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103 lines
3.6 KiB
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103 lines
3.6 KiB
Markdown
---
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layout: post
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title: "Crypto-Key Routing"
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date: 2018-11-06 23:00:00 -0000
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author: Neil Alexander
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---
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### Tunnelling over Yggdrasil
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Up until now, Yggdrasil has worked entirely using internal addressing from the
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`0200::/7` range. These addresses are cryptographically bound and allow
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end-to-end communication between any two given nodes. However, this approach is
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somewhat limiting in that it assumes an Yggdrasil node is, at most, a gateway
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for a single /64 IPv6 subnet. This therefore meant that it is very difficult
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to route between or bridge two networks without using another encapsulation
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protocol such as GRE. It also meant that it was very difficult to provide access
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to networks like the Internet internally.
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Today I created a pull request which implements Crypto-Key Routing (CKR), which
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you may already be familiar with if you have used Wireguard. The premise behind
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CKR is that it allows you to define routes stating that specific subnets should
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be routed to a given node on the network, identified by their public encryption
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key. The traffic is encrypted end-to-end, as normal, and sent to the specified
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node, otherwise completely unmodified. This gives us effectively the ability to
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run VPNs over the Yggdrasil network without the need for additional software.
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### Configuration
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The new CKR module proposes the addition of some new configuration options. They
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are summarised below, although may be subject to change at the point that v0.3
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is released:
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```
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TunnelRouting:
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{
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Enable: false
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IPv6Destinations: {}
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IPv6Sources: []
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IPv4Destinations: {}
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IPv4Sources: []
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}
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```
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The `IPv6Destinations` and `IPv4Destinations` options are used to specify
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crypto-key routes. The subnet refers to an encryption public key of another
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node, for example:
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```
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IPv6Destinations: {
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"fd64:642b:1a20::/48": "ef78da7fc983c6c210609529921a701ca3e43fa5cfd79f5f20cc67bf66e45c1a",
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"fd25:8a33:9311:a53b::/64": "417fd0a66a104f050ae3544b3bc03eeb3648dded4a8c1fb085d65ffa25e83d6e"
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}
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```
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As with a typical routing table, more specific routes are preferred.
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The `IPv6Sources` and `IPv4Sources` options are used to specify which source
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addresses are eligible to be routed across a tunnel. For IPv6, this is optional
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as each Yggdrasil node already has an address and a routed subnet, and these are
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always allowed as source addresses. Specifying additional source addresses means
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that you can use the tunnel to route between networks. For IPv4, this is
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mandatory as Yggdrasil nodes do not have IPv4 addresses by default.
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### Bridging networks
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Assume that node A is `a.a.a.a/24` and `aaaa:aaaa:aaaa:aaaa::/64` and node B is `b.b.b.b/24` and `bbbb:bbbb:bbbb:bbbb::/64`. On node A, use the following `TunnelRouting` configuration:
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```
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Enable: true
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IPv6Destinations: {
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"bbbb:bbbb:bbbb:bbbb::/64": "xxxxxxxxxxxxxx"
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}
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IPv6Sources: {
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aaaa:aaaa:aaaa:aaaa::/64
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}
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IPv4Destinations: {
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"b.b.b.b/24": "xxxxxxxxxxxxxx"
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}
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IPv4Sources: {
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a.a.a.a/24
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}
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```
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On node B, use the reverse `TunnelRouting` configuration:
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```
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Enable: true
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IPv6Destinations: {
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"aaaa:aaaa:aaaa:aaaa::/64": "xxxxxxxxxxxxxx"
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}
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IPv6Sources: {
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bbbb:bbbb:bbbb:bbbb::/64
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}
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IPv4Destinations: {
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"a.a.a.a/24": "xxxxxxxxxxxxxx"
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}
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IPv4Sources: {
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b.b.b.b/24
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}
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```
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The Yggdrasil TUN/TAP adapters on each side can now be used to tunnel between `a.a.a.a/24` and `b.b.b.b/24` in IPv4 and `aaaa:aaaa:aaaa:aaaa::/64` and `bbbb:bbbb:bbbb:bbbb/64` in IPv6.
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### Conclusion
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It is my hope that this will be merged into the `develop` branch soon, and will
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be a feature targeted for general release in v0.3. With this, Yggdrasil is able
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to take on more advanced routing tasks and will hopefully be more useful in a
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wider range of scenarios.
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