| # $OpenBSD: limit-keytype.sh,v 1.9 2019/12/16 02:39:05 djm Exp $ |
| # Placed in the Public Domain. |
| |
| tid="restrict pubkey type" |
| |
| # XXX sk-* keys aren't actually tested ATM. |
| |
| rm -f $OBJ/authorized_keys_$USER $OBJ/user_ca_key* $OBJ/user_key* |
| rm -f $OBJ/authorized_principals_$USER $OBJ/cert_user_key* |
| |
| mv $OBJ/sshd_proxy $OBJ/sshd_proxy.orig |
| mv $OBJ/ssh_proxy $OBJ/ssh_proxy.orig |
| |
| ktype1=ed25519; ktype2=ed25519; ktype3=ed25519; |
| ktype4=ed25519; ktype5=ed25519; ktype6=ed25519; |
| for t in $SSH_KEYTYPES ; do |
| case "$t" in |
| ssh-rsa) ktype2=rsa ;; |
| ecdsa*) ktype3=ecdsa ;; # unused |
| ssh-dss) ktype4=dsa ;; |
| sk-ssh-ed25519@openssh.com) ktype5=ed25519-sk ;; |
| sk-ecdsa-sha2-nistp256@openssh.com) ktype6=ecdsa-sk ;; |
| esac |
| done |
| |
| # Create a CA key |
| ${SSHKEYGEN} -q -N '' -t $ktype1 -f $OBJ/user_ca_key ||\ |
| fatal "ssh-keygen failed" |
| |
| # Make some keys and a certificate. |
| ${SSHKEYGEN} -q -N '' -t $ktype1 -f $OBJ/user_key1 || \ |
| fatal "ssh-keygen failed" |
| ${SSHKEYGEN} -q -N '' -t $ktype2 -f $OBJ/user_key2 || \ |
| fatal "ssh-keygen failed" |
| ${SSHKEYGEN} -q -N '' -t $ktype2 -f $OBJ/user_key3 || \ |
| fatal "ssh-keygen failed" |
| ${SSHKEYGEN} -q -N '' -t $ktype4 -f $OBJ/user_key4 || \ |
| fatal "ssh-keygen failed" |
| ${SSHKEYGEN} -q -N '' -t $ktype5 -f $OBJ/user_key5 || \ |
| fatal "ssh-keygen failed" |
| ${SSHKEYGEN} -q -N '' -t $ktype6 -f $OBJ/user_key6 || \ |
| fatal "ssh-keygen failed" |
| ${SSHKEYGEN} -q -s $OBJ/user_ca_key -I "regress user key for $USER" \ |
| -z $$ -n ${USER},mekmitasdigoat $OBJ/user_key3 || |
| fatal "couldn't sign user_key1" |
| # Copy the private key alongside the cert to allow better control of when |
| # it is offered. |
| mv $OBJ/user_key3-cert.pub $OBJ/cert_user_key3.pub |
| |
| grep -v IdentityFile $OBJ/ssh_proxy.orig > $OBJ/ssh_proxy |
| |
| opts="-oProtocol=2 -F $OBJ/ssh_proxy -oIdentitiesOnly=yes" |
| certopts="$opts -i $OBJ/user_key3 -oCertificateFile=$OBJ/cert_user_key3.pub" |
| |
| echo mekmitasdigoat > $OBJ/authorized_principals_$USER |
| cat $OBJ/user_key1.pub > $OBJ/authorized_keys_$USER |
| cat $OBJ/user_key2.pub >> $OBJ/authorized_keys_$USER |
| |
| prepare_config() { |
| ( |
| grep -v "Protocol" $OBJ/sshd_proxy.orig |
| echo "Protocol 2" |
| echo "AuthenticationMethods publickey" |
| echo "TrustedUserCAKeys $OBJ/user_ca_key.pub" |
| echo "AuthorizedPrincipalsFile $OBJ/authorized_principals_%u" |
| for x in "$@" ; do |
| echo "$x" |
| done |
| ) > $OBJ/sshd_proxy |
| } |
| |
| # Return the required parameter for PubkeyAcceptedKeyTypes corresponding to |
| # the supplied key type. |
| keytype() { |
| case "$1" in |
| ecdsa) printf "ecdsa-sha2-*" ;; |
| ed25519) printf "ssh-ed25519" ;; |
| dsa) printf "ssh-dss" ;; |
| rsa) printf "rsa-sha2-256,rsa-sha2-512,ssh-rsa" ;; |
| sk-ecdsa) printf "sk-ecdsa-*" ;; |
| sk-ssh-ed25519) printf "sk-ssh-ed25519-*" ;; |
| esac |
| } |
| |
| prepare_config |
| |
| # Check we can log in with all key types. |
| ${SSH} $certopts proxy true || fatal "cert failed" |
| ${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed" |
| ${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed" |
| |
| # Allow plain Ed25519 and RSA. The certificate should fail. |
| verbose "allow $ktype2,$ktype1" |
| prepare_config \ |
| "PubkeyAcceptedKeyTypes `keytype $ktype2`,`keytype $ktype1`" |
| ${SSH} $certopts proxy true && fatal "cert succeeded" |
| ${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed" |
| ${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed" |
| |
| # Allow Ed25519 only. |
| verbose "allow $ktype1" |
| prepare_config "PubkeyAcceptedKeyTypes `keytype $ktype1`" |
| ${SSH} $certopts proxy true && fatal "cert succeeded" |
| ${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed" |
| if [ "$ktype1" != "$ktype2" ]; then |
| ${SSH} $opts -i $OBJ/user_key2 proxy true && fatal "key2 succeeded" |
| fi |
| |
| # Allow all certs. Plain keys should fail. |
| verbose "allow cert only" |
| prepare_config "PubkeyAcceptedKeyTypes *-cert-v01@openssh.com" |
| ${SSH} $certopts proxy true || fatal "cert failed" |
| ${SSH} $opts -i $OBJ/user_key1 proxy true && fatal "key1 succeeded" |
| ${SSH} $opts -i $OBJ/user_key2 proxy true && fatal "key2 succeeded" |
| |
| # Allow RSA in main config, Ed25519 for non-existent user. |
| verbose "match w/ no match" |
| prepare_config "PubkeyAcceptedKeyTypes `keytype $ktype2`" \ |
| "Match user x$USER" "PubkeyAcceptedKeyTypes +`keytype $ktype1`" |
| ${SSH} $certopts proxy true && fatal "cert succeeded" |
| if [ "$ktype1" != "$ktype2" ]; then |
| ${SSH} $opts -i $OBJ/user_key1 proxy true && fatal "key1 succeeded" |
| fi |
| ${SSH} $opts -i $OBJ/user_key2 proxy true || fatal "key2 failed" |
| |
| # Allow only DSA in main config, Ed25519 for user. |
| verbose "match w/ matching" |
| prepare_config "PubkeyAcceptedKeyTypes `keytype $ktype4`" \ |
| "Match user $USER" "PubkeyAcceptedKeyTypes +`keytype $ktype1`" |
| ${SSH} $certopts proxy true || fatal "cert failed" |
| ${SSH} $opts -i $OBJ/user_key1 proxy true || fatal "key1 failed" |
| ${SSH} $opts -i $OBJ/user_key4 proxy true && fatal "key4 succeeded" |
| |