--- name: "openvpn2" section: "1" platform: "linux" package: "openvpn3-client" version: "24.1+dfsg-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/openvpn2" --- # openvpn2(1) OpenVPN 2 wrapper to OpenVPN 3 Linux ## 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** *\* Use LZO compression - **--compress** *\* 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. - **--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)](/openvpn3-config-manage/1.md) for details. - **allow-compression** Allows the connection to use compression. See [**openvpn3-config-manage**(1)](/openvpn3-config-manage/1.md) 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)](/openvpn3-config-manage/1.md) - **--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** *\* Specify a default gateway for use with **--route**. See [**openvpn**(8)](/openvpn/8.md) 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. ## TECH-PREVIEW OPTIONS These options are only present for testing new bleeding edge features. There are no guarantees they will work, will not change or will not change behaviour in the future. These options are *NOT* ready for production environments. - **--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 as this project does currently not automatically detect and enable the DCO capability of the host. ## 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)](/openvpn3-service-netcfg/8.md) 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** *\* 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)](/openvpn/8.md) 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)](/openvpn3-service-sessionmgr/8.md)) 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)](/openvpn3-service-configmgr/8.md)) and Session Manager (**net.openvpn.v3.sessions**, [**openvpn3-service-sessionmgr**(8)](/openvpn3-service-sessionmgr/8.md)) 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 \\ \[1\] or by studying the source code of [**openvpn2**(1)](/openvpn2/1.md) and [**openvpn3-systemd**(8)](/openvpn3-systemd/8.md), 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)](/openvpn3/1.md) command line interface. ### 3. Subscribing to NetworkChange signals from net.openvpn.v3.netcfg \ \[2\] 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 \\ \[3\] 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)](/openvpn/8.md) [**openvpn3**(1)](/openvpn3/1.md) [**openvpn3-config-manage**(1)](/openvpn3-config-manage/1.md) - \[1\] \ - \[2\] \ - \[3\] \