debian

Easy FoundryVTT Cloud Hosting

Foundry is a wonderful virtual tabletop tool well-suited to playing tabletop roleplaying games with your friends, no matter how far away they are. It compares very favourably to the market leader Roll20, once you get past some of the initial set-up challenges and a moderate learning curve.

You can run it on your own computer and let your friends “connect in” to it, so long as you’re able to reconfigure your router a little, but you’ll be limited by the speed of your home Internet connection and people won’t be able to drop in and e.g. tweak their character sheet except when you’ve specifically got the application running.

A generally better option is to host your Foundry server in the cloud. For most of its history, I’ve run mine on Fox, my NAS, but I’ve recently set one up on a more-conventional cloud virtual machine too. A couple of friends have asked me about how to set up their own, so here’s a quick guide:

Screenshot from Linode showing a server, "Foundry", running, with specs as described below. — I used Linode to spin up a server because I still had a stack of free credits following a recent project. The instructions will work on any cloud host where you can spin up a Debian 12 virtual machine, and can be adapted for other distributions of Linux.

You will need…

A Foundry license ($50 USD / £48 GBP, one-off payment¹)
A domain name for which you control the DNS records; you’ll need to point a domain, like “danq.me” (or a subdomain of it, e.g. “vtt.danq.me”), at an IP address you’ll get later by creating an “A” record: your domain name registrar can probably help with this – I mostly use Gandi and, ignoring my frustration with recent changes to their email services, I think they’re great
An account with a cloud hosting provider: this example uses Linode but you can adapt for any of them
A basic level of comfort with the command-line

1. Spin up a server

Getting a virtual server is really easy nowadays.

You’ll need:

The operating system to be Debian 12 (or else you’ll need to adapt the instructions below)
The location to be somewhere convenient for your players: pick a server location that’s relatively-local to the majority of them to optimise for connection speeds
Approximately 2 CPUs and 4GB of RAM, per Foundry’s recommended server specifications
An absolute minimum of 1GB of storage space, I’d recommend plenty more: The Levellers’ campaign currently uses about 10GB for all of its various maps, art, videos, and game data, so give yourself some breathing room (space is pretty cheap) – I’ve gone with 80GB for this example, because that’s what comes as standard with the 2 CPU/4GB RAM server that Linode offer

Choose a root password when you set up your server. If you’re a confident SSH user, add your public key so you can log in easily (and then disable password authentication entirely!).

For laziness, this guide has you run Foundry as root on your new server. Ensure you understand the implications of this.²

2. Point your (sub)domain at it

DNS propogation can be pretty fast, but… sometimes it isn’t. So get this step underway before you need it.

Your newly-created server will have an IP address, and you’ll be told what it is. Put that IP address into an A-record for your domain.

3. Configure your server

In my examples, my domain name is vtt.danq.me and my server is at 1.2.3.4. Yours will be different!

Connect to your new server using SSH. Your host might even provide a web interface if you don’t have an SSH client installed: e.g. Linode’s “Launch LISH Console” button will do pretty-much exactly that for you. Log in as root using the password you chose when you set up the server (or your SSH private key, if that’s your preference). Then, run each of the commands below in order (the full script is available as a single file if you prefer).

3.1. Install prerequisites

You’ll need unzip (to decompress Foundry), nodejs (to run Foundry), ufw (a firewall, to prevent unexpected surprises), nginx (a webserver, to act as a reverse proxy to Foundry), certbot (to provide a free SSL certificate for Nginx), nvm (to install pm2) and pm2 (to keep Foundry running in the background). You can install them all like this:

apt update
apt upgrade
apt install -y unzip nodejs ufw nginx certbot nvm
npm install -g pm2

3.2. Enable firewall

By default, Foundry runs on port 30000. If we don’t configure it carefully, it can be accessed directly, which isn’t what we intend: we want connections to go through the webserver (over https, with http redirecting to https). So we configure our firewall to allow only these ports to be accessed. You’ll also want ssh enabled so we can remotely connect into the server, unless you’re exclusively using an emergency console like LISH for this purpose:

ufw allow ssh
ufw allow http
ufw allow https
ufw enable

3.3. Specify domain name

Putting the domain name we’re using into a variable for the remainder of the instructions saves us from typing it out again and again. Make sure you type your domain name (that you pointed to your server in step 2), not mine (vtt.danq.me):

DOMAIN=vtt.danq.me

3.4. Get an SSL certificate with automatic renewal

So long as the DNS change you made has propogated, this should Just Work. If it doesn’t, you might need to wait for a bit then try again.

certbot certonly --agree-tos --register-unsafely-without-email --rsa-key-size 4096 --webroot -w /var/www/html -d $DOMAIN

Don’t continue past this point until you’ve succeeded in getting the SSL certificate sorted.

The certificate will renew itself automatically, but you also need Nginx to restart itself whenever that happens. You can set that up like this:

printf "#!/bin/bash\nservice nginx restart\n" > /etc/letsencrypt/renewal-hooks/post/restart-nginx.sh
chmod +x /etc/letsencrypt/renewal-hooks/post/restart-nginx.sh

3.5. Configure Nginx to act as a reverse proxy for Foundry

You can, of course, manually write the Nginx configuration file: just remove the > /etc/nginx/sites-available/foundry from the end of the printf line to see the configuration it would write and then use/adapt to your satisfaction.

set +H
printf "server {\n listen 80;\n listen [::]:80;\n server_name $DOMAIN;\n\n # Redirect everything except /.well-known/* (used for ACME) to HTTPS\n root /var/www/html/;\n if (\$request_uri !~ \"^/.well-known/\") {\n return 301 https://\$host\$request_uri;\n }\n}\n\nserver {\n listen 443 ssl http2;\n listen [::]:443 ssl http2;\n server_name $DOMAIN;\n\n ssl_certificate /etc/letsencrypt/live/$DOMAIN/fullchain.pem;\n ssl_certificate_key /etc/letsencrypt/live/$DOMAIN/privkey.pem;\n\n client_max_body_size 300M;\n\n location / {\n # Set proxy headers\n proxy_set_header Host \$host;\n proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;\n proxy_set_header X-Forwarded-Proto \$scheme;\n\n # These are important to support WebSockets\n proxy_set_header Upgrade \$http_upgrade;\n proxy_set_header Connection \"Upgrade\";\n\n proxy_pass http://127.0.0.1:30000/;\n }\n}\n" > /etc/nginx/sites-available/foundry
ln -sf /etc/nginx/sites-available/foundry /etc/nginx/sites-enabled/foundry
service nginx restart

3.6. Install Foundry

3.6.1. Create a place for Foundry to live

mkdir {vtt,data}
cd vtt

3.6.2. Download and decompress it

Screenshot from FoundryVTT showing where to find the "Timed URL" download link button. — For this step, you’ll need to get a Timed URL from the Purchased Licenses page on your FoundryVTT account.

Substitute in your Timed URL in place of <url from website> (keep the quotation marks – " – though!):

wget -O foundryvtt.zip "<url from website>"
unzip foundryvtt.zip
rm foundryvtt.zip

3.6.3. Configure PM2 to run Foundry and keep it running

Now you’re finally ready to launch Foundry! We’ll use PM2 to get it to run automatically in the background and keep running:

pm2 start --name "Foundry" node -- resources/app/main.js --dataPath=/root/data

You can watch the logs for Foundry with PM2, too. It’s a good idea to take a quick peep at them to check it launched okay (press CTRL-C to exit):

pm2 logs 0

4. Start adventuring!

Provide your license key to get started, and then immediately change the default password: a new instance of Foundry has a blank default password, which means that anybody on Earth can administer your server: get that changed to something secure!

Now you’re running on Foundry!

¹ Which currency you pay in, and therefore how much you pay, for a Foundry license depends on ~~where in the world you are~~ where your VPN endpoint says you are. You might like to plan accordingly.

² Running Foundry as root is dangerous, and you should consider the risks for yourself. Adding a new user is relatively simple, but for a throwaway server used for a single game session and then destroyed, I wouldn’t bother. Specifically, the risk is that a vulnerability in Foundry, if exploited, could allow an attacker to reconfigure any part of your new server, e.g. to host content of their choice or to relay spam emails. Running as a non-root user means that an attacker who finds such a vulnerability can only trash your Foundry instance.

Debian + DKIM for Dummies

Earlier this year, for reasons of privacy/love of selfhosting, I moved the DanQ.me mailing list from Mailchimp to Listmonk (there’s a blog post about how I set it up), relaying outbound messages via an SMTP server provided by my domain registrar, Gandi.

I assume that you knew that you can get an email, no more than once per day or once per week (your choice!) of what I get up to online, right? Email not your jam: there are plenty of other options too!

Unfortunately, Gandi recently announced that they’ll no longer be providing email services for free, so rather than fork out €4/month for an email address I won’t even read, I decided to inhouse it.

And because I learned a few things while doing so, I wrote this blog post so that next time I have to configure Postfix + DKIM, I’ll know where to find a guide. If it helps you in the meantime, that’s just a bonus.

Photograph of a French Bulldog on a wooden floor playing tug-of-war using a multicoloured plaited rope (the human holding the other end of the rope is behind the camera). — If the first rule of computing is “never roll your own crypto” (based on Schneier’s Law), the second rule might be “don’t run your own mailserver”. I don’t have a good picture to illustrate that, so here’s a photo of my dog playing tug-of-war.

Postfix

Running your own mailserver is a pain. I used to do it for all of my email, but – like many other nerds – when spam reached its peak and deliverability became an issue, I gave up and oursourced it¹.

Screenshot of a Weekly Digest email from DanQ.me, showing in Mozilla Thunderbird. — Fun fact: when I’m at my desktop, I use a classic desktop email application for my personal email, like it’s the 90s or something².

Luckily, I don’t need it to do much. I just need a mail transfer agent with an (unauthenticated, but local-only) SMTP endpoint: something that Listmonk can dump emails into, which will then reach out to the mailservers representing each of the recipients and relay them on. A default install of Postfix does all that out-of-the-box, so I ran sudo apt install postfix, accepted all the default options, and put the details into Listmonk.

Screenshot showing Listmonk's SMTP configuration screen. The host "192.168.2.12" and port "25" have been entered, TLS has been set to "STARTTLS", Skip TLS verification is enabled, and Auth Protocol is set to "None". — Listmonk makes adding an SMTP server very easy, and even includes a quick “test connection” link with which you can try out your settings.

Next, I tweaked my DNS configuration to add an SPF record, and tested it. This ought to have been enough to achieve approximate parity with what Gandi had been providing me with. Not bad.

$ dig +short -t TXT danq.link
"v=spf1 a mx a:fox.q-t-a.uk ip4:83.151.206.115 ~all"

You really can’t be doing without an SPF record as a minimum these days.

I sent a test email to a Gmail account, where I noticed two problems:

Screenshot from GMail showing a message with a red slashed padlock icon, which when clicked advises that "mail.danq.link did not encrypt this message". — It turns out that since the last time I ran a mailserver “for real”, the use of TLS for inter-server communication has become… basically mandatory. You don’t strictly have to do it, but if you don’t, some big email providers will put scary security warnings on your messages. This is a good thing.

The first problem was that Postfix on Debian isn’t configured by-default to use opportunistic TLS when talking to other mailservers. That’s a bit weird, but I’m sure there’s a good reason for it. The solution was to add smtp_tls_security_level = may to my /etc/postfix/main.cf.

The second problem was that without a valid DKIM signature on them, about half of my test emails were going straight to the spam folder. Again, it seems that since the last time I seriously ran a mailserver 20 years ago, this has become something that isn’t strictly required… but your emails aren’t going to get through if you don’t.

I’ve put it off this long, but I think it’s finally time for me to learn some practical DKIM.

Understanding DKIM

What’s DKIM, then?

A server that wants to send email from a domain generates a cryptographic keypair.
The public part of the key is published using DNS. The private part is kept securely on the server.
When the server relays mail on behalf of a user, it uses the private key to sign the message body and a stated subset of the headers³, and attaches the signature as an email header.
When a receiving server (or, I suppose, a client) receives mail, it can check the signature by acquiring the public key via DNS and validating the signature.

In this way, a recipient can be sure that an email received from a domain was sent with the authorisation of the owner of that domain. Properly-implemented, this is a strong mitigation against email spoofing.

OpenDKIM

To set up my new server to sign outgoing mail, I installed OpenDKIM and its keypair generator using sudo apt install opendkim opendkim-tools. It’s configuration file at /etc/opendkim.conf needed the following lines added to it:

# set up a socket for Postfix to connect to:
Socket inet:12301@localhost

# set up a file to specify which IPs/hosts can send through us without authentication and get their messages signed:
ExternalIgnoreList      refile:/etc/opendkim/TrustedHosts
InternalHosts           refile:/etc/opendkim/TrustedHosts

# set up a file to specify which selector/domain are used to each incoming email address:
SigningTable            refile:/etc/opendkim/SigningTable

# set up a file to specify which signing key to use for each selector/domain:
KeyTable                refile:/etc/opendkim/KeyTable

Into /etc/opendkim/TrustedHosts I put a list of local IPs/domains that would have their emails signed by this server. Mine looks like this (in this example I’m using example.com as my domain name, and default as the selector for it: the selector can be anything you like, it only matters if you’ve got multiple mailservers signing mail for the same domain). Note that 192.168.0.0/16 is the internal subnet on which my sending VM will run.

127.0.0.0.1
::1
192.168.0.0/16
*.example.com
example.com

/etc/opendkim/SigningTable maps email addresses (I’m using a wildcard) to the subdomain whose TXT record will hold the public key for the signature. This also goes on to inform the KeyTable which private key to use:

*@example.com default._domainkey.example.com

And then /etc/opendkim/KeyTable says where to find the private key for that:

default._domainkey.example.com example.com:default:/etc/opendkim/keys/example.com/default.private

Next, we need to create and secure that keypair. In /etc/opendkim/keys/example.com/, we run:

sudo opendkim-genkey -s default -d example.com
sudo chown opendkim:opendkim default.private

At last, we can configure Postfix to filter all mail through OpenDKIM by adding to our /etc/postfix/main.cf file:

milter_protocol = 2
milter_default_action = accept
smtpd_milters = inet:localhost:12301
non_smtpd_milters = inet:localhost:12301

DNS

The public key needs publishing via DNS. Conveniently, when you create a keypair using its tools, OpenDKIM provides a sample (in BIND-style) for you to copy-paste from or adapt: look in /etc/opendkim/keys/example.com/default.txt!

Once we’ve restarted both services (sudo service postfix restart; sudo service opendkim restart), we can test it!

Screenshot from GMail showing "DKIM: 'PASS' with domain danq.link". — Once the major email providers – who have the worst spam problem to deal with – say that your email signature looks good, you’re good.

So I learned something new today.

If you, too, love to spend your Saturday mornings learning something new, have a look at those subscription options to decide how you’d like to hear about whatever I get up to next.

¹ I still outsource my personal email, and I sing the praises of the excellent folks behind ProtonMail.

² My desktop email client also doubles as my newsreader, because, yes, of course you can still find me on USENET. Which, by the way, is undergoing a mini-revival…

³ Why doesn’t DKIM sign all the headers in an email? Because intermediary servers and email clients will probably add their own headers, thereby invalidating the signature! DKIM gets used to sign the From: header, for obvious reasons, and ought to be used for other headers whose tampering could be significant such as the Date: and Subject:, but it’s really up to the signing server to choose a subset.