mesh-host/internal/link/messages_test.go

package link

import (
	"context"
	"crypto/ed25519"
	"encoding/json"
	"testing"
)

// verified runs what Run does to a delivery body, without a broker: unmarshal, check the
// signature, and only then apply. Isolating it keeps this test about the check rather than about
// AMQP, which is tested against a real broker in the lab.
func verified(t *testing.T, signer ed25519.PublicKey, body []byte) (Report, bool) {
	t.Helper()
	applied := false
	report := handleBody(context.Background(), Membership{Node: "anchor", Signer: signer}, body,
		func(context.Context, []byte, []byte) Report {
			applied = true
			return Report{Applied: []string{"something"}}
		})
	return report, applied
}

func signedBody(t *testing.T, private ed25519.PrivateKey, declaration string) []byte {
	t.Helper()
	raw, err := json.Marshal(Signed{
		Declaration: []byte(declaration),
		Signature:   ed25519.Sign(private, []byte(declaration)),
	})
	if err != nil {
		t.Fatal(err)
	}
	return raw
}

func TestTheMeshsOwnDeclarationIsApplied(t *testing.T) {
	public, private, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}
	report, applied := verified(t, public, signedBody(t, private, `{"declaration":1}`))
	if !applied {
		t.Fatalf("a declaration the mesh signed was not applied: %s", report.Refused)
	}
}

// Defends novox/hq ADR 0002: everything reaching a node arrives over the broker — and therefore
// ADR 0004's consequence, that the broker is not trusted to say who is speaking.
//
// A transport nobody authenticates per-message would let whatever holds the connection attribute
// a declaration to any node it liked.
func TestAForgedDeclarationIsNeverApplied(t *testing.T) {
	// The check that stands between "the mesh changes this machine" and "anybody does". The host
	// applies whatever the link delivers, so a forged declaration is the whole machine.
	public, _, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}
	_, other, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}

	report, applied := verified(t, public, signedBody(t, other, `{"declaration":1}`))
	if applied {
		t.Fatal("a declaration signed by another key was applied")
	}
	if report.Refused != ErrForged.Error() {
		t.Errorf("refused, but not as a forgery: %q", report.Refused)
	}
}

func TestATamperedDeclarationIsNeverApplied(t *testing.T) {
	// A broker that changed the declaration in flight, keeping the signature. This is what makes
	// pinning the transport insufficient on its own.
	public, private, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}
	raw, err := json.Marshal(Signed{
		Declaration: []byte(`{"declaration":1,"resources":["something else entirely"]}`),
		Signature:   ed25519.Sign(private, []byte(`{"declaration":1}`)),
	})
	if err != nil {
		t.Fatal(err)
	}

	report, applied := verified(t, public, raw)
	if applied {
		t.Fatal("a declaration altered after signing was applied")
	}
	if report.Refused != ErrForged.Error() {
		t.Errorf("refused, but not as a forgery: %q", report.Refused)
	}
}

func TestAMalformedMessageIsToldApartFromAForgery(t *testing.T) {
	// novox/hq ADR 0004 requires these to be distinguishable: one means somebody is trying, the
	// other means something is broken, and they need different responses from a person.
	public, _, err := ed25519.GenerateKey(nil)
	if err != nil {
		t.Fatal(err)
	}
	report, applied := verified(t, public, []byte("this is not a message"))
	if applied {
		t.Fatal("something unparseable was applied")
	}
	if report.Refused == ErrForged.Error() {
		t.Error("a malformed message was reported as a forgery; those must be distinguishable")
	}
}

func TestTheWireFormatIsExactlyTheseFieldNames(t *testing.T) {
	// The contract with the control plane, which defines these separately. A matching test lives
	// there; rename a field on either side and both fail.
	for _, c := range []struct {
		value  any
		expect []string
	}{
		{Signed{Declaration: []byte("{}"), Signature: []byte("x")}, []string{"declaration", "signature"}},
		{Report{Node: "n", Applied: []string{"a"}, Failed: map[string]string{"k": "v"}, Refused: "r"},
			[]string{"node", "applied", "failed", "refused"}},
	} {
		raw, err := json.Marshal(c.value)
		if err != nil {
			t.Fatal(err)
		}
		var fields map[string]any
		if err := json.Unmarshal(raw, &fields); err != nil {
			t.Fatal(err)
		}
		for _, want := range c.expect {
			if _, ok := fields[want]; !ok {
				t.Errorf("%T has no %q field; the control plane uses that name", c.value, want)
			}
		}
		if len(fields) != len(c.expect) {
			t.Errorf("%T has %d fields, expected %d: %v", c.value, len(fields), len(c.expect), fields)
		}
	}
}