Merge pull request 'Ask a node's engine which of its directories the walk would refuse, read-only (issue 358)' (#258) from fix/358-judge-directories-read-only into main

cmd/mesh-controller/handover_test.go

@@ -167,3 +167,54 @@ func TestASetuidSearchAsksOnlyAKnownNodeAndFailsOnARefusal(t *testing.T) {
 		t.Fatalf("a start: %v, printed %q", err, out.String())
 	}
 }
+
+// The directory judgement's line asks only a known node, one name and nothing else, fails on a refusal, and says it
+// changed nothing (novox/hq issue 358).
+func TestADirectoryJudgementAsksOnlyAKnownNodeAndSaysItIsReadOnly(t *testing.T) {
+	t.Setenv(link.CallerVar, "jo through mesh-cli on anchor")
+	asked := 0
+	ask := func(answer link.HandOverAnswer) func(node, by string) (link.HandOverAnswer, error) {
+		return func(node, by string) (link.HandOverAnswer, error) {
+			asked++
+			if node != "novox" || by != "jo through mesh-cli on anchor" {
+				t.Fatalf("asked %q %q", node, by)
+			}
+			return answer, nil
+		}
+	}
+	known := func(string) error { return nil }
+	var out bytes.Buffer
+	for _, args := range [][]string{nil, {"novox", "extra"}, {"-x"}} {
+		if err := judgeDirectoriesAsked(args, known, ask(link.HandOverAnswer{Said: "x"}), &out); err == nil || asked != 0 {
+			t.Fatalf("%v was asked: %v", args, err)
+		}
+	}
+	if err := judgeDirectoriesAsked([]string{"novox"}, func(string) error { return errors.New("no node called novox") },
+		ask(link.HandOverAnswer{Said: "x"}), &out); err == nil || asked != 0 {
+		t.Fatalf("an unknown node: %v", err)
+	}
+	if err := judgeDirectoriesAsked([]string{"novox"}, known, ask(link.HandOverAnswer{Refused: "no; nothing was judged"}),
+		&out); err == nil || !strings.Contains(err.Error(), "novox refused") || out.Len() != 0 {
+		t.Fatalf("a refusal: %v, printed %q", err, out.String())
+	}
+	said := "2 directories declared: 1 placed, 1 would be refused\n/var/lib/a: placed\n/var/lib/b: would be refused: …"
+	if err := judgeDirectoriesAsked([]string{"novox"}, known, ask(link.HandOverAnswer{Said: said}), &out); err != nil ||
+		out.String() != "novox (read-only: nothing on novox was changed)\n"+said+"\n" {
+		t.Fatalf("a judgement: %v, printed %q", err, out.String())
+	}
+}
+
+// The judgement is a seat verb an agent may call — it reads, and changes nothing on the node — and runs exactly
+// `node judge-directories <node>` (novox/hq issue 358).
+func TestTheDirectoryJudgementIsAVerbThatOnlyReads(t *testing.T) {
+	argv, err := argvFor("judge-directories", map[string]any{"node": "novox"})
+	if err != nil || strings.Join(argv, " ") != "node judge-directories novox" {
+		t.Fatalf("the verb runs %v, %v", argv, err)
+	}
+	if _, err := argvFor("judge-directories", map[string]any{}); err == nil {
+		t.Fatal("the verb ran with no node")
+	}
+	if !readingVerbs["judge-directories"] {
+		t.Fatal("the judgement is not counted a reading verb")
+	}
+}

cmd/mesh-controller/nodes.go

@@ -127,9 +127,14 @@ func nodeCommand(ctx context.Context, args []string) error {
 		// and whoever may call a verb includes agents.
 		return nodeSetuidSearch(ctx, open, args[1:])
 
+	case "judge-directories":
+		// Which of a node's declared directories the walk that follows no link another account could make would
+		// refuse (novox/hq issue 358). Read-only on the node and here, so a verb may run it too.
+		return nodeJudgeDirectories(ctx, open, args[1:])
+
 	default:
-		return fmt.Errorf("node has no %q; it has add, list, show, public-domain, account, agent-account, hand-over "+
-			"and setuid-search", args[0])
+		return fmt.Errorf("node has no %q; it has add, list, show, public-domain, account, agent-account, hand-over, "+
+			"setuid-search and judge-directories", args[0])
 	}
 }
 
@@ -937,3 +942,57 @@ func printJSONTo(w io.Writer, v any) error {
 	fmt.Fprintln(w, string(body))
 	return nil
 }
+
+const judgeDirectoriesUsage = "node judge-directories <node> — read-only: which of the directories <node> is " +
+	"declared the node-engine's walk that follows no link another account could make would refuse, one line each " +
+	"(novox/hq issue 358). Nothing is made, chmodded or chowned"
+
+// nodeJudgeDirectories asks the node's engine to judge its declared directories, signed with the mesh's key as a
+// hand-over is. Read-only: the engine changes nothing and keeps nothing.
+func nodeJudgeDirectories(ctx context.Context, open *stores, args []string) error {
+	known := func(node string) error {
+		_, err := open.inventory.NodeByName(ctx, node)
+		return err
+	}
+	ask := func(node, by string) (link.HandOverAnswer, error) {
+		ident, err := open.Identity(ctx)
+		if err != nil {
+			return link.HandOverAnswer{}, fmt.Errorf("the mesh's signing key cannot be read, so nothing was asked of %s: %w",
+				node, err)
+		}
+		address, err := broker.BusAddress()
+		if err != nil {
+			return link.HandOverAnswer{}, err
+		}
+		js, err := broker.Dial(address)
+		if err != nil {
+			return link.HandOverAnswer{}, fmt.Errorf("cannot reach the bus, so nothing was asked of %s: %w", node, err)
+		}
+		defer js.Close()
+		return link.AskJudgeDirectories(ctx, js.Conn(), ident, node, by, link.HandOverWithin)
+	}
+	return judgeDirectoriesAsked(args, known, ask, os.Stdout)
+}
+
+// judgeDirectoriesAsked is the line with its two acts given: whether the mesh knows the node, and the ask. The
+// engine's refusal is this command's failure.
+func judgeDirectoriesAsked(args []string, known func(node string) error,
+	ask func(node, by string) (link.HandOverAnswer, error), out io.Writer) error {
+	if len(args) != 1 || args[0] == "" || strings.HasPrefix(args[0], "-") {
+		return errors.New(judgeDirectoriesUsage)
+	}
+	node := args[0]
+	if err := known(node); err != nil {
+		return fmt.Errorf("nothing was asked: %w", err)
+	}
+	answer, err := ask(node, handOverBy())
+	if err != nil {
+		return err
+	}
+	if answer.Refused != "" {
+		return fmt.Errorf("%s refused: %s", node, answer.Refused)
+	}
+	fmt.Fprintf(out, "%s (read-only: nothing on %s was changed)\n", node, node)
+	fmt.Fprintln(out, answer.Said)
+	return nil
+}

cmd/mesh-controller/seatverbs.go

@@ -314,6 +314,11 @@ func (a *verbArguments) commandLine() ([]string, error) {
 			return nil, err
 		}
 		return []string{"node", "show", str("node")}, nil
+	case "judge-directories":
+		if err := need("node"); err != nil {
+			return nil, err
+		}
+		return []string{"node", "judge-directories", str("node")}, nil
 	case "modules":
 		return []string{"module", "list", "--json"}, nil
 	case "seats":
@@ -1479,7 +1484,9 @@ func seatAnnouncement(handlers map[string]link.ToolHandler) micro.Info {
 }
 
 // nodeReads are the `node` subcommands a verb may run: the ones that only read.
-var nodeReads = map[string]bool{"list": true, "show": true}
+var nodeReads = map[string]bool{"list": true, "show": true,
+	// Read-only on the node too: the engine judges its directories and changes nothing (novox/hq issue 358).
+	"judge-directories": true}
 
 // flagsOnly says a command line's rest names no subcommand: empty, or beginning with a flag. For a command
 // with no subcommands every word is a flag, its value or a name it reads.

cmd/mesh-controller/status_summary.go

@@ -172,7 +172,7 @@ func composeStatus(open *stores) func(context.Context) ([]byte, error) {
 var readingVerbs = map[string]bool{
 	"tools": true, "calls": true, "status": true, "nodes": true, "node": true, "modules": true,
 	"seats": true, "builds": true, "plan": true, "queue": true, "durations": true, "hand-acts": true,
-	"doctor": true, "conditions": true, "healers": true,
+	"doctor": true, "conditions": true, "healers": true, "judge-directories": true,
 }
 
 // nudgingListener is the enrolment, nudging the summary when a machine said something new.