Key Point 1: 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.
Key Point 2: Each network interface has a private key and a list of peers.
Key Point 3: Each peer has a public key. Public keys are short and simple, and are used by peers to authenticate each other.
They can be passed around for use in configuration files by any out-of-band method, similar to how one might send their SSH public key to a friend for access to a shell server.
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.
Key Point: 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.
Any combination of IPv4 and IPv6 can be used, for any of the fields. WireGuard is fully capable of encapsulating one inside the other if necessary.
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.
DM Comment: Key Concepts to inwardly digest … comprehension is the road to success with WireGuard … KISS please.
EXTRACTED From: https://www.wireguard.com/
