mesh-sdk/go/delivery/composed_signature_test.go

package delivery

import (
	"crypto/ed25519"
	"crypto/rand"
	"encoding/json"
	"strings"
	"testing"
)

func aSigningKey(t *testing.T) (ed25519.PublicKey, ed25519.PrivateKey) {
	t.Helper()
	pub, priv, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		t.Fatal(err)
	}
	return pub, priv
}

func aComposition() Composed {
	return Composed{Node: "ace", Module: "m", FP: fp2of('a'), Resources: []json.RawMessage{
		json.RawMessage(`{"id":"m.f","type":"file","module":"m","path":"/etc/m","content":"x"}`)}}
}

// 1943/AC5: a composition signed by the controller's key or by the operator's verifies against the two trusted keys,
// keeps its digest, and survives its encoding; one signed by another key, unsigned, or changed by one byte after it was
// signed does not verify, and nothing of it is to be applied.
func TestACompositionIsSignedByATrustedKey(t *testing.T) {
	controllerPub, controller := aSigningKey(t)
	operatorPub, operator := aSigningKey(t)
	_, stranger := aSigningKey(t)
	trusted := []ed25519.PublicKey{controllerPub, operatorPub}
	c := aComposition()
	want, _ := ComposedDigestOf(c)

	for name, key := range map[string]ed25519.PrivateKey{"controller": controller, "operator": operator} {
		signed, err := SignComposed(c, key)
		if err != nil {
			t.Fatalf("%s: %v", name, err)
		}
		raw, err := EncodeComposed(signed)
		if err != nil {
			t.Fatal(err)
		}
		back, err := DecodeComposed(raw)
		if err != nil {
			t.Fatal(err)
		}
		digest, err := VerifyComposed(back, trusted)
		if err != nil || digest != want {
			t.Errorf("%s's signature: %q, %v; want the digest %s", name, digest, err, want)
		}
		if d, _ := ComposedDigestOf(back); d != want {
			t.Errorf("%s's signature changed the digest: %s", name, d)
		}

		changed := strings.Replace(string(raw), `"content":"x"`, `"content":"y"`, 1)
		if changed == string(raw) {
			t.Fatal("the test changed nothing")
		}
		if tampered, err := DecodeComposed([]byte(changed)); err != nil {
			t.Fatal(err)
		} else if _, err := VerifyComposed(tampered, trusted); err == nil || !strings.Contains(err.Error(), "signature") {
			t.Errorf("%s: a composition changed by one byte verified: %v", name, err)
		}
	}

	byStranger, _ := SignComposed(c, stranger)
	if _, err := VerifyComposed(byStranger, trusted); err == nil || !strings.Contains(err.Error(), "not a trusted") {
		t.Errorf("a stranger's signature = %v, want refused as no trusted signer", err)
	}
	if _, err := VerifyComposed(c, trusted); err == nil || !strings.Contains(err.Error(), "unsigned") {
		t.Errorf("an unsigned composition = %v, want refused", err)
	}
	signed, _ := SignComposed(c, controller)
	forged := signed
	forged.Signature = &Signature{Signer: signed.Signature.Signer, Sig: byStranger.Signature.Sig}
	if _, err := VerifyComposed(forged, trusted); err == nil {
		t.Errorf("a stranger's signature under the controller's name verified")
	}
	if _, err := EncodeComposed(Composed{Node: "ace", Module: "m", FP: fp2of('a'), Resources: c.Resources,
		Signature: &Signature{Signer: "not base64!", Sig: "x"}}); err == nil {
		t.Errorf("a signature naming no key was encoded")
	}
}

// 1943/AC5: a signer that keeps its private half signs through a function, and the composition verifies as one signed
// with the key; a function that signs with another key than the one named is refused.
func TestACompositionIsSignedByAKeptKey(t *testing.T) {
	pub, priv := aSigningKey(t)
	_, other := aSigningKey(t)
	c := aComposition()
	signed, err := SignComposedBy(c, pub, func(m []byte) ([]byte, error) { return ed25519.Sign(priv, m), nil })
	if err != nil {
		t.Fatal(err)
	}
	if _, err := VerifyComposed(signed, []ed25519.PublicKey{pub}); err != nil {
		t.Errorf("a composition signed through the function does not verify: %v", err)
	}
	if _, err := SignComposedBy(c, pub, func(m []byte) ([]byte, error) { return ed25519.Sign(other, m), nil }); err == nil {
		t.Errorf("a signature by another key than the one named was accepted")
	}
}