mdw@git.distorted.org.uk Git - firewall/blob - prologue.m4

   1 ### -*-sh-*-
   2 ###
   3 ### Failsafe prologue for firewall scripts
   4 ###
   5 ### (c) 2008 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This program is free software; you can redistribute it and/or modify
  11 ### it under the terms of the GNU General Public License as published by
  12 ### the Free Software Foundation; either version 2 of the License, or
  13 ### (at your option) any later version.
  14 ###
  15 ### This program is distributed in the hope that it will be useful,
  16 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ### GNU General Public License for more details.
  19 ###
  20 ### You should have received a copy of the GNU General Public License
  21 ### along with this program; if not, write to the Free Software Foundation,
  22 ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  23
  24 m4_divert(10)m4_dnl
  25 ###--------------------------------------------------------------------------
  26 ### Failsafe prologue.
  27
  28 revert () {
  29   escape=$1 badness=$2
  30   ## Report a firewall script failure and retreat to a safe place.
  31
  32   echo "$2!  Retreating to safe version..."
  33   if [ -f /var/run/firewall.save ] && [ -f /var/run/firewall6.save ]; then
  34     echo "Trying to loading saved firewall state..."
  35     if iptables-restore </var/run/firewall.save &&
  36        ip6tables-restore </var/run/firewall6.save; then
  37       echo "Previous firewall state restored."
  38       return
  39     else
  40       echo "Failed!  Falling back to plan B."
  41     fi
  42   fi
  43   if ! "$1" revert; then
  44     echo >&2 "Safe firewall failed.  You're screwed.  Good luck."
  45     exit 1
  46   fi
  47   echo >&2 "Phew!  Fallback to safe version successful."
  48   exit 1
  49 }
  50
  51 finished () {
  52   echo "Done."
  53   exit 0
  54 }
  55
  56 try () {
  57   old=$1 new=$2
  58   ## Install the NEW firewall rules.  If it fails, revert to the OLD ones.
  59   ## Updating firewall rules can fail spectacularly, so be careful.  Leave a
  60   ## timebomb in the form of NEW.errors: if this isn't removed in 10 seconds
  61   ## after the NEW rules complete successfully, then revert.  Write errors to
  62   ## NEW.errors.
  63
  64   ## Make sure we have an escape route.
  65   iptables-save >/var/run/firewall.save.new
  66   ip6tables-save >/var/run/firewall6.save.new
  67   mv /var/run/firewall.save.new /var/run/firewall.save
  68   mv /var/run/firewall6.save.new /var/run/firewall6.save
  69
  70   ## Clear the air and make the errors file.
  71   rm -f "$new.errors" "$new.timebomb" "$new.grabbed"
  72   exec >"$new.errors" 2>&1
  73
  74   ## Now try to install the new firewall.
  75   "$new" install || revert "$old" "Failed"
  76
  77   ## Set up the time bomb.  Leave the errors file there if we failed.
  78   (sleep 10
  79    if [ -f "$new.errors" ]; then
  80      mv "$new.errors" "$new.timebomb"
  81      revert "$old" "Time bomb"
  82    fi)&
  83 }
  84
  85 catch () {
  86   new=$1
  87   ## Report successful installation of the script.
  88
  89   if mv "$new.errors" "$new.grabbed" 2>/dev/null; then
  90     rc=0
  91     echo "Installed OK."
  92   else
  93     mv "$new.timebomb" "$new.grabbed"
  94     echo "Timebomb went off."
  95     rc=1
  96   fi
  97   cat "$new.grabbed" >&2
  98   rm -f "$new.grabbed"
  99   return $rc
 100 }
 101
 102 exit_after_clearing=:
 103 export FWCOOKIE=magical
 104 case "$#,${1-update}" in
 105   1,start | 1,restart | 1,reload | 1,force-reload)
 106     echo -n "Starting up firewall... "
 107     "$firewall_script" install || revert "$firewall_failsafe" "Failed"
 108     finished
 109     ;;
 110   1,stop)
 111     echo -n "Shutting down firewall... "
 112     exit_after_clearing=finished
 113     ;;
 114   1,replace | 1,test)
 115     echo -n "Running new firewall... "
 116     if ! (try "$firewall_script" "$0"); then
 117       echo "FAILED."
 118       cat "$0.errors" >&2
 119       exit
 120     fi
 121     echo "done."
 122     echo "Can you hear me?"
 123     (trap 'exit 127' TERM
 124      while :; do
 125        if [ -f "$0.timebomb" ]; then
 126          kill $$
 127          echo "Timebomb went off!"
 128          cat "$0.timebomb"
 129          exit 1
 130        fi
 131        sleep 1
 132      done)&
 133     read answer
 134     kill $!
 135     catch "$0"
 136     case "$1,$answer" in
 137       replace,y* | replace,Y*)
 138         install -m755 "$0" "$firewall_script"
 139         echo "Cool.  Firewall script replaced."
 140         exit 0
 141         ;;
 142       test,y* | test,Y*)
 143         echo "Cool.  Everything seems good."
 144         exit 0
 145         ;;
 146       *)
 147         revert "$firewall_script" "Bogus"
 148         ;;
 149     esac
 150     ;;
 151   1,remote-prepare)
 152     try "$firewall_script" "$0"
 153     exit 0
 154     ;;
 155   1,remote-commit)
 156     catch "$0"
 157     install -m755 "$0" "$firewall_script"
 158     exit 0
 159     ;;
 160   1,install | 1,revert)
 161     ;;
 162   *)
 163     cat >&2 <<EOF
 164 Usage:
 165         $0 start|stop|reload|restart|force-reload
 166         $0 replace|test|remote-prepare|remote-commit
 167 EOF
 168     exit 1
 169     ;;
 170 esac
 171
 172 m4_divert(-1)
 173 ###----- That's all, folks --------------------------------------------------