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https://github.com/boinkor-net/tsnsrv

A reverse proxy that exposes services on your tailnet (as their own tailscale participants)
https://github.com/boinkor-net/tsnsrv

golang http reverse-proxy tailscale

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A reverse proxy that exposes services on your tailnet (as their own tailscale participants)

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# tsnsrv - a reverse proxy on your tailnet



This package includes a little go program that sets up a reverse proxy

listening on your tailnet (optionally with a funnel), forwarding

requests to a service reachable from the machine running this

program. This is directly and extremely inspired by the [amazing talk

by Xe Iaso](https://tailscale.dev/blog/tsup-tsnet) about the wonderful

things one can do with

[`tsnet`](https://pkg.go.dev/tailscale.com/tsnet).



## Why use this?



First, you'll want to watch the talk linked above. But if you still

have that question: Say you run a service that you haven't written

yourself (we can't all be as wildly productive as Xe), but you'd still

like to benefit from tailscale's access control, encrypted

communication and automatic HTTPS cert provisioning? Then you can just

run that service, have it listen on localhost or a unix domain socket,

then run `tsnsrv` and have that expose the service on your tailnet

(or, as I mentioned, on the funnel).



### Is this probably full of horrible bugs that will make you less secure or more unhappy?



Almost certainly:



* I have not thought much request forgery.



* You're by definition forwarding requests of one degree of

  trustedness to a thing of another degree of trustedness.



* This tool uses go's `httputil.ReverseProxy`, which seems notorious

  for having bugs in its mildly overly-naive URL path rewriting

  (especially resulting in an extraneous `/` getting appended to the

  destination URL path).



## So how do you use this?



First, you have to have a service you want to proxy to, reachable from

the machine that runs tsnsrv. I'll assume it serves plaintext HTTP on

`127.0.0.1:8000`, but it could be on any address, reachable over ipv4

or v6. Assume the service is called `happy-computer`.



Then, you have options:



* Expose the service on your tailnet (and only your tailnet):

  `tsnsrv -name happy-computer http://127.0.0.1:8000`



* Expose the entire service on your tailnet and on the internet:

  `tsnsrv -name happy-computer -funnel http://127.0.0.1:8000`



### Access control to public funnel endpoints



Now, running a whole service on the internet doesn't feel great

(especially if the authentication/authorization story depended on it

being reachable only on your tailnet); you might want to expose only a

webhook endpoint from a separate tsnsrv invocation, that allows access

only to one or a few subpaths. Assuming you want to run a matrix

server:



```sh

tsnsrv -name happy-computer-webhook -funnel -stripPrefix=false -prefix /_matrix -prefix /_synapse/client http://127.0.0.1:8000

```



Each `-prefix` flag adds a path to the list of URLs that external

clients can see (Anything outside that list returns a 404).



The `-stripPrefix` flag tells tsnsrv to leave the prefix intact: By default, it strips off the matched portion, so that you can run it with:

`tsnsrv -name hydra-webhook -funnel -prefix /api/push-github http://127.0.0.1:3001/api/push-github`

which would be identical to

`tsnsrv -name hydra-webhook -funnel -prefix /api/push-github -stripPrefix=false http://127.0.0.1:3001`



### Passing requestor information to upstream services



Unless given the `-suppressWhois` flag, `tsnsrv` will look up

information about the requesting user and their node, and attach the

following headers:



* `X-Tailscale-User` - numeric ID of the user that made the request

* `X-Tailscale-User-LoginName` - login name of the user that made the request: e.g., `[email protected]`

* `X-Tailscale-User-LoginName-Localpart` - login name of the user that made the request, but only the local part (e.g., `foo`)

* `X-Tailscale-User-LoginName-Domain` - login name of the user that made the request, but only the domain name (e.g., `example.com`)

* `X-Tailscale-User-DisplayName` - display name of the user

* `X-Tailscale-User-ProfilePicURL` - their profile picture, if one exists

* `X-Tailscale-Caps` - user capabilities

* `X-Tailscale-Node` - numeric ID of the node originating the request

* `X-Tailscale-Node-Name` - name of the node originating the request

* `X-Tailscale-Node-Caps` - node device capabilities

* `X-Tailscale-Node-Tags` - ACL tags on the origin node