| 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 | RECOV KEEPER [NUB] |
| 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 NUB, or stdin if NUB is omitted or \`-'. |
| 36 | HELP |
| 37 | |
| 38 | ## Parse the command line. |
| 39 | case $# in |
| 40 | 2) if [ -t 0 ]; then echo >&2 "$quis: stdin is a terminal"; exit 1; fi ;; |
| 41 | 3) ;; |
| 42 | *) usage_err ;; |
| 43 | esac |
| 44 | recov=$1 keeper=$2; shift 2 |
| 45 | checklabel "recovery key" "$recov" |
| 46 | case "$recov" in |
| 47 | */*) ;; |
| 48 | *) recov=$recov/current ;; |
| 49 | esac |
| 50 | checkword "keeper set label" "$keeper" |
| 51 | |
| 52 | ## Check that this is a sensible thing to do. |
| 53 | if [ ! -f $KEYS/keeper/$keeper/meta ]; then |
| 54 | echo >&2 "$quis: unknown keeper set \`$keeper'" |
| 55 | exit 1 |
| 56 | fi |
| 57 | if [ ! -d $KEYS/recov/$recov ]; then |
| 58 | echo >&2 "$quis: unknown recovery key \`$recov'" |
| 59 | exit 1 |
| 60 | fi |
| 61 | if [ ! -f $KEYS/recov/$recov/$keeper.param ]; then |
| 62 | echo >&2 "$quis: recovery key \`$recov' not kept by keeper set \`$keeper'" |
| 63 | exit 1 |
| 64 | fi |
| 65 | |
| 66 | ## Grab the key, because we'll need to read it several times. |
| 67 | mktmp |
| 68 | cat -- "$@" >$tmp/secret |
| 69 | |
| 70 | ## Read the threshold from the recovery metadata. |
| 71 | read param <$KEYS/recov/$recov/$keeper.param |
| 72 | case "$param" in |
| 73 | shamir-params:*) ;; |
| 74 | *) |
| 75 | echo >&2 "$quis: secret sharing parameter file damaged (wrong header)" |
| 76 | exit 1 |
| 77 | ;; |
| 78 | esac |
| 79 | t=";${param#*:}" |
| 80 | case "$t" in |
| 81 | *";t="*) ;; |
| 82 | *) |
| 83 | echo >&2 "$quis: secret sharing parameter file damaged (missing t)" |
| 84 | exit 1 |
| 85 | ;; |
| 86 | esac |
| 87 | t=${t#*;t=} |
| 88 | t=${t%%;*} |
| 89 | |
| 90 | ## Find out which keeper index it corresponds to. |
| 91 | read n hunoz <$KEYS/keeper/$keeper/meta |
| 92 | i=0 |
| 93 | foundp=nil |
| 94 | while [ $i -lt $n ]; do |
| 95 | c_sysprepare $KEYS/keeper/$keeper/$i |
| 96 | nubbin=$(nubid <$tmp/secret) |
| 97 | nubid=$(cat $KEYS/keeper/$keeper/$i/nubid) |
| 98 | case "$nubbin" in "$nubid") foundp=t; break ;; esac |
| 99 | i=$(( $i + 1 )) |
| 100 | done |
| 101 | case $foundp in |
| 102 | nil) echo >&2 "$quis: nub doesn't match keeper \`$keeper'"; exit 1 ;; |
| 103 | esac |
| 104 | |
| 105 | ## Establish the recovery staging area. See whether we've done enough |
| 106 | ## already. |
| 107 | reqsafe |
| 108 | tag=$(echo $recov | tr / .) |
| 109 | mkdir -p -m700 $SAFE/keys.reveal |
| 110 | reveal=$SAFE/keys.reveal/$tag |
| 111 | if [ ! -d $reveal ]; then mkdir -m700 $reveal; fi |
| 112 | cd $reveal |
| 113 | if [ -f nub ]; then |
| 114 | echo >&2 "$quis: recovery key \`$recov' already revealed" |
| 115 | exit 1 |
| 116 | fi |
| 117 | |
| 118 | ## Decrypt the share. |
| 119 | umask 077 |
| 120 | if [ -f $keeper.$i.share ]; then |
| 121 | echo >&2 "$quis: share $i already revealed" |
| 122 | else |
| 123 | c_sysdecrypt $KEYS/keeper/$keeper/$i $tmp/secret \ |
| 124 | <$KEYS/recov/$recov/$keeper.$i.share \ |
| 125 | >$keeper.$i.new |
| 126 | mv $keeper.$i.new $keeper.$i.share |
| 127 | fi |
| 128 | |
| 129 | ## See if there's enough for a recovery. |
| 130 | n=0 |
| 131 | for j in $keeper.*.share; do if [ -f "$j" ]; then n=$(( $n + 1 )); fi; done |
| 132 | if [ $n -lt $t ]; then |
| 133 | echo >&2 "$quis: share $i revealed; $(( $t - $n )) more required" |
| 134 | else |
| 135 | cat $KEYS/recov/$recov/$keeper.param $keeper.*.share >$keeper.shares |
| 136 | shamir recover <$keeper.shares >nub.new |
| 137 | c_sysprepare $KEYS/recov/$recov/store |
| 138 | nubbin=$(nubid <nub.new) |
| 139 | nubid=$(cat $KEYS/recov/$recov/store/nubid) |
| 140 | case "$nubbin" in |
| 141 | "$nubid") ;; |
| 142 | *) |
| 143 | echo >&2 "$quis: recovered nub doesn't match stored hash" |
| 144 | exit 1 |
| 145 | ;; |
| 146 | esac |
| 147 | mv nub.new nub |
| 148 | rm -f $keeper.* |
| 149 | echo >&2 "$quis: recovery key \`$recov' revealed" |
| 150 | fi |
| 151 | |
| 152 | ###----- That's all, folks -------------------------------------------------- |