ahmed: Add certificates for local DNS

1 files changed, 52 insertions, 0 deletions

diff --git a/hosts/ahmed/local-dns/certificates.nix b/hosts/ahmed/local-dns/certificates.nix
new file mode 100644
index 0000000..25784c1
--- /dev/null
+++ b/hosts/ahmed/local-dns/certificates.nix
@@ -0,0 +1,52 @@
+# Getting HTTPS to work for local domains is pretty hard. The approach I've
+# gone with is to request a wildcard domain for `*.rumpenettet.linus.onl`. We
+# can do this because `linus.onl` is a public domain which we have control
+# over.
+#
+# This module requests a certificate from letsencrypt using DNS-01
+# verification. I have an API token which can modify DNS records for
+# `linus.onl`. This is how Lego (i.e. `security.acme`) proves domain ownership
+# when renewing the certificate.
+#
+# Any services running under `rumpenettet.local.onl` and use this certificate.
+# For NGINX that happens via `useACMEHost` and one of the options that enable
+# HTTPS.
+{
+  lib,
+  config,
+  ...
+}: {
+  security.acme = {
+    certs.${config.linus.local-dns.domain} = {
+      dnsProvider = "cloudflare";
+      dnsResolver = "1.1.1.1:53";
+      environmentFile = config.age.secrets.cloudflare-acme-token.path;
+      dnsPropagationCheck = true;
+      domain = "*.${config.linus.local-dns.domain}";
+
+      group = config.services.nginx.group;
+      reloadServices = ["nginx"];
+    };
+  };
+
+  # This file contains the variables that Lego needs to authenticate to
+  # Cloudflare. This is how we prove ownership of the domain.
+  #
+  # See: https://go-acme.github.io/lego/dns/cloudflare/
+  # See: https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html#EnvironmentFile=
+  age.secrets.cloudflare-acme-token.file = ../../../secrets/cloudflare-acme-token.env.age;
+
+  # Use the certificate for each subdomain in NGINX. Luckily, we can be pretty
+  # opinionated since this isn't reusable logic.
+  #
+  # NOTE: This assumes that each subdomain *has* an NGINX virtual host, which
+  #       may not be the case in the future.
+  services.nginx.virtualHosts = let
+    virtualHostConfig = subdomain:
+      lib.nameValuePair "${subdomain}.${config.linus.local-dns.domain}" {
+        forceSSL = true;
+        useACMEHost = config.linus.local-dns.domain; # Same as security.acme.certs.${...} above.
+      };
+  in
+    builtins.listToAttrs (map virtualHostConfig config.linus.local-dns.subdomains);
+}