hostkey-rotate.sh revision 1.10 
1#	$OpenBSD: hostkey-rotate.sh,v 1.10 2022/01/05 08:25:05 djm Exp $
2#	Placed in the Public Domain.
3
4tid="hostkey rotate"
5
6rm -f $OBJ/hkr.* $OBJ/ssh_proxy.orig $OBJ/ssh_proxy.orig
7
8grep -vi 'hostkey' $OBJ/sshd_proxy > $OBJ/sshd_proxy.orig
9mv $OBJ/ssh_proxy $OBJ/ssh_proxy.orig
10grep -vi 'globalknownhostsfile' $OBJ/ssh_proxy.orig > $OBJ/ssh_proxy
11echo "UpdateHostkeys=yes" >> $OBJ/ssh_proxy
12echo "GlobalKnownHostsFile=none" >> $OBJ/ssh_proxy
13rm $OBJ/known_hosts
14
15# The "primary" key type is ed25519 since it's supported even when built
16# without OpenSSL.  The secondary is RSA if it's supported.
17primary="ssh-ed25519"
18secondary="$primary"
19
20trace "prepare hostkeys"
21nkeys=0
22all_algs=""
23for k in $SSH_HOSTKEY_TYPES; do
24	${SSHKEYGEN} -qt $k -f $OBJ/hkr.$k -N '' || fatal "ssh-keygen $k"
25	echo "Hostkey $OBJ/hkr.${k}" >> $OBJ/sshd_proxy.orig
26	nkeys=`expr $nkeys + 1`
27	test "x$all_algs" = "x" || all_algs="${all_algs},"
28	case "$k" in
29	ssh-rsa)
30		secondary="ssh-rsa"
31		all_algs="${all_algs}rsa-sha2-256,rsa-sha2-512,$k"
32		;;
33	*)
34		all_algs="${all_algs}$k"
35		;;
36	esac
37done
38
39dossh() {
40	# All ssh should succeed in this test
41	${SSH} -F $OBJ/ssh_proxy "$@" x true || fail "ssh $@ failed"
42}
43
44expect_nkeys() {
45	_expected=$1
46	_message=$2
47	_n=`wc -l $OBJ/known_hosts | awk '{ print $1 }'` || fatal "wc failed"
48	[ "x$_n" = "x$_expected" ] || fail "$_message (got $_n wanted $_expected)"
49}
50
51check_key_present() {
52	_type=$1
53	_kfile=$2
54	test "x$_kfile" = "x" && _kfile="$OBJ/hkr.${_type}.pub"
55	_kpub=`awk "/$_type /"' { print $2 }' < $_kfile` || \
56		fatal "awk failed"
57	fgrep "$_kpub" $OBJ/known_hosts > /dev/null
58}
59
60cp $OBJ/sshd_proxy.orig $OBJ/sshd_proxy
61
62# Connect to sshd with StrictHostkeyChecking=no
63verbose "learn hostkey with StrictHostKeyChecking=no"
64>$OBJ/known_hosts
65dossh -oHostKeyAlgorithms=$primary -oStrictHostKeyChecking=no
66# Verify no additional keys learned
67expect_nkeys 1 "unstrict connect keys"
68check_key_present $primary || fail "unstrict didn't learn key"
69
70# Connect to sshd as usual
71verbose "learn additional hostkeys"
72dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=$all_algs
73# Check that other keys learned
74expect_nkeys $nkeys "learn hostkeys"
75for k in $SSH_HOSTKEY_TYPES; do
76	check_key_present $k || fail "didn't learn keytype $k"
77done
78
79# Check each key type
80for k in $SSH_HOSTKEY_TYPES; do
81	case "$k" in
82	ssh-rsa) alg="rsa-sha2-256,rsa-sha2-512,ssh-rsa" ;;
83	*) alg="$k" ;;
84	esac
85	verbose "learn additional hostkeys, type=$k"
86	dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=$alg,$all_algs
87	expect_nkeys $nkeys "learn hostkeys $k"
88	check_key_present $k || fail "didn't learn $k correctly"
89done
90
91# Change one hostkey (non primary) and relearn
92if [ "$primary" != "$secondary" ]; then
93	verbose "learn changed non-primary hostkey type=${secondary}"
94	mv $OBJ/hkr.${secondary}.pub $OBJ/hkr.${secondary}.pub.old
95	rm -f $OBJ/hkr.${secondary}
96	${SSHKEYGEN} -qt ${secondary} -f $OBJ/hkr.${secondary} -N '' || \
97	    fatal "ssh-keygen $secondary"
98	dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=$all_algs
99	# Check that the key was replaced
100	expect_nkeys $nkeys "learn hostkeys"
101	check_key_present ${secondary} $OBJ/hkr.${secondary}.pub.old && \
102	    fail "old key present"
103	check_key_present ${secondary} || fail "didn't learn changed key"
104fi
105
106# Add new hostkey (primary type) to sshd and connect
107verbose "learn new primary hostkey"
108${SSHKEYGEN} -qt ${primary} -f $OBJ/hkr.${primary}-new -N '' || fatal "ssh-keygen ed25519"
109( cat $OBJ/sshd_proxy.orig ; echo HostKey $OBJ/hkr.${primary}-new ) \
110    > $OBJ/sshd_proxy
111# Check new hostkey added
112dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=${primary},$all_algs
113expect_nkeys `expr $nkeys + 1` "learn hostkeys"
114check_key_present ${primary} || fail "current key missing"
115check_key_present ${primary} $OBJ/hkr.${primary}-new.pub || fail "new key missing"
116
117# Remove old hostkey (primary type) from sshd
118verbose "rotate primary hostkey"
119cp $OBJ/sshd_proxy.orig $OBJ/sshd_proxy
120mv $OBJ/hkr.${primary}.pub $OBJ/hkr.${primary}.pub.old
121mv $OBJ/hkr.${primary}-new.pub $OBJ/hkr.${primary}.pub
122mv $OBJ/hkr.${primary}-new $OBJ/hkr.${primary}
123# Check old hostkey removed
124dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=${primary},$all_algs
125expect_nkeys $nkeys "learn hostkeys"
126check_key_present ${primary} $OBJ/hkr.${primary}.pub.old && fail "old key present"
127check_key_present ${primary} || fail "didn't learn changed key"
128
129# Connect again, forcing rotated key
130verbose "check rotate primary hostkey"
131dossh -oStrictHostKeyChecking=yes -oHostKeyAlgorithms=${primary}
132expect_nkeys 1 "learn hostkeys"
133check_key_present ${primary} || fail "didn't learn changed key"
134