mesh-controller/internal/link/rekey_test.go

package link_test

import (
	"crypto/ed25519"
	"strings"
	"testing"

	"github.com/novox/mesh-controller/internal/identity"
	"github.com/novox/mesh-controller/internal/inventory"
	"github.com/novox/mesh-controller/internal/link"
)

// novox/hq ADR 0105: a hub that enrolled before the mesh knew to take a tunnel over rekeys onto the
// found tunnel's key without re-enrolling — which would rotate every key it holds and remake every
// credential the mesh sealed to it. The rekey rides in a report and is signed with the node's
// identity key; the mesh verifies it against the key it recorded, and refuses one signed by
// another key or one already applied.

const (
	ownKey    = "THE-MESHS-OWN-KEY======================="
	tunnelKey = "TUNNEL-KEY-the-found-interfaces-public-key="
)

func theTunnel() *link.Tunnel {
	return &link.Tunnel{Interface: "wg0", Unit: "wg-quick@wg0", Config: "/etc/wireguard/wg0.conf",
		Port: 51900, Address: "192.0.2.1/24", Range: "192.0.2.0/24", PublicKey: tunnelKey,
		Peers: []link.TunnelPeer{{PublicKey: "PEER-A=", Address: "192.0.2.2/32"}}}
}

// anEnrolledHub is a hub the way it stands before the feature: adopted, placed, its overlay key its
// own, its identity key recorded — and a mesh holding both stores.
func anEnrolledHub(t *testing.T) (link.Enrolment, inventory.Node, ed25519.PrivateKey) {
	t.Helper()
	inv := inventory.ForTest(t)
	ident := identity.ForTest(t)
	ctx := t.Context()
	hub, err := inv.AddNodeAs(ctx, "anchor", true)
	if err != nil {
		t.Fatal(err)
	}
	public, private, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := ident.RecordNodeKey(ctx, hub.ID, public); err != nil {
		t.Fatal(err)
	}
	if err := inv.RecordOverlayKey(ctx, hub.ID, ownKey); err != nil {
		t.Fatal(err)
	}
	if err := inv.SetPlace(ctx, "anchor", "anchor.example:51900", "hosting", true, "10.42.0.1"); err != nil {
		t.Fatal(err)
	}
	return link.Enrolment{Inventory: inv, Identity: ident}, hub, private
}

func TestASignedRekeyMovesTheHubOntoItsTunnel(t *testing.T) {
	e, hub, private := anEnrolledHub(t)
	ctx := t.Context()
	rekey := &link.Rekey{Previous: ownKey, OverlayKey: tunnelKey, Tunnel: theTunnel()}
	rekey.Proof = ed25519.Sign(private, link.RekeyProof("anchor", ownKey, tunnelKey, theTunnel()))

	if err := e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey}); err != nil {
		t.Fatal(err)
	}
	placed, err := e.Inventory.Overlays(ctx)
	if err != nil || len(placed) != 1 {
		t.Fatal(placed, err)
	}
	if placed[0].Key != tunnelKey || placed[0].Address != "192.0.2.1" {
		t.Fatalf("the hub is not on the tunnel's key and address: %+v", placed[0])
	}
	tunnel, _, adopted, err := e.Inventory.AdoptedTunnel(ctx)
	if err != nil || !adopted || tunnel.Range != "192.0.2.0/24" || len(tunnel.Peers) != 1 {
		t.Fatalf("the tunnel is not adopted after the rekey: %+v %t %v", tunnel, adopted, err)
	}
	_ = hub

	// Replayed, it is stale: the previous key it names is no longer the node's.
	err = e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey})
	if err == nil || !strings.Contains(err.Error(), "previous overlay key") {
		t.Fatalf("a replayed rekey was accepted: %v", err)
	}
}

func TestARekeySignedByAnotherKeyIsRefusedAndChangesNothing(t *testing.T) {
	e, _, _ := anEnrolledHub(t)
	ctx := t.Context()
	_, stranger, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}
	rekey := &link.Rekey{Previous: ownKey, OverlayKey: tunnelKey, Tunnel: theTunnel()}
	rekey.Proof = ed25519.Sign(stranger, link.RekeyProof("anchor", ownKey, tunnelKey, theTunnel()))

	err = e.Heard(ctx, link.Report{Node: "anchor", Rekey: rekey})
	if err == nil || !strings.Contains(err.Error(), "not signed by anchor's identity key") {
		t.Fatalf("a rekey signed by a stranger was accepted: %v", err)
	}
	placed, _ := e.Inventory.Overlays(ctx)
	if placed[0].Key != ownKey || placed[0].Address != "10.42.0.1" {
		t.Fatalf("a refused rekey changed the record: %+v", placed[0])
	}
	if _, _, adopted, _ := e.Inventory.AdoptedTunnel(ctx); adopted {
		t.Fatal("a refused rekey recorded a tunnel")
	}

	// And a proof moved to another tunnel — the signature was over one tunnel, the message names
	// another — does not verify either.
	moved := &link.Rekey{Previous: ownKey, OverlayKey: tunnelKey, Tunnel: theTunnel()}
	other := theTunnel()
	other.Port = 51820
	moved.Proof = ed25519.Sign(mustPrivate(t, e, "anchor"), link.RekeyProof("anchor", ownKey, tunnelKey, other))
	if err := e.Heard(ctx, link.Report{Node: "anchor", Rekey: moved}); err == nil {
		t.Fatal("a proof over another tunnel was accepted")
	}
}

// mustPrivate is a fresh key recorded as the node's live one, for signing in a test that needs
// the node's own signature after the fixture's key is out of scope.
func mustPrivate(t *testing.T, e link.Enrolment, node string) ed25519.PrivateKey {
	t.Helper()
	public, private, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}
	n, err := e.Inventory.NodeByName(t.Context(), node)
	if err != nil {
		t.Fatal(err)
	}
	if _, err := e.Identity.RecordNodeKey(t.Context(), n.ID, public); err != nil {
		t.Fatal(err)
	}
	return private
}