vyos-documentation/docs/configuration/vpn/sstp.rst

.. _sstp:

###########
SSTP Server
###########

:abbr:`SSTP (Secure Socket Tunneling Protocol)` is a form of :abbr:`VPN
(Virtual Private Network)` tunnel that provides a mechanism to transport PPP
traffic through an SSL/TLS channel. SSL/TLS provides transport-level security
with key negotiation, encryption and traffic integrity checking. The use of
SSL/TLS over TCP port 443 allows SSTP to pass through virtually all firewalls
and proxy servers except for authenticated web proxies.

SSTP is available for Linux, BSD, and Windows.

VyOS utilizes accel-ppp_ to provide SSTP server functionality. We support both
local and RADIUS authentication.

As SSTP provides PPP via a SSL/TLS channel the use of either publically signed
certificates as well as a private PKI is required.

.. note:: All certificates should be stored on VyOS under ``/config/auth``. If
  certificates are not stored in the ``/config`` directory they will not be
  migrated during a software update.

Certificates
============

Self Signed CA
--------------

To generate the CA, the server private key and certificates the following
commands can be used.

.. code-block:: none

  vyos@vyos:~$ mkdir -p /config/user-data/sstp
  vyos@vyos:~$ openssl req -newkey rsa:4096 -new -nodes -x509 -days 3650 -keyout /config/user-data/sstp/server.key -out /config/user-data/sstp/server.crt

  Generating a 4096 bit RSA private key
  .........................++
  ...............................................................++
  writing new private key to 'server.key'
  [...]
  Country Name (2 letter code) [AU]:
  State or Province Name (full name) [Some-State]:
  Locality Name (eg, city) []:
  Organization Name (eg, company) [Internet Widgits Pty Ltd]:
  Organizational Unit Name (eg, section) []:
  Common Name (e.g. server FQDN or YOUR name) []:
  Email Address []:

  vyos@vyos:~$ openssl req -new -x509 -key /config/user-data/sstp/server.key -out /config/user-data/sstp/ca.crt
  [...]
  Country Name (2 letter code) [AU]:
  State or Province Name (full name) [Some-State]:
  Locality Name (eg, city) []:
  Organization Name (eg, company) [Internet Widgits Pty Ltd]:
  Organizational Unit Name (eg, section) []:
  Common Name (e.g. server FQDN or YOUR name) []:
  Email Address []:


Configuration
=============

.. cfgcmd:: set vpn sstp authentication local-users username <user> password
   <pass>

  Create `<user>` for local authentication on this system. The users password
  will be set to `<pass>`.

.. cfgcmd:: set vpn sstp authentication local-users username <user> disable

  Disable `<user>` account.

.. cfgcmd:: set vpn sstp authentication local-users username <user> static-ip
   <address>

  Assign static IP address to `<user>` account.

.. cfgcmd:: set vpn sstp authentication local-users username <user> rate-limit
   download <bandwidth>

  Download bandwidth limit in kbit/s for `<user>`.

.. cfgcmd:: set vpn sstp authentication local-users username <user> rate-limit
   upload <bandwidth>

  Upload bandwidth limit in kbit/s for `<user>`.

.. cfgcmd:: set vpn sstp authentication protocols
   <pap | chap | mschap | mschap-v2>

  Require the peer to authenticate itself using one of the following protocols:
  pap, chap, mschap, mschap-v2.

.. cfgcmd:: set vpn sstp authentication mode <local | radius>

  Set authentication backend. The configured authentication backend is used
  for all queries.

  * **radius**: All authentication queries are handled by a configured RADIUS
    server.
  * **local**: All authentication queries are handled locally.


.. cfgcmd:: set vpn sstp gateway-address <gateway>

  Specifies single `<gateway>` IP address to be used as local address of PPP
  interfaces.


.. cfgcmd:: set vpn sstp port <port>

  Specifies the port `<port>` that the SSTP port will listen on (default 443).


.. cfgcmd:: set vpn sstp client-ip-pool subnet <subnet>

  Use `<subnet>` as the IP pool for all connecting clients.


.. cfgcmd:: set vpn sstp client-ipv6-pool prefix <address> mask <number-of-bits>

  Use this comand to set the IPv6 address pool from which an SSTP client
  will get an IPv6 prefix of your defined length (mask) to terminate the
  SSTP endpoint at their side. The mask length can be set from 48 to 128
  bit long, the default value is 64.


.. cfgcmd:: set vpn sstp client-ipv6-pool delegate <address> delegation-prefix
   <number-of-bits>

  Use this command to configure DHCPv6 Prefix Delegation (RFC3633) on
  SSTP. You will have to set your IPv6 pool and the length of the
  delegation prefix. From the defined IPv6 pool you will be handing out
  networks of the defined length (delegation-prefix). The length of the
  delegation prefix can be set from 32 to 64 bit long.


.. cfgcmd:: set vpn sstp name-server <address>

  Connected client should use `<address>` as their DNS server. This
  command accepts both IPv4 and IPv6 addresses. Up to two nameservers
  can be configured for IPv4, up to three for IPv6.

Maximum number of IPv4 nameservers

SSL Certificates
----------------

.. cfgcmd:: set vpn sstp ssl ca-cert-file <file>

  Path to `<file>` pointing to the certificate authority certificate.

.. cfgcmd:: set vpn sstp ssl cert-file <file>

  Path to `<file>` pointing to the servers certificate (public portion).


PPP Settings
------------

.. cfgcmd:: set vpn sstp ppp-options lcp-echo-failure <number>

  Defines the maximum `<number>` of unanswered echo requests. Upon reaching the
  value `<number>`, the session will be reset.

.. cfgcmd:: set vpn sstp ppp-options lcp-echo-interval <interval>

  If this option is specified and is greater than 0, then the PPP module will
  send LCP pings of the echo request every `<interval>` seconds.

.. cfgcmd:: set vpn sstp ppp-options lcp-echo-timeout

  Specifies timeout in seconds to wait for any peer activity. If this option
  specified it turns on adaptive lcp echo functionality and "lcp-echo-failure"
  is not used.

.. cfgcmd:: set vpn sstp ppp-options mppe <require | prefer | deny>

  Specifies :abbr:`MPPE (Microsoft Point-to-Point Encryption)` negotioation
  preference.

  * **require** - ask client for mppe, if it rejects drop connection
  * **prefer** - ask client for mppe, if it rejects don't fail
  * **deny** - deny mppe

  Default behavior - don't ask client for mppe, but allow it if client wants.
  Please note that RADIUS may override this option by MS-MPPE-Encryption-Policy
  attribute.


RADIUS
------

Server
^^^^^^

.. cfgcmd:: set vpn sstp authentication radius server <server> port <port>

  Configure RADIUS `<server>` and its required port for authentication requests.

.. cfgcmd:: set vpn sstp authentication radius server <server> key <secret>

  Configure RADIUS `<server>` and its required shared `<secret>` for
  communicating with the RADIUS server.

.. cfgcmd:: set vpn sstp authentication radius server <server> fail-time <time>

  Mark RADIUS server as offline for this given `<time>` in seconds.

.. cfgcmd:: set vpn sstp authentication radius server <server> disable

  Temporary disable this RADIUS server.

Options
^^^^^^^

.. cfgcmd:: set vpn sstp authentication radius acct-timeout <timeout>

  Timeout to wait reply for Interim-Update packets. (default 3 seconds)

.. cfgcmd:: set vpn sstp authentication radius dynamic-author server <address>

  Specifies IP address for Dynamic Authorization Extension server (DM/CoA)

.. cfgcmd:: set vpn sstp authentication radius dynamic-author port <port>

  Port for Dynamic Authorization Extension server (DM/CoA)

.. cfgcmd:: set vpn sstp authentication radius dynamic-author key <secret>

  Secret for Dynamic Authorization Extension server (DM/CoA)

.. cfgcmd:: set vpn sstp authentication radius max-try <number>

  Maximum number of tries to send Access-Request/Accounting-Request queries

.. cfgcmd:: set vpn sstp authentication radius timeout <timeout>

  Timeout to wait response from server (seconds)

.. cfgcmd:: set vpn sstp authentication radius nas-identifier <identifier>

  Value to send to RADIUS server in NAS-Identifier attribute and to be matched
  in DM/CoA requests.

.. cfgcmd:: set vpn sstp authentication radius nas-ip-address <address>

  Value to send to RADIUS server in NAS-IP-Address attribute and to be matched
  in DM/CoA requests. Also DM/CoA server will bind to that address.

.. cfgcmd:: set vpn sstp authentication radius source-address <address>

  Source IPv4 address used in all RADIUS server queires.

.. cfgcmd:: set vpn sstp authentication radius rate-limit attribute <attribute>

  Specifies which RADIUS server attribute contains the rate limit information.
  The default attribute is `Filter-Id`.

.. cfgcmd:: set vpn sstp authentication radius rate-limit enable

  Enables bandwidth shaping via RADIUS.

.. cfgcmd:: set vpn sstp authentication radius rate-limit vendor

  Specifies the vendor dictionary, dictionary needs to be in
  /usr/share/accel-ppp/radius.


Example
=======

* Use local user `foo` with password `bar`
* Client IP addresses will be provided from pool `192.0.2.0/25`

.. code-block:: none

  set vpn sstp authentication local-users username vyos password vyos
  set vpn sstp authentication mode local
  set vpn sstp gateway-address 192.0.2.254
  set vpn sstp client-ip-pool subnet 192.0.2.0/25
  set vpn sstp name-server 10.0.0.1
  set vpn sstp name-server 10.0.0.2
  set vpn sstp ssl ca-cert-file /config/auth/ca.crt
  set vpn sstp ssl cert-file /config/auth/server.crt
  set vpn sstp ssl key-file /config/auth/server.key

Testing SSTP
============

Once you have setup your SSTP server there comes the time to do some basic
testing. The Linux client used for testing is called sstpc_. sstpc_ requires a
PPP configuration/peer file.

The following PPP configuration tests MSCHAP-v2:

.. code-block:: none

  $ cat /etc/ppp/peers/vyos
  usepeerdns
  #require-mppe
  #require-pap
  require-mschap-v2
  noauth
  lock
  refuse-pap
  refuse-eap
  refuse-chap
  refuse-mschap
  #refuse-mschap-v2
  nobsdcomp
  nodeflate
  debug


You can now "dial" the peer with the follwoing command: ``sstpc --log-level 4
--log-stderr --user vyos --password vyos vpn.example.com -- call vyos``.

A connection attempt will be shown as:

.. code-block:: none

  $ sstpc --log-level 4 --log-stderr --user vyos --password vyos vpn.example.com -- call vyos

  Mar 22 13:29:12 sstpc[12344]: Resolved vpn.example.com to 192.0.2.1
  Mar 22 13:29:12 sstpc[12344]: Connected to vpn.example.com
  Mar 22 13:29:12 sstpc[12344]: Sending Connect-Request Message
  Mar 22 13:29:12 sstpc[12344]: SEND SSTP CRTL PKT(14)
  Mar 22 13:29:12 sstpc[12344]:   TYPE(1): CONNECT REQUEST, ATTR(1):
  Mar 22 13:29:12 sstpc[12344]:     ENCAP PROTO(1): 6
  Mar 22 13:29:12 sstpc[12344]: RECV SSTP CRTL PKT(48)
  Mar 22 13:29:12 sstpc[12344]:   TYPE(2): CONNECT ACK, ATTR(1):
  Mar 22 13:29:12 sstpc[12344]:     CRYPTO BIND REQ(4): 40
  Mar 22 13:29:12 sstpc[12344]: Started PPP Link Negotiation
  Mar 22 13:29:15 sstpc[12344]: Sending Connected Message
  Mar 22 13:29:15 sstpc[12344]: SEND SSTP CRTL PKT(112)
  Mar 22 13:29:15 sstpc[12344]:   TYPE(4): CONNECTED, ATTR(1):
  Mar 22 13:29:15 sstpc[12344]:     CRYPTO BIND(3): 104
  Mar 22 13:29:15 sstpc[12344]: Connection Established

  $ ip addr show ppp0
  164: ppp0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1452 qdisc fq_codel state UNKNOWN group default qlen 3
       link/ppp  promiscuity 0
       inet 100.64.2.2 peer 100.64.1.1/32 scope global ppp0
          valid_lft forever preferred_lft forever



.. _sstpc: https://github.com/reliablehosting/sstp-client

.. include:: /_include/common-references.txt