ifupdown-ng/executor-scripts/linux/wifi

#!/bin/sh
# Copyright (c) 2020 Ariadne Conill <ariadne@dereferenced.org>
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# This software is provided 'as is' and without any warranty, express or
# implied.  In no event shall the authors be liable for any damages arising
# from the use of this software.
#
# Manage wifi connections using wpa_supplicant.
#
# Vocabulary:
#   wifi-ssid - The SSID name to connect to.
#   wifi-psk - The pre-shared key to use.
#   wifi-config - A path to a wpa_supplicant config file, for special configs.
#
# If wifi-config is not set, wifi-ssid and wifi-psk are required, and a config
# will be generated as /run/wpa_supplicant.$IFACE.conf.
#
# The wpa_supplicant PID is stored in /run/wpa_supplicant.$IFACE.pid.

die() {
	printf "ERROR: %s\n" "$1" >&2
	exit 1
}

[ -z "$IFACE" ] && die "IFACE not set"
[ -z "$PHASE" ] && die "PHASE not set"
PIDFILE="/run/wpa_supplicant.$IFACE.pid"

# Do not allow mixing wifi-config-path and wifi-ssid/wifi-psk.
[ -n "$IF_WIFI_CONFIG_PATH" -a -n "$IF_WIFI_SSID" ] && die "wifi-config-path cannot be used with wifi-ssid"
[ -n "$IF_WIFI_CONFIG_PATH" -a -n "$IF_WIFI_PSK" ] && die "wifi-config-path cannot be used with wifi-psk"

# Set IF_WIFI_CONFIG_PATH to the default path if not already set.
WIFI_CONFIG_PATH="$IF_WIFI_CONFIG_PATH"
[ -z "$WIFI_CONFIG_PATH" ] && WIFI_CONFIG_PATH="/run/wpa_supplicant.$IFACE.conf"

# Supplicant options.
WPA_SUPPLICANT_OPTS="-qq -B -i$IFACE -c$WIFI_CONFIG_PATH -P$PIDFILE"

# Given $IF_WIFI_SSID and $IF_WIFI_PSK, generate a config file at $WIFI_CONFIG_PATH.
generate_config() {
	[ -z "$IF_WIFI_SSID" ] && die "wifi-ssid not set"
	[ -z "$IF_WIFI_PSK" ] && die "wifi-psk not set"

	# We use a pipeline here to avoid leaking PSK into the process name.
	(echo $IF_WIFI_PSK | /sbin/wpa_passphrase $IF_WIFI_SSID) >$WIFI_CONFIG_PATH

	[ ! -e "$WIFI_CONFIG_PATH" ] && die "failed to write temporary config: $WIFI_CONFIG_PATH"
}

# Should we use the supplicant?
use_supplicant() {
	[ -n "$IF_WIFI_CONFIG_PATH" ] && return 0
	[ -n "$IF_WIFI_PSK" ] && return 0

	return 1
}

# Either start a supplicant process for $IFACE, or use iwconfig to trigger an
# association attempt.
start() {
	if use_supplicant; then
		# If there is no config file located at $WIFI_CONFIG_PATH, generate one.
		[ ! -e "$WIFI_CONFIG_PATH" ] && generate_config

		/sbin/wpa_supplicant $WPA_SUPPLICANT_OPTS
	else
		/usr/sbin/iwconfig $IFACE essid -- "$IF_WIFI_SSID" ap any
	fi
}

# Stop wpa_supplicant safely
stop_wpa_supplicant() {
	# Remove generated config file
	[ -z "$IF_WIFI_CONFIG_PATH" ] && rm -- "$WIFI_CONFIG_PATH"

	# If there is no PIDFILE, there is nothing we can do
	[ ! -f "$PIDFILE" ] && return

	pid=$(cat "$PIDFILE")
	rm -- "$PIDFILE"

	# If there is no process with this PID running, we're done here
	if [ ! -d "/proc/$pid/" ]; then
		return
	fi

	# Verify that the name of the running process matches wpa_supplicant
	progname_path=$(readlink -n "/proc/$pid/exe")
	progname=$(basename "$progname_path")
	if [ "$progname" = "wpa_supplicant" ]; then
		kill -9 $pid 2>/dev/null
	fi
}

# Either stop the supplicant process for $IFACE, or use iwconfig to dissociate
# from the current SSID.
stop() {
	if use_supplicant; then
		stop_wpa_supplicant
	else
		/usr/sbin/iwconfig $IFACE essid any
	fi
}

[ -z "$VERBOSE" ] || set -x

case "$PHASE" in
pre-up)
	start
	;;
post-down)
	stop
	;;
esac