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162 lines
5.5 KiB
Markdown
162 lines
5.5 KiB
Markdown
# nginx-auth
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[](https://tailscale.com/kb/1167/release-stages/#experimental)
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This is a tool that allows users to use Tailscale Whois authentication with
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NGINX as a reverse proxy. This allows users that already have a bunch of
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services hosted on an internal NGINX server to point those domains to the
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Tailscale IP of the NGINX server and then seamlessly use Tailscale for
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authentication.
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Many thanks to [@zrail](https://twitter.com/zrail/status/1511788463586222087) on
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Twitter for introducing the basic idea and offering some sample code. This
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program is based on that sample code with security enhancements. Namely:
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* This listens over a UNIX socket instead of a TCP socket, to prevent
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leakage to the network
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* This uses systemd socket activation so that systemd owns the socket
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and can then lock down the service to the bare minimum required to do
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its job without having to worry about dropping permissions
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* This provides additional information in HTTP response headers that can
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be useful for integrating with various services
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## Configuration
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In order to protect a service with this tool, do the following in the respective
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`server` block:
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Create an authentication location with the `internal` flag set:
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```nginx
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location /auth {
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internal;
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proxy_pass http://unix:/run/tailscale.nginx-auth.sock;
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proxy_pass_request_body off;
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proxy_set_header Host $http_host;
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proxy_set_header Remote-Addr $remote_addr;
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proxy_set_header Remote-Port $remote_port;
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proxy_set_header Original-URI $request_uri;
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}
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```
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Then add the following to the `location /` block:
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```
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auth_request /auth;
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auth_request_set $auth_user $upstream_http_tailscale_user;
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auth_request_set $auth_name $upstream_http_tailscale_name;
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auth_request_set $auth_login $upstream_http_tailscale_login;
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auth_request_set $auth_tailnet $upstream_http_tailscale_tailnet;
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auth_request_set $auth_profile_picture $upstream_http_tailscale_profile_picture;
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proxy_set_header X-Webauth-User "$auth_user";
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proxy_set_header X-Webauth-Name "$auth_name";
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proxy_set_header X-Webauth-Login "$auth_login";
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proxy_set_header X-Webauth-Tailnet "$auth_tailnet";
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proxy_set_header X-Webauth-Profile-Picture "$auth_profile_picture";
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```
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When this configuration is used with a Go HTTP handler such as this:
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```go
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http.HandlerFunc(func (w http.ResponseWriter, r *http.Request) {
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e := json.NewEncoder(w)
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e.SetIndent("", " ")
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e.Encode(r.Header)
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})
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```
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You will get output like this:
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```json
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{
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"Accept": [
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"*/*"
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],
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"Connection": [
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"upgrade"
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],
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"User-Agent": [
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"curl/7.82.0"
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],
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"X-Webauth-Login": [
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"Xe"
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],
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"X-Webauth-Name": [
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"Xe Iaso"
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],
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"X-Webauth-Profile-Picture": [
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"https://avatars.githubusercontent.com/u/529003?v=4"
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],
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"X-Webauth-Tailnet": [
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"cetacean.org.github"
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]
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"X-Webauth-User": [
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"Xe@github"
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]
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}
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```
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## Headers
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The authentication service provides the following headers to decorate your
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proxied requests:
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| Header | Example Value | Description |
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| :------ | :-------------- | :---------- |
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| `Tailscale-User` | `azurediamond@hunter2.net` | The Tailscale username the remote machine is logged in as in user@host form |
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| `Tailscale-Login` | `azurediamond` | The user portion of the Tailscale username the remote machine is logged in as |
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| `Tailscale-Name` | `Azure Diamond` | The "real name" of the Tailscale user the machine is logged in as |
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| `Tailscale-Profile-Picture` | `https://i.kym-cdn.com/photos/images/newsfeed/001/065/963/ae0.png` | The profile picture provided by the Identity Provider your tailnet uses |
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| `Tailscale-Tailnet` | `hunter2.net` | The tailnet name |
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Most of the time you can set `X-Webauth-User` to the contents of the
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`Tailscale-User` header, but some services may not accept a username with an `@`
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symbol in it. If this is the case, set `X-Webauth-User` to the `Tailscale-Login`
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header.
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The `Tailscale-Tailnet` header can help you identify which tailnet the session
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is coming from. If you are using node sharing, this can help you make sure that
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you aren't giving administrative access to people outside your tailnet.
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### Allow Requests From Only One Tailnet
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If you want to prevent node sharing from allowing users to access a service, add
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the `Expected-Tailnet` header to your auth request:
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```nginx
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location /auth {
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# ...
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proxy_set_header Expected-Tailnet "tailnet012345.ts.net";
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}
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```
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If a user from a different tailnet tries to use that service, this will return a
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generic "forbidden" error page:
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```html
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<html>
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<head><title>403 Forbidden</title></head>
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<body>
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<center><h1>403 Forbidden</h1></center>
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<hr><center>nginx/1.18.0 (Ubuntu)</center>
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</body>
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</html>
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```
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You can get the tailnet name from [the admin panel](https://login.tailscale.com/admin/dns).
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## Building
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Install `cmd/mkpkg`:
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```
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cd .. && go install ./mkpkg
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```
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Then run `./mkdeb.sh`. It will emit a `.deb` and `.rpm` package for amd64
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machines (Linux uname flag: `x86_64`). You can add these to your deployment
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methods as you see fit.
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