set vpn sstp authentication local-users username foo password 'bar'
set vpn sstp authentication local-users username foo2 password 'bar2'
set vpn sstp authentication mode 'local'
set vpn sstp client-ipv6-pool prefix 2001:db8::/48
set vpn sstp gateway-address '192.168.122.14'
set vpn sstp ppp-options ipv4 'deny'
set vpn sstp ppp-options ipv6 'allow'
set vpn sstp ssl ca-cert-file '/config/user-data/sstp/ca.crt'
set vpn sstp ssl cert-file '/config/user-data/sstp/server.crt'
set vpn sstp ssl key-file '/config/user-data/sstp/server.key'

vyos@r4-epa2:~$ show sstp-server s
sessions    statistics  
vyos@r4-epa2:~$ show sstp-server sessions 
ifname | username |          ip           |          ip6          | ip6-dp |   calling-sid   | rate-limit | state  |  uptime  | rx-bytes | tx-bytes 
--------+----------+-----------------------+-----------------------+--------+-----------------+------------+--------+----------+----------+----------
 sstp0  | foo2     | 2001:db8:0:0:200::/64 | 2001:db8:0:0:200::/64 |        | 192.168.122.222 |            | active | 00:00:09 | 735 B    | 506 B
vyos@r4-epa2:~$

vyos@r4-epa2:~$ generate openvpn key foo
Generating OpenVPN key to /config/auth/foo
Your new local OpenVPN key has been generated
vyos@r4-epa2:~$ 
vyos@r4-epa2:~$ ls -la /config/auth/
total 12
drwxrwsr-x 2 root vyattacfg 4096 Nov  2 09:00 .
drwxrwxr-x 7 root vyattacfg 4096 Nov  2 08:54 ..
-rw------- 1 root vyattacfg  636 Nov  2 09:00 foo
vyos@r4-epa2:~$