xref: /openbsd-src/share/man/man4/wg.4 (revision 981ba490cda6e67682cbcc126bfb3be7cf105b6e)

.\" $OpenBSD: wg.4,v 1.10 2021/03/14 10:08:38 jmc Exp $
.\" Copyright (c) 2020 Matt Dunwoodie <ncon@noconroy.net>
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.Dd $Mdocdate: March 14 2021 $
.Dt WG 4
.Os
.Sh NAME
.Nm wg
.Nd WireGuard pseudo-device
.Sh SYNOPSIS
.Cd "pseudo-device wg"
.Sh DESCRIPTION
The
.Nm wg
driver provides Virtual Private Network (VPN) interfaces for the secure
exchange of layer 3 traffic with other WireGuard peers using the WireGuard
protocol.
.Pp
A
.Nm wg
interface recognises one or more peers, establishes a secure tunnel with
each on demand, and tracks each peer's UDP endpoint for exchanging encrypted
traffic with.
.Pp
The interfaces can be created at runtime using the
.Ic ifconfig Cm wg Ns Ar N Cm create
command or by setting up a
.Xr hostname.if 5
configuration file for
.Xr netstart 8 .
The interface itself can be configured with
.Xr ifconfig 8 .
.Pp
.Nm wg
interfaces support the following
.Xr ioctl 2 Ns s :
.Bl -tag -width Ds -offset indent
.It Dv SIOCSWG Fa "struct wg_data_io *"
Set the device configuration.
.It Dv SIOCGWG Fa "struct wg_data_io *"
Get the device configuration.
.El
.Pp
The following glossary provides a brief overview of WireGuard
terminology:
.Bl -tag -width indent -offset 3n
.It Peer
Peers exchange IPv4 or IPv6 traffic over secure tunnels.
Each
.Nm wg
interface may be configured to recognise one or more peers.
.It Key
Each peer uses its private key and corresponding public key to
identify itself to others.
A peer configures a
.Nm wg
interface with its own private key and with the public keys of its peers.
.It Preshared key
In addition to the public keys, each peer pair may be configured with a
unique pre-shared symmetric key.
This is used in their handshake to guard against future compromise of the
peers' encrypted tunnel if a quantum-computational attack on their
Diffie-Hellman exchange becomes feasible.
It is optional, but recommended.
.It Allowed IPs
A single
.Nm wg
interface may maintain concurrent tunnels connecting diverse networks.
The interface therefore implements rudimentary routing and reverse-path
filtering functions for its tunneled traffic.
These functions reference a set of allowed IP ranges configured against
each peer.
.Pp
The interface will route outbound tunneled traffic to the peer configured
with the most specific matching allowed IP address range, or drop it
if no such match exists.
.Pp
The interface will accept tunneled traffic only from the peer
configured with the most specific matching allowed IP address range
for the incoming traffic, or drop it if no such match exists.
That is, tunneled traffic routed to a given peer cannot return through
another peer of the same
.Nm wg
interface.
This ensures that peers cannot spoof another's traffic.
.It Handshake
Two peers handshake to mutually authenticate each other and to
establish a shared series of secret ephemeral encryption keys.
Any peer may initiate a handshake.
Handshakes occur only when there is traffic to send, and recur every
two minutes during transfers.
.It Connectionless
Due to the handshake behavior, there is no connected or disconnected
state.
.El
.Ss Keys
Private keys for WireGuard can be generated from any sufficiently
secure random source.
The Curve25519 keys and the preshared keys are both 32 bytes
long and are commonly encoded in base64 for ease of use.
.Pp
Keys can be generated with
.Xr openssl 1
as follows:
.Pp
.Dl $ openssl rand -base64 32
.Pp
Although a valid Curve25519 key must have 5 bits set to
specific values, this is done by the interface and so it
will accept any random 32-byte base64 string.
.Pp
When an interface has a private key set with
.Nm wgkey ,
the corresponding
public key is shown in the status output of the interface:
.Bd -literal -offset indent
# ifconfig wg1 | grep wgpubkey
	wgpubkey NW5l2q2MArV5ZXpVXSZwBOyqhohOf8ImDgUB+jPtJps=
.Ed
.Sh EXAMPLES
Create two
.Nm wg
interfaces in separate
.Xr rdomain 4 Ns s ,
which is of no practical use
but demonstrates two interfaces on the same machine:
.Bd -literal -offset indent
#!/bin/sh

# create interfaces; set random private keys
ifconfig wg1 create wgport 7111 wgkey `openssl rand -base64 32` rdomain 1
ifconfig wg2 create wgport 7222 wgkey `openssl rand -base64 32` rdomain 2

# retrieve the public keys associated with the private keys
PUB1="`ifconfig wg1 | grep 'wgpubkey' | cut -d ' ' -f 2`"
PUB2="`ifconfig wg2 | grep 'wgpubkey' | cut -d ' ' -f 2`"

ifconfig wg1 wgpeer $PUB2 wgendpoint 127.0.0.1 7222 wgaip 192.168.5.2/32
ifconfig wg2 wgpeer $PUB1 wgendpoint 127.0.0.1 7111 wgaip 192.168.5.1/32
ifconfig wg1 192.168.5.1/24
ifconfig wg2 192.168.5.2/24
.Ed
.Pp
After this, ping one interface from the other:
.Pp
.Dl $ route -T1 exec ping 192.168.5.2
.Pp
The two interfaces are able to communicate through the UDP tunnel
which resides in the default
.Xr rdomain 4 .
.Pp
Show the listening sockets:
.Pp
.Dl $ netstat -ln
.Sh DIAGNOSTICS
The
.Nm
interface supports runtime debugging, which can be enabled with:
.Pp
.D1 Ic ifconfig Cm wg Ns Ar N Cm debug
.Pp
Some common error messages include:
.Bl -diag
.It "Handshake for peer X did not complete after 5 seconds, retrying"
Peer X did not reply to our initiation packet, for example because:
.Bl -bullet
.It
The peer does not have the local interface configured as a peer.
Peers must be able to mutually authenticate each other.
.It
The peer endpoint IP address is incorrectly configured.
.It
There are firewall rules preventing communication between hosts.
.El
.It "Invalid handshake initiation"
The incoming handshake packet could not be processed.
This is likely due to the local interface not containing
the correct public key for the peer.
.It "Invalid initiation MAC"
The incoming handshake initiation packet had an invalid MAC.
This is likely because the initiation sender has the wrong public key
for the handshake receiver.
.It "Packet has unallowed src IP from peer X"
After decryption, an incoming data packet has a source IP address that
is not assigned to the allowed IPs of Peer X.
.El
.Sh SEE ALSO
.Xr inet 4 ,
.Xr ip 4 ,
.Xr netintro 4 ,
.Xr hostname.if 5 ,
.Xr pf.conf 5 ,
.Xr ifconfig 8 ,
.Xr netstart 8
.Rs
.%T WireGuard whitepaper
.%U https://www.wireguard.com/papers/wireguard.pdf
.Re
.Sh HISTORY
The
.Nm
driver first appeared in
.Ox 6.8 .
.Sh AUTHORS
.An -nosplit
The
.Ox
.Nm
driver was developed by
.An Matt Dunwoodie Aq Mt ncon@noconroy.net
and
.An Jason A. Donenfeld Aq Mt Jason@zx2c4.com ,
based on code written by
.An Jason A. Donenfeld .