mdw@git.distorted.org.uk Git - distorted-keys/blob - keys.reveal

   1 #! /bin/sh
   2 ###
   3 ### Reveal shares of a secret distributed among keepers
   4 ###
   5 ### (c) 2011 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This file is part of the distorted.org.uk key management suite.
  11 ###
  12 ### distorted-keys is free software; you can redistribute it and/or modify
  13 ### it under the terms of the GNU General Public License as published by
  14 ### the Free Software Foundation; either version 2 of the License, or
  15 ### (at your option) any later version.
  16 ###
  17 ### distorted-keys is distributed in the hope that it will be useful,
  18 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ### GNU General Public License for more details.
  21 ###
  22 ### You should have received a copy of the GNU General Public License
  23 ### along with distorted-keys; if not, write to the Free Software Foundation,
  24 ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25
  26 set -e
  27 case "${KEYSLIB+t}" in t) ;; *) echo >&2 "$0: KEYSLIB unset"; exit 1 ;; esac
  28 . "$KEYSLIB"/keyfunc.sh
  29
  30 defhelp <<HELP
  31 [-i INST] RECOV KEEPER
  32 Reveal a share of a recovery key distributed among keepers.
  33
  34 If enough shares have been revealed, reconstruct the recovery private key.
  35 The keeper nub is read from stdin.
  36 HELP
  37
  38 ## Parse the command line.
  39 inst=current
  40 while getopts "i:" opt; do
  41   case "$opt" in
  42     i) inst=$OPTARG ;;
  43     *) usage_err ;;
  44   esac
  45 done
  46 shift $(( $OPTIND - 1 ))
  47 case $# in 2) ;; *) usage_err ;; esac
  48 recov=$1 keeper=$2; shift 2
  49 checkword "recovery instance" "$inst"
  50 checkword "recovery key" "$recov"
  51 checkword "keeper set label" "$keeper"
  52
  53 ## Check that this is a sensible thing to do.
  54 keepdir=$KEYS/keeper/$keeper
  55 if [ ! -f $keepdir/meta ]; then
  56   echo >&2 "$quis: unknown keeper set \`$keeper'"
  57   exit 1
  58 fi
  59 if [ ! -h $KEYS/recov/$recov/current ]; then
  60   echo >&2 "$quis: unknown recovery key \`$recov'"
  61   exit 1
  62 fi
  63 rdir=$KEYS/recov/$recov/$inst
  64 if [ ! -f $rdir/$keeper.param ]; then
  65   echo >&2 "$quis: recovery key \`$recov' not kept by keeper set \`$keeper'"
  66   exit 1
  67 fi
  68
  69 ## Grab the key, because we'll need to read it several times.
  70 mktmp
  71 cat >$tmp/secret
  72
  73 ## Read the threshold from the recovery metadata.
  74 t=$(sharethresh $rdir/$keeper.param)
  75
  76 ## Find out which keeper index it corresponds to.
  77 read n hunoz <$keepdir/meta
  78 i=0
  79 foundnubp=nil
  80 while [ $i -lt $n ]; do
  81   c_sysprepare $keepdir/$i
  82   nubbin=$(nubid <$tmp/secret)
  83   nubid=$(cat $keepdir/$i/nubid)
  84   case "$nubbin" in "$nubid") foundnubp=t; break ;; esac
  85   i=$(( $i + 1 ))
  86 done
  87 case $foundnubp in
  88   nil) echo >&2 "$quis: nub doesn't match keeper \`$keeper'"; exit 1 ;;
  89 esac
  90
  91 ## Establish the recovery staging area.  See whether we've done enough
  92 ## already.
  93 reqsafe
  94 tag=$recov.$inst
  95 mkdir -p -m700 $SAFE/keys.reveal
  96 reveal=$SAFE/keys.reveal/$tag
  97 if [ ! -d $reveal ]; then mkdir -m700 $reveal; fi
  98 cd $reveal
  99 if [ -f nub ]; then
 100   echo >&2 "$quis: recovery key \`$recov/$inst' already revealed"
 101   exit 1
 102 fi
 103
 104 ## Decrypt the share.
 105 umask 077
 106 if [ -f $keeper.$i.share ]; then
 107   echo >&2 "$quis: share $i already revealed"
 108 else
 109   c_sysdecrypt $keepdir/$i $tmp/secret \
 110     <$rdir/$keeper.$i.share \
 111     >$keeper.$i.new
 112   mv $keeper.$i.new $keeper.$i.share
 113 fi
 114
 115 ## See if there's enough for a recovery.
 116 n=0
 117 for j in $keeper.*.share; do if [ -f "$j" ]; then n=$(( $n + 1 )); fi; done
 118 if [ $n -lt $t ]; then
 119   echo >&2 "$quis: share $i revealed; $(( $t - $n )) more required"
 120 else
 121   cat $rdir/$keeper.param $keeper.*.share >$keeper.shares
 122   $bindir/shamir recover <$keeper.shares >nub.new
 123   c_sysprepare $rdir/store
 124   nubbin=$(nubid <nub.new)
 125   nubid=$(cat $rdir/store/nubid)
 126   case "$nubbin" in
 127     "$nubid") ;;
 128     *)
 129       echo >&2 "$quis: recovered nub doesn't match stored hash"
 130       exit 1
 131       ;;
 132   esac
 133   mv nub.new nub
 134   rm -f $keeper.*
 135   echo >&2 "$quis: recovery key \`$recov/$inst' revealed"
 136 fi
 137
 138 ###----- That's all, folks --------------------------------------------------