1#	$OpenBSD: hostkey-rotate.sh,v 1.8 2019/11/26 23:43:10 djm Exp $
2#	Placed in the Public Domain.
3
4tid="hostkey rotate"
5
6rm -f $OBJ/hkr.* $OBJ/ssh_proxy.orig
7
8grep -vi 'hostkey' $OBJ/sshd_proxy > $OBJ/sshd_proxy.orig
9echo "UpdateHostkeys=yes" >> $OBJ/ssh_proxy
10rm $OBJ/known_hosts
11
12# The "primary" key type is ed25519 since it's supported even when built
13# without OpenSSL.  The secondary is RSA if it's supported.
14primary="ssh-ed25519"
15secondary="$primary"
16
17trace "prepare hostkeys"
18nkeys=0
19all_algs=""
20for k in $SSH_HOSTKEY_TYPES; do
21	${SSHKEYGEN} -qt $k -f $OBJ/hkr.$k -N '' || fatal "ssh-keygen $k"
22	echo "Hostkey $OBJ/hkr.${k}" >> $OBJ/sshd_proxy.orig
23	nkeys=`expr $nkeys + 1`
24	test "x$all_algs" = "x" || all_algs="${all_algs},"
25	all_algs="${all_algs}$k"
26	case "$k" in
27		ssh-rsa)	secondary="ssh-rsa" ;;
28	esac
29done
30
31dossh() {
32	# All ssh should succeed in this test
33	${SSH} -F $OBJ/ssh_proxy "$@" x true || fail "ssh $@ failed"
34}
35
36expect_nkeys() {
37	_expected=$1
38	_message=$2
39	_n=`wc -l $OBJ/known_hosts | awk '{ print $1 }'` || fatal "wc failed"
40	[ "x$_n" = "x$_expected" ] || fail "$_message (got $_n wanted $_expected)"
41}
42
43check_key_present() {
44	_type=$1
45	_kfile=$2
46	test "x$_kfile" = "x" && _kfile="$OBJ/hkr.${_type}.pub"
47	_kpub=`awk "/$_type /"' { print $2 }' < $_kfile` || \
48		fatal "awk failed"
49	fgrep "$_kpub" $OBJ/known_hosts > /dev/null
50}
51
52cp $OBJ/sshd_proxy.orig $OBJ/sshd_proxy
53
54# Connect to sshd with StrictHostkeyChecking=no
55verbose "learn hostkey with StrictHostKeyChecking=no"
56>$OBJ/known_hosts
57dossh -oHostKeyAlgorithms=$primary -oStrictHostKeyChecking=no
58# Verify no additional keys learned
59expect_nkeys 1 "unstrict connect keys"
60check_key_present $primary || fail "unstrict didn't learn key"
61
62# Connect to sshd as usual
63verbose "learn additional hostkeys"
64dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=$all_algs
65# Check that other keys learned
66expect_nkeys $nkeys "learn hostkeys"
67for k in $SSH_HOSTKEY_TYPES; do
68	check_key_present $k || fail "didn't learn keytype $k"
69done
70
71# Check each key type
72for k in $SSH_HOSTKEY_TYPES; do
73	verbose "learn additional hostkeys, type=$k"
74	dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=$k,$all_algs
75	expect_nkeys $nkeys "learn hostkeys $k"
76	check_key_present $k || fail "didn't learn $k correctly"
77done
78
79# Change one hostkey (non primary) and relearn
80if [ "$primary" != "$secondary" ]; then
81	verbose "learn changed non-primary hostkey type=${secondary}"
82	mv $OBJ/hkr.${secondary}.pub $OBJ/hkr.${secondary}.pub.old
83	rm -f $OBJ/hkr.${secondary}
84	${SSHKEYGEN} -qt ${secondary} -f $OBJ/hkr.${secondary} -N '' || \
85	    fatal "ssh-keygen $secondary"
86	dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=$all_algs
87	# Check that the key was replaced
88	expect_nkeys $nkeys "learn hostkeys"
89	check_key_present ${secondary} $OBJ/hkr.${secondary}.pub.old && \
90	    fail "old key present"
91	check_key_present ${secondary} || fail "didn't learn changed key"
92fi
93
94# Add new hostkey (primary type) to sshd and connect
95verbose "learn new primary hostkey"
96${SSHKEYGEN} -qt ${primary} -f $OBJ/hkr.${primary}-new -N '' || fatal "ssh-keygen ed25519"
97( cat $OBJ/sshd_proxy.orig ; echo HostKey $OBJ/hkr.${primary}-new ) \
98    > $OBJ/sshd_proxy
99# Check new hostkey added
100dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=${primary},$all_algs
101expect_nkeys `expr $nkeys + 1` "learn hostkeys"
102check_key_present ${primary} || fail "current key missing"
103check_key_present ${primary} $OBJ/hkr.${primary}-new.pub || fail "new key missing"
104
105# Remove old hostkey (primary type) from sshd
106verbose "rotate primary hostkey"
107cp $OBJ/sshd_proxy.orig $OBJ/sshd_proxy
108mv $OBJ/hkr.${primary}.pub $OBJ/hkr.${primary}.pub.old
109mv $OBJ/hkr.${primary}-new.pub $OBJ/hkr.${primary}.pub
110mv $OBJ/hkr.${primary}-new $OBJ/hkr.${primary}
111# Check old hostkey removed
112dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=${primary},$all_algs
113expect_nkeys $nkeys "learn hostkeys"
114check_key_present ${primary} $OBJ/hkr.${primary}.pub.old && fail "old key present"
115check_key_present ${primary} || fail "didn't learn changed key"
116
117# Connect again, forcing rotated key
118verbose "check rotate primary hostkey"
119dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=${primary}
120expect_nkeys 1 "learn hostkeys"
121check_key_present ${primary} || fail "didn't learn changed key"
122