openvpn2(1)

Name
openvpn2 - OpenVPN 2 wrapper to OpenVPN 3 Linux

SYNOPSIS
openvpn2 [ OPTIONS ]
openvpn2 -h | --help

DESCRIPTION

The openvpn2 command line wrapper to OpenVPN 3 Linux attempts to provide a similar command line interface as the classic OpenVPN 2.x releases. Since OpenVPN 3 does not support all the options available in OpenVPN 2.x, some options is not available or will be ignored.

In addition the OpenVPN 3 Linux project provides only a client at the moment, so all server side related options are not available.

OPTIONS

-h, --help
    show this help message and exit

--auth ALG
    Authenticate packets with HMAC using message digest algorithm alg (default=SHA1)

--auth-retry MODE
    Defines how authentication failures should be handled. Valid modes are:

none
    Disconnect on authentication failures (default)

nointeract
    Reuse already collected credentials

interact
    Ask for new credentials from the user

    Currently, the OpenVPN 3 Linux client implementation ignores this option.

--auth-user-pass
    Authenticate with server using username/password

--ca FILE
    Certificate authority file in .pem format containing root certificate

--cd DIR
    Change working directory to the given directory

--cert FILE
    Certificate authority file in .pem format by a Certificate Authority in --ca file

--cipher ALG
    Encrypt packets with cipher algorithm alg (default=BF- CBC)

--client
    Configures client configuration mode (mandatory)

--comp-lzo <MODE>
    Use LZO compression

--compress <ALG>
    Compress using algorithm ALG

--config FILE
    Read configuration options from file

--daemon
    Run the VPN tunnel in the background

--dev DEV-NAME
    Virtual interface name to use for VPN tunnel. Defaults to tun. Usually ignored, as the interface name is created on-the-fly in OpenVPN 3.

--dev-type DEV-TYPE
    Defines the virtual interface type. Only tun is supported, which is the default.

--dhcp-option OPTION
    Set DHCP options which can be picked up by the OS configuring DNS, etc.

--enable-dco | --disable-dco
    Enable or disabled the Data Channel Offload (DCO) kernel acceleration module support. The default is disabled, but this option is present for compatibility with OpenVPN 2.6. The --enable-dco option is OpenVPN 3 Linux specific.

--extra-certs FILE
    Specify a file containing one or more PEM certs (concatenated together) that complete the local certificate chain.

--float
    Allow remote to change its IP address/port.

--hand-window SEC
    Handshake window. The TLS-based key exchange must finalize within SEC seconds handshake initiation by any peer. (Default 60 seconds)

--http-proxy ARGS
    Connect to a remote host via a specified HTTP proxy. This option takes 2 mandatory options, SERVER and PORT, which defines the HTTP proxy and port to use.

    Optional arguments are AUTH-FLAG which can be auto-nct which enables clear-text passwords to be used.

    OpenVPN 2.x also adds an optional AUTH-METHOD flag as the last argument, this is auto-detected in OpenVPN 3.

--http-proxy-user-pass FILE
    Fetch HTTP proxy credentials from FILE

--ifconfig ARGS
    Configures the TUN/TAP device for IPv4. This option takes two mandatory arguments, the IPv4 address to use and the netmask for the network.

--ifconfig-ipv6 ARGS
    Configures the TUN/TAP device for IPv6. This option takes one mandatory argument, the IPv6 address including its PREFIX. An optional REMOTE_ENDPOINT can be given at the end.

--ignore-unknown-options OPTION
    If the listed OPTION(s) are not understood, the option parser in the OpenVPN 3 Core library will ignore these options instead of complaining about unknown or unused options.

--inactive ARGS
    This option takes one mandatory argument, SECONDS, which defines how many seconds the tunnel can idle before disconnecting. An optional BYTES argument can be added which also takes the number of bytes passed over the tunnel within SECONDS of inactivity. The traffic must be higher than this minimum BYTES to keep the tunnel alive.

--keepalive ARGS
    Instructs the client to ping the server over the OpenVPN Control Channel every PING_SECONDS. An optional argument defines, RECONNECT_SECONDS how long it should go before the client should attempt to reconnect if there is no response from the server.

--key FILE
    Local private key in .pem format

--key-direction DIR
    Set key direction for static keys. Valid values: 0, 1

--local HOST
    Local host name or IP address to to bind against on local side

--lport PORT
    TCP/UDP port number for local bind (default 1194)

--mode MODE
    Operational mode. Only client is accepted.

--mssfix BYTES
    Set upper bound on TCP MSS (Default tun-mtu size)

--ns-cert-type TYPE
    (DEPRECATED) Require that peer certificate is signed with an explicit nsCertType designation. Migrate to --remote-cert-tls as soon as possible. Valid values: client, server

--persist-tun
    Keep tun/tap device open across connection restarts

--ping SECS
    Ping remote once per SECS seconds

--ping-restart SECS
    Restart if n seconds pass without reception of remote ping

--pkcs12 FILE
    PKCS#12 file containing local private key, local certificate and optionally the root CA certificate

--port PORT
    TCP/UDP port number for both local and remote.

--profile-override OVERRIDE
    OpenVPN 3 specific feature, allowing to set some local overrides or disable some functionality. This option takes two arguments, an OVERRIDE-KEY and an OVERRIDE-VALUE. Valid keys and values are:

server-override
    A server host name

port-override
    A port number

proto-override
    Override connection protocol. Valid values: tcp or udp

persist-tun
    Alternative approach to set --persist-tun.

ipv6
    Enable or disable IPv6 inside the tunnel. Valid values: yes, no or default

enable-legacy-algorithms
    Enables non-AEAD ciphers supported by the TLS library. See openvpn3-config-manage(1) for details.

allow-compression
    Allows the connection to use compression. See openvpn3-config-manage(1) for details. Valid values: yes, no or asym

dns-fallback-google
    If set to true, the DNS resolver settings will include Google DNS servers.

dns-setup-disabled
    Disable configuring pushed DNS settings. Valid values: true or false

dns-sync-lookup
    Do synchronous DNS lookup instead of the default, asynchronous. Valid values: true or false

auth-fail-retry
    Try to reconnect even if the server rejected the connection due to authentication failure. Valid values: true or false

proxy-host
    Proxy server host name for the VPN tunnel

proxy-port
    Proxy server port number

proxy-username
    Username used for proxy authentication

proxy-password
    Password used for proxy authentication

proxy-auth-cleartext
    Valid values: true or false

    These overrides are described further in openvpn3-config-manage(1)

--proto PROTO
    Use protocol PROTO for communicating with peer. Valid values: udp, tcp

--push-peer-info
    Push client info to server

--redirect-gateway FLAGS
    Automatically execute routing commands to redirect all outgoing IP traffic through the VPN. Valid flags: autolocal, def1, bypass-dhcp, bypass-dns, block-local, ipv4, !ipv4, ipv6, !ipv6

--redirect-private FLAGS
    Like --redirect-gateway, but omit actually changing default gateway. Valid flags: autolocal, def1, bypass-dhcp, bypass-dns, block-local, ipv4, !ipv4, ipv6, !ipv6

--remote ARGS
    Defines the remote server to connect to. One mandatory argument must be given, containing either an IP address or an hostname to the server. An optional PORT number can be given (default: 1194) and at the end the PROTOCOL can be specified (default: udp). This option can be given multiple times and the client will try all remote entries until it is able to establish a connection. The order of arguments are: HOST/IP, PORT and PROTOCOL

--remote-cert-eku OID
    Require the peer certificate to be signed with explicit extended key usage. OID can be an object identifier or OpenSSL string representation.

--remote-cert-ku ID
    Require that the peer certificate was signed with explicit key usage (ID). More than one ID can be provided. Must be hexadecimal notation of integers

--remote-cert-tls TYPE
    Require that peer certificate is signed with explicit key usage and extended key usage based RFC3280 rules. Valid values: client, server

--remote-random
    If multiple --remote options specified, choose one randomly

--reneg-sec SECS
    Renegotiate data channel key after SECS seconds. (Default: 3600)

--route ARGS
    Add route to routing table after connection is established. Multiple routes can be specified.

    This option takes one mandatory argument, IP-ADDRESS to route over the VPN. The two optional arguments are NETMASK (default: 255.255.255.255) and the gateway to use (defaults to use configured --route-gateway or the VPN server IP address).

--route-gateway <GW|dhcp>
    Specify a default gateway for use with --route. See openvpn(8) man page for dhcp mode

--route-ipv6 ARGS
    Add IPv6 route to routing table after connection is established. Multiple routes can be specified.

    This option takes one mandatory argument IP-RANGE/PREFIX. An optional GATEWAY can be set, which overrides the default server VPN IPv6 address and the second argument which sets the route METRIC value.

--route-metric METRIC
    Specify a default metric for use with --route

--route-nopull
    Do not configure routes pushed by remote server

--server-poll-timeout SECS
    How long to wait for a response from a remote server during connection setup (Default: 120 seconds)

--setenv ARGS
    Set a custom environmental variable to pass to script. This takes two mandatory arguments, variable NAME and VALUE.

--static-challenge ARGS
    Enable static challenge/response protocol. This takes one mandatory option, MESSAGE, which will be presented to the user before the connection attempt. An optional argument, ECHO, indicates if the user input should be echoed back to the user during input entry.

--tcp-queue-limit NUM
    Maximum number (NUM)of queued TCP output packets

--tls-auth ARGS
    Enables an additional HMAC authentication on TLS control channel. This takes a mandatory argument, FILE, which must be a shared secret between server and client. The optional KEY-DIRECTION argument defines which sub-key pair in FILE to use for HMAC signing and verification. Valid values are 0 or 1.

--tls-cert-profile PROFILE
    Sets certificate profile which defines acceptable crypto algorithms. Valid profiles: legacy, preferred, suiteb

--tls-client
    Enable TLS and assume client role during TLS handshake. Implicitly added when using --client

--tls-crypt FILE
    Encrypts the TLS control channel with a shared secret key (FILE). This CANNOT be combined with --tls-auth

--tls-timeout SECS
    Packet retransmit timeout on TLS control channel if no ACK from remote within n seconds. (Default: 2 seconds)

--topology TYPE
    Set tunnel topology type. Default is net30. Recommended: subnet, but this must match the server setting. Valid topologies: subnet, net30

--tran-window SECS
    Transition window -- old data channel key can live this many seconds after new after new key renegotiation begins. (Default: 3600 secs)

--tun-mtu SIZE
    Set TUN/TAP device MTU to SIZE and derive TCP/UDP from it (default is 1500)

--verb LEVEL
    Set log verbosity level. Log levels are NOT compatible with OpenVPN 2 --verb

--verify-x509-name ARGS
    Accept connections only with a host with a specific X509 subject or CN match string. This option takes one mandatory argument, which is a MATCH string and an optional match FLAG.

    FLAG can be:

name
    Match against complete X.509 Common Name field

name-prefix
    The MATCH value must be match the beginning of the X.509 Common Name field. If the X.509 certificate contains server-1.example.org, it will be a match if the MATCH value is server-. It will not be a match if values like server-2 or .example.org is used.

subject
    The MATCH value must be the full and complete X.509 Subject field. This is the default behaviour.

IGNORED OPTIONS

The options in this list will be silently ignored. Some of these options have not yet been implemented in the OpenVPN 3 Core library and others are not relevant any more. But none of these options will break any existing configurations.

--auth-nocache
    Do not cache --askpass or --auth-user-pass in virtual memory. Not applicable with OpenVPN 3 due to different credentials storage model.

--chroot DIR
    Chroot to this directory after initialization. Not applicable with OpenVPN 3, which uses a different execution model.

--data-ciphers CIPHERLIST
    OpenVPN 2.5 introduced this option has a replacement to --ncp-ciphers. This is primarily intended to be used when migrating away from the prior default BF-CBC cipher. With Negotiable Cipher Parameters (NCP), this should not be needed in the future. OpenVPN 3 also has a different way of handling this situation and is believed to not have the same connectivity issues as OpenVPN 2.4 and newer 2.x releases could have against older OpenVPN 2.x servers.

--data-ciphers-fallback ALG
    This is tightly coupled to --data-ciphers and is also not used nor supported by OpenVPN 3.

--dev-node NODE
    OpenVPN 2.x will use /dev/net/tun, /dev/tun, /dev/tap, etc by default when creating the tun/tap interface. This is handled differently in OpenVPN 3 Linux and is not configurable by front-ends like openvpn2 or openvpn3, since the virtual network interface creation is handled by the openvpn3-service-netcfg(8) service.

--down
    Run a script after the tunnel has been torn down. Running scripts via OpenVPN 3 is not supported, and using this option will display a warning. See the NOTES section below for details.

--down-pre
    This is related to when the --down script is being run during the disconnection. See the NOTES section below regarding script execution in OpenVPN 3.

--explicit-exit-notify <ATTEMPTS>
    On exit/restart, send exit signal to remote end. Automatically configured with OpenVPN 3

--group GROUP
    Run OpenVPN with GROUP group credentials. Not needed with OpenVPN 3 which uses a different privilege separation approach

--mute-replay-warnings
    OpenVPN 2.5 and older can hide warnings related to replayed packets. Packet replays are not reported in the same way in OpenVPN 3 Core library, so this option makes no behavioural change.

--ncp-ciphers CIPHERLIST
    OpenVPN 2.4 option renamed to --data-ciphers in OpenVPN 2.5. Ignored in OpenVPN 3.

--nice LEVEL
    Change process priority. Not supported in OpenVPN 3

--nobind
    Do not bind to local address and port. This is default behaviour in OpenVPN 3

--persist-key
    Do not re-read key files across connection restarts. Not needed. OpenVPN 3 keeps keys as embedded file elements in the configuration

--rcvbuf SIZE
    Set the TCP/UDP receive buffer size. Not supported in OpenVPN 3

--resolv-retry SECS
    If hostname resolve fails for --remote, retry resolve for n seconds before failing. Not supported by OpenVPN 3.

--script-security LEVEL
    This option is ignored, as OpenVPN 3 itself does not execute any external scripts.

--sndbuf SIZE
    Set the TCP/UDP send buffer size. Not supported in OpenVPN 3.

--socket-flags FLAGS
    Applies flags to the transport socket. Not supported in OpenVPN 3.

--up
    Run a script after the tunnel has been established. Running scripts via OpenVPN 3 is not supported, and using this option will display a warning. See the NOTES section below for details.

--user USER
    Run OpenVPN with USER user credentials. Not needed with OpenVPN 3 which uses a different privilege separation approach

NOTES

  SCRIPT EXECUTION

OpenVPN 3 does not implement any support for running external scripts or program during its life cycle. This is by design. Running scripts is a security risk, and needs to be handled carefully. In classic OpenVPN 2.x setups, scripts are run with the same privileges as the openvpn(8) process. If the process is started as root, the script may be run as root. Which is why the --script-security option is available and by default disabling running most external programs.

This does not mean it is impossible to trigger programs to perform operations when certain OpenVPN events occur. OpenVPN 3 Linux is using D-Bus actively and it issues several signals as the state changes. It also means you can write your own front-end doing its own calls how you prefer while starting and managing the VPN session at the same time. This allows a much better flexibility and allows one to adopt VPN session management into the execution flow which is needed. And the implementation can do its own security assessments on how it will tackle these scenarios.

There are at least three ways how to adopt to the OpenVPN 3 model:

  1. Watching D-Bus StateChange signals for your own sessions

When a session is started, it is possible to subscribe to signals issued by the VPN client process over D-Bus. It is only possible to subscribe to signals related to the session owner's own sessions. These signals are sent by the Session Manager (net.openvpn.v3.sessions, openvpn3-service-sessionmgr(8))

Example:

    $ dbus-monitor --system --monitor sender=net.openvpn.v3.sessions,interface=net.openvpn.v3.sessions,member=StatusChange

  2. Manage the life cycle of VPN sessions on your own

This means wrapping the starting of VPN sessions on your own. Either you wrap openvpn3 session-start or openvpn2 calls in your own scripts, or you can connect directly to the Configuration Manager (net.openvpn.v3.configuration, openvpn3-service-configmgr(8)) and Session Manager (net.openvpn.v3.sessions, openvpn3-service-sessionmgr(8)) to import configuration profiles and start/stop VPN sessions as needed, as well as subscribing to D-Bus signals as well to handle various the states a VPN session will go through. This is fairly simple to do using the already available openvpn3 Python module. Example code can be found in the OpenVPN 3 Linux source tree <https://github.com/OpenVPN/openvpn3-linux/tree/master/src/tests/python> [1] or by studying the source code of openvpn2(1) and openvpn3-systemd(8), which both are Python scripts.

Configurations and sessions managed via D-Bus by your own scripts can still be further managed by the openvpn3(1) command line interface.

  3. Subscribing to NetworkChange signals from net.openvpn.v3.netcfg <https://github.com/OpenVPN/openvpn3-linux/blob/master/docs/dbus/dbus-service-net.openvpn.v3.netcfg.md> [2]

This is also a scripting possibility, which is more useful for system wide script triggering. A program or script can subscribe to specific network change events caused by OpenVPN sessions. These signals contains information about virtual network interfaces which has been created or removed, IP addresses added or removed from devices, routing configuration as well as DNS resolver changes.

For an example how to do this, see the example script <https://github.com/OpenVPN/openvpn3-linux/blob/master/src/tests/python/netcfg-netchg-subscription> [3] in the OpenVPN 3 Linux source directory.

Please note that, by default, this script must be run as root or the openvpn user on the system. It is possible to allow other users or groups this privilege, by extending the D-Bus policy for the net.openvpn.v3.netcfg service. But granting this privilege too widely may result in unwanted information leakage related to VPN interface configurations.

SEE ALSO

openvpn(8) openvpn3(1) openvpn3-config-manage(1)

[1] <https://github.com/OpenVPN/openvpn3-linux/tree/master/src/tests/python>

[2] <https://github.com/OpenVPN/openvpn3-linux/blob/master/docs/dbus/dbus-service-net.openvpn.v3.netcfg.md>

[3] <https://github.com/OpenVPN/openvpn3-linux/blob/master/src/tests/python/netcfg-netchg-subscription>