ADR 0009: A single domain, maximebertrand.net

Supersedes ADR 0004.

Context

ADR 0004 planned two domains: a .eu for the showcase site and a .fr for the lab. In practice, the domain registered and managed at Cloudflare is maximebertrand.net. Yet the first machines had been given internal names under .eu, a domain I do not own.

Using a domain you do not own, even internally only, is risky: if someone buys it, they answer instead of the internal DNS as soon as a query leaks to the Internet (VPN down, misconfigured workstation) and can hijack connections. It is also impossible to obtain a valid certificate for those names.

Options considered

Keep two domains: a clean separation, but two zones, two API tokens and two certificates to manage.
A single domain with subdomains: one zone, one wildcard certificate, one thing to monitor.

Decision

maximebertrand.net for everything:

Use	Name	Resolution
Showcase site, status page	`maximebertrand.net`, `status.maximebertrand.net`	Public (Cloudflare)
Published personal services	subdomains of `maximebertrand.net`	Public (Cloudflare, “DNS only”)
Internal machines and services	`*.home.maximebertrand.net`	Only through the internal DNS (OPNsense)

Consequences

Internal names sit under a domain I control: no hijacking possible, and valid certificates through Let’s Encrypt’s DNS challenge, without exposing anything.
Certificates: public names each have their own certificate, obtained through an HTTP challenge on the WAF, so as to leave no DNS token on the machine exposed to the Internet (a stolen token would allow the whole zone to be hijacked). These names appear in the Certificate Transparency logs, which is accepted: they are in public DNS anyway. The internal zone uses a wildcard certificate obtained through a DNS challenge from a machine reachable only over the VPN.
Migration on 26/09/2026: internal DNS, hypervisor and tools migrated; the firewall’s system name remains.