principals-command.sh

#	$OpenBSD: principals-command.sh,v 1.4 2017/04/30 23:34:55 djm Exp $
#	Placed in the Public Domain.

tid="authorized principals command"

rm -f $OBJ/user_ca_key* $OBJ/cert_user_key*
cp $OBJ/sshd_proxy $OBJ/sshd_proxy_bak

if [ -z "$SUDO" -a ! -w /var/run ]; then
	echo "skipped (SUDO not set)"
	echo "need SUDO to create file in /var/run, test won't work without"
	exit 0
fi

SERIAL=$$

# Create a CA key and a user certificate.
${SSHKEYGEN} -q -N '' -t ed25519  -f $OBJ/user_ca_key || \
	fatal "ssh-keygen of user_ca_key failed"
${SSHKEYGEN} -q -N '' -t rsa -f $OBJ/cert_user_key || \
	fatal "ssh-keygen of cert_user_key failed"
${SSHKEYGEN} -q -s $OBJ/user_ca_key -I "Joanne User" \
    -z $$ -n ${USER},mekmitasdigoat $OBJ/cert_user_key || \
	fatal "couldn't sign cert_user_key"

CERT_BODY=`cat $OBJ/cert_user_key-cert.pub | awk '{ print $2 }'`
CA_BODY=`cat $OBJ/user_ca_key.pub | awk '{ print $2 }'`
CERT_FP=`${SSHKEYGEN} -lf $OBJ/cert_user_key-cert.pub | awk '{ print $2 }'`
CA_FP=`${SSHKEYGEN} -lf $OBJ/user_ca_key.pub | awk '{ print $2 }'`

# Establish a AuthorizedPrincipalsCommand in /var/run where it will have
# acceptable directory permissions.
PRINCIPALS_COMMAND="/var/run/principals_command_${LOGNAME}"
cat << _EOF | $SUDO sh -c "cat > '$PRINCIPALS_COMMAND'"
#!/bin/sh
test "x\$1" != "x${LOGNAME}" && exit 1
test "x\$2" != "xssh-rsa-cert-v01@openssh.com" && exit 1
test "x\$3" != "xssh-ed25519" && exit 1
test "x\$4" != "xJoanne User" && exit 1
test "x\$5" != "x${SERIAL}" && exit 1
test "x\$6" != "x${CA_FP}" && exit 1
test "x\$7" != "x${CERT_FP}" && exit 1
test "x\$8" != "x${CERT_BODY}" && exit 1
test "x\$9" != "x${CA_BODY}" && exit 1
test -f "$OBJ/authorized_principals_${LOGNAME}" &&
	exec cat "$OBJ/authorized_principals_${LOGNAME}"
_EOF
test $? -eq 0 || fatal "couldn't prepare principals command"
$SUDO chmod 0755 "$PRINCIPALS_COMMAND"

if ! $OBJ/check-perm -m keys-command $PRINCIPALS_COMMAND ; then
	echo "skipping: $PRINCIPALS_COMMAND is unsuitable as " \
	    "AuthorizedPrincipalsCommand"
	$SUDO rm -f $PRINCIPALS_COMMAND
	exit 0
fi

if [ -x $PRINCIPALS_COMMAND ]; then
	# Test explicitly-specified principals
	for privsep in yes no ; do
		_prefix="privsep $privsep"

		# Setup for AuthorizedPrincipalsCommand
		rm -f $OBJ/authorized_keys_$USER
		(
			cat $OBJ/sshd_proxy_bak
			echo "UsePrivilegeSeparation $privsep"
			echo "AuthorizedKeysFile none"
			echo "AuthorizedPrincipalsCommand $PRINCIPALS_COMMAND" \
			    "%u %t %T %i %s %F %f %k %K"
			echo "AuthorizedPrincipalsCommandUser ${LOGNAME}"
			echo "TrustedUserCAKeys $OBJ/user_ca_key.pub"
		) > $OBJ/sshd_proxy

		# XXX test missing command
		# XXX test failing command

		# Empty authorized_principals
		verbose "$tid: ${_prefix} empty authorized_principals"
		echo > $OBJ/authorized_principals_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost true >/dev/null 2>&1
		if [ $? -eq 0 ]; then
			fail "ssh cert connect succeeded unexpectedly"
		fi

		# Wrong authorized_principals
		verbose "$tid: ${_prefix} wrong authorized_principals"
		echo gregorsamsa > $OBJ/authorized_principals_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost true >/dev/null 2>&1
		if [ $? -eq 0 ]; then
			fail "ssh cert connect succeeded unexpectedly"
		fi

		# Correct authorized_principals
		verbose "$tid: ${_prefix} correct authorized_principals"
		echo mekmitasdigoat > $OBJ/authorized_principals_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost true >/dev/null 2>&1
		if [ $? -ne 0 ]; then
			fail "ssh cert connect failed"
		fi

		# authorized_principals with bad key option
		verbose "$tid: ${_prefix} authorized_principals bad key opt"
		echo 'blah mekmitasdigoat' > $OBJ/authorized_principals_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost true >/dev/null 2>&1
		if [ $? -eq 0 ]; then
			fail "ssh cert connect succeeded unexpectedly"
		fi

		# authorized_principals with command=false
		verbose "$tid: ${_prefix} authorized_principals command=false"
		echo 'command="false" mekmitasdigoat' > \
		    $OBJ/authorized_principals_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost true >/dev/null 2>&1
		if [ $? -eq 0 ]; then
			fail "ssh cert connect succeeded unexpectedly"
		fi

		# authorized_principals with command=true
		verbose "$tid: ${_prefix} authorized_principals command=true"
		echo 'command="true" mekmitasdigoat' > \
		    $OBJ/authorized_principals_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost false >/dev/null 2>&1
		if [ $? -ne 0 ]; then
			fail "ssh cert connect failed"
		fi

		# Setup for principals= key option
		rm -f $OBJ/authorized_principals_$USER
		(
			cat $OBJ/sshd_proxy_bak
			echo "UsePrivilegeSeparation $privsep"
		) > $OBJ/sshd_proxy

		# Wrong principals list
		verbose "$tid: ${_prefix} wrong principals key option"
		(
			printf 'cert-authority,principals="gregorsamsa" '
			cat $OBJ/user_ca_key.pub
		) > $OBJ/authorized_keys_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost true >/dev/null 2>&1
		if [ $? -eq 0 ]; then
			fail "ssh cert connect succeeded unexpectedly"
		fi

		# Correct principals list
		verbose "$tid: ${_prefix} correct principals key option"
		(
			printf 'cert-authority,principals="mekmitasdigoat" '
			cat $OBJ/user_ca_key.pub
		) > $OBJ/authorized_keys_$USER
		${SSH} -i $OBJ/cert_user_key \
		    -F $OBJ/ssh_proxy somehost true >/dev/null 2>&1
		if [ $? -ne 0 ]; then
			fail "ssh cert connect failed"
		fi
	done
else
	echo "SKIPPED: $PRINCIPALS_COMMAND not executable " \
	    "(/var/run mounted noexec?)"
fi