Pomerium

# Synology

Pomerium can be used to enable secure access to services on your Synology home server or network attached storage (NAS) device. Pomerium acting as an identity aware access proxy is particularly useful as many self-hosted apps lack or have insufficient built-in authentication mechanisms.

Using Pomerium on your Synology DSM device enables:

  • Secure remote access to docker and synology web-applications without a VPN.
  • Unified, multi-factor authentication with your identity provider of choice.
  • Access to services by sub-domain (e.g. plex.int.nas.example or wiki.int.nas.example)
  • TLS everywhere.

Pomerium is lightweight, can easily handle hundreds of concurrent requests, and a single instance typically uses <20MB of memory and very little CPU.

# Prerequisites

Though any supported identity provider would work, this guide uses google.

# Port forwarding

This will vary depending on what type of router you have but the gist is you want to be forwarding all HTTPS/TLS traffic from port 443 to your NAS on some high port (in this case8443).

Synology configure firewall rules

# DSM

Diskstation manager uses nginx under-the-hood to proxy incoming requests. In the following steps, we'll configure DSM to handle incoming requests and certificates.

# Configure DSM's Reverse Proxy

Go to Control Panel > Application Portal > Reverse Proxy.

Click Create.

Set the following Reverse Proxy Rules.

Field Description
Description pomerium
Source Protocol HTTPS
Source Hostname *
Destination Port 8443
HTTP/2 Enabled
HSTS Enabled
Destination Protocol HTTP
Destination Hostname localhost
Destination Port 32443

Synology setup nginx reverse proxy

This will forward any incoming HTTPS traffic to the Pomerium service that is (not yet) running on port 32443.

# Certificates

Though DSM does support getting LetsEncrypt certificates, they do not support wild-card subdomain certificates which require DNS validation. If you do not already have a wildcard certificate the certificate documentation or included [script] can help you generate one.

Go to Control Panel > Security > Certificate

Click add a new certificate > Import certificate.

Add the certificate chain for your wild-card subdomain certificates.

Once the certificate is showing on the list of certificates screen we need to tell DSM to use that certificate for all incoming traffic on port 8443.

Click configure

Services Certificate
*:8443 *.int.nas.example

Synology assign wildcard certificate

# Docker

# Download

Download and install docker from the package manager.

Package manager > search > docker

Synology download pomerium docker image

Once installed open the docker app.

Docker > Registry > search > pomerium

Download the official Pomerium docker image.

Synology download pomerium docker image

We'll also need a test application to manage access to. For this guide we'll use the canonical test app httpbin but the this could be any self-hosted apps, wiki, download tool, etc.

Synology download httpbin docker image

# Policy

We will create an extremely basic policy where httpbin.int.nas.example is replaced with the subdomain you want to use for the httpbin service, and your.email.address@gmail.com is replaced with your email address. All other users will be denied, and all other routes will be 404.

# policy.yaml
- from: https://httpbin.int.nas.example
  to: http://httpbin
  allowed_users:
    - your.email.address@gmail.com

# Configure

# Httpbin

First, we'll setup our test app httpbin.

Go to Docker > Image

Click httpbin

Set the Container Name to httpbin. Keep the rest of the settings the default.

Click apply

Synology launch httpbin

This will create a small python webserver on port 80. The container name we just used will be used as an alias to route requests as defined in our policy.

# Pomerium

Go to Docker > Image

Click Pomerium

Click Launch

Set the Container Name to Pomerium.

Synology pomerium create container

Click Advanced Settings

Go to Port Settings tab.

Add an entry where the Local Port is 32443 and the container port is 443 and the type is TCP.

Synology pomerium port settings docker

Go to Links tab.

Add an entry where the Container Name is httpbin and the alias is httpbin.

WARNING

The alias value must match the to DNS name from your policy.yaml configuration.

Synology pomerium set alias to app

These are the minimum set of configuration settings to get Pomerium running in this deployment environment.

Go to Environment tab.

Field Value
POLICY output of base64 -i policy.yaml
INSECURE_SERVER TRUE, internal routing within docker will not be encrypted.
IDP_CLIENT_SECRET Values from setting up your identity provider
IDP_CLIENT_ID Values from setting up your identity provider
IDP_PROVIDER Values from setting up your identity provider (e.g. google)
COOKIE_SECRET output of head -c32 /dev/urandom | base64
AUTHENTICATE_SERVICE_URL https://authenticate.int.nas.example
SHARED_SECRET output of head -c32 /dev/urandom | base64

For a detailed explanation, and additional options, please refer to the configuration variable docs. Also note, though not covered in this guide, settings can be made via a mounted configuration file.

Click Launch.

If properly configured you should see something like the following when you see the container's details.

Synology pomerium all setup

If something goes wrong, click the Logs tab.

# Try it out

Navigate to your new service. https://httpbin.int.nas.example

You should be redirected to your identity provider.

Synology redirected login

If you've enabled multi-factor authentication you should see that too.

Synology multi-factor authentication

If that user is authorized to see the httpbin service, you should be redirected back to httpbin!

Synology done

You can also navigate to the special pomerium endpoint httpbin.your.domain.example/.pomerium/ to see your current user details.

currently logged in user

And just to be safe, try logging in from another google account to see what happens. You should be greeted with a 403 unauthorized access page.

Synology done

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