cdk-tailscale-bastion/README.md

Deploys a AWS Bastion Host preconfigured for Tailscale access

# cdk-tailscale-bastion

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This packages creates an AWS EC2 (Bastion) configured for Tailscale. This covers the [Tailscale AWS VPC guide](https://tailscale.com/kb/1021/install-aws/) as well as most of the [Tailscale RDS guide](https://tailscale.com/kb/1141/aws-rds/).

Using Tailscale to access your VPC permits high performance connectivity whilst avoiding SSH or the overhead & limitations of Session Manager.

## Installation

JS/TS: `npm i cdk-tailscale-bastion -D`

C#: `dotnet add package CDK.Tailscale.Bastion`

## Instructions

The Tailscale Auth key should be passed in via secrets manager and NOT hardcoded in your application. 

```typescript
import { TailscaleBastion } from 'cdk-tailscale-bastion';

// Secrets Manager
const secret = Secret.fromSecretNameV2(stack, 'ApiSecrets', 'tailscale');

const bastion = new TailscaleBastion(stack, 'Sample-Bastion', {
  vpc,
  tailscaleCredentials: {
    secretsManager: {
      secret: secret,
      key: 'AUTH_KEY',
    },
  },
});

```

Whatever resource you intend to reach should permit connections from the bastion on the relevant port, naturally. 

## Tailscale Auth Key

I recommend generating an Ephemeral key that includes the bastion as a tag for ease of teardown and tracking:

<img src="https://user-images.githubusercontent.com/975824/177150876-ab21b4ac-00f7-4a75-befa-cf7d2e9ca7f7.png" height="200px" />

## Tailscale Configuration

Once deployed, unless you have [auto approval](https://tailscale.com/kb/1018/acls/#auto-approvers-for-routes-and-exit-nodes) enabled, you'll need to manually [enable the subnet routes](https://tailscale.com/kb/1019/subnets/#step-3-enable-subnet-routes-from-the-admin-console) in the tailscale console.

You'll also need to setup the nameserver. The bastion construct conveniently outputs the settings you require for Tailscale's DNS configuration:

<img src="https://user-images.githubusercontent.com/975824/177154488-3f3c1d02-35c6-432b-96fc-9dca691ea94c.png" height="250px" />

Given your configuration is correct, a direct connection to your internal resources should now be possible.


## 4via6 Support

If you wish to use [4via6 subnet routers](https://tailscale.com/kb/1201/4via6-subnets/), you can pass the IPv6 address via the `advertiseRoute` property:

```ts
new TailscaleBastion(stack, 'Cdk-Sample-Lib', {
  vpc,
  tailscaleCredentials: ...,
  advertiseRoute: 'fd7a:115c:a1e0:b1a:0:7:a01:100/120',
});
```

## Incoming routes

If you have other subnet routers configured in Tailscale, you can use the `incomingRoutes` property to configure VPC route table entries for all private subnets.

```ts
new TailscaleBastion(stack, 'Sample-Bastion', {
  vpc,
  tailscaleCredentials: ...,
  incomingRoutes: [
    '192.168.1.0/24',
  ],
});
```