virtuallypotato/content/posts/secure-networking-made-simple-with-tailscale/index.md at 121a59f602d0902765fbc63750502ca2cc1a754c

vPotato/virtuallypotato

Fork 0

mirror of https://github.com/jbowdre/virtuallypotato.git synced 2024-11-22 06:52:18 +00:00

John Bowdre 31e547980a collapse post contents directly under content/posts/

2022-07-22 16:01:30 -05:00

24 KiB

Raw Blame History

title

date

lastmod

description

featured

toc

usePageBundles

featureImage

featureImageAlt

thumbnail

codeLineNumbers

series

Getting started

The first step in getting up and running with Tailscale is to sign up at https://login.tailscale.com/start. You'll need to use an existing Google, Microsoft, or GitHub account to sign up, which also lets you leverage the 2FA and other security protections already enabled on those accounts.

Once you have a Tailscale account, you're ready to install the Tailscale client. The download page outlines how to install it on various platforms, and also provides a handy-dandy one-liner to install it on Linux:

curl -fsSL https://tailscale.com/install.sh | sh

After the install completes, it will tell you exactly what you need to do next:

Installation complete! Log in to start using Tailscale by running:

sudo tailscale up

There are also Tailscale apps available for iOS and Android - and the Android app works brilliantly on Chromebooks too!

Basic `tailscale up`

Running sudo tailscale up then reveals the next step:

❯ sudo tailscale up

To authenticate, visit:

        https://login.tailscale.com/a/1872939939df

I can copy that address into a browser and I'll get prompted to log in to my Tailscale account. And that's it. Tailscale is installed, configured to run as a service, and connected to my Tailscale account. This also creates my tailnet.

That was pretty easy, right? But what about if I can't easily get to a web browser from the terminal session on a certain device? No worries, tailscale up has a flag for that:

sudo tailscale up --qr

That will convert the URL to a QR code that I can scan from my phone.

Advanced `tailscale up`

There are a few additional flags that can be useful under certain situations:

--advertise-exit-node to tell the tailnet that this could be used as an exit node for internet traffic

sudo tailscale up --advertise-exit-node

--advertise-routes to let the node perform subnet routing functions to provide connectivity to specified local subnets

sudo tailscale up --advertise-routes "192.168.1.0/24,172.16.0.0/16"

--advertise-tags⁴ to associate the node with certain tags for ACL purposes (like tag:home to identify stuff in my home network and tag:cloud to label external cloud-hosted resources)

sudo tailscale up --advertise-tags "tag:cloud"

--hostname to manually specific a hostname to use within the tailnet

sudo tailscale up --hostname "tailnode"

--shields-up to block incoming traffic

sudo tailscale up --shields-up

These flags can also be combined with each other:

sudo tailscale up --hostname "tailnode" --advertise-exit-node --qr

Sidebar: Tailscale on VyOS

Getting Tailscale on my VyOS virtual router was unfortunately a little more involved than leveraging the built-in WireGuard capability. I found the vyos-tailscale project to help with building a customized VyOS installation ISO with the tailscaled daemon added in. I was then able to copy the ISO over to my VyOS instance and install it as if it were a standard upgrade. I could then bring up the interface, advertise my home networks, and make it available as an exit node with:

sudo tailscale up --advertise-exit-node --advertise-routes "192.168.1.0/24,172.16.0.0/16"

Other `tailscale` commands

Once there are a few members, I can use the tailscale status command to see a quick overview of the tailnet:

❯ tailscale status
100.115.115.39  deb01                john@        linux   -
100.118.115.69  ipam                 john@        linux   -
100.116.90.109  johns-iphone         john@        iOS     -
100.116.31.85   matrix               john@        linux   -
100.114.140.112 pixel6pro            john@        android -
100.94.127.1    pixelbook            john@        android -
100.75.110.50   snikket              john@        linux   -
100.96.24.81    vyos                 john@        linux   -
100.124.116.125 win01                john@        windows -

Without doing any other configuration beyond just installing Tailscale and connecting it to my account, I can now easily connect from any of these devices to any of the other devices using the listed Tailscale IP⁵. Entering ssh 100.116.31.85 will connect me to my Matrix server.

tailscale ping lets me check the latency between two Tailscale nodes at the Tailscale layer; the first couple of pings will likely be delivered through a nearby DERP server until the NAT traversal magic is able to kick in:

❯ tailscale ping snikket
pong from snikket (100.75.110.50) via DERP(nyc) in 34ms
pong from snikket (100.75.110.50) via DERP(nyc) in 35ms
pong from snikket (100.75.110.50) via DERP(nyc) in 35ms
pong from snikket (100.75.110.50) via [PUBLIC_IP]:41641 in 23ms

The tailscale netcheck command will give me some details about my local Tailscale node, like whether it's able to pass UDP traffic, which DERP server is the closest, and the latency to all Tailscale DERP servers:

❯ tailscale netcheck

Report:
        * UDP: true
        * IPv4: yes, [LOCAL_PUBLIC_IP]:52661
        * IPv6: no
        * MappingVariesByDestIP: false
        * HairPinning: false
        * PortMapping:
        * Nearest DERP: Chicago
        * DERP latency:
                - ord: 23.4ms  (Chicago)
                - dfw: 26.8ms  (Dallas)
                - nyc: 28.6ms  (New York City)
                - sea: 71.5ms  (Seattle)
                - sfo: 77.8ms  (San Francisco)
                - lhr: 102.2ms (London)
                - fra: 114.8ms (Frankfurt)
                - sao: 133.1ms (São Paulo)
                - tok: 154.9ms (Tokyo)
                - syd: 215.3ms (Sydney)
                - sin: 243.7ms (Singapore)
                - blr: 244.6ms (Bangalore)

Tailscale management

Now that the Tailscale client is installed on my devices and I've verified that they can talk to each other, it might be a good time to log in at login.tailscale.com to take a look at the Tailscale admin console.

Subnets and Exit Nodes

See how the vyos node has little labels on it about "Subnets (!)" and "Exit Node (!)"? The exclamation marks are there because the node is advertising subnets and its exit node eligibility, but those haven't actually been turned on it. To enable the vyos node to function as a subnet router (for the 172.16.0.0/16 and 192.168.1.0/24 networks listed beneath its Tailscale IP) and as an exit node (for internet-bound traffic from other Tailscale nodes), I need to click on the little three-dot menu icon at the right edge of the row and select the "Edit route settings..." option.

Now I can approve the subnet routes (individually or simultaneously and at the same time) and allow the node to route traffic to the internet as well⁶.

Cool! But now that's giving me another warning...

Key expiry

By default, Tailscale expires each node's encryption keys every 180 days. This improves security (particularly over vanilla WireGuard, which doesn't require any key rotation) but each node will need to reauthenticate (via tailscale up) in order to get a new key. It may not make sense to do that for systems acting as subnet routers or exit nodes since they would stop passing all Tailscale traffic once the key expires. That would also hurt for my cloud servers which are only accessible via Tailscale; if I can't log in through SSH (since it's blocked at the firewall) then I can't reauthenticate Tailscale to regain access. For those systems, I can click that three-dot menu again and select the "Disable key expiry" option. I tend to do this for my "always on" tailnet members and just enforce the key expiry for my "client" type devices which could potentially be physically lost or stolen.

Configuring DNS

It's great that all my Tailscale machines can talk to each other directly by their respective Tailscale IP addresses, but who wants to keep up with IPs? I sure don't. Let's do some DNS. I'll start out by clicking on the DNS tab in the admin console.

I need to add a Global Nameserver before I can enable MagicDNS so I'll click on the appropriate button to enter in the Tailscale IP⁷ of my home DNS server (which is using NextDNS as the upstream resolver).

I'll also enable the toggle to "Override local DNS" to make sure all queries from connected clients are going through this server (and thus extend the NextDNS protection to all clients without having to configure them individually).

I can also define search domains to be used for unqualified DNS queries by adding another name server with the same IP address, enabling the "Restrict to search domain" option, and entering the desired domain:

This will let me resolve hostnames when connected remotely to my lab without having to type the domain suffix (ex, vcsa versus vcsa.lab.bowdre.net).

And, finally, I can click the "Enable MagicDNS" button to turn on the magic. This adds a new nameserver with a private Tailscale IP which will resolve Tailscale hostnames to their internal IP addresses.

Now I can log in to my Matrix server by simply typing ssh matrix. Woohoo!

Access control

Right now, all of my Tailscale nodes can access all of my other Tailscale nodes. That's certainly very convenient, but I'd like to break things up a bit. I can use access control policies to define which devices should be able to talk to which other devices, and I can use ACL tags to logically group resources together to make this easier.

ACLs

By default, Tailscale implements an implicit "Allow All" ACL. As soon as you start modifying the ACL, though, that switches to an implicit "Deny All". So I'll add new rules to explicitly state what communication should be permitted and everything else will be blocked.

Each ACL rule consists of four named parts:

action - what to do with the traffic, the only valid option is allow.
users - a list of traffic sources, can be specific users, Tailscale IPs, hostnames, subnets, groups, or tags.
proto - (optional) protocol for the traffic which should be permitted.
ports - a list of destinations (and optional ports).

So I'll add this to the top of my policy file:

{
  "acls": [
    {
      // home servers can access other servers
      "action": "accept",
      "users": ["tag:home"],
      "ports": [
        "tag:home:*",
        "tag:cloud:*"
        ]
    },
    {
      // clients can access everything
      "action": "accept",
      "users": ["tag:client"],
      "ports": ["*:*"]
    }
  ]
}

This policy becomes active as soon as I click the Save button at the bottom of the page, and I notice a problem very shortly. Do you see it?

Earlier I configured Tailscale to force all nodes to use my home DNS server for resolving all queries, and I just set an ACL which prevents my cloud servers from talking to my home servers... which includes the DNS server. I can think of two ways to address this:

Re-register the servers by passing the --accept-dns=false flag to tailscale up so they'll ignore the DNS configured in the admin console.
Add a new ACL rule to allow DNS traffic to reach the DNS server from the cloud.

Option 2 sounds better to me so that's what I'm going to do. Instead of putting an IP address directly into the ACL rule I'd rather use a hostname, and unfortunately the Tailscale host names aren't available within ACL rule declarations. But I can define a host alias in the policy to map a friendly name to the IP:

{
  "hosts": {
    "win01": "100.124.116.125"
  }
}

And I can then create a new rule for "users": ["tag:cloud"] to add an exception for win01:53:

{
  "acls": [
    {
      // cloud servers can only access other cloud servers plus my internal DNS server
      "action": "accept",
      "users": ["tag:cloud"],
      "ports": [
        "win01:53"
      ]
    }
  ]
}

And that gets DNS working again for my cloud servers while still serving the results from my NextDNS configuration. Here's the complete policy configuration:

{
  "acls": [
    {
      // home servers can access other servers
      "action": "accept",
      "users": ["tag:home"],
      "ports": [
        "tag:home:*",
        "tag:cloud:*"
        ]
    },
    {
      // cloud servers can only access my internal DNS server
      "action": "accept",
      "users": ["tag:cloud"],
      "ports": [
        "win01:53"
      ]
    },      
    {
      // clients can access everything
      "action": "accept",
      "users": ["tag:client"],
      "ports": ["*:*"]
    }
  ],
  "hosts": {
    "win01": "100.124.116.125"
  },
  "groups": {
    "group:admins": ["john@example.com"],
  },
  "tagOwners": {
    "tag:home": ["group:admins"],
    "tag:cloud": ["group:admins"],
    "tag:client": ["group:admins"]
  }
}

Wrapping up

This post has really only scratched the surface on the cool capabilities provided by Tailscale. I didn't even get into its options for enabling HTTPS with valid certificates, custom DERP servers, sharing tailnet nodes with other users, or file transfer using Taildrop. The Next Steps section of the official Getting Started doc has some other cool ideas for Tailscale-powered use cases, and there are a ton more listed in the Solutions and Guides categories as well.

It's amazing to me that a VPN solution can be this simple to set up and manage while still offering such incredible flexibility. Tailscale is proof that secure networking doesn't have to be hard.

Plus the GCP egress charges started to slowly stack up to a few ones of dollars each month. ↩︎
May I just say that I love this acronym? ↩︎
There's also a reasonably-priced Personal Pro option which comes with 100 devices, 2 routers, and custom auth periods for $48/year. I'm using that since it's less than I was going to spend on WireGuard egress through GCP and I want to support the project in a small way. ↩︎
Before being able to assign tags at the command line, you must first define tag owners who can manage the tag. On a personal account, you've only got one user to worry with but you still have to set this up first. I'll go over this in a bit but here's the documentation if you want to skip ahead. ↩︎
I could also connect using the Tailscale hostname, if MagicDNS is enabled - but I'm getting ahead of myself. ↩︎
Once subnets are allowed, they're made available to all members of the tailnet so that traffic destined for those networks can be routed accordingly. Clients will need to opt-in to using the Exit Node though; I typically only do that when I'm on a wireless network I don't control and want to make sure that no one can eavesdrop on my internet traffic, but I like to have that option available for when I need it. ↩︎
Using the Tailscale IP will allow queries to go straight to the DNS server without having to go through the VyOS router first. Configuring my clients to use a tailnet node for DNS queries also has the added benefit of sending that traffic through the encrypted tunnels instead of across the internet in the clear. I get secure DNS without having to configure secure DNS! ↩︎

24 KiB Raw Blame History Unescape Escape