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24898273d6fc6ab41691583bbe716e8c84048118
[code/molly-guard.git] / shutdown
1 #!/bin/sh
2 #
3 # shutdown -- wrapper script to prevent erroneous shutdowns via SSH
4 #
5 # Copyright © martin f. krafft <madduck@madduck.net>
6 # Released under the terms of the Artistic Licence 2.0
7 #
8 # $Id: shutdown 299 2006-10-16 14:40:47Z madduck $
9 #
10 set -eu
11
12 ME=molly-guard
13
14 CMD="${0##*/}"
15 EXEC="/sbin/$CMD"
16
17 case "$CMD" in
18   halt|reboot|shutdown|poweroff)
19     if [ ! -f $EXEC ]; then
20       echo "E: $ME: not a regular file: $EXEC" >&2
21       exit 4
22     fi
23     if [ ! -x $EXEC ]; then
24       echo "E: $ME: not an executable: $EXEC" >&2
25       exit 3
26     fi
27     ;;
28   *)
29     echo "E: $ME: unsupported command: $CMD" >&2
30     exit 1
31     ;;
32 esac
33
34 usage()
35 {
36   cat <<-_eousage
37         Usage: $ME [options]
38                (shielding $EXEC)
39
40         Instead of invoking $EXEC directly, $ME will prompt the user for the
41         machine's hostname to guard against accidental shutdowns/reboots, if the
42         current shell is a child of an SSH connection (or --pretend-ssh) has been
43         given on the command line, if the shell is connected to an interactive
44         terminal, and the actual command to execute is does not involve --help or is
45         \`shutdown -c'.
46
47         Only if the user enters the machine's hostname correctly will $ME take
48         action. Specifying --molly-guard-do-nothing as argument to the command will
49         make $ME echo the command it would execute rather than actually executing
50         it.
51
52         The actual command's help output follows:
53
54         _eousage
55 }
56
57 ARGS=
58 DO_NOTHING=0
59 PRETEND_SSH=0
60 for arg in "$@"; do
61   case "$arg" in
62     (*-molly-guard-do-nothing) DO_NOTHING=1;;
63     (*-help)
64       usage 2>&1
65       eval $EXEC --help 2>&1
66       exit 0
67       ;;
68     (*-pretend-ssh) PRETEND_SSH=1;;
69     *) ARGS="${ARGS:+$ARGS }$arg";;
70   esac
71 done
72
73 do_real_cmd()
74 {
75   if [ $DO_NOTHING -eq 1 ]; then
76     echo "$ME: would run: $EXEC $ARGS"
77     exit 0
78   else
79     eval exec $EXEC "$ARGS"
80   fi
81 }
82
83 if [ $DO_NOTHING -eq 1 ]; then
84   echo "I: demo mode; $ME will not do anything due to --molly-guard-do-nothing."
85 fi
86
87 # require an interactive terminal connected to stdin
88 test -t 0                    || do_real_cmd
89
90 # only run if we are being called over SSH, that is if the current terminal
91 # was created by sshd.
92 PTS=$(readlink /proc/$$/fd/0)
93 if ! pgrep -f "^sshd.+${PTS#/dev/}[[:space:]]*$" >/dev/null; then
94   if [ $PRETEND_SSH -eq 1 ]; then
95     echo "I: this is not an SSH session, but --pretend-ssh was given..."
96   else
97     do_real_cmd
98   fi
99 else
100   echo "W: $ME: SSH session detected!"
101 fi
102
103 # pass through certain commands
104 case "$CMD $ARGS" in
105   (*shutdown\ *-c*) 
106     echo "I: executing $CMD $ARGS regardless of SSH session."
107     do_real_cmd
108     ;;
109 esac
110
111 HOSTNAME="$(hostname --short)"
112
113 sigh()
114 {
115   echo "Good thing I asked; I won't $CMD $HOSTNAME ..."
116   exit 2
117 }
118
119 trap 'echo;sigh' 1 2 3 9 10 12 15
120
121 echo -n "Please type in hostname of the machine to $CMD: "
122 read HOSTNAME_USER || :
123
124 [ "$HOSTNAME_USER" = "$HOSTNAME" ] || sigh
125
126 trap - 1 2 3 9 10 12 15
127
128 do_real_cmd