Take a module's own secret through a hidden prompt on the operator's desk, so a bot token never passes through an agent's session (hq ADR 0259 §10)
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jochen
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package main
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import (
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"strings"
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"time"
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"github.com/nats-io/nats.go"
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"github.com/novox/mesh-controller/internal/link"
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"github.com/novox/mesh-controller/internal/secrets"
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)
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// A module's own secret given at the operator's desk (novox/hq ADR 0259 §10).
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//
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// **The value never passes through whoever asked for it.** An agent, or the operator at the mesh MCP
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// server, calls `give` with the machine, the module, the secret's name and the desk — never a value. The
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// controller makes a sealing keypair for this one call, asks the desk's `node-launcher.secret` to prompt the
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// operator without showing what is typed, and is answered with what was typed **sealed to that key**: no
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// plaintext on the bus, in a runtime's log or in any call's record. It opens it here, seals it to the
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// module's machine exactly as `secret accept` does, and forgets it. What it answers says only that the
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// value was taken, or why not.
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//
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// **What remains** (ADR 0234's accepted residual risk): on an X11 desk any program of the operator's
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// account can read the keys as they are typed. And a program that calls the desk's prompt itself, with a
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// key of its own, is answered with what the operator typed into a prompt they did not ask for — as it could
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// draw a window of its own. The prompt says who asks and for what, so the operator types only into a
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// prompt they started.
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// deskPromptWithin is how long the prompt waits for the operator: below the runtime's thirty seconds for
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// one call, as the launcher's menu is.
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const deskPromptWithin = 25
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// deskGive is the desk path, its four reaches given so a test needs no store and no bus.
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type deskGive struct {
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// declares refuses a module or a secret the mesh would refuse, before anybody is asked to type.
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declares func(module, name string) error
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// ask asks one machine's node-launcher.secret and answers its result, or the holder's refusal.
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ask func(machine string, args map[string]any) (json.RawMessage, error)
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// accept seals the value as `secret accept` does, and says whether it lives until the module's start.
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accept func(value string) (untilStart bool, err error)
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// record writes the act in the hand-act log.
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record func(link.HandAct) error
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}
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// errNothingGiven is a prompt dismissed, or not answered in time: nothing changes.
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var errNothingGiven = errors.New("nothing was given")
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// give asks the desk for the value and seals it; it answers the words said to the caller.
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func (d deskGive) give(node, module, name, desk string) (string, error) {
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for what, v := range map[string]string{"the machine": node, "the module": module, "the secret": name, "the desk": desk} {
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if strings.TrimSpace(v) == "" {
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return "", fmt.Errorf("%s is not named", what)
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}
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}
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if err := d.declares(module, name); err != nil {
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return "", fmt.Errorf("nobody was asked to type anything: %w", err)
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}
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public, private, err := secrets.Keypair()
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if err != nil {
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return "", fmt.Errorf("no key could be made to take the value: %w", err)
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}
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raw, err := d.ask(desk, map[string]any{
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"prompt": name + " for " + module,
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"message": fmt.Sprintf("The mesh asks for %s, the own secret of %s on %s. What you type is not shown, "+
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"and is sealed before it leaves this machine. Type it only if you asked for this.", name, module, node),
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"seal_to": public,
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"timeout_seconds": deskPromptWithin,
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})
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if err != nil {
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return "", fmt.Errorf("the desk on %s could not be asked: %w", desk, err)
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}
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var answer struct {
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Sealed string `json:"sealed"`
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Cancelled bool `json:"cancelled"`
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TimedOut bool `json:"timed_out"`
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}
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if err := json.Unmarshal(raw, &answer); err != nil {
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return "", fmt.Errorf("the desk on %s answered something that is not the prompt's answer", desk)
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}
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switch {
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case answer.TimedOut:
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return "", fmt.Errorf("%w: the prompt on %s was not answered within %d seconds", errNothingGiven, desk, deskPromptWithin)
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case answer.Cancelled:
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return "", fmt.Errorf("%w: the prompt on %s was dismissed", errNothingGiven, desk)
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case answer.Sealed == "":
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return "", fmt.Errorf("the desk on %s answered no sealed value", desk)
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}
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opened, err := secrets.Open(private, answer.Sealed)
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if err != nil {
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// Never the value, never what failed to open: only that it was not sealed to this call.
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return "", fmt.Errorf("the desk on %s answered a value not sealed to this call; nothing was taken", desk)
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}
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value := asSupplied(string(opened))
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for i := range opened {
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opened[i] = 0
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}
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if strings.TrimSpace(value) == "" {
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return "", fmt.Errorf("%w: the prompt on %s was answered empty", errNothingGiven, desk)
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}
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untilStart, err := d.accept(value)
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value = ""
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if err != nil {
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return "", err
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}
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act := link.HandAct{Verb: "secret accept", Args: []string{node, module, name, "--at-desk", desk},
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Why: fmt.Sprintf("the operator gave %s for %s on %s at the desk on %s", name, module, node, desk),
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Cause: "given-at-the-desk"}
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recorded := ""
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if err := d.record(act); err != nil {
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recorded = fmt.Sprintf("\n this act could NOT be recorded in the hand-act log, and is done anyway: %v", err)
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}
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words := fmt.Sprintf("%s on %s now holds %q, given at the desk on %s and sealed to %s; the mesh cannot read it "+
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"back.\n run `push %s` to send it", module, node, name, desk, node, node)
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if untilStart {
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words += fmt.Sprintf("\n it lives until %s next starts well under the mesh, and is then replaced with a value "+
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"the mesh makes (ADR 0228)", module)
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}
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return words + recorded, nil
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}
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// giveAtDesk is `secret accept <node> <module> <name> --at-desk <machine>`: the desk path, on this
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// controller's stores and bus.
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func giveAtDesk(ctx context.Context, node, module, name, desk string) error {
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open, err := openStores(ctx)
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if err != nil {
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return err
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}
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defer open.Close()
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d := deskGive{
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declares: func(module, name string) error { return open.inventory.DeclaresOwnSecret(ctx, module, name) },
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ask: func(machine string, args map[string]any) (json.RawMessage, error) {
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var result json.RawMessage
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err := onTheBus(func(conn *nats.Conn) error {
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answer, err := link.AskSeatTool(ctx, conn, "node-launcher", "secret", machine, args,
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time.Duration(deskPromptWithin+5)*time.Second)
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if err != nil {
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return err
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}
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if answer.Error != "" {
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return errors.New(answer.Error)
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}
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result = answer.Result
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return nil
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})
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return result, err
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},
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accept: func(value string) (bool, error) {
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return open.inventory.AcceptGivenSecret(ctx, node, module, name, value)
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},
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record: func(act link.HandAct) error {
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return onTheBus(func(conn *nats.Conn) error {
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_, err := link.RecordHandAct(ctx, conn, act)
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return err
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})
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},
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}
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words, err := d.give(node, module, name, desk)
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if err != nil {
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return err
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}
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fmt.Println(words)
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return nil
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}
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