Hardening

Lock down a working install before it runs untrusted code or takes real users. Each step below is independent.

Keep production mode on

setup.sh writes PT_PRODUCTION=1 and generates every secret. In production mode the server refuses to start while ADMIN_TOKEN, EDGE_HMAC_SECRET or DATABASE_URL hold a development default.

# on the control plane, in platinum/infra/compose
grep '^PT_PRODUCTION=' .env        # PT_PRODUCTION=1
ls -l .env                         # -rw------- (setup.sh writes mode 600)

On each host, /etc/platinum/host.env and /etc/platinum/edge-proxy.env hold secrets too. The installer writes both with mode 600.

Firewall every machine

Deny inbound by default and open only these ports.

Machine	Port	Allow from	For
Control plane	80, 443	Anywhere	Caddy: the API, previews, the console
Control plane	5432	Each sandbox host	Postgres, for the edge proxies
Control plane	9000	Each sandbox host	The bundled object store, if you run it
Sandbox host	80	The control plane	The edge proxy
Sandbox host	18048	The control plane	The control channel
Sandbox host	20000–29999	Anywhere	Direct TCP exposures, only if you use them

Keep SSH open from your own addresses on both.

Tighten the host firewall

The installer writes /etc/nftables.conf. Its input chain accepts 22, 80, 443, 3000, 8080 and 20000–29999 from anywhere, and the control-channel setup allows :18048 from the control plane only.

Restrict the rest in that file, then reload it. Rules added with nft add rule are gone after a reboot.

Gate each host's edge proxy

A request sent straight to a host's :80 skips the control plane's metering and admission. Set the control plane's addresses as the edge's trusted peers, before you enroll hosts:

# in platinum/infra/compose/.env, then docker compose up -d
EDGE_TRUSTED_PEERS=<control-plane-ip>

The installer then writes EDGE_TRUSTED_PEERS and EDGE_PEER_GATE=enforce into each new host's /etc/platinum/edge-proxy.env. Any other peer gets 404 peer-not-trusted. Addresses and CIDRs are separated by commas or spaces.

Restrict sign-ups and admin access

Setting	Do
`PT_SIGNUP_MODE`	Keep `invite-only` (written by `setup.sh`). The server's own default is `open`.
`PT_ADMIN_EMAILS`	List only operators: these accounts become platform admins.
`PT_ADMIN_IP_ALLOWLIST`	Restrict `/_admin/` and `/internal/admin/` to your addresses or CIDRs.
`ADMIN_TOKEN`	Treat it as root for the whole install. Keep it out of shell history and scripts.

Keep the host baseline

The installer boots each host with SMT off and lockdown=integrity, and runs Cloud Hypervisor as the unprivileged platinum-vmm user. Keep these when you tune a host.

cat /sys/devices/system/cpu/smt/active   # 0
cat /sys/kernel/security/lockdown        # … [integrity] …

Revoke unused install tokens

An unused install token downloads a script that contains your object storage keys and the control-channel token. List and revoke them: see Sandbox hosts.