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diff --git a/docs/configuration/interfaces/openvpn.rst b/docs/configuration/interfaces/openvpn.rst new file mode 100644 index 00000000..8b32743f --- /dev/null +++ b/docs/configuration/interfaces/openvpn.rst @@ -0,0 +1,590 @@ +.. _openvpn: + +####### +OpenVPN +####### + +Traditionally hardware routers implement IPsec exclusively due to relative +ease of implementing it in hardware and insufficient CPU power for doing +encryption in software. Since VyOS is a software router, this is less of a +concern. OpenVPN has been widely used on UNIX platform for a long time and is +a popular option for remote access VPN, though it's also capable of +site-to-site connections. + +Advantages of OpenVPN are: + +* It uses a single TCP or UDP connection and does not rely on packet source + addresses, so it will work even through a double NAT: perfect for public + hotspots and such + +* It's easy to setup and offers very flexible split tunneling + +* There's a variety of client GUI frontends for any platform + +Disadvantages are: + +* It's slower than IPsec due to higher protocol overhead and the fact it runs + in user mode while IPsec, on Linux, is in kernel mode + +* None of the operating systems have client software installed by default + +In the VyOS CLI, a key point often overlooked is that rather than being +configured using the `set vpn` stanza, OpenVPN is configured as a network +interface using `set interfaces openvpn`. + +Site-To-Site +============ + +While many are aware of OpenVPN as a Client VPN solution, it is often +overlooked as a site-to-site VPN solution due to lack of support for this mode +in many router platforms. + +Site-to-site mode supports x.509 but doesn't require it and can also work with +static keys, which is simpler in many cases. In this example, we'll configure +a simple site-to-site OpenVPN tunnel using a 2048-bit pre-shared key. + +First, one of the systems generate the key using the operational command +``generate openvpn key <filename>``. This will generate a key with the name +provided in the ``/config/auth/`` directory. Once generated, you will need to +copy this key to the remote router. + +In our example, we used the filename ``openvpn-1.key`` which we will reference +in our configuration. + +* The public IP address of the local side of the VPN will be 198.51.100.10 +* The remote will be 203.0.113.11 +* The tunnel will use 10.255.1.1 for the local IP and 10.255.1.2 for the remote. +* OpenVPN allows for either TCP or UDP. UDP will provide the lowest latency, + while TCP will work better for lossy connections; generally UDP is preferred + when possible. +* The official port for OpenVPN is 1194, which we reserve for client VPN; we + will use 1195 for site-to-site VPN. +* The ``persistent-tunnel`` directive will allow us to configure tunnel-related + attributes, such as firewall policy as we would on any normal network + interface. +* If known, the IP of the remote router can be configured using the + ``remote-host`` directive; if unknown, it can be omitted. We will assume a + dynamic IP for our remote router. + +Local Configuration: + +.. code-block:: none + + set interfaces openvpn vtun1 mode site-to-site + set interfaces openvpn vtun1 protocol udp + set interfaces openvpn vtun1 persistent-tunnel + set interfaces openvpn vtun1 local-host '198.51.100.10' + set interfaces openvpn vtun1 local-port '1195' + set interfaces openvpn vtun1 remote-port '1195' + set interfaces openvpn vtun1 shared-secret-key-file '/config/auth/openvpn-1.key' + set interfaces openvpn vtun1 local-address '10.255.1.1' + set interfaces openvpn vtun1 remote-address '10.255.1.2' + +Remote Configuration: + +.. code-block:: none + + set interfaces openvpn vtun1 mode site-to-site + set interfaces openvpn vtun1 protocol udp + set interfaces openvpn vtun1 persistent-tunnel + set interfaces openvpn vtun1 remote-host '198.51.100.10' + set interfaces openvpn vtun1 local-port '1195' + set interfaces openvpn vtun1 remote-port '1195' + set interfaces openvpn vtun1 shared-secret-key-file '/config/auth/openvpn-1.key' + set interfaces openvpn vtun1 local-address '10.255.1.2' + set interfaces openvpn vtun1 remote-address '10.255.1.1' + +The configurations above will default to using 256-bit AES in GCM mode +for encryption (if both sides supports NCP) and SHA-1 for HMAC authentication. +SHA-1 is considered weak, but other hashing algorithms are available, as are +encryption algorithms: + +For Encryption: + +This sets the cipher when NCP (Negotiable Crypto Parameters) is disabled or +OpenVPN version < 2.4.0. + +.. code-block:: none + + vyos@vyos# set interfaces openvpn vtun1 encryption cipher + Possible completions: + des DES algorithm + 3des DES algorithm with triple encryption + bf128 Blowfish algorithm with 128-bit key + bf256 Blowfish algorithm with 256-bit key + aes128 AES algorithm with 128-bit key CBC + aes128gcm AES algorithm with 128-bit key GCM + aes192 AES algorithm with 192-bit key CBC + aes192gcm AES algorithm with 192-bit key GCM + aes256 AES algorithm with 256-bit key CBC + aes256gcm AES algorithm with 256-bit key GCM + +This sets the accepted ciphers to use when version => 2.4.0 and NCP is +enabled (which is default). Default NCP cipher for versions >= 2.4.0 is +aes256gcm. The first cipher in this list is what server pushes to clients. + +.. code-block:: none + + vyos@vyos# set int open vtun0 encryption ncp-ciphers + Possible completions: + des DES algorithm + 3des DES algorithm with triple encryption + aes128 AES algorithm with 128-bit key CBC + aes128gcm AES algorithm with 128-bit key GCM + aes192 AES algorithm with 192-bit key CBC + aes192gcm AES algorithm with 192-bit key GCM + aes256 AES algorithm with 256-bit key CBC + aes256gcm AES algorithm with 256-bit key GCM + +For Hashing: + +.. code-block:: none + + vyos@vyos# set interfaces openvpn vtun1 hash + Possible completions: + md5 MD5 algorithm + sha1 SHA-1 algorithm + sha256 SHA-256 algorithm + sha512 SHA-512 algorithm + +If you change the default encryption and hashing algorithms, be sure that the +local and remote ends have matching configurations, otherwise the tunnel will +not come up. + +Static routes can be configured referencing the tunnel interface; for example, +the local router will use a network of 10.0.0.0/16, while the remote has a +network of 10.1.0.0/16: + +Local Configuration: + +.. code-block:: none + + set protocols static route 10.1.0.0/16 interface vtun1 + +Remote Configuration: + +.. code-block:: none + + set protocols static route 10.0.0.0/16 interface vtun1 + +Firewall policy can also be applied to the tunnel interface for `local`, `in`, +and `out` directions and function identically to ethernet interfaces. + +If making use of multiple tunnels, OpenVPN must have a way to distinguish +between different tunnels aside from the pre-shared-key. This is either by +referencing IP address or port number. One option is to dedicate a public IP +to each tunnel. Another option is to dedicate a port number to each tunnel +(e.g. 1195,1196,1197...). + +OpenVPN status can be verified using the `show openvpn` operational commands. +See the built-in help for a complete list of options. + +Server +====== + +Multi-client server is the most popular OpenVPN mode on routers. It always uses +x.509 authentication and therefore requires a PKI setup. Refer this section +**Generate X.509 Certificate and Keys** to generate a CA certificate, +a server certificate and key, a certificate revocation list, a Diffie-Hellman +key exchange parameters file. You do not need client certificates and keys for +the server setup. + +In this example we will use the most complicated case: a setup where each +client is a router that has its own subnet (think HQ and branch offices), since +simpler setups are subsets of it. + +Suppose you want to use 10.23.1.0/24 network for client tunnel endpoints and +all client subnets belong to 10.23.0.0/20. All clients need access to the +192.168.0.0/16 network. + +First we need to specify the basic settings. 1194/UDP is the default. The +``persistent-tunnel`` option is recommended, it prevents the TUN/TAP device from +closing on connection resets or daemon reloads. + +.. note:: Using **openvpn-option -reneg-sec** can be tricky. This option is + used to renegotiate data channel after n seconds. When used at both server + and client, the lower value will trigger the renegotiation. If you set it to + 0 on one side of the connection (to disable it), the chosen value on the + other side will determine when the renegotiation will occur. + +.. code-block:: none + + set interfaces openvpn vtun10 mode server + set interfaces openvpn vtun10 local-port 1194 + set interfaces openvpn vtun10 persistent-tunnel + set interfaces openvpn vtun10 protocol udp + +Then we need to specify the location of the cryptographic materials. Suppose +you keep the files in `/config/auth/openvpn` + +.. code-block:: none + + set interfaces openvpn vtun10 tls ca-cert-file /config/auth/openvpn/ca.crt + set interfaces openvpn vtun10 tls cert-file /config/auth/openvpn/server.crt + set interfaces openvpn vtun10 tls key-file /config/auth/openvpn/server.key + set interfaces openvpn vtun10 tls crl-file /config/auth/openvpn/crl.pem + set interfaces openvpn vtun10 tls dh-file /config/auth/openvpn/dh2048.pem + +Now we need to specify the server network settings. In all cases we need to +specify the subnet for client tunnel endpoints. Since we want clients to access +a specific network behind out router, we will use a push-route option for +installing that route on clients. + +.. code-block:: none + + set interfaces openvpn vtun10 server push-route 192.168.0.0/16 + set interfaces openvpn vtun10 server subnet 10.23.1.0/24 + +Since it's a HQ and branch offices setup, we will want all clients to have +fixed addresses and we will route traffic to specific subnets through them. We +need configuration for each client to achieve this. + +.. note:: Clients are identified by the CN field of their x.509 certificates, + in this example the CN is ``client0``: + +.. code-block:: none + + set interfaces openvpn vtun10 server client client0 ip 10.23.1.10 + set interfaces openvpn vtun10 server client client0 subnet 10.23.2.0/25 + +OpenVPN **will not** automatically create routes in the kernel for client +subnets when they connect and will only use client-subnet association +internally, so we need to create a route to the 10.23.0.0/20 network ourselves: + +.. code-block:: none + + set protocols static route 10.23.0.0/20 interface vtun10 + +Generate X.509 Certificate and Keys +----------------------------------- + +OpenVPN ships with a set of scripts called Easy-RSA that can generate the +appropriate files needed for an OpenVPN setup using X.509 certificates. +Easy-RSA comes installed by default on VyOS routers. + +Copy the Easy-RSA scripts to a new directory to modify the values. + +.. code-block:: none + + cp -r /usr/share/easy-rsa/ /config/my-easy-rsa-config + cd /config/my-easy-rsa-config + +To ensure the consistent use of values when generating the PKI, set default +values to be used by the PKI generating scripts. Rename the vars.example +filename to vars + +.. code-block:: none + + mv vars.example vars + +Following is the instance of the file after editing. You may also change other +values in the file at your discretion/need, though for most cases the defaults +should be just fine. (do not leave any of these parameters blank) + +.. code-block:: none + + set_var EASYRSA_DN "org" + set_var EASYRSA_REQ_COUNTRY "US" + set_var EASYRSA_REQ_PROVINCE "California" + set_var EASYRSA_REQ_CITY "San Francisco" + set_var EASYRSA_REQ_ORG "Copyleft Certificate Co" + set_var EASYRSA_REQ_EMAIL "me@example.net" + set_var EASYRSA_REQ_OU "My Organizational Unit" + set_var EASYRSA_KEY_SIZE 2048 + + +init-pki option will create a new pki directory or will delete any previously +generated certificates stored in that folder. The term 'central' is used to +refer server and 'branch' for client + +.. note:: Remember the “CA Key Passphrase” prompted in build-ca command, + as it will be asked in signing the server/client certificate. + +.. code-block:: none + + vyos@vyos:/config/my-easy-rsa-config$./easyrsa init-pki + vyos@vyos:/config/my-easy-rsa-config$./easyrsa build-ca + vyos@vyos:/config/my-easy-rsa-config$./easyrsa gen-req central nopass + vyos@vyos:/config/my-easy-rsa-config$./easyrsa sign-req server central + vyos@vyos:/config/my-easy-rsa-config$./easyrsa gen-dh + vyos@vyos:/config/my-easy-rsa-config$./easyrsa build-client-full branch1 nopass + +To generate a certificate revocation list for any client, execute these +commands: + +.. code-block:: none + + vyos@vyos:/config/my-easy-rsa-config$./easyrsa revoke client1 + vyos@vyos:/config/my-easy-rsa-config$ ./easyrsa gen-crl + +Copy the files to /config/auth/openvpn/ to use in OpenVPN tunnel creation + +.. code-block:: none + + vyos@vyos:/config/my-easy-rsa-config$ sudo mkdir /config/auth/openvpn + vyos@vyos:/config/my-easy-rsa-config$ sudo cp pki/ca.crt /config/auth/openvpn + vyos@vyos:/config/my-easy-rsa-config$ sudo cp pki/dh.pem /config/auth/openvpn + vyos@vyos:/config/my-easy-rsa-config$ sudo cp pki/private/central.key /config/auth/openvpn + vyos@vyos:/config/my-easy-rsa-config$ sudo cp pki/issued/central.crt /config/auth/openvpn + vyos@vyos:/config/my-easy-rsa-config$ sudo cp pki/crl.pem /config/auth/openvpn + +Additionally, each client needs a copy of ca.crt and its own client key and +cert files. The files are plaintext so they may be copied either manually, +or through a remote file transfer tool like scp. Whichever method you use, +the files need to end up in the proper location on each router. +For example, Branch 1's router might have the following files: + +.. code-block:: none + + vyos@branch1-rtr:$ ls /config/auth/openvpn + ca.crt branch1.crt branch1.key + +Client Authentication +===================== + +LDAP +---- + +Enterprise installations usually ship a kind of directory service which is used +to have a single password store for all employees. VyOS and OpenVPN support +using LDAP/AD as single user backend. + +Authentication is done by using the ``openvpn-auth-ldap.so`` plugin which is +shipped with every VyOS installation. A dedicated configuration file is +required. It is best practise to store it in ``/config`` to survive image +updates + +.. code-block:: none + + set interfaces openvpn vtun0 openvpn-option "--plugin /usr/lib/openvpn/openvpn-auth-ldap.so /config/auth/ldap-auth.config" + +The required config file may look like: + +.. code-block:: none + + <LDAP> + # LDAP server URL + URL ldap://ldap.example.com + # Bind DN (If your LDAP server doesn't support anonymous binds) + BindDN cn=LDAPUser,dc=example,dc=com + # Bind Password password + Password S3cr3t + # Network timeout (in seconds) + Timeout 15 + </LDAP> + + <Authorization> + # Base DN + BaseDN "ou=people,dc=example,dc=com" + # User Search Filter + SearchFilter "(&(uid=%u)(objectClass=shadowAccount))" + # Require Group Membership - allow all users + RequireGroup false + </Authorization> + +Active Directory +^^^^^^^^^^^^^^^^ + +Despite the fact that AD is a superset of LDAP + +.. code-block:: none + + <LDAP> + # LDAP server URL + URL ldap://dc01.example.com + # Bind DN (If your LDAP server doesn’t support anonymous binds) + BindDN CN=LDAPUser,DC=example,DC=com + # Bind Password + Password mysecretpassword + # Network timeout (in seconds) + Timeout 15 + # Enable Start TLS + TLSEnable no + # Follow LDAP Referrals (anonymously) + FollowReferrals no + </LDAP> + + <Authorization> + # Base DN + BaseDN "DC=example,DC=com" + # User Search Filter, user must be a member of the VPN AD group + SearchFilter "(&(sAMAccountName=%u)(memberOf=CN=VPN,OU=Groups,DC=example,DC=com))" + # Require Group Membership + RequireGroup false # already handled by SearchFilter + <Group> + BaseDN "OU=Groups,DC=example,DC=com" + SearchFilter "(|(cn=VPN))" + MemberAttribute memberOf + </Group> + </Authorization> + +If you only want to check if the user account is enabled and can authenticate +(against the primary group) the following snipped is sufficient: + +.. code-block:: none + + <LDAP> + URL ldap://dc01.example.com + BindDN CN=SA_OPENVPN,OU=ServiceAccounts,DC=example,DC=com + Password ThisIsTopSecret + Timeout 15 + TLSEnable no + FollowReferrals no + </LDAP> + + <Authorization> + BaseDN "DC=example,DC=com" + SearchFilter "sAMAccountName=%u" + RequireGroup false + </Authorization> + +A complete LDAP auth OpenVPN configuration could look like the following +example: + +.. code-block:: none + + vyos@vyos# show interfaces openvpn + openvpn vtun0 { + mode server + openvpn-option "--tun-mtu 1500 --fragment 1300 --mssfix" + openvpn-option "--plugin /usr/lib/openvpn/openvpn-auth-ldap.so /config/auth/ldap-auth.config" + openvpn-option "--push redirect-gateway" + openvpn-option --duplicate-cn + openvpn-option --client-cert-not-required + openvpn-option --comp-lzo + openvpn-option --persist-key + openvpn-option --persist-tun + server { + domain-name example.com + max-connections 5 + name-server 203.0.113.0.10 + name-server 198.51.100.3 + subnet 172.18.100.128/29 + } + tls { + ca-cert-file /config/auth/ca.crt + cert-file /config/auth/server.crt + dh-file /config/auth/dh1024.pem + key-file /config/auth/server.key + } + } + +Client +====== + +VyOS can not only act as an OpenVPN site-to-site or Server for multiple clients. +You can indeed also configure any VyOS OpenVPN interface as an OpenVPN client +connecting to a VyOS OpenVPN server or any other OpenVPN server. + +Given the following example we have one VyOS router acting as OpenVPN server +and another VyOS router acting as OpenVPN client. The Server also pushes a +static client IP address to the OpenVPN client. Remember, clients are identified +using their CN attribute in the SSL certificate. + +Server +------ + +.. code-block:: none + + set interfaces openvpn vtun10 encryption cipher 'aes256' + set interfaces openvpn vtun10 hash 'sha512' + set interfaces openvpn vtun10 local-host '172.18.201.10' + set interfaces openvpn vtun10 local-port '1194' + set interfaces openvpn vtun10 mode 'server' + set interfaces openvpn vtun10 persistent-tunnel + set interfaces openvpn vtun10 protocol 'udp' + set interfaces openvpn vtun10 server client client1 ip '10.10.0.10' + set interfaces openvpn vtun10 server domain-name 'vyos.net' + set interfaces openvpn vtun10 server max-connections '250' + set interfaces openvpn vtun10 server name-server '172.16.254.30' + set interfaces openvpn vtun10 server subnet '10.10.0.0/24' + set interfaces openvpn vtun10 server topology 'subnet' + set interfaces openvpn vtun10 tls ca-cert-file '/config/auth/ca.crt' + set interfaces openvpn vtun10 tls cert-file '/config/auth/server.crt' + set interfaces openvpn vtun10 tls dh-file '/config/auth/dh.pem' + set interfaces openvpn vtun10 tls key-file '/config/auth/server.key' + set interfaces openvpn vtun10 use-lzo-compression + +Client +------ + +.. code-block:: none + + set interfaces openvpn vtun10 encryption cipher 'aes256' + set interfaces openvpn vtun10 hash 'sha512' + set interfaces openvpn vtun10 mode 'client' + set interfaces openvpn vtun10 persistent-tunnel + set interfaces openvpn vtun10 protocol 'udp' + set interfaces openvpn vtun10 remote-host '172.18.201.10' + set interfaces openvpn vtun10 remote-port '1194' + set interfaces openvpn vtun10 tls ca-cert-file '/config/auth/ca.crt' + set interfaces openvpn vtun10 tls cert-file '/config/auth/client1.crt' + set interfaces openvpn vtun10 tls key-file '/config/auth/client1.key' + set interfaces openvpn vtun10 use-lzo-compression + +Options +======= + +We do not have CLI nodes for every single OpenVPN options. If an option is +missing, a feature request should be opened at Phabricator_ so all users can +benefit from it (see :ref:`issues_features`). + +If you are a hacker or want to try on your own we support passing raw OpenVPN +options to OpenVPN. + +.. cfgcmd:: set interfaces openvpn vtun10 openvpn-option 'persistent-key' + +Will add ``persistent-key`` at the end of the generated OpenVPN configuration. +Please use this only as last resort - things might break and OpenVPN won't start +if you pass invalid options/syntax. + +.. cfgcmd:: set interfaces openvpn vtun10 openvpn-option + 'push "keepalive 1 10"' + +Will add ``push "keepalive 1 10"`` to the generated OpenVPN config file. + +.. note:: Sometimes option lines in the generated OpenVPN configurarion require + quotes. This is done through a hack on our config generator. You can pass + quotes using the ``"`` statement. + + +Troubleshooting +=============== + +VyOS provides some operational commands on OpenVPN. + +Check status +------------ + +The following commands let you check tunnel status. + +.. opcmd:: show openvpn client + + Use this command to check the tunnel status for OpenVPN client interfaces. + +.. opcmd:: show openvpn server + + Use this command to check the tunnel status for OpenVPN server interfaces. + +.. opcmd:: show openvpn site-to-site + + Use this command to check the tunnel status for OpenVPN site-to-site + interfaces. + + +Reset OpenVPN +------------- + +The following commands let you reset OpenVPN. + +.. opcmd:: reset openvpn client <text> + + Use this command to reset specified OpenVPN client. + +.. opcmd:: reset openvpn interface <interface> + + Uset this command to reset the OpenVPN process on a specific interface. + + + +.. include:: /_include/common-references.txt |