WireGuard

WireGuard is a communication protocol and free and open-source software that implements encrypted virtual private networks (VPNs). It aims to be lighter and better performing than IPsec and OpenVPN, two common tunneling protocols. The WireGuard protocol passes traffic over UDP.

In March 2020, the Linux version of the software reached a stable production release and was incorporated into the Linux 5.6 kernel, and backported to earlier Linux kernels in some Linux distributions. The Linux kernel components are licensed under the GNU General Public License (GPL) version 2; other implementations are under GPLv2 or other free/open-source licenses.

The name WireGuard is a registered trademark of Jason A. Donenfeld.

Protocol
WireGuard uses the following:
 * Curve25519 for key exchange
 * ChaCha20 for symmetric encryption
 * Poly1305 for message authentication codes
 * SipHash24 for hashtable keys
 * BLAKE2s for cryptographic hash function
 * HKDF for key derivation function
 * UDP-based only
 * Base64-encoded private keys, public keys and preshared keys

In May 2019, researchers from INRIA published a machine-checked proof of the WireGuard protocol, produced using the CryptoVerif proof assistant.

Optional pre-shared symmetric key mode
WireGuard supports pre-shared symmetric key mode, which provides an additional layer of symmetric encryption to mitigate future advances in quantum computing. This addresses the risk that traffic may be stored until quantum computers are capable of breaking Curve25519, at which point traffic could be decrypted. Pre-shared keys are "usually troublesome from a key management perspective and might be more likely stolen", but in the shorter term, if the symmetric key is compromised, the Curve25519 keys still provide more than sufficient protection.

Networking
WireGuard uses only UDP, due to the potential disadvantages of TCP-over-TCP. Tunneling TCP over a TCP-based connection is known as "TCP-over-TCP", and doing so can induce a dramatic loss in transmission performance (a problem known as "TCP meltdown"). TCP meltdown occurs when a TCP connection is stacked on top of another. The underlying layer may detect a problem and attempt to compensate, and the layer above it then overcompensates because of that, and this overcompensation causes said delays and degraded transmission performance.

Its default server port is UDP 51820.

WireGuard fully supports IPv6, both inside and outside of tunnel. It supports only layer 3 for both IPv4 and IPv6 and can encapsulate v4-in-v6 and vice versa.

MTU overhead
The overhead of WireGuard breaks down as follows:


 * 20-byte IPv4 header or 40 bytes IPv6 header
 * 8-byte UDP header
 * 4-byte type
 * 4-byte key index
 * 8-byte nonce
 * N-byte encrypted data
 * 16-byte authentication tag

MTU operational considerations
Assuming the underlay network transporting the WireGuard packets maintains a 1500 bytes MTU, configuring the WireGuard interface to 1420 bytes MTU for all involved peers is ideal for transporting IPv6 + IPv4 traffic. However, when exclusively carrying legacy IPv4 traffic, a higher MTU of 1440 bytes for the WireGuard interface suffices.

From an operational perspective and for network configuration uniformity, choosing to configure a 1420 MTU network-wide for the WireGuard interfaces would be advantageous. This approach ensures consistency and facilitates a smoother transition to enabling IPv6 for the WireGuard peers and interfaces in the future.

Caveat
There may be situations where, for instance, a peer is behind a network with 1500 bytes MTU, and a second peer is behind a wireless network such as an LTE network, where often times, the carrier opted to use an MTU that is far lower than 1420 bytes — In such cases, the underlying IP networking stack of the host will fragment the UDP encapsulated packet and send the packets through, the packets inside the tunnel however will remain consistent and will not be required to fragment as PMTUD will detect the MTU between the peers (in this example, that would be 1420 bytes) and send a fixed packet size between the peers.

Extensibility
WireGuard is designed to be extended by third-party programmes and scripts. This has been used to augment WireGuard with various features including more user-friendly management interfaces (including easier setting up of keys), logging, dynamic firewall updates, dynamic IP assignment, and LDAP integration.

Excluding such complex features from the minimal core codebase improves its stability and security. For ensuring security, WireGuard restricts the options for implementing cryptographic controls, limits the choices for key exchange processes, and maps algorithms to a small subset of modern cryptographic primitives. If a flaw is found in any of the primitives, a new version can be released that resolves the issue.

Reception
A review by Ars Technica found that WireGuard was easy to set up and use, used strong ciphers, and had a minimal codebase that provided for a small attack surface.

WireGuard has received funding from the Open Technology Fund. and donations from Mullvad, Private Internet Access, IVPN, the NLnet Foundation and OVPN.

Oregon senator Ron Wyden has recommended to the National Institute of Standards and Technology (NIST) that they evaluate WireGuard as a replacement for existing technologies.

Implementations
Implementations of the WireGuard protocol include:
 * Donenfeld's initial implementation, written in C and Go.
 * Cloudflare's BoringTun, a user space implementation written in Rust.
 * Matt Dunwoodie's implementation for OpenBSD, written in C.
 * Ryota Ozaki's wg(4) implementation for NetBSD, written in C.
 * The FreeBSD implementation is written in C and shares most of the data path with the OpenBSD implementation.
 * Native Windows kernel implementation named "wireguard-nt", since August 2021.
 * AVM Fritz!Box modem-routers that support Fritz!OS version 7.39 and later. Permits site-to-site WireGuard connections from version 7.50 onwards.

History
Early snapshots of the code base exist from 30 June 2016. Four early adopters of WireGuard were the VPN service providers Mullvad, AzireVPN, IVPN and cryptostorm.

On 9 December 2019, David Miller – primary maintainer of the Linux networking stack – accepted the WireGuard patches into the "net-next" maintainer tree, for inclusion in an upcoming kernel.

On 28 January 2020, Linus Torvalds merged David Miller's net-next tree, and WireGuard entered the mainline Linux kernel tree.

On 20 March 2020, Debian developers enabled the module build options for WireGuard in their kernel config for the Debian 11 version (testing).

On 29 March 2020 WireGuard was incorporated into the Linux 5.6 release tree. The Windows version of the software remains at beta.

On 30 March 2020, Android developers added native kernel support for WireGuard in their Generic Kernel Image.

On 22 April 2020, NetworkManager developer Beniamino Galvani merged GUI support for WireGuard in GNOME.

On 12 May 2020, Matt Dunwoodie proposed patches for native kernel support of WireGuard in OpenBSD.

On 22 June 2020, after the work of Matt Dunwoodie and Jason A. Donenfeld, WireGuard support was imported into OpenBSD.

On 23 November 2020, Jason A. Donenfeld released an update of the Windows package improving installation, stability, ARM support, and enterprise features.

On 29 November 2020, WireGuard support was imported into the FreeBSD 13 kernel.

On 19 January 2021, WireGuard support was added for preview in pfSense Community Edition (CE) 2.5.0 development snapshots.

In March 2021, kernel-mode WireGuard support was removed from FreeBSD 13.0, still in testing, after an urgent code cleanup in FreeBSD WireGuard could not be completed quickly. FreeBSD-based pfSense Community Edition (CE) 2.5.0 and pfSense Plus 21.02 removed kernel-based WireGuard as well.

In May 2021, WireGuard support was re-introduced back into pfSense CE and pfSense Plus development snapshots as an experimental package written by a member of the pfSense community, Christian McDonald. The WireGuard package for pfSense incorporates the ongoing kernel-mode WireGuard development work by Jason A. Donenfeld that was originally sponsored by Netgate.

In June 2021, the official package repositories for both pfSense CE 2.5.2 and pfSense Plus 21.05 included the WireGuard package.

In 2023, WireGuard got over 200,000 Euros support from Germany's Sovereign Tech Fund.