limit-keytype.sh revision 296781 
1#	$OpenBSD: limit-keytype.sh,v 1.4 2015/10/29 08:05:17 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 -N '' -t dsa -f $OBJ/user_key4 || \
24	fatal "ssh-keygen failed"
25${SSHKEYGEN} -q -s $OBJ/user_ca_key -I "regress user key for $USER" \
26	-z $$ -n ${USER},mekmitasdigoat $OBJ/user_key3 ||
27		fatal "couldn't sign user_key1"
28# Copy the private key alongside the cert to allow better control of when
29# it is offered.
30mv $OBJ/user_key3-cert.pub $OBJ/cert_user_key3.pub
31
32grep -v IdentityFile $OBJ/ssh_proxy.orig > $OBJ/ssh_proxy
33
34opts="-oProtocol=2 -F $OBJ/ssh_proxy -oIdentitiesOnly=yes"
35certopts="$opts -i $OBJ/user_key3 -oCertificateFile=$OBJ/cert_user_key3.pub"
36
37echo mekmitasdigoat > $OBJ/authorized_principals_$USER
38cat $OBJ/user_key1.pub > $OBJ/authorized_keys_$USER
39cat $OBJ/user_key2.pub >> $OBJ/authorized_keys_$USER
40
41prepare_config() {
42	(
43		grep -v "Protocol"  $OBJ/sshd_proxy.orig
44		echo "Protocol 2"
45		echo "AuthenticationMethods publickey"
46		echo "TrustedUserCAKeys $OBJ/user_ca_key.pub"
47		echo "AuthorizedPrincipalsFile $OBJ/authorized_principals_%u"
48		for x in "$@" ; do
49			echo "$x"
50		done
51 	) > $OBJ/sshd_proxy
52}
53
54prepare_config
55
56# Check we can log in with all key types.
57${SSH} $certopts proxy true || fatal "cert failed"
58${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed"
59${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed"
60
61# Allow plain Ed25519 and RSA. The certificate should fail.
62verbose "allow rsa,ed25519"
63prepare_config "PubkeyAcceptedKeyTypes ssh-rsa,ssh-ed25519"
64${SSH} $certopts proxy true && fatal "cert succeeded"
65${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed"
66${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed"
67
68# Allow Ed25519 only.
69verbose "allow ed25519"
70prepare_config "PubkeyAcceptedKeyTypes ssh-ed25519"
71${SSH} $certopts proxy true && fatal "cert succeeded"
72${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed"
73${SSH} $opts -i $OBJ/user_key2 proxy true && fatal "key2 succeeded"
74
75# Allow all certs. Plain keys should fail.
76verbose "allow cert only"
77prepare_config "PubkeyAcceptedKeyTypes ssh-*-cert-v01@openssh.com"
78${SSH} $certopts proxy true || fatal "cert failed"
79${SSH} $opts -i $OBJ/user_key1 proxy true && fatal "key1 succeeded"
80${SSH} $opts -i $OBJ/user_key2 proxy true && fatal "key2 succeeded"
81
82# Allow RSA in main config, Ed25519 for non-existent user.
83verbose "match w/ no match"
84prepare_config "PubkeyAcceptedKeyTypes ssh-rsa" \
85	"Match user x$USER" "PubkeyAcceptedKeyTypes +ssh-ed25519"
86${SSH} $certopts proxy true && fatal "cert succeeded"
87${SSH} $opts -i $OBJ/user_key1 proxy true && fatal "key1 succeeded"
88${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed"
89
90# Allow only DSA in main config, Ed25519 for user.
91verbose "match w/ matching"
92prepare_config "PubkeyAcceptedKeyTypes ssh-dss" \
93	"Match user $USER" "PubkeyAcceptedKeyTypes +ssh-ed25519"
94${SSH} $certopts proxy true || fatal "cert failed"
95${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed"
96${SSH} $opts -i $OBJ/user_key4 proxy true && fatal "key4 succeeded"
97
98