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#!/bin/sh
#
# 30-ask-hostname - request the user to type in the hostname of the local host
#
# Copyright © 2006-2009 martin f. krafft <madduck@madduck.net>
# Copyright © 2012 Ludovico Gardenghi <lu@dovi.co>
# Copyright © 2014 Josh Triplett <josh@joshtriplett.org>
# Copyright © 2015 Francois Marier <francois@debian.org>
# Copyright © 2017 Simó Albert i Beltran <sim6@probeta.net>
# Released under the terms of the Artistic Licence 2.0
#
set -eu
ME=molly-guard
# Walk up the process tree until PID 1 is reached or a process with 'sshd' in
# its /proc/<pid>/cmdline is met. Return success if such a process is found.
is_child_of_sshd_or_mosh_server() {
pid=$$
ppid=$PPID
# Be a bit paranoid with the guard, should some horribly broken system
# provide a strange process hierarchy. '[ $pid -ne 1 ]' should be enough for
# sane systems.
[ -z "$pid" ] || [ -z "$ppid" ] && return 2
while [ $pid -gt 1 ] && [ $pid -ne $ppid ]; do
if egrep -q 'sshd|mosh-server' /proc/$ppid/cmdline; then
return 0
fi
pid=$ppid
ppid=$(grep ^PPid: /proc/$pid/status | tr -dc 0-9)
done
return 1
}
[ -f "$MOLLYGUARD_SETTINGS" ] && . "$MOLLYGUARD_SETTINGS"
PRETEND_SSH=0
for arg in "$@"; do
case "$arg" in
(*-pretend-ssh) PRETEND_SSH=1;;
esac
done
# require an interactive terminal connected to stdin
test -t 0 || exit 0
# we've been asked to always protect this host
case "${ALWAYS_QUERY_HOSTNAME:-0}" in
0|false|False|no|No|off|Off)
# only run if we are being called over SSH, that is if the current terminal
# was created by sshd.
command -v tty >/dev/null 2>&1 || exit 0
PTS=$(tty)
if ! pgrep -f "^sshd.+${PTS#/dev/}\>" >/dev/null \
&& [ -z "${SSH_CONNECTION:-}" ] \
&& ! is_child_of_sshd_or_mosh_server; then
if [ $PRETEND_SSH -eq 1 ]; then
echo "I: $ME: this is not an SSH session, but --pretend-ssh was given..." >&2
else
exit 0
fi
else
echo "W: $ME: SSH session detected!" >&2
fi
;;
*)
echo "I: $ME: $MOLLYGUARD_CMD is always molly-guarded on this system." >&2
;;
esac
case "${USE_FQDN:-0}" in
0|false|False|no|No|off|Off)
HOSTNAME="$(hostname --short)"
;;
*)
HOSTNAME="$(hostname --fqdn)"
;;
esac
sigh()
{
echo "Good thing I asked; I won't $MOLLYGUARD_CMD $HOSTNAME ..." >&2
exit 1
}
trap 'echo;sigh' 1 2 3 9 10 12 15
echo -n "Please type in hostname of the machine to $MOLLYGUARD_CMD: "
read HOSTNAME_USER || :
HOSTNAME="$(echo "$HOSTNAME" | tr '[:upper:]' '[:lower:]')"
HOSTNAME_USER="$(echo "$HOSTNAME_USER" | tr '[:upper:]' '[:lower:]')"
[ "$HOSTNAME_USER" = "$HOSTNAME" ] || sigh
trap - 1 2 3 9 10 12 15
exit 0
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