nethserver-openvpn

Supported VPN are:

  • Client to server (roadwarrior)
  • Network to network (net2net)

Events

  • openvpn-tunnel-create: fired when a new tunnel is created, takes the tunnel name as argument
  • openvpn-tunnel-delete: fired when a new tunnel is deleted, takes the tunnel name as argument
  • openvpn-tunnel-modify: fired when a new tunnel is modified, takes the tunnel name as argument
  • nethserver-vpn-save: fired when roadwarrior account or server is changed
  • openvpn-tunnel-upload: used to transform a given file to a read-to-use tunnel client

Roadwarrior accounts

Accounts are used to identify clients connecting to the server itself. There are two types of account:

  • user account: system user with VPN access using user name and password
  • vpn-only account: simple account with only VPN access

Each account can be used in a roadwarrior connection (host to net). If a net to net tunnel is needed, VPNRemoteNetwork and VPNRemoteNetmask properties must be set to inform the server about remote routes. When a new account is created, a certificate with same name is generated inside /var/lib/nethserver/certs directory.

Properties:

  • VPNRemoteNetwork: remote network
  • VPNRemoteNetmask: remote netmask
  • OpenVpnIp: reserved IP for the client

Database reference

Database: vpn

<name>=vpn
   VPNRemoteNetwork=
   VPNRemoteNetmask=
   OpenVpnIp=

Roadwarrior server

Certificates

All certificates are signed using NethServer default RSA key (/etc/pki/tls/private/NSRV.key).

CA environment

CA configuration is stored inside /var/lib/nethserver/ directory, all certificates are stored inside /var/lib/nethserver/certs. The nethserver-openvpn-conf action creates:

  • serial, certindex.attr and /certindex: database of valid and revoked certificates
  • crlnumber and /etc/openvpn/certs/crl.pem: certificate revocation list
  • dh1024.pem: key for TLS negotation

Certificate creation

Certificates in PEM format can be created using the command:

/usr/libexec/nethserver/pki-vpn-gencert <commonName>

The commonName parameter is an unique name stored inside the certificate. The command will generate key, crt and csr file. Each generated certificate is referred with a numeric id and saved inside certindex database. OpenSSL will also create a certificated called as with the generated id (eg. 02.pem).

Certificate revocation

Certificate revocation is done via the command:

/usr/libexec/nethserver/pki-vpn-revoke [-d] <commonName>

The commonName parameter is an unique name stored inside the certificate. If ‘-d’ option is enabled, also delete crt, csr, pem and key files

Certificate renewal

All certificates will expire after X days, where X is the value of CertificateDuration property inside pki key. Renew is done via the command:

/usr/libexec/nethserver/pki-vpn-renew <commonName>

The commonName parameter is an unique name stored inside the certificate.

Client configuration is generated using /usr/libexec/nethserver/openvpn-local-client command. The file will contain the CA certificate inside the <ca>.

Example:

/usr/libexec/nethserver/openvpn-local-client myuser

The OpenVPN server listens on a management socket: /var/spool/openvpn/host-to-net. It’s possible to retrieve server status and execute commands using the socket.

Available scripts:

  • /usr/libexec/nethserver/openvpn-status: retrieve status of connected clients and return result in JSON format
  • /usr/libexec/nethserver/openvpn-kill: kill a connected client, exits 0 on success, 1 otherwise

Example with netcat:

>INFO:OpenVPN Management Interface Version 1 -- type 'help' for more info
status
OpenVPN CLIENT LIST
Updated,Thu Jan 23 09:22:24 2014
Common Name,Real Address,Bytes Received,Bytes Sent,Connected Since
ROUTING TABLE
Virtual Address,Common Name,Real Address,Last Ref
GLOBAL STATS
Max bcast/mcast queue length,0
END

See more on management option: http://openvpn.net/index.php/open-source/documentation/miscellaneous/79-management-interface.html

Configuration database

Properties:

  • status: enable or disabled the OpenVPN server, can be enabled or disabled, default is disabled
  • AuthMode: authentication mode, can be password, certificate or password-certificate
  • UDPPort: server listen port, default is 1194
  • Mode: network mode, can be routed or bridged. Default is routed.
  • ClientToClient: can be enabled or disabled, default is disabled. When enabled, traffic between VPN clients is allowed
  • Compression: can be enabled or disabled, default is disabled. When enabled, adaptive LZO compression is used
  • Remote: comma-separated list of IPs or host names, it’s used as multiple remote option inside client configuration generation script
  • PushDns: if set, push the specified DNS as DHCP option
  • PushDomain: if set, push the specified domain as DHCP option
  • PushExtraRoutes: if disabled, only routes for green interface are pushed, if enabled also all static routes will be pushed. Default is enabled
  • PushNbdd: if set, push the specified NBDD as DHCP option
  • PushWins: if set, push the specified WINS as DHCP option

If mode is bridged:

  • BridgeEndIP: first client IP pool, must be inside the LAN range and outside DHCP range
  • BridgeStartIP: last client IP pool, must be inside the LAN range and outside DHCP range
  • BridgeName: name of the bridge, default is br0
  • TapInterface: name of bridged tap interface, default is tap0

If mode is routed:

  • Network: network of VPN clients, eg. 192.168.6.0
  • Netmask: netmask of VPN clients, eg. 255.255.255.0
  • RouteToVPN: can be enabled or disabled, default is disabled. When enabled, all traffic from client will be routed via VPN tunnel

Reference

Example:

openvpn@host-to-net=service
   AuthMode=password
   BridgeEndIP=192.168.1.122
   BridgeName=br0
   BridgeStartIP=192.168.1.121
   ClientToClient=disabled
   Mode=routed
   Netmask=255.255.255.0
   Network=192.168.6.0
   PushDns=
   PushDomain=
   PushExtraRoutes=enabled
   PushNbdd=
   PushWins=
   Remote=
   RouteToVPN=disabled
   TapInterfaces=tap0
   UDPPort=1194
   access=green,red
   status=enabled

Tunnel topology

Available topology are subnet and p2p

If topology is p2p:

  • only psk authentication mode is available
  • options LocalPeerIP and RemotePeerIP must be set for both server and client
  • options RemoteNetworks must be set if the client should be able to reach networks behind the tunnel server

If topology is subnet:

  • only password, certificate or password-certificate authentication mode are available
  • options Network must be set for the server

Tunnel clients

OpenVPN clients are used to connect to a tunnel server obtaining a net2net VPN.

Common properties:

  • AuthMode: default value is certificate. Possible values:
    • certificate: use x509 certificate. Certificates, including CA and private key, are saved in /var/lib/nethserver/certs/clients directory in a PEM file named key.pem
    • password: use user name and password
    • password-certificate: use user name, password and a valid x509 certificate
    • psk: use a pre-shared key
  • Cipher: a valid OpenVPN cipher among openvpn --show-ciphers
  • Compression: can be enabled or disabled, default is enabled. Enable/disable adaptive LZO compression.
  • LocalPeerIP and RemotePeerIP: IP for the Point to Point hosts
  • Password: password used for authentication, if AuthMode is password or password-certificate
  • Protocol: can be udp or tcp, default is udp
  • RemoteHost: a list of remote server hostnames or ip addresses
  • RemoteNetworks: list of networks in CIDR format, for each network will be created a route
  • RemotePort: remote host port
  • User: username used for authentication, if AuthMode is password or password-certificate
  • WanPriorities: an ordered list of red interfaces which will be used to connect to the server, can be used to prefer a faster WAN other than a slower one
  • Topology: can be subnet (default) or p2p
  • status: enable or disabled the OpenVPN server, can be enabled or disabled, default is enabled

Files:

  • pre-shared key: /var/lib/nethserver/certs/clients/<name>.key
  • certificates: /var/lib/nethserver/certs/<name>.{pem,key}

Database reference

Database: vpn

c1=tunnel
   AuthMode=psk
   Cipher=
   Compression=disabled
   Crt=
   Mode=routed
   Protocol=udp
   Psk=
   RemoteHost=1.2.3.4,8.8.6.7
   RemotePort=1122
   Topology=subnet
   WanPriorities=eth2,eth1
   status=enabled

clntnh2d=tunnel
   AuthMode=certificate
   Cipher=
   Compression=enabled
   Mode=routed
   Protocol=udp
   RemoteHost=1.2.3.4,8.8.6.7
   RemotePort=1244
   Topology=subnet
   status=enabled

Tunnel servers

Servers are instance of OpenVPN listening for incoming connections. Each server runs on its own port can handle many client.

When a server is created the following files will be generated:

  • a certificate and a private key: /var/lib/nethserver/openvpn-tunnels/<name>.crt and /var/lib/nethserver/openvpn-tunnels/keys/<name>.key
  • a pre-shared key /var/lib/nethserver/openvpn-tunnels/<name>.key

Certificate generation uses a custom version of easy-rsa, see /usr/share/nethserver-openvpn directory content.

Properties: * Cipher: a valid OpenVPN cipher among openvpn --show-ciphers * Compression: can be enabled or disabled, default is enabled. Enable/disable adaptive LZO compression. * LocalNetworks: list of networks in CIDR format, each network will be pushed as route to the client * LocalPeerIP and RemotePeerIP: IP for the Point to Point hosts * Network: network address of the VPN tunnel * Port: listen port * Protocol: can be udp or tcp, default is udp * PublicAddresses: list of public IPs or host names used by clients to connect to the server * RemoteNetworks: list of networks in CIDR format, for each network will be created a local route * Topology: can be subnet (default) or p2p * status: enable or disabled the OpenVPN server, can be enabled or disabled, default is disabled

Database reference

Database: vpn

server1=openvpn-tunnel-server
   Cipher=
   Compression=enabled
   LocalNetworks=192.168.1.0/24
   RemotelNetworks=192.168.6.0/24
   Network=10.10.11.0/24
   Port=1282
   Protocol=udp
   PublicAddresses=1.2.3.4,test.local.neth.eu
   Topology=subnet
   status=enabled

psk1=openvpn-tunnel-server
   Cipher=
   Compression=enabled
   LocalNetworks=10.132.0.0/16
   LocalPeer=10.68.218.1
   Port=1248
   Protocol=udp
   PublicAddresses=1.2.3.4,myfw.host.org
   RemotePeer=10.68.218.2
   Topology=p2p
   status=disabled

Templates

The main templates for the configuration are:

  • /etc/e-smith/templates/etc/openvpn/host-to-net.conf: allows the customization of roadwarrior server
  • /etc/e-smith/templates/openvpn-tunnel-server/: allows the customization of tunnel server, it’s expanded in /etc/openvpn/<tunnel_server_name>.conf
  • /etc/e-smith/templates/openvpn-tunnel-client/: allows the customization of tunnel client, it’s expanded in /etc/openvpn/<tunnel_client_name>.conf

Log files and systemd instances

All OpenVPN services are handled using systemd instances of the openvpn service.

Every instance has the following form: openvpn@<instance_name> where instance_name is name of the key inside the vpn e-smith db. The roadwarrior server has a fixed name: host-to-net.

Instances can be inspected using systemctl command:

systemctl status openvpn@host-to-net
systemctl status openvpn@server1

The roadwarrior can be found here:

  • /var/log/openvpn/host-to-net-status.log
  • /var/log/openvpn/openvpn.log

The log if each OpenVPN instance can be seen using journalctl command. Example:

journalctl -u openvpn@client1
journalctl -u openvpn@host-to-net