

	log_success "No pending kernel upgrades"
}

function initialCheck() {
	log_debug "Checking root privileges..."
	if ! isRoot; then
		log_fatal "Sorry, you need to run this script as root."
	fi
	log_debug "Root check passed"

	log_debug "Checking TUN device availability..."
	if ! tunAvailable; then
		log_fatal "TUN is not available."
	fi
	log_debug "TUN device available at /dev/net/tun"

	log_debug "Detecting operating system..."
	checkOS
	log_debug "Detected OS: $OS (${PRETTY_NAME:-unknown})"
	checkArchPendingKernelUpgrade
}

# Check if OpenVPN version is at least the specified version
# Usage: openvpnVersionAtLeast "2.5"
# Returns 0 if version is >= specified, 1 otherwise
function openvpnVersionAtLeast() {
	local required_version="$1"
	local installed_version

	if ! command -v openvpn &>/dev/null; then
		return 1
	fi

	installed_version=$(openvpn --version 2>/dev/null | head -1 | awk '{print $2}')
	if [[ -z "$installed_version" ]]; then
		return 1
	fi

	# Compare versions using sort -V
	if [[ "$(printf '%s\n' "$required_version" "$installed_version" | sort -V | head -n1)" == "$required_version" ]]; then
		return 0
	fi
	return 1
}

# Check if kernel version is at least the specified version
# Usage: kernelVersionAtLeast "6.16"
# Returns 0 if version is >= specified, 1 otherwise
function kernelVersionAtLeast() {
	local required_version="$1"
	local kernel_version

	kernel_version=$(uname -r | cut -d'-' -f1)
	if [[ -z "$kernel_version" ]]; then
		return 1
	fi

	if [[ "$(printf '%s\n' "$required_version" "$kernel_version" | sort -V | head -n1)" == "$required_version" ]]; then
		return 0
	fi
	return 1
}

# Check if Data Channel Offload (DCO) is available
# DCO requires: OpenVPN 2.6+, kernel support (Linux 6.16+ or ovpn-dco module)
# Returns 0 if DCO is available, 1 otherwise
function isDCOAvailable() {
	# DCO requires OpenVPN 2.6+
	if ! openvpnVersionAtLeast "2.6"; then
		return 1
	fi

	# DCO is built into Linux 6.16+, or available via ovpn-dco module
	if kernelVersionAtLeast "6.16"; then
		return 0
	elif lsmod 2>/dev/null | grep -q "^ovpn_dco" || modinfo ovpn-dco &>/dev/null; then
		return 0
	fi
	return 1
}

function installOpenVPNRepo() {
	log_info "Setting up official OpenVPN repository..."

	if [[ $OS =~ (debian|ubuntu) ]]; then
		run_cmd_fatal "Update package lists" apt-get update
		run_cmd_fatal "Installing prerequisites" apt-get install -y ca-certificates curl

		# Create keyrings directory
		run_cmd "Creating keyrings directory" mkdir -p /etc/apt/keyrings

		# Download and install GPG key
		if ! run_cmd "Downloading OpenVPN GPG key" curl -fsSL https://swupdate.openvpn.net/repos/repo-public.gpg -o /etc/apt/keyrings/openvpn-repo-public.asc; then
			log_fatal "Failed to download OpenVPN repository GPG key"
		fi

		# Add repository - using stable release
		if [[ -z "${VERSION_CODENAME}" ]]; then
			log_fatal "VERSION_CODENAME is not set. Unable to configure OpenVPN repository."
		fi
		echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/openvpn-repo-public.asc] https://build.openvpn.net/debian/openvpn/stable ${VERSION_CODENAME} main" >/etc/apt/sources.list.d/openvpn-aptrepo.list

		log_info "Updating package lists with new repository..."
		run_cmd_fatal "Update package lists" apt-get update

		log_info "OpenVPN official repository configured"

	elif [[ $OS =~ (centos|oracle) ]]; then
		# For RHEL-based systems, use Fedora Copr (OpenVPN 2.6 stable)
		# EPEL is required for pkcs11-helper dependency
		log_info "Configuring OpenVPN Copr repository for RHEL-based system..."

		# Oracle Linux uses oracle-epel-release-el* instead of epel-release
		if [[ $OS == "oracle" ]]; then
			EPEL_PACKAGE="oracle-epel-release-el${VERSION_ID%.*}"
		else
			EPEL_PACKAGE="epel-release"
		fi

		if ! command -v dnf &>/dev/null; then
			run_cmd_fatal "Installing EPEL repository" yum install -y "$EPEL_PACKAGE"
			run_cmd_fatal "Installing yum-plugin-copr" yum install -y yum-plugin-copr
			run_cmd_fatal "Enabling OpenVPN Copr repo" yum copr enable -y @OpenVPN/openvpn-release-2.6
		else
			run_cmd_fatal "Installing EPEL repository" dnf install -y "$EPEL_PACKAGE"
			run_cmd_fatal "Installing dnf-plugins-core" dnf install -y dnf-plugins-core
			run_cmd_fatal "Enabling OpenVPN Copr repo" dnf copr enable -y @OpenVPN/openvpn-release-2.6
		fi

		log_info "OpenVPN Copr repository configured"

	elif [[ $OS == "fedora" ]]; then
		# Fedora already ships with recent OpenVPN 2.6.x, no Copr needed
		log_info "Fedora already has recent OpenVPN packages, using distribution version"

	else
		log_info "No official OpenVPN repository available for this OS, using distribution packages"
	fi
}

function installUnbound() {
	log_info "Installing Unbound DNS resolver..."

	# Install Unbound if not present
	if [[ ! -e /etc/unbound/unbound.conf ]]; then
		if [[ $OS =~ (debian|ubuntu) ]]; then
			run_cmd_fatal "Installing Unbound" apt-get install -y unbound
		elif [[ $OS =~ (centos|oracle) ]]; then
			run_cmd_fatal "Installing Unbound" yum install -y unbound
		elif [[ $OS =~ (fedora|amzn2023) ]]; then
			run_cmd_fatal "Installing Unbound" dnf install -y unbound
		elif [[ $OS == "opensuse" ]]; then
			run_cmd_fatal "Installing Unbound" zypper install -y unbound
		elif [[ $OS == "arch" ]]; then
			run_cmd_fatal "Installing Unbound" pacman -Syu --noconfirm unbound
		fi
	fi

	# Configure Unbound for OpenVPN (runs whether freshly installed or pre-existing)
	# Create conf.d directory (works on all distros)
	run_cmd "Creating Unbound config directory" mkdir -p /etc/unbound/unbound.conf.d

	# Ensure main config includes conf.d directory
	# Modern Debian/Ubuntu use include-toplevel, others need include directive
	if ! grep -qE "include(-toplevel)?:\s*.*/etc/unbound/unbound.conf.d" /etc/unbound/unbound.conf 2>/dev/null; then
		# Add include directive for conf.d if not present
		echo 'include: "/etc/unbound/unbound.conf.d/*.conf"' >>/etc/unbound/unbound.conf
	fi

	# Generate OpenVPN-specific Unbound configuration
	# Using consistent best-practice settings across all distros
	{
		echo 'server:'
		echo '    # OpenVPN DNS resolver configuration'

		# IPv4 VPN interface (only if clients get IPv4)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo "    interface: $VPN_GATEWAY_IPV4"
			echo "    access-control: $VPN_SUBNET_IPV4/24 allow"
		fi

		# IPv6 VPN interface (only if clients get IPv6)
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo "    interface: $VPN_GATEWAY_IPV6"
			echo "    access-control: ${VPN_SUBNET_IPV6}/112 allow"
		fi

		echo ''
		echo '    # Security hardening'
		echo '    hide-identity: yes'
		echo '    hide-version: yes'
		echo '    harden-glue: yes'
		echo '    harden-dnssec-stripped: yes'
		echo ''
		echo '    # Performance optimizations'
		echo '    prefetch: yes'
		echo '    use-caps-for-id: yes'
		echo '    qname-minimisation: yes'
		echo ''
		echo '    # Allow binding before tun interface exists'
		echo '    ip-freebind: yes'
		echo ''
		echo '    # DNS rebinding protection'
		echo '    private-address: 10.0.0.0/8'
		echo '    private-address: 172.16.0.0/12'
		echo '    private-address: 192.168.0.0/16'
		echo '    private-address: 169.254.0.0/16'
		echo '    private-address: 127.0.0.0/8'
		echo '    private-address: fd00::/8'
		echo '    private-address: fe80::/10'
		echo '    private-address: ::ffff:0:0/96'

		# Add VPN subnet to private addresses if IPv6 enabled
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo "    private-address: ${VPN_SUBNET_IPV6}/112"
		fi

		# Disable remote-control (requires SSL certs on openSUSE)
		if [[ $OS == "opensuse" ]]; then
			echo ''
			echo 'remote-control:'
			echo '    control-enable: no'
		fi
	} >/etc/unbound/unbound.conf.d/openvpn.conf

	run_cmd "Enabling Unbound service" systemctl enable unbound
	run_cmd "Starting Unbound service" systemctl restart unbound

	# Validate Unbound is running
	for i in {1..10}; do
		if pgrep -x unbound >/dev/null; then
			return 0
		fi
		sleep 1
	done
	log_fatal "Unbound failed to start. Check 'journalctl -u unbound' for details."
}

function resolvePublicIPv4() {
	local public_ip=""

	# Try to resolve public IPv4 using: https://api.seeip.org
	if [[ -z $public_ip ]]; then
		public_ip=$(curl -f -m 5 -sS --retry 2 --retry-connrefused -4 https://api.seeip.org 2>/dev/null)
	fi

	# Try to resolve using: https://ifconfig.me
	if [[ -z $public_ip ]]; then
		public_ip=$(curl -f -m 5 -sS --retry 2 --retry-connrefused -4 https://ifconfig.me 2>/dev/null)
	fi

	# Try to resolve using: https://api.ipify.org
	if [[ -z $public_ip ]]; then
		public_ip=$(curl -f -m 5 -sS --retry 2 --retry-connrefused -4 https://api.ipify.org 2>/dev/null)
	fi

	# Try to resolve using: ns1.google.com
	if [[ -z $public_ip ]]; then
		public_ip=$(dig -4 TXT +short o-o.myaddr.l.google.com @ns1.google.com | tr -d '"')
	fi

	echo "$public_ip"
}

function resolvePublicIPv6() {
	local public_ip=""

	# Try to resolve public IPv6 using: https://api6.seeip.org
	if [[ -z $public_ip ]]; then
		public_ip=$(curl -f -m 5 -sS --retry 2 --retry-connrefused -6 https://api6.seeip.org 2>/dev/null)
	fi

	# Try to resolve using: https://ifconfig.me (IPv6)
	if [[ -z $public_ip ]]; then
		public_ip=$(curl -f -m 5 -sS --retry 2 --retry-connrefused -6 https://ifconfig.me 2>/dev/null)
	fi

	# Try to resolve using: https://api64.ipify.org (dual-stack, prefer IPv6)
	if [[ -z $public_ip ]]; then
		public_ip=$(curl -f -m 5 -sS --retry 2 --retry-connrefused -6 https://api64.ipify.org 2>/dev/null)
	fi

	# Try to resolve using: ns1.google.com
	if [[ -z $public_ip ]]; then
		public_ip=$(dig -6 TXT +short o-o.myaddr.l.google.com @ns1.google.com | tr -d '"')
	fi

	echo "$public_ip"
}

# Legacy wrapper for backward compatibility
function resolvePublicIP() {
	if [[ $ENDPOINT_TYPE == "6" ]]; then
		resolvePublicIPv6
	else
		resolvePublicIPv4
	fi
}

# Detect server's IPv4 and IPv6 addresses
function detect_server_ips() {
	IP_IPV4=$(ip -4 addr | sed -ne 's|^.* inet \([^/]*\)/.* scope global.*$|\1|p' | head -1)
	IP_IPV6=$(ip -6 addr | sed -ne 's|^.* inet6 \([^/]*\)/.* scope global.*$|\1|p' | head -1)

	# Set IP based on ENDPOINT_TYPE
	if [[ $ENDPOINT_TYPE == "6" ]]; then
		IP="$IP_IPV6"
	else
		IP="$IP_IPV4"
	fi
}

# Calculate derived network configuration values
function prepare_network_config() {
	# Calculate IPv4 gateway (always needed for leak prevention)
	VPN_GATEWAY_IPV4="${VPN_SUBNET_IPV4%.*}.1"

	# Calculate IPv6 gateway if IPv6 is enabled
	if [[ $CLIENT_IPV6 == "y" ]]; then
		VPN_GATEWAY_IPV6="${VPN_SUBNET_IPV6}1"
	fi

	# Set legacy variable for backward compatibility
	IPV6_SUPPORT="$CLIENT_IPV6"
}

function installQuestions() {
	log_header "OpenVPN Installer"
	log_prompt "The git repository is available at: https://github.com/angristan/openvpn-install"

	log_prompt "I need to ask you a few questions before starting the setup."
	log_prompt "You can leave the default options and just press enter if you are okay with them."

	# ==========================================================================
	# Step 1: Detect server IP addresses
	# ==========================================================================
	log_menu ""
	log_prompt "Detecting server IP addresses..."

	# Detect IPv4 address
	IP_IPV4=$(ip -4 addr | sed -ne 's|^.* inet \([^/]*\)/.* scope global.*$|\1|p' | head -1)
	# Detect IPv6 address
	IP_IPV6=$(ip -6 addr | sed -ne 's|^.* inet6 \([^/]*\)/.* scope global.*$|\1|p' | head -1)

	if [[ -n $IP_IPV4 ]]; then
		log_prompt "  IPv4 address detected: $IP_IPV4"
	else
		log_prompt "  No IPv4 address detected"
	fi
	if [[ -n $IP_IPV6 ]]; then
		log_prompt "  IPv6 address detected: $IP_IPV6"
	else
		log_prompt "  No IPv6 address detected"
	fi

	# ==========================================================================
	# Step 2: Endpoint type selection
	# ==========================================================================
	log_menu ""
	log_prompt "What IP version should clients use to connect to this server?"

	# Determine default based on available addresses
	if [[ -n $IP_IPV4 ]]; then
		ENDPOINT_TYPE_DEFAULT=1
	elif [[ -n $IP_IPV6 ]]; then
		ENDPOINT_TYPE_DEFAULT=2
	else
		log_fatal "No IPv4 or IPv6 address detected on this server."
	fi

	log_menu "   1) IPv4"
	log_menu "   2) IPv6"
	until [[ $ENDPOINT_TYPE_CHOICE =~ ^[1-2]$ ]]; do
		read -rp "Endpoint type [1-2]: " -e -i $ENDPOINT_TYPE_DEFAULT ENDPOINT_TYPE_CHOICE
	done
	case $ENDPOINT_TYPE_CHOICE in
	1)
		ENDPOINT_TYPE="4"
		IP="$IP_IPV4"
		;;
	2)
		ENDPOINT_TYPE="6"
		IP="$IP_IPV6"
		;;
	esac

	# ==========================================================================
	# Step 3: Endpoint address (handle NAT for IPv4, direct for IPv6)
	# ==========================================================================
	APPROVE_IP=${APPROVE_IP:-n}
	if [[ $APPROVE_IP =~ n ]]; then
		log_menu ""
		if [[ $ENDPOINT_TYPE == "4" ]]; then
			log_prompt "Server listening IPv4 address:"
			read -rp "IPv4 address: " -e -i "$IP" IP
		else
			log_prompt "Server listening IPv6 address:"
			read -rp "IPv6 address: " -e -i "$IP" IP
		fi
	fi

	# If IPv4 and private IP, server is behind NAT
	if [[ $ENDPOINT_TYPE == "4" ]] && echo "$IP" | grep -qE '^(10\.|172\.1[6789]\.|172\.2[0-9]\.|172\.3[01]\.|192\.168)'; then
		log_menu ""
		log_prompt "It seems this server is behind NAT. What is its public IPv4 address or hostname?"
		log_prompt "We need it for the clients to connect to the server."

		if [[ -z $ENDPOINT ]]; then
			DEFAULT_ENDPOINT=$(resolvePublicIPv4)
		fi

		until [[ $ENDPOINT != "" ]]; do
			read -rp "Public IPv4 address or hostname: " -e -i "$DEFAULT_ENDPOINT" ENDPOINT
		done
	elif [[ $ENDPOINT_TYPE == "6" ]]; then
		# For IPv6, check if it's a link-local address (starts with fe80)
		if echo "$IP" | grep -qiE '^fe80'; then
			log_menu ""
			log_prompt "The detected IPv6 address is link-local. What is the public IPv6 address or hostname?"
			log_prompt "We need it for the clients to connect to the server."

			if [[ -z $ENDPOINT ]]; then
				DEFAULT_ENDPOINT=$(resolvePublicIPv6)
			fi

			until [[ $ENDPOINT != "" ]]; do
				read -rp "Public IPv6 address or hostname: " -e -i "$DEFAULT_ENDPOINT" ENDPOINT
			done
		fi
	fi

	# ==========================================================================
	# Step 4: Client IP versions
	# ==========================================================================
	log_menu ""
	log_prompt "What IP versions should VPN clients use?"
	log_prompt "This determines both their VPN addresses and internet access through the tunnel."

	# Check IPv6 connectivity for suggestion
	if type ping6 >/dev/null 2>&1; then
		PING6="ping6 -c1 -W2 ipv6.google.com > /dev/null 2>&1"
	else
		PING6="ping -6 -c1 -W2 ipv6.google.com > /dev/null 2>&1"
	fi
	HAS_IPV6_CONNECTIVITY="n"
	if eval "$PING6"; then
		HAS_IPV6_CONNECTIVITY="y"
	fi

	# Default suggestion based on connectivity
	if [[ $HAS_IPV6_CONNECTIVITY == "y" ]]; then
		CLIENT_IP_DEFAULT=3 # Dual-stack if IPv6 available
	else
		CLIENT_IP_DEFAULT=1 # IPv4 only otherwise
	fi

	log_menu "   1) IPv4 only"
	log_menu "   2) IPv6 only"
	log_menu "   3) Dual-stack (IPv4 + IPv6)"
	until [[ $CLIENT_IP_CHOICE =~ ^[1-3]$ ]]; do
		read -rp "Client IP versions [1-3]: " -e -i $CLIENT_IP_DEFAULT CLIENT_IP_CHOICE
	done
	case $CLIENT_IP_CHOICE in
	1)
		CLIENT_IPV4="y"
		CLIENT_IPV6="n"
		;;
	2)
		CLIENT_IPV4="n"
		CLIENT_IPV6="y"
		;;
	3)
		CLIENT_IPV4="y"
		CLIENT_IPV6="y"
		;;
	esac

	# ==========================================================================
	# Step 5: IPv4 subnet (prompt only if IPv4 enabled, but always set for leak prevention)
	# ==========================================================================
	if [[ $CLIENT_IPV4 == "y" ]]; then
		log_menu ""
		log_prompt "IPv4 VPN subnet:"
		log_menu "   1) Default: 10.8.0.0/24"
		log_menu "   2) Custom"
		until [[ $SUBNET_IPV4_CHOICE =~ ^[1-2]$ ]]; do
			read -rp "IPv4 subnet choice [1-2]: " -e -i 1 SUBNET_IPV4_CHOICE
		done
		case $SUBNET_IPV4_CHOICE in
		1)
			VPN_SUBNET_IPV4="10.8.0.0"
			;;
		2)
			# Skip prompt if VPN_SUBNET_IPV4 is already set (e.g., via environment variable)
			if [[ -z $VPN_SUBNET_IPV4 ]]; then
				until [[ $VPN_SUBNET_IPV4 =~ ^(10\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])|172\.(1[6-9]|2[0-9]|3[0-1])\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])|192\.168\.(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9]))\.0$ ]]; do
					read -rp "Custom IPv4 subnet (e.g., 10.9.0.0): " VPN_SUBNET_IPV4
				done
			fi
			;;
		esac
	else
		# IPv6-only mode: still need IPv4 subnet for leak prevention (redirect-gateway def1)
		VPN_SUBNET_IPV4="10.8.0.0"
	fi

	# ==========================================================================
	# Step 6: IPv6 subnet (if IPv6 enabled for clients)
	# ==========================================================================
	if [[ $CLIENT_IPV6 == "y" ]]; then
		log_menu ""
		log_prompt "IPv6 VPN subnet:"
		log_menu "   1) Default: fd42:42:42:42::/112"
		log_menu "   2) Custom"
		until [[ $SUBNET_IPV6_CHOICE =~ ^[1-2]$ ]]; do
			read -rp "IPv6 subnet choice [1-2]: " -e -i 1 SUBNET_IPV6_CHOICE
		done
		case $SUBNET_IPV6_CHOICE in
		1)
			VPN_SUBNET_IPV6="fd42:42:42:42::"
			;;
		2)
			# Skip prompt if VPN_SUBNET_IPV6 is already set (e.g., via environment variable)
			if [[ -z $VPN_SUBNET_IPV6 ]]; then
				until [[ $VPN_SUBNET_IPV6 =~ ^fd[0-9a-fA-F]{0,2}(:[0-9a-fA-F]{0,4}){0,6}::$ ]]; do
					read -rp "Custom IPv6 subnet (e.g., fd12:3456:789a::): " VPN_SUBNET_IPV6
				done
			fi
			;;
		esac
	fi

	log_menu ""
	log_prompt "What port do you want OpenVPN to listen to?"
	log_menu "   1) Default: 1194"
	log_menu "   2) Custom"
	log_menu "   3) Random [49152-65535]"
	until [[ $PORT_CHOICE =~ ^[1-3]$ ]]; do
		read -rp "Port choice [1-3]: " -e -i 1 PORT_CHOICE
	done
	case $PORT_CHOICE in
	1)
		PORT="1194"
		;;
	2)
		until [[ $PORT =~ ^[0-9]+$ ]] && [ "$PORT" -ge 1 ] && [ "$PORT" -le 65535 ]; do
			read -rp "Custom port [1-65535]: " -e -i 1194 PORT
		done
		;;
	3)
		# Generate random number within private ports range
		PORT=$(shuf -i 49152-65535 -n1)
		log_info "Random Port: $PORT"
		;;
	esac
	log_menu ""
	log_prompt "What protocol do you want OpenVPN to use?"
	log_prompt "UDP is faster. Unless it is not available, you shouldn't use TCP."
	log_menu "   1) UDP"
	log_menu "   2) TCP"
	until [[ $PROTOCOL_CHOICE =~ ^[1-2]$ ]]; do
		read -rp "Protocol [1-2]: " -e -i 1 PROTOCOL_CHOICE
	done
	case $PROTOCOL_CHOICE in
	1)
		PROTOCOL="udp"
		;;
	2)
		PROTOCOL="tcp"
		;;
	esac
	log_menu ""
	log_prompt "What DNS resolvers do you want to use with the VPN?"
	local dns_labels=("Current system resolvers (from /etc/resolv.conf)" "Self-hosted DNS Resolver (Unbound)" "Cloudflare (Anycast: worldwide)" "Quad9 (Anycast: worldwide)" "Quad9 uncensored (Anycast: worldwide)" "FDN (France)" "DNS.WATCH (Germany)" "OpenDNS (Anycast: worldwide)" "Google (Anycast: worldwide)" "Yandex Basic (Russia)" "AdGuard DNS (Anycast: worldwide)" "NextDNS (Anycast: worldwide)" "Custom")
	local dns_valid=false
	until [[ $dns_valid == true ]]; do
		select_with_labels "DNS" dns_labels DNS_PROVIDERS "cloudflare" DNS
		if [[ $DNS == "unbound" ]] && [[ -e /etc/unbound/unbound.conf ]]; then
			log_menu ""
			log_prompt "Unbound is already installed."
			log_prompt "You can allow the script to configure it in order to use it from your OpenVPN clients"
			log_prompt "We will simply add a second server to /etc/unbound/unbound.conf for the OpenVPN subnet."
			log_prompt "No changes are made to the current configuration."
			log_menu ""

			local unbound_continue
			until [[ $unbound_continue =~ ^[yn]$ ]]; do
				read -rp "Apply configuration changes to Unbound? [y/n]: " -e unbound_continue
			done
			if [[ $unbound_continue == "n" ]]; then
				unset DNS
			else
				dns_valid=true
			fi
		elif [[ $DNS == "custom" ]]; then
			until [[ $DNS1 =~ ^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$ ]]; do
				read -rp "Primary DNS: " -e DNS1
			done
			until [[ $DNS2 =~ ^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$ ]]; do
				read -rp "Secondary DNS (optional): " -e DNS2
				if [[ $DNS2 == "" ]]; then
					break
				fi
			done
			dns_valid=true
		else
			dns_valid=true
		fi
	done
	log_menu ""
	log_prompt "Do you want to allow a single .ovpn profile to be used on multiple devices simultaneously?"
	log_prompt "Note: Enabling this disables persistent IP addresses for clients."
	until [[ $MULTI_CLIENT =~ (y|n) ]]; do
		read -rp "Allow multiple devices per client? [y/n]: " -e -i n MULTI_CLIENT
	done
	log_menu ""
	log_prompt "Do you want to customize the tunnel MTU?"
	log_menu "   MTU controls the maximum packet size. Lower values can help"
	log_menu "   with connectivity issues on some networks (e.g., PPPoE, mobile)."
	log_menu "   1) Default (1500) - works for most networks"
	log_menu "   2) Custom"
	until [[ $MTU_CHOICE =~ ^[1-2]$ ]]; do
		read -rp "MTU choice [1-2]: " -e -i 1 MTU_CHOICE
	done
	if [[ $MTU_CHOICE == "2" ]]; then
		until [[ $MTU =~ ^[0-9]+$ ]] && [[ $MTU -ge 576 ]] && [[ $MTU -le 65535 ]]; do
			read -rp "MTU [576-65535]: " -e -i 1500 MTU
		done
	fi
	log_menu ""
	log_prompt "Do you want to customize encryption settings?"
	log_prompt "Unless you know what you're doing, you should stick with the default parameters provided by the script."
	log_prompt "Note that whatever you choose, all the choices presented in the script are safe (unlike OpenVPN's defaults)."
	log_prompt "See https://github.com/angristan/openvpn-install#security-and-encryption to learn more."
	log_menu ""
	until [[ $CUSTOMIZE_ENC =~ (y|n) ]]; do
		read -rp "Customize encryption settings? [y/n]: " -e -i n CUSTOMIZE_ENC
	done
	if [[ $CUSTOMIZE_ENC == "n" ]]; then
		# Use default, sane and fast parameters
		CIPHER="AES-128-GCM"
		CERT_TYPE="ecdsa"
		CERT_CURVE="prime256v1"
		CC_CIPHER="TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256"
		TLS13_CIPHERSUITES="TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256"
		TLS_VERSION_MIN="1.2"
		TLS_GROUPS="X25519:prime256v1:secp384r1:secp521r1"
		HMAC_ALG="SHA256"
		TLS_SIG="crypt-v2"
	else
		log_menu ""
		log_prompt "Choose which cipher you want to use for the data channel:"
		log_menu "   1) AES-128-GCM (recommended)"
		log_menu "   2) AES-192-GCM"
		log_menu "   3) AES-256-GCM"
		log_menu "   4) AES-128-CBC"
		log_menu "   5) AES-192-CBC"
		log_menu "   6) AES-256-CBC"
		log_menu "   7) CHACHA20-POLY1305 (requires OpenVPN 2.5+, good for devices without AES-NI)"
		until [[ $CIPHER_CHOICE =~ ^[1-7]$ ]]; do
			read -rp "Cipher [1-7]: " -e -i 1 CIPHER_CHOICE
		done
		case $CIPHER_CHOICE in
		1)
			CIPHER="AES-128-GCM"
			;;
		2)
			CIPHER="AES-192-GCM"
			;;
		3)
			CIPHER="AES-256-GCM"
			;;
		4)
			CIPHER="AES-128-CBC"
			;;
		5)
			CIPHER="AES-192-CBC"
			;;
		6)
			CIPHER="AES-256-CBC"
			;;
		7)
			CIPHER="CHACHA20-POLY1305"
			;;
		esac
		log_menu ""
		log_prompt "Choose what kind of certificate you want to use:"
		log_menu "   1) ECDSA (recommended)"
		log_menu "   2) RSA"
		local cert_type_choice
		until [[ $cert_type_choice =~ ^[1-2]$ ]]; do
			read -rp "Certificate key type [1-2]: " -e -i 1 cert_type_choice
		done
		case $cert_type_choice in
		1)
			CERT_TYPE="ecdsa"
			log_menu ""
			log_prompt "Choose which curve you want to use for the certificate's key:"
			select_from_array "Curve" CERT_CURVES "prime256v1" CERT_CURVE
			;;
		2)
			CERT_TYPE="rsa"
			log_menu ""
			log_prompt "Choose which size you want to use for the certificate's RSA key:"
			select_from_array "RSA key size" RSA_KEY_SIZES "2048" RSA_KEY_SIZE
			;;
		esac
		log_menu ""
		log_prompt "Choose which cipher you want to use for the control channel:"
		local cc_labels cc_values
		if [[ $CERT_TYPE == "ecdsa" ]]; then
			cc_labels=("ECDHE-ECDSA-AES-128-GCM-SHA256 (recommended)" "ECDHE-ECDSA-AES-256-GCM-SHA384" "ECDHE-ECDSA-CHACHA20-POLY1305 (OpenVPN 2.5+)")
			cc_values=("TLS-ECDHE-ECDSA-WITH-AES-128-GCM-SHA256" "TLS-ECDHE-ECDSA-WITH-AES-256-GCM-SHA384" "TLS-ECDHE-ECDSA-WITH-CHACHA20-POLY1305-SHA256")
		else
			cc_labels=("ECDHE-RSA-AES-128-GCM-SHA256 (recommended)" "ECDHE-RSA-AES-256-GCM-SHA384" "ECDHE-RSA-CHACHA20-POLY1305 (OpenVPN 2.5+)")
			cc_values=("TLS-ECDHE-RSA-WITH-AES-128-GCM-SHA256" "TLS-ECDHE-RSA-WITH-AES-256-GCM-SHA384" "TLS-ECDHE-RSA-WITH-CHACHA20-POLY1305-SHA256")
		fi
		select_with_labels "Control channel cipher" cc_labels cc_values "${cc_values[0]}" CC_CIPHER
		log_menu ""
		log_prompt "Choose the minimum TLS version:"
		log_menu "   1) TLS 1.2 (recommended, compatible with all clients)"
		log_menu "   2) TLS 1.3 (more secure, requires OpenVPN 2.5+ clients)"
		until [[ $TLS_VERSION_MIN_CHOICE =~ ^[1-2]$ ]]; do
			read -rp "Minimum TLS version [1-2]: " -e -i 1 TLS_VERSION_MIN_CHOICE
		done
		case $TLS_VERSION_MIN_CHOICE in
		1)
			TLS_VERSION_MIN="1.2"
			;;
		2)
			TLS_VERSION_MIN="1.3"
			;;
		esac
		log_menu ""
		log_prompt "Choose TLS 1.3 cipher suites (used when TLS 1.3 is negotiated):"
		log_menu "   1) All secure ciphers (recommended)"
		log_menu "   2) AES-256-GCM only"
		log_menu "   3) AES-128-GCM only"
		log_menu "   4) ChaCha20-Poly1305 only"
		until [[ $TLS13_CIPHER_CHOICE =~ ^[1-4]$ ]]; do
			read -rp "TLS 1.3 cipher suite [1-4]: " -e -i 1 TLS13_CIPHER_CHOICE
		done
		case $TLS13_CIPHER_CHOICE in
		1)
			TLS13_CIPHERSUITES="TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:TLS_CHACHA20_POLY1305_SHA256"
			;;
		2)
			TLS13_CIPHERSUITES="TLS_AES_256_GCM_SHA384"
			;;
		3)
			TLS13_CIPHERSUITES="TLS_AES_128_GCM_SHA256"
			;;
		4)
			TLS13_CIPHERSUITES="TLS_CHACHA20_POLY1305_SHA256"
			;;
		esac
		log_menu ""
		log_prompt "Choose TLS key exchange groups (for ECDH key exchange):"
		log_menu "   1) All modern curves (recommended)"
		log_menu "   2) X25519 only (most secure, may have compatibility issues)"
		log_menu "   3) NIST curves only (prime256v1, secp384r1, secp521r1)"
		until [[ $TLS_GROUPS_CHOICE =~ ^[1-3]$ ]]; do
			read -rp "TLS groups [1-3]: " -e -i 1 TLS_GROUPS_CHOICE
		done
		case $TLS_GROUPS_CHOICE in
		1)
			TLS_GROUPS="X25519:prime256v1:secp384r1:secp521r1"
			;;
		2)
			TLS_GROUPS="X25519"
			;;
		3)
			TLS_GROUPS="prime256v1:secp384r1:secp521r1"
			;;
		esac
		log_menu ""
		# The "auth" options behaves differently with AEAD ciphers (GCM, ChaCha20-Poly1305)
		if [[ $CIPHER =~ CBC$ ]]; then
			log_prompt "The digest algorithm authenticates data channel packets and tls-auth packets from the control channel."
		elif [[ $CIPHER =~ GCM$ ]] || [[ $CIPHER == "CHACHA20-POLY1305" ]]; then
			log_prompt "The digest algorithm authenticates tls-auth packets from the control channel."
		fi
		log_prompt "Which digest algorithm do you want to use for HMAC?"
		log_menu "   1) SHA-256 (recommended)"
		log_menu "   2) SHA-384"
		log_menu "   3) SHA-512"
		until [[ $HMAC_ALG_CHOICE =~ ^[1-3]$ ]]; do
			read -rp "Digest algorithm [1-3]: " -e -i 1 HMAC_ALG_CHOICE
		done
		case $HMAC_ALG_CHOICE in
		1)
			HMAC_ALG="SHA256"
			;;
		2)
			HMAC_ALG="SHA384"
			;;
		3)
			HMAC_ALG="SHA512"
			;;
		esac
		log_menu ""
		log_prompt "You can add an additional layer of security to the control channel."
		local tls_sig_labels=("tls-crypt-v2 (recommended): Encrypts control channel, unique key per client" "tls-crypt: Encrypts control channel, shared key for all clients" "tls-auth: Authenticates control channel, no encryption")
		select_with_labels "Control channel security" tls_sig_labels TLS_SIG_MODES "crypt-v2" TLS_SIG
	fi
	log_menu ""
	log_prompt "Okay, that was all I needed. We are ready to setup your OpenVPN server now."
	log_prompt "You will be able to generate a client at the end of the installation."
	APPROVE_INSTALL=${APPROVE_INSTALL:-n}
	if [[ $APPROVE_INSTALL =~ n ]]; then
		read -n1 -r -p "Press any key to continue..."
	fi
}

function installOpenVPN() {
	if [[ $NON_INTERACTIVE_INSTALL == "y" ]]; then
		# Resolve public IP if ENDPOINT not set
		if [[ -z $ENDPOINT ]]; then
			ENDPOINT=$(resolvePublicIP)
		fi

		# Log non-interactive mode and parameters
		log_info "=== OpenVPN Non-Interactive Install ==="
		log_info "Running in non-interactive mode with the following settings:"
		log_info "  ENDPOINT=$ENDPOINT"
		log_info "  ENDPOINT_TYPE=$ENDPOINT_TYPE"
		log_info "  CLIENT_IPV4=$CLIENT_IPV4"
		log_info "  CLIENT_IPV6=$CLIENT_IPV6"
		log_info "  VPN_SUBNET_IPV4=$VPN_SUBNET_IPV4"
		log_info "  VPN_SUBNET_IPV6=$VPN_SUBNET_IPV6"
		log_info "  PORT=$PORT"
		log_info "  PROTOCOL=$PROTOCOL"
		log_info "  DNS=$DNS"
		[[ -n $MTU ]] && log_info "  MTU=$MTU"
		log_info "  MULTI_CLIENT=$MULTI_CLIENT"
		log_info "  CLIENT=$CLIENT"
		log_info "  CLIENT_CERT_DURATION_DAYS=$CLIENT_CERT_DURATION_DAYS"
		log_info "  SERVER_CERT_DURATION_DAYS=$SERVER_CERT_DURATION_DAYS"
	fi

	# Get the "public" interface from the default route
	NIC=$(ip -4 route ls | grep default | grep -Po '(?<=dev )(\S+)' | head -1)
	if [[ -z $NIC ]] && [[ $CLIENT_IPV6 == 'y' ]]; then
		NIC=$(ip -6 route show default | sed -ne 's/^default .* dev \([^ ]*\) .*$/\1/p')
	fi

	# $NIC can not be empty for script rm-openvpn-rules.sh
	if [[ -z $NIC ]]; then
		log_warn "Could not detect public interface."
		log_info "This needs for setup MASQUERADE."
		until [[ $CONTINUE =~ (y|n) ]]; do
			read -rp "Continue? [y/n]: " -e CONTINUE
		done
		if [[ $CONTINUE == "n" ]]; then
			exit 1
		fi
	fi

	# If OpenVPN isn't installed yet, install it. This script is more-or-less
	# idempotent on multiple runs, but will only install OpenVPN from upstream
	# the first time.
	if [[ ! -e /etc/openvpn/server/server.conf ]]; then
		log_header "Installing OpenVPN"

		# Setup official OpenVPN repository for latest versions
		installOpenVPNRepo

		log_info "Installing OpenVPN and dependencies..."
		if [[ $OS =~ (debian|ubuntu) ]]; then
			run_cmd_fatal "Installing OpenVPN" apt-get install -y openvpn iptables openssl curl ca-certificates tar dnsutils
		elif [[ $OS == 'centos' ]]; then
			run_cmd_fatal "Installing OpenVPN" yum install -y openvpn iptables openssl ca-certificates curl tar bind-utils 'policycoreutils-python*'
		elif [[ $OS == 'oracle' ]]; then
			run_cmd_fatal "Installing OpenVPN" yum install -y openvpn iptables openssl ca-certificates curl tar bind-utils policycoreutils-python-utils
		elif [[ $OS == 'amzn2023' ]]; then
			run_cmd_fatal "Installing OpenVPN" dnf install -y openvpn iptables openssl ca-certificates curl tar bind-utils
		elif [[ $OS == 'fedora' ]]; then
			run_cmd_fatal "Installing OpenVPN" dnf install -y openvpn iptables openssl ca-certificates curl tar bind-utils policycoreutils-python-utils
		elif [[ $OS == 'opensuse' ]]; then
			run_cmd_fatal "Installing OpenVPN" zypper install -y openvpn iptables openssl ca-certificates curl tar bind-utils
		elif [[ $OS == 'arch' ]]; then
			run_cmd_fatal "Installing OpenVPN" pacman --needed --noconfirm -Syu openvpn iptables openssl ca-certificates curl tar bind
		fi

		# Verify ChaCha20-Poly1305 compatibility if selected
		if [[ $CIPHER == "CHACHA20-POLY1305" ]] || [[ $CC_CIPHER =~ CHACHA20 ]]; then
			local installed_version
			installed_version=$(openvpn --version 2>/dev/null | head -1 | awk '{print $2}')
			if ! openvpnVersionAtLeast "2.5"; then
				log_fatal "ChaCha20-Poly1305 requires OpenVPN 2.5 or later. Installed version: $installed_version"
			fi
			log_info "OpenVPN version supports ChaCha20-Poly1305"
		fi

		# Check Data Channel Offload (DCO) availability
		if isDCOAvailable; then
			# Check if configuration is DCO-compatible (udp or udp6)
			if [[ $PROTOCOL =~ ^udp ]] && [[ $CIPHER =~ (GCM|CHACHA20-POLY1305) ]]; then
				log_info "Data Channel Offload (DCO) is available and will be used for improved performance"
			else
				log_info "Data Channel Offload (DCO) is available but not enabled (requires UDP, AEAD cipher)"
			fi
		else
			log_info "Data Channel Offload (DCO) is not available (requires OpenVPN 2.6+ and kernel support)"
		fi

		# Create the server directory (OpenVPN 2.4+ directory structure)
		run_cmd_fatal "Creating server directory" mkdir -p /etc/openvpn/server
	fi

	# Determine which user/group OpenVPN should run as
	# - Fedora/RHEL/Amazon create 'openvpn' user with 'openvpn' group
	# - Arch creates 'openvpn' user with 'network' group
	# - Debian/Ubuntu/openSUSE don't create a dedicated user, use 'nobody'
	#
	# Also check if the systemd service file already handles user/group switching.
	# If so, we shouldn't add user/group to config (would cause double privilege drop).
	SYSTEMD_HANDLES_USER=false
	for service_file in /usr/lib/systemd/system/openvpn-server@.service /lib/systemd/system/openvpn-server@.service; do
		if [[ -f "$service_file" ]] && grep -q "^User=" "$service_file"; then
			SYSTEMD_HANDLES_USER=true
			break
		fi
	done

	if id openvpn &>/dev/null; then
		OPENVPN_USER=openvpn
		# Get the openvpn user's primary group (e.g., 'openvpn' on Fedora, 'network' on Arch)
		OPENVPN_GROUP=$(id -gn openvpn 2>/dev/null || echo openvpn)
	else
		OPENVPN_USER=nobody
		if grep -qs "^nogroup:" /etc/group; then
			OPENVPN_GROUP=nogroup
		else
			OPENVPN_GROUP=nobody
		fi
	fi

	# Install the latest version of easy-rsa from source, if not already installed.
	if [[ ! -d /etc/openvpn/server/easy-rsa/ ]]; then
		run_cmd_fatal "Downloading Easy-RSA v${EASYRSA_VERSION}" curl -fL --retry 5 -o ~/easy-rsa.tgz "https://github.com/OpenVPN/easy-rsa/releases/download/v${EASYRSA_VERSION}/EasyRSA-${EASYRSA_VERSION}.tgz"
		log_info "Verifying Easy-RSA checksum..."
		CHECKSUM_OUTPUT=$(echo "${EASYRSA_SHA256}  $HOME/easy-rsa.tgz" | sha256sum -c 2>&1) || {
			_log_to_file "[CHECKSUM] $CHECKSUM_OUTPUT"
			run_cmd "Cleaning up failed download" rm -f ~/easy-rsa.tgz
			log_fatal "SHA256 checksum verification failed for easy-rsa download!"
		}
		_log_to_file "[CHECKSUM] $CHECKSUM_OUTPUT"
		run_cmd_fatal "Creating Easy-RSA directory" mkdir -p /etc/openvpn/server/easy-rsa
		run_cmd_fatal "Extracting Easy-RSA" tar xzf ~/easy-rsa.tgz --strip-components=1 --no-same-owner --directory /etc/openvpn/server/easy-rsa
		run_cmd "Cleaning up archive" rm -f ~/easy-rsa.tgz

		cd /etc/openvpn/server/easy-rsa/ || return
		case $CERT_TYPE in
		ecdsa)
			echo "set_var EASYRSA_ALGO ec" >vars
			echo "set_var EASYRSA_CURVE $CERT_CURVE" >>vars
			;;
		rsa)
			echo "set_var EASYRSA_KEY_SIZE $RSA_KEY_SIZE" >vars
			;;
		esac

		# Generate a random, alphanumeric identifier of 16 characters for CN and one for server name
		# Note: 2>/dev/null suppresses "Broken pipe" errors from fold when head exits early
		SERVER_CN="cn_$(head /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 2>/dev/null | head -n 1)"
		echo "$SERVER_CN" >SERVER_CN_GENERATED
		SERVER_NAME="server_$(head /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 16 2>/dev/null | head -n 1)"
		echo "$SERVER_NAME" >SERVER_NAME_GENERATED

		# Create the PKI, set up the CA, the DH params and the server certificate
		log_info "Initializing PKI..."
		run_cmd_fatal "Initializing PKI" ./easyrsa init-pki
		export EASYRSA_CA_EXPIRE=$DEFAULT_CERT_VALIDITY_DURATION_DAYS
		log_info "Building CA..."
		run_cmd_fatal "Building CA" ./easyrsa --batch --req-cn="$SERVER_CN" build-ca nopass

		export EASYRSA_CERT_EXPIRE=${SERVER_CERT_DURATION_DAYS:-$DEFAULT_CERT_VALIDITY_DURATION_DAYS}
		log_info "Building server certificate..."
		run_cmd_fatal "Building server certificate" ./easyrsa --batch build-server-full "$SERVER_NAME" nopass
		export EASYRSA_CRL_DAYS=$DEFAULT_CRL_VALIDITY_DURATION_DAYS
		run_cmd_fatal "Generating CRL" ./easyrsa gen-crl

		log_info "Generating TLS key..."
		case $TLS_SIG in
		crypt-v2)
			# Generate tls-crypt-v2 server key
			run_cmd_fatal "Generating tls-crypt-v2 server key" openvpn --genkey tls-crypt-v2-server /etc/openvpn/server/tls-crypt-v2.key
			;;
		crypt)
			# Generate tls-crypt key
			run_cmd_fatal "Generating tls-crypt key" openvpn --genkey secret /etc/openvpn/server/tls-crypt.key
			;;
		auth)
			# Generate tls-auth key
			run_cmd_fatal "Generating tls-auth key" openvpn --genkey secret /etc/openvpn/server/tls-auth.key
			;;
		esac
	else
		# If easy-rsa is already installed, grab the generated SERVER_NAME
		# for client configs
		cd /etc/openvpn/server/easy-rsa/ || return
		SERVER_NAME=$(cat SERVER_NAME_GENERATED)
	fi

	# Move all the generated files
	log_info "Copying certificates..."
	run_cmd_fatal "Copying certificates to /etc/openvpn/server" cp pki/ca.crt pki/private/ca.key "pki/issued/$SERVER_NAME.crt" "pki/private/$SERVER_NAME.key" /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server

	# Make cert revocation list readable for non-root
	run_cmd "Setting CRL permissions" chmod 644 /etc/openvpn/server/crl.pem

	# Generate server.conf
	log_info "Generating server configuration..."
	echo "port $PORT" >/etc/openvpn/server/server.conf

	# Protocol selection: use proto6 variants if endpoint is IPv6
	if [[ $ENDPOINT_TYPE == "6" ]]; then
		echo "proto ${PROTOCOL}6" >>/etc/openvpn/server/server.conf
	else
		echo "proto $PROTOCOL" >>/etc/openvpn/server/server.conf
	fi

	if [[ $MULTI_CLIENT == "y" ]]; then
		echo "duplicate-cn" >>/etc/openvpn/server/server.conf
	fi

	echo "dev tun" >>/etc/openvpn/server/server.conf
	# Only add user/group if systemd doesn't handle it (avoids double privilege drop)
	if [[ $SYSTEMD_HANDLES_USER == "false" ]]; then
		echo "user $OPENVPN_USER
group $OPENVPN_GROUP" >>/etc/openvpn/server/server.conf
	fi
	echo "persist-key
persist-tun
keepalive 10 120
topology subnet" >>/etc/openvpn/server/server.conf

	# IPv4 server directive - always assign IPv4 to clients for proper routing
	# Even for IPv6-only mode, we need IPv4 addresses so redirect-gateway def1 can block IPv4 leaks
	echo "server $VPN_SUBNET_IPV4 255.255.255.0" >>/etc/openvpn/server/server.conf

	# IPv6 server directive (only if clients get IPv6)
	if [[ $CLIENT_IPV6 == "y" ]]; then
		{
			echo "server-ipv6 ${VPN_SUBNET_IPV6}/112"
			echo "tun-ipv6"
			echo "push tun-ipv6"
		} >>/etc/openvpn/server/server.conf
	fi

	# ifconfig-pool-persist is incompatible with duplicate-cn
	if [[ $MULTI_CLIENT != "y" ]]; then
		echo "ifconfig-pool-persist ipp.txt" >>/etc/openvpn/server/server.conf
	fi

	# DNS resolvers
	case $DNS in
	system)
		# Locate the proper resolv.conf
		# Needed for systems running systemd-resolved
		if grep -q "127.0.0.53" "/etc/resolv.conf"; then
			RESOLVCONF='/run/systemd/resolve/resolv.conf'
		else
			RESOLVCONF='/etc/resolv.conf'
		fi
		# Obtain the resolvers from resolv.conf and use them for OpenVPN
		sed -ne 's/^nameserver[[:space:]]\+\([^[:space:]]\+\).*$/\1/p' $RESOLVCONF | while read -r line; do
			# Copy IPv4 resolvers if client has IPv4, or IPv6 resolvers if client has IPv6
			if [[ $line =~ ^[0-9.]*$ ]] && [[ $CLIENT_IPV4 == 'y' ]]; then
				echo "push \"dhcp-option DNS $line\"" >>/etc/openvpn/server/server.conf
			elif [[ $line =~ : ]] && [[ $CLIENT_IPV6 == 'y' ]]; then
				echo "push \"dhcp-option DNS $line\"" >>/etc/openvpn/server/server.conf
			fi
		done
		;;
	unbound)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo "push \"dhcp-option DNS $VPN_GATEWAY_IPV4\"" >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo "push \"dhcp-option DNS $VPN_GATEWAY_IPV6\"" >>/etc/openvpn/server/server.conf
		fi
		;;
	cloudflare)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 1.0.0.1"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 1.1.1.1"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2606:4700:4700::1001"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2606:4700:4700::1111"' >>/etc/openvpn/server/server.conf
		fi
		;;
	quad9)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 9.9.9.9"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 149.112.112.112"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2620:fe::fe"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2620:fe::9"' >>/etc/openvpn/server/server.conf
		fi
		;;
	quad9-uncensored)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 9.9.9.10"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 149.112.112.10"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2620:fe::10"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2620:fe::fe:10"' >>/etc/openvpn/server/server.conf
		fi
		;;
	fdn)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 80.67.169.40"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 80.67.169.12"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2001:910:800::40"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2001:910:800::12"' >>/etc/openvpn/server/server.conf
		fi
		;;
	dnswatch)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 84.200.69.80"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 84.200.70.40"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2001:1608:10:25::1c04:b12f"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2001:1608:10:25::9249:d69b"' >>/etc/openvpn/server/server.conf
		fi
		;;
	opendns)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 208.67.222.222"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 208.67.220.220"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2620:119:35::35"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2620:119:53::53"' >>/etc/openvpn/server/server.conf
		fi
		;;
	google)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 8.8.8.8"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 8.8.4.4"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2001:4860:4860::8888"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2001:4860:4860::8844"' >>/etc/openvpn/server/server.conf
		fi
		;;
	yandex)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 77.88.8.8"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 77.88.8.1"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2a02:6b8::feed:0ff"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2a02:6b8:0:1::feed:0ff"' >>/etc/openvpn/server/server.conf
		fi
		;;
	adguard)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 94.140.14.14"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 94.140.15.15"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2a10:50c0::ad1:ff"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2a10:50c0::ad2:ff"' >>/etc/openvpn/server/server.conf
		fi
		;;
	nextdns)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo 'push "dhcp-option DNS 45.90.28.167"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 45.90.30.167"' >>/etc/openvpn/server/server.conf
		fi
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo 'push "dhcp-option DNS 2a07:a8c0::"' >>/etc/openvpn/server/server.conf
			echo 'push "dhcp-option DNS 2a07:a8c1::"' >>/etc/openvpn/server/server.conf
		fi
		;;
	custom)
		echo "push \"dhcp-option DNS $DNS1\"" >>/etc/openvpn/server/server.conf
		if [[ $DNS2 != "" ]]; then
			echo "push \"dhcp-option DNS $DNS2\"" >>/etc/openvpn/server/server.conf
		fi
		;;
	esac

	# Redirect gateway settings - always redirect both IPv4 and IPv6 to prevent leaks
	# For IPv4: redirect-gateway def1 routes all IPv4 through VPN (or drops it if IPv4 not configured)
	# For IPv6: route-ipv6 + redirect-gateway ipv6 routes all IPv6, or block-ipv6 drops it
	echo 'push "redirect-gateway def1 bypass-dhcp"' >>/etc/openvpn/server/server.conf
	if [[ $CLIENT_IPV6 == "y" ]]; then
		echo 'push "route-ipv6 2000::/3"' >>/etc/openvpn/server/server.conf
		echo 'push "redirect-gateway ipv6"' >>/etc/openvpn/server/server.conf
	else
		# Block IPv6 on clients to prevent IPv6 leaks when VPN only handles IPv4
		echo 'push "block-ipv6"' >>/etc/openvpn/server/server.conf
	fi

	if [[ -n $MTU ]]; then
		echo "tun-mtu $MTU" >>/etc/openvpn/server/server.conf
	fi

	# Use ECDH key exchange (dh none) with tls-groups for curve negotiation
	echo "dh none" >>/etc/openvpn/server/server.conf
	echo "tls-groups $TLS_GROUPS" >>/etc/openvpn/server/server.conf

	case $TLS_SIG in
	crypt-v2)
		echo "tls-crypt-v2 tls-crypt-v2.key" >>/etc/openvpn/server/server.conf
		;;
	crypt)
		echo "tls-crypt tls-crypt.key" >>/etc/openvpn/server/server.conf
		;;
	auth)
		echo "tls-auth tls-auth.key 0" >>/etc/openvpn/server/server.conf
		;;
	esac

	echo "crl-verify crl.pem
ca ca.crt
cert $SERVER_NAME.crt
key $SERVER_NAME.key
auth $HMAC_ALG
cipher $CIPHER
ignore-unknown-option data-ciphers
data-ciphers $CIPHER
ncp-ciphers $CIPHER
tls-server
tls-version-min $TLS_VERSION_MIN
remote-cert-tls client
tls-cipher $CC_CIPHER
tls-ciphersuites $TLS13_CIPHERSUITES
client-config-dir ccd
status /var/log/openvpn/status.log
verb 3" >>/etc/openvpn/server/server.conf

	# Create client-config-dir dir
	run_cmd_fatal "Creating client config directory" mkdir -p /etc/openvpn/server/ccd
	# Create log dir
	run_cmd_fatal "Creating log directory" mkdir -p /var/log/openvpn

	# On distros that use a dedicated OpenVPN user (not "nobody"), e.g., Fedora, RHEL, Arch,
	# set ownership so OpenVPN can read config/certs and write to log directory
	if [[ $OPENVPN_USER != "nobody" ]]; then
		log_info "Setting ownership for OpenVPN user..."
		chown -R "$OPENVPN_USER:$OPENVPN_GROUP" /etc/openvpn/server
		chown "$OPENVPN_USER:$OPENVPN_GROUP" /var/log/openvpn
	fi

	# Enable routing
	log_info "Enabling IP forwarding..."
	run_cmd_fatal "Creating sysctl.d directory" mkdir -p /etc/sysctl.d

	# Enable IPv4 forwarding if clients get IPv4
	if [[ $CLIENT_IPV4 == 'y' ]]; then
		echo 'net.ipv4.ip_forward=1' >/etc/sysctl.d/99-openvpn.conf
	else
		echo '# IPv4 forwarding not needed (no IPv4 clients)' >/etc/sysctl.d/99-openvpn.conf
	fi
	# Enable IPv6 forwarding if clients get IPv6
	if [[ $CLIENT_IPV6 == 'y' ]]; then
		echo 'net.ipv6.conf.all.forwarding=1' >>/etc/sysctl.d/99-openvpn.conf
	fi
	# Apply sysctl rules
	run_cmd "Applying sysctl rules" sysctl --system

	# If SELinux is enabled and a custom port was selected, we need this
	if hash sestatus 2>/dev/null; then
		if sestatus | grep "Current mode" | grep -qs "enforcing"; then
			if [[ $PORT != '1194' ]]; then
				# Strip "6" suffix from protocol (semanage expects "udp" or "tcp", not "udp6"/"tcp6")
				SELINUX_PROTOCOL="${PROTOCOL%6}"
				run_cmd "Configuring SELinux port" semanage port -a -t openvpn_port_t -p "$SELINUX_PROTOCOL" "$PORT"
			fi
		fi
	fi

	# Finally, restart and enable OpenVPN
	# OpenVPN 2.4+ uses openvpn-server@.service with config in /etc/openvpn/server/
	log_info "Configuring OpenVPN service..."

	# Find the service file (location and name vary by distro)
	# Modern distros: openvpn-server@.service in /usr/lib/systemd/system/ or /lib/systemd/system/
	# openSUSE: openvpn@.service (old-style) that we need to adapt
	if [[ -f /usr/lib/systemd/system/openvpn-server@.service ]]; then
		SERVICE_SOURCE="/usr/lib/systemd/system/openvpn-server@.service"
	elif [[ -f /lib/systemd/system/openvpn-server@.service ]]; then
		SERVICE_SOURCE="/lib/systemd/system/openvpn-server@.service"
	elif [[ -f /usr/lib/systemd/system/openvpn@.service ]]; then
		# openSUSE uses old-style service, we'll create our own openvpn-server@.service
		SERVICE_SOURCE="/usr/lib/systemd/system/openvpn@.service"
	elif [[ -f /lib/systemd/system/openvpn@.service ]]; then
		SERVICE_SOURCE="/lib/systemd/system/openvpn@.service"
	else
		log_fatal "Could not find openvpn-server@.service or openvpn@.service file"
	fi

	# Don't modify package-provided service, copy to /etc/systemd/system/
	run_cmd_fatal "Copying OpenVPN service file" cp "$SERVICE_SOURCE" /etc/systemd/system/openvpn-server@.service

	# Workaround to fix OpenVPN service on OpenVZ
	run_cmd "Patching service file (LimitNPROC)" sed -i 's|LimitNPROC|#LimitNPROC|' /etc/systemd/system/openvpn-server@.service

	# Ensure the service uses /etc/openvpn/server/ as working directory
	# This is needed for openSUSE which uses old-style paths by default
	if grep -q "cd /etc/openvpn/" /etc/systemd/system/openvpn-server@.service; then
		run_cmd "Patching service file (paths)" sed -i 's|/etc/openvpn/|/etc/openvpn/server/|g' /etc/systemd/system/openvpn-server@.service
	fi

	run_cmd "Reloading systemd" systemctl daemon-reload
	run_cmd "Enabling OpenVPN service" systemctl enable openvpn-server@server
	run_cmd "Starting OpenVPN service" systemctl restart openvpn-server@server

	if [[ $DNS == "unbound" ]]; then
		installUnbound
	fi

	# Configure firewall rules
	# Use source-based rules for VPN traffic (works reliably regardless of which tun interface OpenVPN uses)
	log_info "Configuring firewall rules..."

	if systemctl is-active --quiet firewalld; then
		# Use firewalld native commands for systems with firewalld active
		log_info "firewalld detected, using firewall-cmd..."
		run_cmd "Adding OpenVPN port to firewalld" firewall-cmd --permanent --add-port="$PORT/$PROTOCOL"
		run_cmd "Adding masquerade to firewalld" firewall-cmd --permanent --add-masquerade

		# Add rich rules for VPN traffic (source-based only, as firewalld doesn't reliably
		# support interface patterns with direct rules when using nftables backend)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			run_cmd "Adding IPv4 VPN subnet rule" firewall-cmd --permanent --add-rich-rule="rule family=\"ipv4\" source address=\"$VPN_SUBNET_IPV4/24\" accept"
		fi

		if [[ $CLIENT_IPV6 == 'y' ]]; then
			run_cmd "Adding IPv6 VPN subnet rule" firewall-cmd --permanent --add-rich-rule="rule family=\"ipv6\" source address=\"${VPN_SUBNET_IPV6}/112\" accept"
		fi

		run_cmd "Reloading firewalld" firewall-cmd --reload
	elif systemctl is-active --quiet nftables; then
		# Use nftables native rules for systems with nftables active
		log_info "nftables detected, configuring nftables rules..."
		run_cmd_fatal "Creating nftables directory" mkdir -p /etc/nftables

		# Create nftables rules file
		{
			echo "table inet openvpn {"
			echo "	chain input {"
			echo "		type filter hook input priority 0; policy accept;"
			if [[ $CLIENT_IPV4 == 'y' ]]; then
				echo "		iifname \"tun*\" ip saddr $VPN_SUBNET_IPV4/24 accept"
			fi
			if [[ $CLIENT_IPV6 == 'y' ]]; then
				echo "		iifname \"tun*\" ip6 saddr ${VPN_SUBNET_IPV6}/112 accept"
			fi
			echo "		iifname \"$NIC\" $PROTOCOL dport $PORT accept"
			echo "	}"
			echo ""
			echo "	chain forward {"
			echo "		type filter hook forward priority 0; policy accept;"
			if [[ $CLIENT_IPV4 == 'y' ]]; then
				echo "		iifname \"tun*\" ip saddr $VPN_SUBNET_IPV4/24 accept"
				echo "		oifname \"tun*\" ip daddr $VPN_SUBNET_IPV4/24 accept"
			fi
			if [[ $CLIENT_IPV6 == 'y' ]]; then
				echo "		iifname \"tun*\" ip6 saddr ${VPN_SUBNET_IPV6}/112 accept"
				echo "		oifname \"tun*\" ip6 daddr ${VPN_SUBNET_IPV6}/112 accept"
			fi
			echo "	}"
			echo "}"
		} >/etc/nftables/openvpn.nft

		# IPv4 NAT rules (only if clients get IPv4)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo "
table ip openvpn-nat {
	chain postrouting {
		type nat hook postrouting priority 100; policy accept;
		ip saddr $VPN_SUBNET_IPV4/24 oifname \"$NIC\" masquerade
	}
}" >>/etc/nftables/openvpn.nft
		fi

		# IPv6 NAT rules (only if clients get IPv6)
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo "
table ip6 openvpn-nat {
	chain postrouting {
		type nat hook postrouting priority 100; policy accept;
		ip6 saddr ${VPN_SUBNET_IPV6}/112 oifname \"$NIC\" masquerade
	}
}" >>/etc/nftables/openvpn.nft
		fi

		# Add include to nftables.conf if not already present
		if ! grep -q 'include.*/etc/nftables/openvpn.nft' /etc/nftables.conf; then
			run_cmd "Adding include to nftables.conf" sh -c 'echo "include \"/etc/nftables/openvpn.nft\"" >> /etc/nftables.conf'
		fi

		# Reload nftables to apply rules
		run_cmd "Reloading nftables" systemctl reload nftables
	else
		# Use iptables for systems without firewalld or nftables
		run_cmd_fatal "Creating iptables directory" mkdir -p /etc/iptables

		# Script to add rules
		echo "#!/bin/sh" >/etc/iptables/add-openvpn-rules.sh

		# IPv4 rules (only if clients get IPv4)
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo "iptables -t nat -I POSTROUTING 1 -s $VPN_SUBNET_IPV4/24 -o $NIC -j MASQUERADE
iptables -I INPUT 1 -i tun+ -s $VPN_SUBNET_IPV4/24 -j ACCEPT
iptables -I FORWARD 1 -i tun+ -s $VPN_SUBNET_IPV4/24 -j ACCEPT
iptables -I FORWARD 1 -o tun+ -d $VPN_SUBNET_IPV4/24 -j ACCEPT
iptables -I INPUT 1 -i $NIC -p $PROTOCOL --dport $PORT -j ACCEPT" >>/etc/iptables/add-openvpn-rules.sh
		fi

		# IPv6 rules (only if clients get IPv6)
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo "ip6tables -t nat -I POSTROUTING 1 -s ${VPN_SUBNET_IPV6}/112 -o $NIC -j MASQUERADE
ip6tables -I INPUT 1 -i tun+ -s ${VPN_SUBNET_IPV6}/112 -j ACCEPT
ip6tables -I FORWARD 1 -i tun+ -s ${VPN_SUBNET_IPV6}/112 -j ACCEPT
ip6tables -I FORWARD 1 -o tun+ -d ${VPN_SUBNET_IPV6}/112 -j ACCEPT
ip6tables -I INPUT 1 -i $NIC -p $PROTOCOL --dport $PORT -j ACCEPT" >>/etc/iptables/add-openvpn-rules.sh
		fi

		# Script to remove rules
		echo "#!/bin/sh" >/etc/iptables/rm-openvpn-rules.sh

		# IPv4 removal rules
		if [[ $CLIENT_IPV4 == 'y' ]]; then
			echo "iptables -t nat -D POSTROUTING -s $VPN_SUBNET_IPV4/24 -o $NIC -j MASQUERADE
iptables -D INPUT -i tun+ -s $VPN_SUBNET_IPV4/24 -j ACCEPT
iptables -D FORWARD -i tun+ -s $VPN_SUBNET_IPV4/24 -j ACCEPT
iptables -D FORWARD -o tun+ -d $VPN_SUBNET_IPV4/24 -j ACCEPT
iptables -D INPUT -i $NIC -p $PROTOCOL --dport $PORT -j ACCEPT" >>/etc/iptables/rm-openvpn-rules.sh
		fi

		# IPv6 removal rules
		if [[ $CLIENT_IPV6 == 'y' ]]; then
			echo "ip6tables -t nat -D POSTROUTING -s ${VPN_SUBNET_IPV6}/112 -o $NIC -j MASQUERADE
ip6tables -D INPUT -i tun+ -s ${VPN_SUBNET_IPV6}/112 -j ACCEPT
ip6tables -D FORWARD -i tun+ -s ${VPN_SUBNET_IPV6}/112 -j ACCEPT
ip6tables -D FORWARD -o tun+ -d ${VPN_SUBNET_IPV6}/112 -j ACCEPT
ip6tables -D INPUT -i $NIC -p $PROTOCOL --dport $PORT -j ACCEPT" >>/etc/iptables/rm-openvpn-rules.sh
		fi

		run_cmd "Making add-openvpn-rules.sh executable" chmod +x /etc/iptables/add-openvpn-rules.sh
		run_cmd "Making rm-openvpn-rules.sh executable" chmod +x /etc/iptables/rm-openvpn-rules.sh

		# Handle the rules via a systemd script
		echo "[Unit]
Description=iptables rules for OpenVPN
After=firewalld.service
Before=network-online.target
Wants=network-online.target

[Service]
Type=oneshot
ExecStart=/etc/iptables/add-openvpn-rules.sh
ExecStop=/etc/iptables/rm-openvpn-rules.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target" >/etc/systemd/system/iptables-openvpn.service

		# Enable service and apply rules
		run_cmd "Reloading systemd" systemctl daemon-reload
		run_cmd "Enabling iptables service" systemctl enable iptables-openvpn
		run_cmd "Starting iptables service" systemctl start iptables-openvpn
	fi

	# If the server is behind a NAT, use the correct IP address for the clients to connect to
	if [[ $ENDPOINT != "" ]]; then
		IP=$ENDPOINT
	fi

	# client-template.txt is created so we have a template to add further users later
	log_info "Creating client template..."
	echo "client" >/etc/openvpn/server/client-template.txt
	if [[ $PROTOCOL == 'udp' ]]; then
		echo "proto udp" >>/etc/openvpn/server/client-template.txt
		echo "explicit-exit-notify" >>/etc/openvpn/server/client-template.txt
	elif [[ $PROTOCOL == 'udp6' ]]; then
		echo "proto udp6" >>/etc/openvpn/server/client-template.txt
		echo "explicit-exit-notify" >>/etc/openvpn/server/client-template.txt
	elif [[ $PROTOCOL == 'tcp' ]]; then
		echo "proto tcp-client" >>/etc/openvpn/server/client-template.txt
	elif [[ $PROTOCOL == 'tcp6' ]]; then
		echo "proto tcp6-client" >>/etc/openvpn/server/client-template.txt
	fi
	echo "remote $IP $PORT
dev tun
resolv-retry infinite
nobind
persist-key
persist-tun
remote-cert-tls server
verify-x509-name $SERVER_NAME name
auth $HMAC_ALG
auth-nocache
cipher $CIPHER
ignore-unknown-option data-ciphers
data-ciphers $CIPHER
ncp-ciphers $CIPHER
tls-client
tls-version-min $TLS_VERSION_MIN
tls-cipher $CC_CIPHER
tls-ciphersuites $TLS13_CIPHERSUITES
ignore-unknown-option block-outside-dns
setenv opt block-outside-dns # Prevent Windows 10 DNS leak
verb 3" >>/etc/openvpn/server/client-template.txt

	if [[ -n $MTU ]]; then
		echo "tun-mtu $MTU" >>/etc/openvpn/server/client-template.txt
	fi

	# Generate the custom client.ovpn
	if [[ $NEW_CLIENT == "n" ]]; then
		log_info "No clients added. To add clients, simply run the script again."
	else
		log_info "Generating first client certificate..."
		newClient
		log_success "If you want to add more clients, you simply need to run this script another time!"
	fi
}

# Helper function to get the home directory for storing client configs
function getHomeDir() {
	local client="$1"
	if [ -d "/home/${client}" ]; then
		echo "/home/${client}"
	elif [ "${SUDO_USER}" ]; then
		if [ "${SUDO_USER}" == "root" ]; then
			echo "/root"
		else
			echo "/home/${SUDO_USER}"
		fi
	else
		echo "/root"
	fi
}

# Helper function to get the owner of a client config file (if client matches a system user)
function getClientOwner() {
	local client="$1"
	# Check if client name corresponds to an existing system user with a home directory
	if id "$client" &>/dev/null && [ -d "/home/${client}" ]; then
		echo "${client}"
	elif [ "${SUDO_USER}" ] && [ "${SUDO_USER}" != "root" ]; then
		echo "${SUDO_USER}"
	fi
}

# Helper function to set proper ownership and permissions on client config file
function setClientConfigPermissions() {
	local filepath="$1"
	local owner="$2"

	if [[ -n "$owner" ]]; then
		local owner_group
		owner_group=$(id -gn "$owner")
		chmod go-rw "$filepath"
		chown "$owner:$owner_group" "$filepath"
	fi
}

# Helper function to write client config file with proper path and permissions
# Usage: writeClientConfig <client_name>
# Uses CLIENT_FILEPATH env var if set, otherwise defaults to home directory
# Side effects: sets GENERATED_CONFIG_PATH global variable with the final path
function writeClientConfig() {
	local client="$1"
	local clientFilePath

	# Determine output file path
	if [[ -n "$CLIENT_FILEPATH" ]]; then
		clientFilePath="$CLIENT_FILEPATH"
		# Ensure parent directory exists for custom paths
		local parentDir
		parentDir=$(dirname "$clientFilePath")
		if [[ ! -d "$parentDir" ]]; then
			run_cmd_fatal "Creating directory $parentDir" mkdir -p "$parentDir"
		fi
	else
		local homeDir
		homeDir=$(getHomeDir "$client")
		clientFilePath="$homeDir/$client.ovpn"
	fi

	# Generate the .ovpn config file
	generateClientConfig "$client" "$clientFilePath"

	# Set proper ownership and permissions if client matches a system user
	local clientOwner
	clientOwner=$(getClientOwner "$client")
	setClientConfigPermissions "$clientFilePath" "$clientOwner"

	# Export path for caller to use
	GENERATED_CONFIG_PATH="$clientFilePath"
}

# Helper function to regenerate the CRL after certificate changes
function regenerateCRL() {
	export EASYRSA_CRL_DAYS=$DEFAULT_CRL_VALIDITY_DURATION_DAYS
	run_cmd_fatal "Regenerating CRL" ./easyrsa gen-crl
	run_cmd "Removing old CRL" rm -f /etc/openvpn/server/crl.pem
	run_cmd_fatal "Copying new CRL" cp /etc/openvpn/server/easy-rsa/pki/crl.pem /etc/openvpn/server/crl.pem
	run_cmd "Setting CRL permissions" chmod 644 /etc/openvpn/server/crl.pem
}

# Helper function to generate .ovpn client config file
# Usage: generateClientConfig <client_name> <filepath>
function generateClientConfig() {
	local client="$1"
	local filepath="$2"

	# Determine if we use tls-crypt-v2, tls-crypt, or tls-auth
	local tls_sig=""
	if grep -qs "^tls-crypt-v2" /etc/openvpn/server/server.conf; then
		tls_sig="1"
	elif grep -qs "^tls-crypt" /etc/openvpn/server/server.conf; then
		tls_sig="2"
	elif grep -qs "^tls-auth" /etc/openvpn/server/server.conf; then
		tls_sig="3"
	fi

	# Generate the custom client.ovpn
	run_cmd "Creating client config" cp /etc/openvpn/server/client-template.txt "$filepath"
	{
		echo "<ca>"
		cat "/etc/openvpn/server/easy-rsa/pki/ca.crt"
		echo "</ca>"

		echo "<cert>"
		awk '/BEGIN/,/END CERTIFICATE/' "/etc/openvpn/server/easy-rsa/pki/issued/$client.crt"
		echo "</cert>"

		echo "<key>"
		cat "/etc/openvpn/server/easy-rsa/pki/private/$client.key"
		echo "</key>"

		case $tls_sig in
		1)
			# Generate per-client tls-crypt-v2 key in /etc/openvpn/server/
			# Using /tmp would fail on Ubuntu 25.04+ due to AppArmor restrictions
			tls_crypt_v2_tmpfile=$(mktemp /etc/openvpn/server/tls-crypt-v2-client.XXXXXX)
			if [[ -z "$tls_crypt_v2_tmpfile" ]] || [[ ! -f "$tls_crypt_v2_tmpfile" ]]; then
				log_error "Failed to create temporary file for tls-crypt-v2 client key"
				exit 1
			fi
			if ! openvpn --tls-crypt-v2 /etc/openvpn/server/tls-crypt-v2.key \
				--genkey tls-crypt-v2-client "$tls_crypt_v2_tmpfile"; then
				rm -f "$tls_crypt_v2_tmpfile"
				log_error "Failed to generate tls-crypt-v2 client key"
				exit 1
			fi
			echo "<tls-crypt-v2>"
			cat "$tls_crypt_v2_tmpfile"
			echo "</tls-crypt-v2>"
			rm -f "$tls_crypt_v2_tmpfile"
			;;
		2)
			echo "<tls-crypt>"
			cat /etc/openvpn/server/tls-crypt.key
			echo "</tls-crypt>"
			;;
		3)
			echo "key-direction 1"
			echo "<tls-auth>"
			cat /etc/openvpn/server/tls-auth.key
			echo "</tls-auth>"
			;;
		esac
	} >>"$filepath"
}

# Helper function to list valid clients and select one
# Arguments: show_expiry (optional, "true" to show expiry info)
# Sets global variables:
#   CLIENT - the selected client name
#   CLIENTNUMBER - the selected client number (1-based index)
#   NUMBEROFCLIENTS - total count of valid clients
function selectClient() {
	local show_expiry="${1:-false}"
	local client_number

	NUMBEROFCLIENTS=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -c "^V")
	if [[ $NUMBEROFCLIENTS == '0' ]]; then
		log_fatal "You have no existing clients!"
	fi

	# If CLIENT is set, validate it exists as a valid client
	if [[ -n $CLIENT ]]; then
		if tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | grep -qx "$CLIENT"; then
			return
		else
			log_fatal "Client '$CLIENT' not found or not valid"
		fi
	fi

	if [[ $show_expiry == "true" ]]; then
		local i=1
		while read -r client; do
			local client_cert="/etc/openvpn/server/easy-rsa/pki/issued/$client.crt"
			local days
			days=$(getDaysUntilExpiry "$client_cert")
			local expiry
			expiry=$(formatExpiry "$days")
			echo "     $i) $client $expiry"
			((i++))
		done < <(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2)
	else
		tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | nl -s ') '
	fi

	until [[ ${CLIENTNUMBER:-$client_number} -ge 1 && ${CLIENTNUMBER:-$client_number} -le $NUMBEROFCLIENTS ]]; do
		if [[ $NUMBEROFCLIENTS == '1' ]]; then
			read -rp "Select one client [1]: " client_number
		else
			read -rp "Select one client [1-$NUMBEROFCLIENTS]: " client_number
		fi
	done
	CLIENTNUMBER="${CLIENTNUMBER:-$client_number}"
	CLIENT=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep "^V" | cut -d '=' -f 2 | sed -n "$CLIENTNUMBER"p)
}

# Escape a string for JSON output
function json_escape() {
	local str="$1"
	# Escape backslashes first, then quotes, then control characters
	str="${str//\\/\\\\}"
	str="${str//\"/\\\"}"
	str="${str//$'\n'/\\n}"
	str="${str//$'\r'/\\r}"
	str="${str//$'\t'/\\t}"
	printf '%s' "$str"
}

function listClients() {
	local index_file="/etc/openvpn/server/easy-rsa/pki/index.txt"
	local cert_dir="/etc/openvpn/server/easy-rsa/pki/issued"
	local number_of_clients
	local format="${OUTPUT_FORMAT:-table}"

	# Exclude server certificates (CN starting with server_)
	number_of_clients=$(tail -n +2 "$index_file" | grep "^[VR]" | grep -cv "/CN=server_")

	if [[ $number_of_clients == '0' ]]; then
		if [[ $format == "json" ]]; then
			echo '{"clients":[]}'
		else
			log_warn "You have no existing client certificates!"
		fi
		return
	fi

	# Collect client data
	local clients_data=()
	while read -r line; do
		local status="${line:0:1}"
		local client_name
		client_name=$(echo "$line" | sed 's/.*\/CN=//')

		local status_text
		if [[ "$status" == "V" ]]; then
			status_text="valid"
		elif [[ "$status" == "R" ]]; then
			status_text="revoked"
		else
			status_text="unknown"
		fi

		local cert_file="$cert_dir/$client_name.crt"
		local expiry_date="unknown"
		local days_remaining="null"

		if [[ -f "$cert_file" ]]; then
			local enddate
			enddate=$(openssl x509 -enddate -noout -in "$cert_file" 2>/dev/null | cut -d= -f2)

			if [[ -n "$enddate" ]]; then
				local expiry_epoch
				expiry_epoch=$(date -d "$enddate" +%s 2>/dev/null || date -j -f "%b %d %H:%M:%S %Y %Z" "$enddate" +%s 2>/dev/null)

				if [[ -n "$expiry_epoch" ]]; then
					expiry_date=$(date -d "@$expiry_epoch" +%Y-%m-%d 2>/dev/null || date -r "$expiry_epoch" +%Y-%m-%d 2>/dev/null)
					local now_epoch
					now_epoch=$(date +%s)
					days_remaining=$(((expiry_epoch - now_epoch) / 86400))
				fi
			fi
		fi

		clients_data+=("$client_name|$status_text|$expiry_date|$days_remaining")
	done < <(tail -n +2 "$index_file" | grep "^[VR]" | grep -v "/CN=server_" | sort -t$'\t' -k2)

	if [[ $format == "json" ]]; then
		# Output JSON
		echo '{"clients":['
		local first=true
		for client_entry in "${clients_data[@]}"; do
			IFS='|' read -r name status expiry days <<<"$client_entry"
			[[ $first == true ]] && first=false || printf ','
			# Handle null for days_remaining (no quotes for JSON null)
			local days_json
			if [[ "$days" == "null" || -z "$days" ]]; then
				days_json="null"
			else
				days_json="$days"
			fi
			printf '{"name":"%s","status":"%s","expiry":"%s","days_remaining":%s}\n' \
				"$(json_escape "$name")" "$(json_escape "$status")" "$(json_escape "$expiry")" "$days_json"
		done
		echo ']}'
	else
		# Output table
		log_header "Client Certificates"
		log_info "Found $number_of_clients client certificate(s)"
		log_menu ""
		printf "   %-25s %-10s %-12s %s\n" "Name" "Status" "Expiry" "Remaining"
		printf "   %-25s %-10s %-12s %s\n" "----" "------" "------" "---------"

		for client_entry in "${clients_data[@]}"; do
			IFS='|' read -r name status expiry days <<<"$client_entry"
			local relative
			if [[ $days == "null" ]]; then
				relative="unknown"
			elif [[ $days -lt 0 ]]; then
				relative="$((-days)) days ago"
			elif [[ $days -eq 0 ]]; then
				relative="today"
			elif [[ $days -eq 1 ]]; then
				relative="1 day"
			else
				relative="$days days"
			fi
			# Capitalize status for table display
			local status_display="${status^}"
			printf "   %-25s %-10s %-12s %s\n" "$name" "$status_display" "$expiry" "$relative"
		done
		log_menu ""
	fi
}

function formatBytes() {
	local bytes=$1
	# Validate input is numeric
	if ! [[ "$bytes" =~ ^[0-9]+$ ]]; then
		echo "N/A"
		return
	fi
	if [[ $bytes -ge 1073741824 ]]; then
		awk "BEGIN {printf \"%.1fG\", $bytes/1073741824}"
	elif [[ $bytes -ge 1048576 ]]; then
		awk "BEGIN {printf \"%.1fM\", $bytes/1048576}"
	elif [[ $bytes -ge 1024 ]]; then
		awk "BEGIN {printf \"%.1fK\", $bytes/1024}"
	else
		echo "${bytes}B"
	fi
}

function listConnectedClients() {
	local status_file="/var/log/openvpn/status.log"
	local format="${OUTPUT_FORMAT:-table}"

	if [[ ! -f "$status_file" ]]; then
		if [[ $format == "json" ]]; then
			echo '{"error":"Status file not found","clients":[]}'
		else
			log_warn "Status file not found: $status_file"
			log_info "Make sure OpenVPN is running."
		fi
		return
	fi

	local client_count
	client_count=$(grep -c "^CLIENT_LIST" "$status_file" 2>/dev/null) || client_count=0

	if [[ "$client_count" -eq 0 ]]; then
		if [[ $format == "json" ]]; then
			echo '{"clients":[]}'
		else
			log_header "Connected Clients"
			log_info "No clients currently connected."
			log_info "Note: Data refreshes every 60 seconds."
		fi
		return
	fi

	# Collect client data
	local clients_data=()
	while IFS=',' read -r _ name real_addr vpn_ip _ bytes_recv bytes_sent connected_since _; do
		clients_data+=("$name|$real_addr|$vpn_ip|$bytes_recv|$bytes_sent|$connected_since")
	done < <(grep "^CLIENT_LIST" "$status_file")

	if [[ $format == "json" ]]; then
		echo '{"clients":['
		local first=true
		for client_entry in "${clients_data[@]}"; do
			IFS='|' read -r name real_addr vpn_ip bytes_recv bytes_sent connected_since <<<"$client_entry"
			[[ $first == true ]] && first=false || printf ','
			printf '{"name":"%s","real_address":"%s","vpn_ip":"%s","bytes_received":%s,"bytes_sent":%s,"connected_since":"%s"}\n' \
				"$(json_escape "$name")" "$(json_escape "$real_addr")" "$(json_escape "$vpn_ip")" \
				"${bytes_recv:-0}" "${bytes_sent:-0}" "$(json_escape "$connected_since")"
		done
		echo ']}'
	else
		log_header "Connected Clients"
		log_info "Found $client_count connected client(s)"
		log_menu ""
		printf "   %-20s %-22s %-16s %-20s %s\n" "Name" "Real Address" "VPN IP" "Connected Since" "Transfer"
		printf "   %-20s %-22s %-16s %-20s %s\n" "----" "------------" "------" "---------------" "--------"

		for client_entry in "${clients_data[@]}"; do
			IFS='|' read -r name real_addr vpn_ip bytes_recv bytes_sent connected_since <<<"$client_entry"
			local recv_human sent_human
			recv_human=$(formatBytes "$bytes_recv")
			sent_human=$(formatBytes "$bytes_sent")
			local transfer="↓${recv_human} ↑${sent_human}"
			printf "   %-20s %-22s %-16s %-20s %s\n" "$name" "$real_addr" "$vpn_ip" "$connected_since" "$transfer"
		done
		log_menu ""
		log_info "Note: Data refreshes every 60 seconds."
	fi
}

function newClient() {
	log_header "New Client Setup"

	# Only prompt for client name if not already set or invalid
	if ! is_valid_client_name "$CLIENT"; then
		log_prompt "Tell me a name for the client."
		log_prompt "The name must consist of alphanumeric characters, underscores, or dashes (max $MAX_CLIENT_NAME_LENGTH characters)."
		until is_valid_client_name "$CLIENT"; do
			read -rp "Client name: " -e CLIENT
		done
	fi

	# Only prompt for cert duration if not already set
	if [[ -z $CLIENT_CERT_DURATION_DAYS ]] || ! [[ $CLIENT_CERT_DURATION_DAYS =~ ^[0-9]+$ ]] || [[ $CLIENT_CERT_DURATION_DAYS -lt 1 ]]; then
		log_menu ""
		log_prompt "How many days should the client certificate be valid for?"
		until [[ $CLIENT_CERT_DURATION_DAYS =~ ^[0-9]+$ ]] && [[ $CLIENT_CERT_DURATION_DAYS -ge 1 ]]; do
			read -rp "Certificate validity (days): " -e -i $DEFAULT_CERT_VALIDITY_DURATION_DAYS CLIENT_CERT_DURATION_DAYS
		done
	fi

	# Only prompt for password if not already set
	if ! [[ $PASS =~ ^[1-2]$ ]]; then
		log_menu ""
		log_prompt "Do you want to protect the configuration file with a password?"
		log_prompt "(e.g. encrypt the private key with a password)"
		log_menu "   1) Add a passwordless client"
		log_menu "   2) Use a password for the client"
		until [[ $PASS =~ ^[1-2]$ ]]; do
			read -rp "Select an option [1-2]: " -e -i 1 PASS
		done
	fi

	CLIENTEXISTS=$(tail -n +2 /etc/openvpn/server/easy-rsa/pki/index.txt | grep -E "^V" | grep -c -E "/CN=$CLIENT\$")
	if [[ $CLIENTEXISTS != '0' ]]; then
		log_error "The specified client CN was already found in easy-rsa, please choose another name."
		exit 1
	else
		cd /etc/openvpn/server/easy-rsa/ || return
		log_info "Generating client certificate..."
		export EASYRSA_CERT_EXPIRE=$CLIENT_CERT_DURATION_DAYS
		case $PASS in
		1)
			run_cmd_fatal "Building client certificate" ./easyrsa --batch build-client-full "$CLIENT" nopass
			;;
		2)
			if [[ -z "$PASSPHRASE" ]]; then
				log_warn "You will be asked for the client password below"
				# Run directly (not via run_cmd) so password prompt is visible to user
				if ! ./easyrsa --batch build-client-full "$CLIENT"; then
					log_fatal "Building client certificate failed"
				fi
			else
				log_info "Using provided passphrase for client certificate"
				# Use env var to avoid exposing passphrase in install log
				export EASYRSA_PASSPHRASE="$PASSPHRASE"
				run_cmd_fatal "Building client certificate" ./easyrsa --batch --passin=env:EASYRSA_PASSPHRASE --passout=env:EASYRSA_PASSPHRASE build-client-full "$CLIENT"
				unset EASYRSA_PASSPHRASE
			fi
			;;
		esac
		log_success "Client $CLIENT added and is valid for $CLIENT_CERT_DURATION_DAYS days."
	fi

	# Write the .ovpn config file with proper path and permissions
	writeClientConfig "$CLIENT"

	log_menu ""
	log_success "The configuration file has been written to $GENERATED_CONFIG_PATH."
	log_info "Download the .ovpn file and import it in your OpenVPN client."

	exit 0
}

function revokeClient() {
	log_header "Revoke Client"
	log_prompt "Select the existing client certificate you want to revoke"
	selectClient

	cd /etc/openvpn/server/easy-rsa/ || return
	log_info "Revoking certificate for $CLIENT..."
	run_cmd_fatal "Revoking certificate" ./easyrsa --batch revoke-issued "$CLIENT"
	regenerateCRL
	run_cmd "Removing client config from /home" find /home/ -maxdepth 2 -name "$CLIENT.ovpn" -delete
	run_cmd "Removing client config from /root" rm -f "/root/$CLIENT.ovpn"
	run_cmd "Removing IP assignment" sed -i "/^$CLIENT,.*/d" /etc/openvpn/server/ipp.txt
	run_cmd "Backing up index" cp /etc/openvpn/server/easy-rsa/pki/index.txt{,.bk}

	log_success "Certificate for client $CLIENT revoked."
}

function renewClient() {
	local client_cert_duration_days

	log_header "Renew Client Certificate"
	log_prompt "Select the existing client certificate you want to renew"
	selectClient "true"

	# Allow user to specify renewal duration (use CLIENT_CERT_DURATION_DAYS env var for headless mode)
	if [[ -z $CLIENT_CERT_DURATION_DAYS ]] || ! [[ $CLIENT_CERT_DURATION_DAYS =~ ^[0-9]+$ ]] || [[ $CLIENT_CERT_DURATION_DAYS -lt 1 ]]; then
		log_menu ""
		log_prompt "How many days should the renewed certificate be valid for?"
		until [[ $client_cert_duration_days =~ ^[0-9]+$ ]] && [[ $client_cert_duration_days -ge 1 ]]; do
			read -rp "Certificate validity (days): " -e -i $DEFAULT_CERT_VALIDITY_DURATION_DAYS client_cert_duration_days
		done
	else
		client_cert_duration_days=$CLIENT_CERT_DURATION_DAYS
	fi

	cd /etc/openvpn/server/easy-rsa/ || return
	log_info "Renewing certificate for $CLIENT..."

	# Backup the old certificate before renewal
	run_cmd "Backing up old certificate" cp "/etc/openvpn/server/easy-rsa/pki/issued/$CLIENT.crt" "/etc/openvpn/server/easy-rsa/pki/issued/$CLIENT.crt.bak"

	# Renew the certificate (keeps the same private key)
	export EASYRSA_CERT_EXPIRE=$client_cert_duration_days
	run_cmd_fatal "Renewing certificate" ./easyrsa --batch renew "$CLIENT"

	# Revoke the old certificate
	run_cmd_fatal "Revoking old certificate" ./easyrsa --batch revoke-renewed "$CLIENT"

	# Regenerate the CRL
	regenerateCRL

	# Write the .ovpn config file with proper path and permissions
	writeClientConfig "$CLIENT"

	log_menu ""
	log_success "Certificate for client $CLIENT renewed and is valid for $client_cert_duration_days days."
	log_info "The new configuration file has been written to $GENERATED_CONFIG_PATH."
	log_info "Download the new .ovpn file and import it in your OpenVPN client."
}

function renewServer() {
	local server_name server_cert_duration_days

	log_header "Renew Server Certificate"

	# Get the server name from the config (extract basename since path may be relative)
	server_name=$(basename "$(grep '^cert ' /etc/openvpn/server/server.conf | cut -d ' ' -f 2)" .crt)
	if [[ -z "$server_name" ]]; then
		log_fatal "Could not determine server certificate name from /etc/openvpn/server/server.conf"
	fi

	log_prompt "This will renew the server certificate: $server_name"
	log_warn "The OpenVPN service will be restarted after renewal."
	if [[ -z $CONTINUE ]]; then
		read -rp "Do you want to continue? [y/n]: " -e -i n CONTINUE
	fi
	if [[ $CONTINUE != "y" ]]; then
		log_info "Renewal aborted."
		return
	fi

	# Allow user to specify renewal duration (use SERVER_CERT_DURATION_DAYS env var for headless mode)
	if [[ -z $SERVER_CERT_DURATION_DAYS ]] || ! [[ $SERVER_CERT_DURATION_DAYS =~ ^[0-9]+$ ]] || [[ $SERVER_CERT_DURATION_DAYS -lt 1 ]]; then
		log_menu ""
		log_prompt "How many days should the renewed certificate be valid for?"
		until [[ $server_cert_duration_days =~ ^[0-9]+$ ]] && [[ $server_cert_duration_days -ge 1 ]]; do
			read -rp "Certificate validity (days): " -e -i $DEFAULT_CERT_VALIDITY_DURATION_DAYS server_cert_duration_days
		done
	else
		server_cert_duration_days=$SERVER_CERT_DURATION_DAYS
	fi

	cd /etc/openvpn/server/easy-rsa/ || return
	log_info "Renewing server certificate..."

	# Backup the old certificate before renewal
	run_cmd "Backing up old certificate" cp "/etc/openvpn/server/easy-rsa/pki/issued/$server_name.crt" "/etc/openvpn/server/easy-rsa/pki/issued/$server_name.crt.bak"

	# Renew the certificate (keeps the same private key)
	export EASYRSA_CERT_EXPIRE=$server_cert_duration_days
	run_cmd_fatal "Renewing certificate" ./easyrsa --batch renew "$server_name"

	# Revoke the old certificate
	run_cmd_fatal "Revoking old certificate" ./easyrsa --batch revoke-renewed "$server_name"

	# Regenerate the CRL
	regenerateCRL

	# Copy the new certificate to /etc/openvpn/server/
	run_cmd_fatal "Copying new certificate" cp "/etc/openvpn/server/easy-rsa/pki/issued/$server_name.crt" /etc/openvpn/server/

	# Restart OpenVPN
	log_info "Restarting OpenVPN service..."
	run_cmd "Restarting OpenVPN" systemctl restart openvpn-server@server

	log_success "Server certificate renewed successfully and is valid for $server_cert_duration_days days."
}

function getDaysUntilExpiry() {
	local cert_file="$1"
	if [[ -f "$cert_file" ]]; then
		local expiry_date
		expiry_date=$(openssl x509 -in "$cert_file" -noout -enddate | cut -d= -f2)
		local expiry_epoch
		expiry_epoch=$(date -d "$expiry_date" +%s 2>/dev/null || date -j -f "%b %d %T %Y %Z" "$expiry_date" +%s 2>/dev/null)
		if [[ -z "$expiry_epoch" ]]; then
			echo "?"
			return
		fi
		local now_epoch
		now_epoch=$(date +%s)
		echo $(((expiry_epoch - now_epoch) / 86400))
	else
		echo "?"
	fi
}

function formatExpiry() {
	local days="$1"
	if [[ "$days" == "?" ]]; then
		echo "(unknown expiry)"
	elif [[ $days -lt 0 ]]; then
		echo "(EXPIRED $((-days)) days ago)"
	elif [[ $days -eq 0 ]]; then
		echo "(expires today)"
	elif [[ $days -eq 1 ]]; then
		echo "(expires in 1 day)"
	else
		echo "(expires in $days days)"
	fi
}

function renewMenu() {
	local server_name server_cert server_days server_expiry renew_option

	log_header "Certificate Renewal"

	# Get server certificate expiry for menu display (extract basename since path may be relative)
	server_name=$(basename "$(grep '^cert ' /etc/openvpn/server/server.conf | cut -d ' ' -f 2)" .crt)
	if [[ -z "$server_name" ]]; then
		server_expiry="(unknown expiry)"
	else
		server_cert="/etc/openvpn/server/easy-rsa/pki/issued/$server_name.crt"
		server_days=$(getDaysUntilExpiry "$server_cert")
		server_expiry=$(formatExpiry "$server_days")
	fi

	log_menu ""
	log_prompt "What do you want to renew?"
	log_menu "   1) Renew a client certificate"
	log_menu "   2) Renew the server certificate $server_expiry"
	log_menu "   3) Back to main menu"
	until [[ ${RENEW_OPTION:-$renew_option} =~ ^[1-3]$ ]]; do
		read -rp "Select an option [1-3]: " renew_option
	done
	renew_option="${RENEW_OPTION:-$renew_option}"

	case $renew_option in
	1)
		renewClient
		;;
	2)
		renewServer
		;;
	3)
		manageMenu
		;;
	esac
}

function removeUnbound() {
	run_cmd "Removing OpenVPN Unbound config" rm -f /etc/unbound/unbound.conf.d/openvpn.conf

	# Clean up include directive if conf.d directory is now empty
	if [[ -d /etc/unbound/unbound.conf.d ]] && [[ -z "$(ls -A /etc/unbound/unbound.conf.d)" ]]; then
		run_cmd "Cleaning up Unbound include directive" \
			sed -i '/^include: "\/etc\/unbound\/unbound\.conf\.d\/\*\.conf"$/d' /etc/unbound/unbound.conf
	fi

	until [[ $REMOVE_UNBOUND =~ (y|n) ]]; do
		log_info "If you were already using Unbound before installing OpenVPN, I removed the configuration related to OpenVPN."
		read -rp "Do you want to completely remove Unbound? [y/n]: " -e REMOVE_UNBOUND
	done

	if [[ $REMOVE_UNBOUND == 'y' ]]; then
		log_info "Removing Unbound..."
		run_cmd "Stopping Unbound" systemctl stop unbound

		if [[ $OS =~ (debian|ubuntu) ]]; then
			run_cmd "Removing Unbound" apt-get remove --purge -y unbound
		elif [[ $OS == 'arch' ]]; then
			run_cmd "Removing Unbound" pacman --noconfirm -R unbound
		elif [[ $OS =~ (centos|oracle) ]]; then
			run_cmd "Removing Unbound" yum remove -y unbound
		elif [[ $OS =~ (fedora|amzn2023) ]]; then
			run_cmd "Removing Unbound" dnf remove -y unbound
		elif [[ $OS == 'opensuse' ]]; then
			run_cmd "Removing Unbound" zypper remove -y unbound
		fi

		run_cmd "Removing Unbound config" rm -rf /etc/unbound/
		log_success "Unbound removed!"
	else
		run_cmd "Restarting Unbound" systemctl restart unbound
		log_info "Unbound wasn't removed."
	fi
}

function removeOpenVPN() {
	log_header "Remove OpenVPN"
	if [[ -z $REMOVE ]]; then
		read -rp "Do you really want to remove OpenVPN? [y/n]: " -e -i n REMOVE
	fi
	if [[ $REMOVE == 'y' ]]; then
		# Get OpenVPN configuration
		PORT=$(grep '^port ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
		PROTOCOL=$(grep '^proto ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
		# Strip "6" suffix for firewall/SELinux commands (they expect "udp"/"tcp", not "udp6"/"tcp6")
		PROTOCOL_BASE="${PROTOCOL%6}"
		# Extract IPv4 subnet (may be empty if IPv4 not enabled)
		VPN_SUBNET_IPV4=$(grep '^server ' /etc/openvpn/server/server.conf | cut -d " " -f 2)
		# Extract IPv6 subnet (may be empty if IPv6 not enabled)
		VPN_SUBNET_IPV6=$(grep '^server-ipv6 ' /etc/openvpn/server/server.conf | cut -d " " -f 2 | sed 's|/.*||')

		# Stop OpenVPN
		log_info "Stopping OpenVPN service..."
		run_cmd "Disabling OpenVPN service" systemctl disable openvpn-server@server
		run_cmd "Stopping OpenVPN service" systemctl stop openvpn-server@server
		# Remove customised service
		run_cmd "Removing service file" rm -f /etc/systemd/system/openvpn-server@.service

		# Remove firewall rules
		log_info "Removing firewall rules..."
		if systemctl is-active --quiet firewalld && firewall-cmd --list-ports | grep -q "$PORT/$PROTOCOL_BASE"; then
			# firewalld was used
			run_cmd "Removing OpenVPN port from firewalld" firewall-cmd --permanent --remove-port="$PORT/$PROTOCOL_BASE"
			run_cmd "Removing masquerade from firewalld" firewall-cmd --permanent --remove-masquerade
			# Remove IPv4 rich rule if configured
			if [[ -n $VPN_SUBNET_IPV4 ]]; then
				firewall-cmd --permanent --remove-rich-rule="rule family=\"ipv4\" source address=\"$VPN_SUBNET_IPV4/24\" accept" 2>/dev/null || true
			fi
			# Remove IPv6 rich rule if configured
			if [[ -n $VPN_SUBNET_IPV6 ]]; then
				firewall-cmd --permanent --remove-rich-rule="rule family=\"ipv6\" source address=\"${VPN_SUBNET_IPV6}/112\" accept" 2>/dev/null || true
			fi
			run_cmd "Reloading firewalld" firewall-cmd --reload
		elif [[ -f /etc/nftables/openvpn.nft ]]; then
			# nftables was used
			# Delete tables (suppress errors in case tables don't exist)
			nft delete table inet openvpn 2>/dev/null || true
			nft delete table ip openvpn-nat 2>/dev/null || true
			nft delete table ip6 openvpn-nat 2>/dev/null || true
			run_cmd "Removing include from nftables.conf" sed -i '/include.*openvpn\.nft/d' /etc/nftables.conf
			run_cmd "Removing nftables rules file" rm -f /etc/nftables/openvpn.nft
		elif [[ -f /etc/systemd/system/iptables-openvpn.service ]]; then
			# iptables was used
			run_cmd "Stopping iptables service" systemctl stop iptables-openvpn
			run_cmd "Disabling iptables service" systemctl disable iptables-openvpn
			run_cmd "Removing iptables service file" rm /etc/systemd/system/iptables-openvpn.service
			run_cmd "Reloading systemd" systemctl daemon-reload
			run_cmd "Removing iptables add script" rm -f /etc/iptables/add-openvpn-rules.sh
			run_cmd "Removing iptables rm script" rm -f /etc/iptables/rm-openvpn-rules.sh
		fi

		# SELinux
		if hash sestatus 2>/dev/null; then
			if sestatus | grep "Current mode" | grep -qs "enforcing"; then
				if [[ $PORT != '1194' ]]; then
					run_cmd "Removing SELinux port" semanage port -d -t openvpn_port_t -p "$PROTOCOL_BASE" "$PORT"
				fi
			fi
		fi

		log_info "Removing OpenVPN package..."
		if [[ $OS =~ (debian|ubuntu) ]]; then
			run_cmd "Removing OpenVPN" apt-get remove --purge -y openvpn
			# Remove OpenVPN official repository and GPG key
			if [[ -e /etc/apt/sources.list.d/openvpn-aptrepo.list ]]; then
				run_cmd "Removing OpenVPN repo" rm /etc/apt/sources.list.d/openvpn-aptrepo.list
			fi
			if [[ -e /etc/apt/keyrings/openvpn-repo-public.asc ]]; then
				run_cmd "Removing OpenVPN GPG key" rm /etc/apt/keyrings/openvpn-repo-public.asc
			fi
			run_cmd_fatal "Updating package lists" apt-get update
		elif [[ $OS == 'arch' ]]; then
			run_cmd "Removing OpenVPN" pacman --noconfirm -R openvpn
		elif [[ $OS =~ (centos|oracle) ]]; then
			run_cmd "Removing OpenVPN" yum remove -y openvpn
			# Disable Copr repo if it was enabled
			if command -v dnf &>/dev/null; then
				run_cmd "Disabling OpenVPN Copr repo" dnf copr disable -y @OpenVPN/openvpn-release-2.6 2>/dev/null || true
			else
				run_cmd "Disabling OpenVPN Copr repo" yum copr disable -y @OpenVPN/openvpn-release-2.6 2>/dev/null || true
			fi
		elif [[ $OS == 'amzn2023' ]]; then
			run_cmd "Removing OpenVPN" dnf remove -y openvpn
		elif [[ $OS == 'fedora' ]]; then
			run_cmd "Removing OpenVPN" dnf remove -y openvpn
		elif [[ $OS == 'opensuse' ]]; then
			run_cmd "Removing OpenVPN" zypper remove -y openvpn
		fi

		# Cleanup
		run_cmd "Removing client configs from /home" find /home/ -maxdepth 2 -name "*.ovpn" -delete
		run_cmd "Removing client configs from /root" find /root/ -maxdepth 1 -name "*.ovpn" -delete
		run_cmd "Removing /etc/openvpn" rm -rf /etc/openvpn
		run_cmd "Removing OpenVPN docs" rm -rf /usr/share/doc/openvpn*
		run_cmd "Removing sysctl config" rm -f /etc/sysctl.d/99-openvpn.conf
		run_cmd "Removing OpenVPN logs" rm -rf /var/log/openvpn

		# Unbound
		if [[ -e /etc/unbound/unbound.conf.d/openvpn.conf ]]; then
			removeUnbound
		fi
		log_success "OpenVPN removed!"
	else
		log_info "Removal aborted!"
	fi
}

function manageMenu() {
	local menu_option

	log_header "OpenVPN Management"
	log_prompt "The git repository is available at: https://github.com/angristan/openvpn-install"
	log_success "OpenVPN is already installed."
	log_menu ""
	log_prompt "What do you want to do?"
	log_menu "   1) Add a new user"
	log_menu "   2) List client certificates"
	log_menu "   3) Revoke existing user"
	log_menu "   4) Renew certificate"
	log_menu "   5) Remove OpenVPN"
	log_menu "   6) List connected clients"
	log_menu "   7) Exit"
	until [[ ${MENU_OPTION:-$menu_option} =~ ^[1-7]$ ]]; do
		read -rp "Select an option [1-7]: " menu_option
	done
	menu_option="${MENU_OPTION:-$menu_option}"

	case $menu_option in
	1)
		newClient
		;;
	2)
		listClients
		;;
	3)
		revokeClient
		;;
	4)
		renewMenu
		;;
	5)
		removeOpenVPN
		;;
	6)
		listConnectedClients
		;;
	7)
		exit 0
		;;
	esac
}

# =============================================================================
# Main Entry Point
# =============================================================================
parse_args "$@"