limit-keytype.sh revision 295367 
1#	$OpenBSD: limit-keytype.sh,v 1.1 2015/01/13 07:49:49 djm Exp $
2#	Placed in the Public Domain.
3
4tid="restrict pubkey type"
5
6rm -f $OBJ/authorized_keys_$USER $OBJ/user_ca_key* $OBJ/user_key*
7rm -f $OBJ/authorized_principals_$USER $OBJ/cert_user_key*
8
9mv $OBJ/sshd_proxy $OBJ/sshd_proxy.orig
10mv $OBJ/ssh_proxy $OBJ/ssh_proxy.orig
11
12# Create a CA key
13${SSHKEYGEN} -q -N '' -t ed25519  -f $OBJ/user_ca_key ||\
14	fatal "ssh-keygen failed"
15
16# Make some keys and a certificate.
17${SSHKEYGEN} -q -N '' -t ed25519 -f $OBJ/user_key1 || \
18	fatal "ssh-keygen failed"
19${SSHKEYGEN} -q -N '' -t rsa -f $OBJ/user_key2 || \
20	fatal "ssh-keygen failed"
21${SSHKEYGEN} -q -N '' -t rsa -f $OBJ/user_key3 || \
22	fatal "ssh-keygen failed"
23${SSHKEYGEN} -q -s $OBJ/user_ca_key -I "regress user key for $USER" \
24	-z $$ -n ${USER},mekmitasdigoat $OBJ/user_key3 ||
25		fatal "couldn't sign user_key1"
26# Copy the private key alongside the cert to allow better control of when
27# it is offered.
28mv $OBJ/user_key3-cert.pub $OBJ/cert_user_key3.pub
29cp -p $OBJ/user_key3 $OBJ/cert_user_key3
30
31grep -v IdentityFile $OBJ/ssh_proxy.orig > $OBJ/ssh_proxy
32
33opts="-oProtocol=2 -F $OBJ/ssh_proxy -oIdentitiesOnly=yes"
34fullopts="$opts -i $OBJ/cert_user_key3 -i $OBJ/user_key1 -i $OBJ/user_key2"
35
36echo mekmitasdigoat > $OBJ/authorized_principals_$USER
37cat $OBJ/user_key1.pub > $OBJ/authorized_keys_$USER
38cat $OBJ/user_key2.pub >> $OBJ/authorized_keys_$USER
39
40prepare_config() {
41	(
42		grep -v "Protocol"  $OBJ/sshd_proxy.orig
43		echo "Protocol 2"
44		echo "AuthenticationMethods publickey"
45		echo "TrustedUserCAKeys $OBJ/user_ca_key.pub"
46		echo "AuthorizedPrincipalsFile $OBJ/authorized_principals_%u"
47		for x in "$@" ; do
48			echo "$x"
49		done
50 	) > $OBJ/sshd_proxy
51}
52
53prepare_config
54
55# Check we can log in with all key types.
56${SSH} $opts -i $OBJ/cert_user_key3 proxy true || fatal "cert failed"
57${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed"
58${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed"
59
60# Allow plain Ed25519 and RSA. The certificate should fail.
61verbose "privsep=$privsep allow rsa,ed25519"
62prepare_config "PubkeyAcceptedKeyTypes ssh-rsa,ssh-ed25519"
63${SSH} $opts -i $OBJ/cert_user_key3 proxy true && fatal "cert succeeded"
64${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed"
65${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed"
66
67# Allow Ed25519 only.
68verbose "privsep=$privsep allow ed25519"
69prepare_config "PubkeyAcceptedKeyTypes ssh-ed25519"
70${SSH} $opts -i $OBJ/cert_user_key3 proxy true && fatal "cert succeeded"
71${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed"
72${SSH} $opts -i $OBJ/user_key2 proxy true && fatal "key2 succeeded"
73
74# Allow all certs. Plain keys should fail.
75verbose "privsep=$privsep allow cert only"
76prepare_config "PubkeyAcceptedKeyTypes ssh-*-cert-v01@openssh.com"
77${SSH} $opts -i $OBJ/cert_user_key3 proxy true || fatal "cert failed"
78${SSH} $opts -i $OBJ/user_key1 proxy true && fatal "key1 succeeded"
79${SSH} $opts -i $OBJ/user_key2 proxy true && fatal "key2 succeeded"
80
81