#!/bin/sh # # shutdown -- wrapper script to prevent erroneous shutdowns via SSH # # Copyright © martin f. krafft # Released under the terms of the Artistic Licence 2.0 # # $Id: shutdown 299 2006-10-16 14:40:47Z madduck $ # set -eu ME=molly-guard CMD="${0##*/}" EXEC="/sbin/$CMD" case "$CMD" in halt|reboot|shutdown|poweroff) if [ ! -f $EXEC ]; then echo "E: $ME: not a regular file: $EXEC" >&2 exit 4 fi if [ ! -x $EXEC ]; then echo "E: $ME: not an executable: $EXEC" >&2 exit 3 fi ;; *) echo "E: $ME: unsupported command: $CMD" >&2 exit 1 ;; esac usage() { cat <<-_eousage Usage: $ME [options] (shielding $EXEC) Instead of invoking $EXEC directly, $ME will prompt the user for the machine's hostname to guard against accidental shutdowns/reboots, if the current shell is a child of an SSH connection (or --pretend-ssh) has been given on the command line, if the shell is connected to an interactive terminal, and the actual command to execute is does not involve --help or is \`shutdown -c'. Only if the user enters the machine's hostname correctly will $ME take action. Specifying --molly-guard-do-nothing as argument to the command will make $ME echo the command it would execute rather than actually executing it. The actual command's help output follows: _eousage } ARGS= DO_NOTHING=0 PRETEND_SSH=0 for arg in "$@"; do case "$arg" in (*-molly-guard-do-nothing) DO_NOTHING=1;; (*-help) usage 2>&1 eval $EXEC --help 2>&1 exit 0 ;; (*-pretend-ssh) PRETEND_SSH=1;; *) ARGS="${ARGS:+$ARGS }$arg";; esac done do_real_cmd() { if [ $DO_NOTHING -eq 1 ]; then echo "$ME: would run: $EXEC $ARGS" exit 0 else eval exec $EXEC "$ARGS" fi } if [ $DO_NOTHING -eq 1 ]; then echo "I: demo mode; $ME will not do anything due to --molly-guard-do-nothing." fi # require an interactive terminal connected to stdin test -t 0 || do_real_cmd # only run if we are being called over SSH, that is if the current terminal # was created by sshd. PTS=$(readlink /proc/$$/fd/0) if ! pgrep -f "^sshd.+${PTS#/dev/}[[:space:]]*$" >/dev/null \ && [ -z "${SSH_CONNECTION:-}" ]; then if [ $PRETEND_SSH -eq 1 ]; then echo "I: this is not an SSH session, but --pretend-ssh was given..." else do_real_cmd fi else echo "W: $ME: SSH session detected!" fi # pass through certain commands case "$CMD $ARGS" in (*shutdown\ *-c*) echo "I: executing $CMD $ARGS regardless of SSH session." do_real_cmd ;; esac HOSTNAME="$(hostname --short)" sigh() { echo "Good thing I asked; I won't $CMD $HOSTNAME ..." exit 2 } trap 'echo;sigh' 1 2 3 9 10 12 15 echo -n "Please type in hostname of the machine to $CMD: " read HOSTNAME_USER || : [ "$HOSTNAME_USER" = "$HOSTNAME" ] || sigh trap - 1 2 3 9 10 12 15 do_real_cmd