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 ! "$1" revert; then
  34     echo >&2 "Safe firewall failed.  You're screwed.  Good luck."
  35     exit 1
  36   fi
  37   echo >&2 "Phew!  Fallback to safe version successful."
  38   exit 1
  39 }
  40
  41 finished () {
  42   echo "Done."
  43   exit 0
  44 }
  45
  46 try () {
  47   old=$1 new=$2
  48   ## Install the NEW firewall rules.  If it fails, revert to the OLD ones.
  49   ## Updating firewall rules can fail spectacularly, so be careful.  Leave a
  50   ## timebomb in the form of NEW.errors: if this isn't removed in 10 seconds
  51   ## after the NEW rules complete successfully, then revert.  Write errors to
  52   ## NEW.errors.
  53
  54   ## Make sure we have an escape route.
  55   if [ ! -x "$old" ]; then
  56     echo >&2 "$0: no escape plan: \`$old' is missing"
  57     exit 1
  58   fi
  59
  60   ## Clear the air and make the errors file.
  61   rm -f "$new.errors" "$new.timebomb" "$new.grabbed"
  62   exec >"$new.errors" 2>&1
  63
  64   ## Now try to install the new firewall.
  65   "$new" install || revert "$old" "Failed"
  66
  67   ## Set up the time bomb.  Leave the errors file there if we failed.
  68   (sleep 10
  69    if [ -f "$new.errors" ]; then
  70      mv "$new.errors" "$new.timebomb"
  71      revert "$old" "Time bomb"
  72    fi)&
  73 }
  74
  75 catch () {
  76   new=$1
  77   ## Report successful installation of the script.
  78
  79   if mv "$new.errors" "$new.grabbed" 2>/dev/null; then
  80     rc=0
  81     echo "Installed OK."
  82   else
  83     mv "$new.timebomb" "$new.grabbed"
  84     echo "Timebomb went off."
  85     rc=1
  86   fi
  87   cat "$new.grabbed" >&2
  88   rm -f "$new.grabbed"
  89   return $rc
  90 }
  91
  92 exit_after_clearing=:
  93 export FWCOOKIE=magical
  94 case "$#,${1-update}" in
  95   1,start | 1,restart | 1,reload | 1,force-reload)
  96     echo -n "Starting up firewall... "
  97     "$firewall_script" install || revert "$firewall_failsafe" "Failed"
  98     finished
  99     ;;
 100   1,stop)
 101     echo -n "Shutting down firewall... "
 102     exit_after_clearing=finished
 103     ;;
 104   1,replace | 1,test)
 105     echo -n "Running new firewall... "
 106     if ! (try "$firewall_script" "$0"); then
 107       echo "FAILED."
 108       cat "$0.errors" >&2
 109       exit
 110     fi
 111     echo "done."
 112     echo "Can you hear me?"
 113     (trap 'exit 127' TERM
 114      while :; do
 115        if [ -f "$0.timebomb" ]; then
 116          kill $$
 117          echo "Timebomb went off!"
 118          cat "$0.timebomb"
 119          exit 1
 120        fi
 121        sleep 1
 122      done)&
 123     read answer
 124     kill $!
 125     catch "$0"
 126     case "$1,$answer" in
 127       replace,y* | replace,Y*)
 128         install -m755 "$0" "$firewall_script"
 129         echo "Cool.  Firewall script replaced."
 130         exit 0
 131         ;;
 132       test,y* | test,Y*)
 133         echo "Cool.  Everything seems good."
 134         exit 0
 135         ;;
 136       *)
 137         revert "$firewall_script" "Bogus"
 138         ;;
 139     esac
 140     ;;
 141   1,remote-prepare)
 142     try "$firewall_script" "$0"
 143     exit 0
 144     ;;
 145   1,remote-commit)
 146     catch "$0"
 147     install -m755 "$0" "$firewall_script"
 148     exit 0
 149     ;;
 150   1,install | 1,revert)
 151     ;;
 152   *)
 153     cat >&2 <<EOF
 154 Usage:
 155         $0 start|stop|reload|restart|force-reload
 156         $0 replace|test|remote-prepare|remote-commit
 157 EOF
 158     exit 1
 159     ;;
 160 esac
 161
 162 m4_divert(-1)
 163 ###----- That's all, folks --------------------------------------------------