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Makefile.am: Distinctive `SUBST' indicator for `confsubst' rules.
[distorted-keys] / keys.reveal
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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
26set -e
27case "${KEYSLIB+t}" in t) ;; *) echo >&2 "$0: KEYSLIB unset"; exit 1 ;; esac
28. "$KEYSLIB"/keyfunc.sh
29
30defhelp <<HELP
31RECOV KEEPER
32Reveal a share of a recovery key distributed among keepers.
33
34If enough shares have been revealed, reconstruct the recovery private key.
35The keeper nub is read from stdin.
36HELP
37
38## Parse the command line.
39case $# in 2) ;; *) usage_err ;; esac
40recov=$1 keeper=$2; shift 2
41checklabel "recovery key" "$recov"
42case "$recov" in
43 */*) ;;
44 *) recov=$recov/current ;;
45esac
46checkword "keeper set label" "$keeper"
47
48## Check that this is a sensible thing to do.
49if [ ! -f $KEYS/keeper/$keeper/meta ]; then
50 echo >&2 "$quis: unknown keeper set \`$keeper'"
51 exit 1
52fi
53if [ ! -d $KEYS/recov/$recov ]; then
54 echo >&2 "$quis: unknown recovery key \`$recov'"
55 exit 1
56fi
57if [ ! -f $KEYS/recov/$recov/$keeper.param ]; then
58 echo >&2 "$quis: recovery key \`$recov' not kept by keeper set \`$keeper'"
59 exit 1
60fi
61
62## Grab the key, because we'll need to read it several times.
63mktmp
64cat >$tmp/secret
65
66## Read the threshold from the recovery metadata.
67read param <$KEYS/recov/$recov/$keeper.param
68case "$param" in
69 shamir-params:*) ;;
70 *)
71 echo >&2 "$quis: secret sharing parameter file damaged (wrong header)"
72 exit 1
73 ;;
74esac
75t=";${param#*:}"
76case "$t" in
77 *";t="*) ;;
78 *)
79 echo >&2 "$quis: secret sharing parameter file damaged (missing t)"
80 exit 1
81 ;;
82esac
83t=${t#*;t=}
84t=${t%%;*}
85
86## Find out which keeper index it corresponds to.
87read n hunoz <$KEYS/keeper/$keeper/meta
88i=0
89foundp=nil
90while [ $i -lt $n ]; do
91 c_sysprepare $KEYS/keeper/$keeper/$i
92 nubbin=$(nubid <$tmp/secret)
93 nubid=$(cat $KEYS/keeper/$keeper/$i/nubid)
94 case "$nubbin" in "$nubid") foundp=t; break ;; esac
95 i=$(( $i + 1 ))
96done
97case $foundp in
98 nil) echo >&2 "$quis: nub doesn't match keeper \`$keeper'"; exit 1 ;;
99esac
100
101## Establish the recovery staging area. See whether we've done enough
102## already.
103reqsafe
104tag=$(echo $recov | tr / .)
105mkdir -p -m700 $SAFE/keys.reveal
106reveal=$SAFE/keys.reveal/$tag
107if [ ! -d $reveal ]; then mkdir -m700 $reveal; fi
108cd $reveal
109if [ -f nub ]; then
110 echo >&2 "$quis: recovery key \`$recov' already revealed"
111 exit 1
112fi
113
114## Decrypt the share.
115umask 077
116if [ -f $keeper.$i.share ]; then
117 echo >&2 "$quis: share $i already revealed"
118else
119 c_sysdecrypt $KEYS/keeper/$keeper/$i $tmp/secret \
120 <$KEYS/recov/$recov/$keeper.$i.share \
121 >$keeper.$i.new
122 mv $keeper.$i.new $keeper.$i.share
123fi
124
125## See if there's enough for a recovery.
126n=0
127for j in $keeper.*.share; do if [ -f "$j" ]; then n=$(( $n + 1 )); fi; done
128if [ $n -lt $t ]; then
129 echo >&2 "$quis: share $i revealed; $(( $t - $n )) more required"
130else
131 cat $KEYS/recov/$recov/$keeper.param $keeper.*.share >$keeper.shares
132 $bindir/shamir recover <$keeper.shares >nub.new
133 c_sysprepare $KEYS/recov/$recov/store
134 nubbin=$(nubid <nub.new)
135 nubid=$(cat $KEYS/recov/$recov/store/nubid)
136 case "$nubbin" in
137 "$nubid") ;;
138 *)
139 echo >&2 "$quis: recovered nub doesn't match stored hash"
140 exit 1
141 ;;
142 esac
143 mv nub.new nub
144 rm -f $keeper.*
145 echo >&2 "$quis: recovery key \`$recov' revealed"
146fi
147
148###----- That's all, folks --------------------------------------------------