mesh-controller/internal/broker/users.go

package broker

import (
	"fmt"
	"sort"
)

// Every user the composed file should contain, derived from what the mesh knows.
//
// **The list is derived, never kept.** A stored user list would be a second account of who may
// reach the bus, able to disagree with the records it came from — and the disagreement would be
// invisible, because both would look internally consistent. So this is a pure function of the
// mesh's records, run again every time the file is written.
//
// Records are mirrored into this package's own types rather than imported from the catalogue, for
// the reason DeclaredSeat is: composing authority is a different job from parsing a manifest, and
// this package stays free of the other's types so a change to a manifest field cannot quietly widen
// a permission.

// Declared is one module on one node, as composing its authority needs it.
type Declared struct {
	Module   string
	Emits    []string
	Consumes []string
	Serves   []string
	// Holds are the seats this module claims, with the protocol each seat declares. A seat the
	// mesh defines for itself declares no protocol, so holding one grants nothing on the bus —
	// which is right: those seats are about who does a job, not about who may say what.
	Holds []Seat
	// Uses are the seats this module sends to.
	Uses []Seat
	// Watches are the seats whose events it consumes.
	Watches []Seat
	// Invokes are the tools it calls, `<module>.<tool>` or `*` (novox/hq ADR 0152).
	Invokes []string
	// State is the state it keeps, each a bucket its instances write (novox/hq ADR 0201).
	State []Bucket
	// Reads are other modules' state it reads, each `<module>.<name>` (novox/hq ADR 0201).
	Reads []string
	// KeyedReads are keys of other modules' state it reads, each one key alone: what a seat's holder is
	// granted for the pieces the modules beside it offer (novox/hq ADR 0260).
	KeyedReads []KeyedRead
	// NoAccount says the module declares no own secret named broker, so no account could ever be
	// delivered to it and nothing can connect as it (novox/hq issue 195). Said in the negative so a
	// record that does not say is composed as it always was.
	NoAccount bool
	// SnapshotsTheBus says the module holds mesh-broker — it is the bus — and so is the one module
	// granted the snapshot API, to copy the bus's streams for the night's backup (novox/hq ADR 0235).
	SnapshotsTheBus bool
	// Checks are the module's own tools its health asks, each `<module>.<tool>` (novox/hq ADR 0240, to-be
	// 48 §3): the machine's node-engine asks them of its own node tools, and is granted that and no more.
	Checks []string
	// RunsAs is the account the module runs as in a runtime of its own (novox/hq ADR 0259 §8): it is never
	// carried by the machine's runtime, and reaches the bus on its own account.
	RunsAs string
}

// Records is what composing a user list needs to know about the mesh, and nothing more.
type Records struct {
	// Nodes is every machine the mesh knows. Each gets a host user.
	Nodes []string
	// Assigned is the modules on each node, as they declare themselves.
	Assigned map[string][]Declared
	// Enrolling is every node with a live token — one enrolment user each, because the inbox an
	// answer goes to is scoped to the token and a shared one is one machine reading another's
	// sealed credentials (design 25 §6).
	Enrolling []string
	// People is each person's name against the tools they may invoke, `*` for an administrator.
	People map[string][]string
	// Interchangeable is each module whose definition says its instances are the same anywhere
	// (ADR 0160), which decides whether the module's plain subject is issued to every instance.
	Interchangeable map[string]bool
}

// Users is every user the composed file should contain, in the order it will be written.
//
// The controller is always first and always present: a mesh whose own controller is not in the file
// is a mesh that cannot be told anything, and there is no state of the records in which that is
// correct.
func Users(r Records) ([]Principal, error) {
	out := []Principal{{Kind: KindController}}

	for _, node := range sortedCopy(r.Nodes) {
		witness := false
		var checks []string
		for _, d := range r.Assigned[node] {
			if d.Module == controllerModule {
				witness = true
			}
			checks = append(checks, d.Checks...)
		}
		out = append(out, Principal{Kind: KindNode, Node: node, WitnessesController: witness, Checks: checks})
		// **Where the runtime is assigned, the machine gets one runtime principal in place of the
		// runtime module's own** (novox/hq ADR 0175, to-be 38). It carries every module on the
		// node: its serving grants are the union of theirs. Every other module keeps its own
		// principal — a module still serving tools from its own container holds its own
		// credential until it moves, and the two serve side by side in the meantime.
		runtimeHere := false
		for _, d := range r.Assigned[node] {
			if d.Module == RuntimeModule {
				runtimeHere = true
			}
		}
		for _, d := range r.Assigned[node] {
			if runtimeHere && d.Module == RuntimeModule {
				continue
			}
			// **A module with nowhere to read an account is no user** (novox/hq issue 195). `module
			// issue` refuses it one (issue 078: an account nothing reads is an orphan), so its user
			// could only ever be left out of the file for want of a password — and every such module
			// was named, on every status and plan, as a credential the mesh had not minted. Where the
			// runtime is, it speaks for the module; where it is not, the module cannot speak at all,
			// and a user would not change that.
			if d.NoAccount {
				continue
			}
			out = append(out, Principal{
				Kind: KindModule, Node: node, Module: d.Module,
				Emits: d.Emits, Consumes: d.Consumes, Serves: d.Serves,
				Holds: d.Holds, Uses: d.Uses, Watches: d.Watches, Invokes: d.Invokes,
				State: stateNames(d.State), Reads: d.Reads, SnapshotsTheBus: d.SnapshotsTheBus,
				PerMachine: perMachineNames(d.State), KeyedReads: d.KeyedReads,
			})
		}
		if runtimeHere {
			var carried []Declared
			for _, d := range r.Assigned[node] {
				if d.RunsAs == "" {
					carried = append(carried, d)
				}
			}
			out = append(out, Principal{Kind: KindNodeTools, Node: node, Module: RuntimeModule, Carries: carried})
		}
	}
	for _, node := range sortedCopy(r.Enrolling) {
		out = append(out, Principal{Kind: KindEnrolment, Node: node})
	}
	for _, person := range sortedNames(r.People) {
		out = append(out, Principal{Kind: KindPerson, Module: person, Invokes: r.People[person]})
	}

	// Refused here rather than discovered by the server. Two users with one name is a file the
	// server reads as one of them, and which one depends on the order — so a module assigned to a
	// node twice, or a person named after nothing, is a composition that must not be written.
	seen := map[string]string{}
	for _, p := range out {
		name := p.Username()
		if name == "" || name == "." {
			return nil, fmt.Errorf("a %s user has no name, so nothing could authenticate as it", p.Kind)
		}
		if first, already := seen[name]; already {
			return nil, fmt.Errorf(
				"two users would be called %q (a %s and a %s): the server would read the file as "+
					"one of them, and which one depends on the order", name, first, p.Kind)
		}
		seen[name] = string(p.Kind)
	}
	return out, nil
}

// WithPasswords fills each user's hash from what the mesh minted, and says which users have none.
//
// **Separated from Users because they fail differently.** A user missing from the records is a bug
// in deriving them; a user with no password is a step that has not happened yet — a module assigned
// but never given a credential, a node enrolled before this existed. The second is ordinary and its
// remedy is to mint one, so it is named rather than returned as an error, and the caller decides
// whether a partial composition is worth writing.
func WithPasswords(principals []Principal, hashes map[string]string) (filled []Principal, missing []string) {
	for _, p := range principals {
		hash, ok := hashes[p.Username()]
		if !ok || hash == "" {
			missing = append(missing, p.Username())
			continue
		}
		p.PasswordHash = hash
		filled = append(filled, p)
	}
	return filled, missing
}

func sortedCopy(in []string) []string {
	out := append([]string(nil), in...)
	sort.Strings(out)
	return out
}

func sortedNames(in map[string][]string) []string {
	out := make([]string, 0, len(in))
	for k := range in {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}

// controllerModule is the controller's module: the machine assigned it witnesses its upgrades.
const controllerModule = "mesh-controller"