iptables-apply

   1 #!/bin/bash
   2 #
   3 # iptables-apply -- a safer way to update iptables remotely
   4 #
   5 # Copyright © Martin F. Krafft <madduck@madduck.net>
   6 # Released under the terms of the Artistic Licence 2.0
   7 #
   8 set -eu
   9
  10 PROGNAME="${0##*/}";
  11 VERSION=1.0
  12
  13 TIMEOUT=10
  14 DEFAULT_FILE=/etc/network/iptables
  15
  16 function blurb()
  17 {
  18         cat <<-_eof
  19         $PROGNAME $VERSION -- a safer way to update iptables remotely
  20         _eof
  21 }
  22
  23 function copyright()
  24 {
  25         cat <<-_eof
  26         $PROGNAME is C Martin F. Krafft <madduck@madduck.net>.
  27
  28         The program has been published under the terms of the Artistic Licence 2.0
  29         _eof
  30 }
  31
  32 function about()
  33 {
  34         blurb
  35         echo
  36         copyright
  37 }
  38
  39 function usage()
  40 {
  41         cat <<-_eof
  42         Usage: $PROGNAME [options] ruleset
  43
  44         The script will try to apply a new ruleset (as output by iptables-save/read
  45         by iptables-restore) to iptables, then prompt the user whether the changes
  46         are okay. If the new ruleset cut the existing connection, the user will not
  47         be able to answer affirmatively. In this case, the script rolls back to the
  48         previous ruleset.
  49
  50         The following options may be specified, using standard conventions:
  51
  52         -t | --timeout  Specify the timeout in seconds (default: $TIMEOUT)
  53         -V | --version  Display version information
  54         -h | --help     Display this help text
  55         _eof
  56 }
  57
  58 SHORTOPTS="t:Vh";
  59 LONGOPTS="timeout:,version,help";
  60
  61 OPTS=$(getopt -s bash -o "$SHORTOPTS" -l "$LONGOPTS" -n "$PROGNAME" -- "$@") || exit $?
  62 for opt in $OPTS; do
  63         case "$opt" in
  64                 (-*) unset OPT_STATE;;
  65                 (*)
  66                         case "${OPT_STATE:-}" in
  67                                 (SET_TIMEOUT)
  68                                         eval TIMEOUT=$opt
  69                                         case "$TIMEOUT" in
  70                                                 ([0-9]*) :;;
  71                                                 (*)
  72                                                         echo "E: non-numeric timeout value." >&2
  73                                                         exit 1
  74                                                         ;;
  75                                         esac
  76                                         ;;
  77                         esac
  78                         ;;
  79         esac
  80
  81         case "$opt" in
  82                 (-h|--help) usage >&2; exit 0;;
  83                 (-V|--version) about >&2; exit 0;;
  84                 (-t|--timeout) OPT_STATE=SET_TIMEOUT;;
  85                 (--) break;;
  86         esac
  87         shift
  88 done
  89
  90 FILE="${1:-$DEFAULT_FILE}";
  91
  92 if [[ -z "$FILE" ]]; then
  93         echo "E: missing file argument." >&2
  94         exit 1
  95 fi
  96
  97 if [[ ! -r "$FILE" ]]; then
  98         echo "E: cannot read $FILE" >&2
  99         exit 2
 100 fi
 101
 102 case "${0##*/}" in
 103         (*6*)
 104                 SAVE=ip6tables-save
 105                 RESTORE=ip6tables-restore
 106                 ;;
 107         (*)
 108                 SAVE=iptables-save
 109                 RESTORE=iptables-restore
 110                 ;;
 111 esac
 112
 113 COMMANDS=(tempfile "$SAVE" "$RESTORE")
 114
 115 for cmd in "${COMMANDS[@]}"; do
 116         if ! command -v $cmd >/dev/null; then
 117                 echo "E: command not found: $cmd" >&2
 118                 exit 127
 119         fi
 120 done
 121
 122 umask 0700
 123
 124 TMPFILE=$(tempfile -p iptap)
 125 trap "rm -f $TMPFILE" EXIT 1 2 3 4 5 6 7 8 10 11 12 13 14 15
 126
 127 if ! "$SAVE" >"$TMPFILE"; then
 128         if ! grep -q ipt /proc/modules 2>/dev/null; then
 129                 echo "E: iptables support lacking from the kernel." >&2
 130                 exit 3
 131         else
 132                 echo "E: unknown error saving current iptables ruleset." >&2
 133                 exit 4
 134         fi
 135 fi
 136
 137 [ -x /etc/init.d/fail2ban ] && /etc/init.d/fail2ban stop
 138
 139 echo -n "Applying new ruleset... "
 140 if ! "$RESTORE" <"$FILE"; then
 141         echo "failed."
 142         echo "E: unknown error applying new iptables ruleset." >&2
 143         exit 5
 144 else
 145         echo done.
 146 fi
 147
 148 echo -n "Can you establish NEW connections to the machine? (y/N) "
 149
 150 read -n1 -t "${TIMEOUT:-15}" ret 2>&1 || :
 151 case "${ret:-}" in
 152         (y*|Y*)
 153                 echo
 154                 echo ... then my job is done. See you next time.
 155                 ;;
 156         (*)
 157                 if [[ -z "${ret:-}" ]]; then
 158                         echo "apparently not..."
 159                 else
 160                         echo
 161                 fi
 162                 echo "Timeout. Something happened (or did not). Better play it safe..."
 163                 echo -n "Reverting to old ruleset... "
 164                 "$RESTORE" <"$TMPFILE";
 165                 echo done.
 166                 exit 255
 167                 ;;
 168 esac
 169
 170 [ -x /etc/init.d/fail2ban ] && /etc/init.d/fail2ban start
 171
 172 exit 0
 173
 174 # vim:noet:sw=8