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Jake McGinty 733118a463 README: add security recommendations for services

2021-04-25 01:59:48 +09:00

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innernet

A private network system that uses WireGuard under the hood. See the announcement blog post for a longer-winded explanation.

innernet is similar in its goals to Slack's nebula or Tailscale, but takes a bit of a different approach. It aims to take advantage of existing networking concepts like CIDRs and the security properties of WireGuard to turn your computer's basic IP networking into more powerful ACL primitives.

innernet is not an official WireGuard project, and WireGuard is a registered trademark of Jason A. Donenfeld.

This has not received an independent security audit, and should be considered experimental software at this early point in its lifetime.

Usage

Server Creation

Every innernet network needs a coordination server to manage peers and provide endpoint information so peers can directly connect to each other. Create a new one with

sudo innernet-server new

The init wizard will ask you questions about your network and give you some reasonable defaults. It's good to familiarize yourself with network CIDRs as a lot of innernet's access control is based upon them. As an example, let's say the root CIDR for this network is 10.60.0.0/16. Server initialization creates a special "infra" CIDR which contains the innernet server itself and is reachable from all CIDRs on the network.

Next we'll also create a humans CIDR where we can start adding some peers.

sudo innernet-server add-cidr <interface>

For the parent CIDR, you can simply choose your network's root CIDR. The name will be humans, and the CIDR will be 10.60.64.0/24 (not a great example unless you only want to support 256 humans, but it works for now...).

By default, peers which exist in this new CIDR will only be able to contact peers in the same CIDR, and the special "infra" CIDR which was created when the server was initialized.

A typical workflow for creating a new network is to create an admin peer from the innernet-server CLI, and then continue using that admin peer via the innernet client CLI to add any further peers or network CIDRs.

sudo innernet-server add-peer <interface>

Select the humans CIDR, and the CLI will automatically suggest the next available IP address. Any name is fine, just answer "yes" when asked if you would like to make the peer an admin. The process of adding a peer results in an invitation file. This file contains just enough information for the new peer to contact the innernet server and redeem its invitation. It should be transferred securely to the new peer, and it can only be used once to initialize the peer.

You can run the server with innernet-server serve <interface>, or if you're on Linux and want to run it via systemctl, run systemctl enable --now innernet-server@<interface>. If you're on a home network, don't forget to configure port forwarding to the Listen Port you specified when creating the innernet server.

Peer Initialization

Let's assume the invitation file generated in the steps above have been transferred to the machine a network admin will be using.

You can initialize the client with

sudo inn install /path/to/invitation.toml

You can customize the network name if you want to, or leave it at the default. innernet will then connect to the innernet server via WireGuard, generate a new key pair, and register that pair with the server. The private key in the invitation file can no longer be used.

If everything was successful, the new peer is on the network. You can run things like

sudo inn list

sudo inn list --tree

to view the current network and all CIDRs visible to this peer.

Since we created an admin peer, we can also add new peers and CIDRs from this peer via innernet instead of having to always run commands on the server.

Adding Associations between CIDRs

In order for peers from one CIDR to be able to contact peers in another CIDR, those two CIDRs must be "associated" with each other.

With the admin peer we created above, let's add a new CIDR for some theoretical CI servers we have.

sudo inn add-cidr <interface>

The name is ci-servers and the CIDR is 10.60.64.0/24, but for this example it can be anything.

For now, we want peers in the humans CIDR to be able to access peers in the ci-servers CIDR.

sudo inn add-association <interface>

The CLI will ask you to select the two CIDRs you want to associate. That's all it takes to allow peers in two different CIDRs to communicate!

You can verify the association with

sudo inn list-associations <interface>

and associations can be deleted with

sudo inn delete-associations <interface>

Enabling/Disabling Peers

For security reasons, IP addresses cannot be re-used by new peers, and therefore peers cannot be deleted. However, they can be disabled. Disabled peers will not show up in the list of peers when fetching the config for an interface.

Disable a peer with

sudo inn disable-peer <interface>

Or re-enable a peer with

sudo inn enable-peer <interface>

Specifying a Manual Endpoint

The innernet server will try to use the internet endpoint it sees from a peer so other peers can connect to that peer as well. This doesn't always work and you may want to set an endpoint explicitly. To set an endpoint, use

sudo inn override-endpoint <interface>

You can go back to automatic endpoint discovery with

sudo inn override-endpoint -u <interface>

Setting the Local WireGuard Listen Port

If you want to change the port which WireGuard listens on, use

sudo inn set-listen-port <interface>

or unset the port and use a randomized port with

sudo innernet set-listen-port -u <interface>

Security recommendations

If you're running a service on innernet, there are some important security considerations.

Enable strict Reverse Path Filtering (RFC 3704)

Strict RPF prevents packets from other interfaces from having internal source IP addresses. This is not the default on Linux, even though it is the right choice for 99.99% of situations. You can enable it by adding the following to a /etc/sysctl.d/60-network-security.conf:

net.ipv4.conf.all.rp_filter=1
net.ipv4.conf.default.rp_filter=1

Bind to the WireGuard device

If possible, to ensure that packets are only ever transmitted over the WireGuard interface, it's recommended that you use SO_BINDTODEVICE on Linux or IP_BOUND_IF on macOS/BSDs. If you have strict reverse path filtering, though, this is less of a concern.

IP addresses alone often aren't enough authentication

Even following all the above precautions, rogue applications on a peer's machines could be able to make requests on their behalf unless you add extra layers of authentication to mitigate this CSRF-type vector.

It's recommended that you carefully consider this possibility before deciding that the source IP is sufficient for your authentication needs on a service.

Installation

innernet has only officially been tested on Linux and MacOS, but we hope to support as many platforms as is feasible!

Runtime Dependencies

It's assumed that WireGuard is installed on your system, either via the kernel module in Linux 5.6 and later, or via the wireguard-go userspace implementation.

WireGuard Installation Instructions

Arch Linux

pacman -S innernet

Ubuntu

Fetch the appropriate .deb packages from https://github.com/tonarino/innernet/releases and install with

sudo apt install ./innernet*.deb

macOS

brew install tonarino/innernet/innernet

Cargo

git clone https://github.com/tonarino/innernet
cd innernet
cargo install --path client
cargo install --path server

Development

`innernet-server` Build dependencies

rustc / cargo (version 1.50.0 or higher)
libclang (see more info at https://crates.io/crates/clang-sys)
libsqlite3

Build:

cargo build --release --bin innernet-server

The resulting binary will be located at ./target/release/innernet-server

`innernet` Client CLI Build dependencies

rustc / cargo (version 1.50.0 or higher)
libclang (see more info at https://crates.io/crates/clang-sys)