hyperhive/docs/boundary.md

The operator/agent boundary

Design rationale for hyperhive's two-principal trust model. The implementation work — container network isolation, the unifying gateway, core-daemon privsep — is tracked as area:ops issues on the forge.

The operator/agent boundary is technically enforced, not just a convention: containers run in private netns (network isolation is always on), the gateway proxies all operator-facing traffic, and hive-c0re runs as the unprivileged hive-core user.

Two principals, two paths

• Operator — reaches every UI (the dashboard + every per-agent page) through the gateway, on one origin. Operator-authority actions (approve / deny, answer-as-operator, lifecycle POSTs) are served by the core daemon and only reachable via the gateway.
• Agent — speaks only for itself, only over its per-agent unix socket. The socket's identity is the agent (see docs/conventions.md, "identity = socket"). An agent must not be able to reach the core daemon's HTTP surface, another agent's socket, or another agent's web UI.

Design rule

Operator-authority actions never get a per-agent-socket entry point. They live on the core backend.

Worked example — answering an operator-targeted question is a POST /api/answer-question/{id} on the core dashboard, never a per-agent-socket Request variant. If it were a per-agent-socket request, an agent could curl its own socket and spoof an operator answer. The per-agent web UI POSTs cross-origin to the core for these (see the inline-answer feature — the loose-ends section on each agent page).

Why network isolation is the load-bearing step

Without network isolation, containers share the host network namespace and can reach localhost:<core-port>, the dashboard, and every other agent's web port — the operator/agent split is on the honour system and every boundary claim above is aspirational. Network isolation is what makes the boundary real; the gateway and privsep are ergonomics and defence-in-depth layered on top.

Network isolation is complete and always on: every agent container runs in a private netns behind the hive bridge, and there is no shared-netns mode. See docs/network.md.

Concretely, the core daemon's dashboard /api carries no application-layer authentication — operator-authority routes are served unauthenticated at the HTTP layer. Their protection is entirely (a) the gateway, which fronts all operator traffic and is where operator auth lives, and (b) network isolation, which keeps agents — and hive-ci's untrusted PR builds — off host-loopback so nothing can reach 127.0.0.1:<dashboard_port> directly. This is deliberate given the load-bearing role of network isolation above, but it is a standing invariant: the /api must never be bound to a non-loopback address or exposed outside the gateway, and every new operator-authority route inherits that assumption. hive-ci is treated like an agent for this purpose — it runs untrusted PR code and is netns-isolated for the same reason.

The boundary rests on three layers:

1. Gateway — fronts all surfaces (dashboard + every per-agent UI) on one origin. An nginx nixos-container proxies per-agent UIs under /agent/<name>/, which is what lets the inline-answer POST to /answer-question/{id} go same-origin instead of needing a cross-origin CORS shim. Pure ergonomics — no behavioural risk on its own.
2. Network isolation — the load-bearing layer: every agent container runs in a private netns behind the hive bridge, always on and unconditional. This is what turns the operator/agent split from an honour-system convention into an enforced boundary.
3. Privsep — defence in depth on the core process; hive-c0re runs as the unprivileged hive-core user and delegates root operations to hive-priv, a narrow socket-activated helper. See docs/security.md for the privilege boundary table.

hive-priv socket activation

hive-priv is always socket-activated by the hive-priv.socket systemd unit. The unit binds /run/hive/priv.sock with SocketGroup=hive-core and mode 0660 and passes the ready listener to the helper as fd 3 (LISTEN_FDS). The helper requires this and bails if it isn't socket-activated.

⚠️ There is intentionally no self-bind fallback: if hive-priv bound the socket itself, it would create the file owned by root's primary group rather than hive-core, and a hive-core client couldn't connect the way the socket unit's SocketGroup grant intends. Requiring socket activation everywhere keeps dev and prod on the exact same path, so the group grant always holds.

the per-agent socket dir

/run/hive-agent/<name>/ is shared by three principals that share no group, which is why its mode is what it is:

principal	reaches	needs
the agent's harness	binds + unlinks agent.sock, web.sock	owner, rwx
hive-c0re	dials agent.sock (todo wakes)	traverse
the gateway's nginx	dials web.sock	traverse

The last two land in "other", so the dir is 0751, owned by the agent's container uid/gid — o=--x is traverse without listing, and both sockets are 0666, which is all a dialer needs.

Ownership is declared, not repaired. The tmpfiles.d entry written by SyncAgentTmpfiles names the uid/gid directly. Do not add a chown alongside it: d re-applies on every boot and every agent spawn/destroy, so ownership set afterwards is reverted the next time any agent changes — which is exactly how this dir spent a long time at 0777 root root while a privileged chown appeared to be fixing it.

The mode is load-bearing, not cosmetic. Write permission on a directory is what confers the right to unlink its entries, whoever owns them, and the sticky bit is the only thing that would restrain that (it is not set here). A world-writable socket dir therefore lets anything able to reach the path delete an agent's socket and bind its own — and nginx reaches all of /run/hive-agent as a plain host path. Dropping o=w removes that permission rather than qualifying it.

⚠️ The gateway's nginx and dnsmasq are host services, next to hive-c0re (see docs/gateway.md) — there is no namespace between them and the rest of the host. That costs no network isolation: nginx binds the host's :80/:443 and reaches localhost upstreams, which a netns would have to be opened up for anyway. 🔑 It does mean nothing implicitly scopes the privileged reload verb — see docs/security.md for how PrivRequest::ReloadGatewayNginx's containment works.

⚠️ Contrast /shared, which is sticky world-writable (1777): it has many legitimate writers, so sticky is the best available answer there. This dir has exactly one writer, so it needs no world write at all.

host admin socket access (hivectl)

hivectl drives the whole hive — spawn / kill / destroy / rebuild / deploy — over the host admin socket /run/hyperhive/host.sock, socket-activated by the hive-c0re.socket unit. That socket is the full-control surface, so who can connect to it is a real trust boundary.

By default the socket is 0660 group-owned by hive-admin, an empty group — so it is effectively root-only until an operator is explicitly granted access. Grant sudoless hivectl by listing login users in services.hyperhive.c0re.adminUsers; each is added to hive-admin, and members connect without sudo. The runtime dir /run/hyperhive is 0751 (traverse-only, no listing) so the group can reach the socket path; the socket's own 0660 hive-admin mode gates the connection, and the per-agent subdirs under it keep their own restrictive perms. Keep adminUsers to trusted operators — membership is equivalent to root over the hive.