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Wireguard

Wireguard is an simple yet fast and modern VPN that utilizes state-of-the-art cryptography. It aims to be faster, simpler, leaner, and more useful than IPsec, while avoiding the massive headache. It intends to be considerably more performant than OpenVPN. WireGuard is a general purpose VPN for running on embedded interfaces and super computers alike. Initially released for the Linux kernel, it's now cross-platform (Windows, macOS, BSD, iOS, Android) and widely deployable. Although it's under heavy development, it already might be the most secure, easiest to use, and simplest VPN solution in the industry.

Features:

  • Simple and easy to use: WireGuard aims to be as easy to configure and deploy as SSH. A VPN connection is made by exchanging public keys – exactly like exchanging SSH keys – and all the rest is transparently handled by WireGuard. It's even capable of roaming between IP addresses, like Mosh. There is no need to manage connections, worry about state, manage daemons, or worry about what's under the hood. WireGuard presents a basic yet powerful interface.

  • Cryptographically Sound: WireGuard uses state-of-the-art cryptography, such as the Noise protocol framework, Curve25519, ChaCha20, Poly1305, BLAKE2, SipHash24, HKDF, and secure trusted constructions. It makes conservative and reasonable choices and has been reviewed by cryptographers.

  • Minimal Attack Surface: WireGuard is designed with ease-of-implementation and simplicity in mind. It's meant to be implemented in very few lines of code, and auditable for security vulnerabilities. Compared to behemoths like *Swan/IPsec or OpenVPN/OpenSSL, in which auditing the gigantic codebases is an overwhelming task even for large teams of security experts, WireGuard is meant to be comprehensively reviewable by single individuals.

  • High Performance: A combination of extremely high-speed cryptographic primitives and the fact that WireGuard lives inside the Linux kernel means that secure networking can be very high-speed. It is suitable for both small embedded devices like smartphones and fully loaded backbone routers.

  • Well Defined & Thoroughly Considered: WireGuard is the result of a lengthy and thoroughly considered academic process, resulting in the technical whitepaper, an academic research paper which clearly defines the protocol and the intense considerations that went into each decision.

Plus it's created by the same guy as pass, which uses Gentoo, I like this guy.

Conceptual Overview⚑

WireGuard securely encapsulates IP packets over UDP. You add a WireGuard interface, configure it with your private key and your peers' public keys, and then you send packets across it. All issues of key distribution and pushed configurations are out of scope of WireGuard; these are issues much better left for other layers. It mimics the model of SSH and Mosh; both parties have each other's public keys, and then they're simply able to begin exchanging packets through the interface.

Simple Network Interface⚑

WireGuard works by adding network interfaces, called wg0 (or wg1, wg2, wg3, etc). This network interface can then be configured normally using the ordinary networking utilities. The specific WireGuard aspects of the interface are configured using the wg tool. This interface acts as a tunnel interface.

WireGuard associates tunnel IP addresses with public keys and remote endpoints. When the interface sends a packet to a peer, it does the following:

  • This packet is meant for 192.168.30.8. Which peer is that? Let me look... Okay, it's for peer ABCDEFGH. (Or if it's not for any configured peer, drop the packet.)
  • Encrypt entire IP packet using peer ABCDEFGH's public key.
  • What is the remote endpoint of peer ABCDEFGH? Let me look... Okay, the endpoint is UDP port 53133 on host 216.58.211.110.
  • Send encrypted bytes from step 2 over the Internet to 216.58.211.110:53133 using UDP.

When the interface receives a packet, this happens:

  • I just got a packet from UDP port 7361 on host 98.139.183.24. Let's decrypt it!
  • It decrypted and authenticated properly for peer LMNOPQRS. Okay, let's remember that peer LMNOPQRS's most recent Internet endpoint is 98.139.183.24:7361 using UDP.
  • Once decrypted, the plain-text packet is from 192.168.43.89. Is peer LMNOPQRS allowed to be sending us packets as 192.168.43.89?
  • If so, accept the packet on the interface. If not, drop it.

Behind the scenes there is much happening to provide proper privacy, authenticity, and perfect forward secrecy, using state-of-the-art cryptography.

Cryptokey Routing⚑

At the heart of WireGuard is a concept called Cryptokey Routing, which works by associating public keys with a list of tunnel IP addresses that are allowed inside the tunnel. Each network interface has a private key and a list of peers. Each peer has a public key.

For example, a server computer might have this configuration:

[Interface]
PrivateKey = yAnz5TF+lXXJte14tji3zlMNq+hd2rYUIgJBgB3fBmk=
ListenPort = 51820

[Peer]
PublicKey = xTIBA5rboUvnH4htodjb6e697QjLERt1NAB4mZqp8Dg=
AllowedIPs = 10.192.122.3/32, 10.192.124.1/24

[Peer]
PublicKey = TrMvSoP4jYQlY6RIzBgbssQqY3vxI2Pi+y71lOWWXX0=
AllowedIPs = 10.192.122.4/32, 192.168.0.0/16

[Peer]
PublicKey = gN65BkIKy1eCE9pP1wdc8ROUtkHLF2PfAqYdyYBz6EA=
AllowedIPs = 10.10.10.230/32

And a client computer might have this simpler configuration:

[Interface]
PrivateKey = gI6EdUSYvn8ugXOt8QQD6Yc+JyiZxIhp3GInSWRfWGE=
ListenPort = 21841

[Peer]
PublicKey = HIgo9xNzJMWLKASShiTqIybxZ0U3wGLiUeJ1PKf8ykw=
Endpoint = 192.95.5.69:51820
AllowedIPs = 0.0.0.0/0

In the server configuration, each peer (a client) will be able to send packets to the network interface with a source IP matching his corresponding list of allowed IPs. For example, when a packet is received by the server from peer gN65BkIK..., after being decrypted and authenticated, if its source IP is 10.10.10.230, then it's allowed onto the interface; otherwise it's dropped.

In the server configuration, when the network interface wants to send a packet to a peer (a client), it looks at that packet's destination IP and compares it to each peer's list of allowed IPs to see which peer to send it to. For example, if the network interface is asked to send a packet with a destination IP of 10.10.10.230, it will encrypt it using the public key of peer gN65BkIK..., and then send it to that peer's most recent Internet endpoint.

In the client configuration, its single peer (the server) will be able to send packets to the network interface with any source IP (since 0.0.0.0/0 is a wildcard). For example, when a packet is received from peer HIgo9xNz..., if it decrypts and authenticates correctly, with any source IP, then it's allowed onto the interface; otherwise it's dropped.

In the client configuration, when the network interface wants to send a packet to its single peer (the server), it will encrypt packets for the single peer with any destination IP address (since 0.0.0.0/0 is a wildcard). For example, if the network interface is asked to send a packet with any destination IP, it will encrypt it using the public key of the single peer HIgo9xNz..., and then send it to the single peer's most recent Internet endpoint.

In other words, when sending packets, the list of allowed IPs behaves as a sort of routing table, and when receiving packets, the list of allowed IPs behaves as a sort of access control list.

This is what we call a Cryptokey Routing Table: the simple association of public keys and allowed IPs.

Because all packets sent on the WireGuard interface are encrypted and authenticated, and because there is such a tight coupling between the identity of a peer and the allowed IP address of a peer, system administrators do not need complicated firewall extensions, such as in the case of IPsec, but rather they can simply match on "is it from this IP? on this interface?", and be assured that it is a secure and authentic packet. This greatly simplifies network management and access control, and provides a great deal more assurance that your iptables rules are actually doing what you intended for them to do.

Built-in Roaming⚑

The client configuration contains an initial endpoint of its single peer (the server), so that it knows where to send encrypted data before it has received encrypted data. The server configuration doesn't have any initial endpoints of its peers (the clients). This is because the server discovers the endpoint of its peers by examining from where correctly authenticated data originates. If the server itself changes its own endpoint, and sends data to the clients, the clients will discover the new server endpoint and update the configuration just the same. Both client and server send encrypted data to the most recent IP endpoint for which they authentically decrypted data. Thus, there is full IP roaming on both ends.

Last update: 2020-09-21