A composition is applied only when the controller or the operator signed it; the node agent's integration tests on an embedded bus (R6-A A9, A1, A5)

internal/agent/agent.go

@@ -12,6 +12,7 @@ package agent
 import (
 	"bytes"
 	"context"
+	"crypto/ed25519"
 	"encoding/json"
 	"fmt"
 	"sort"
@@ -87,10 +88,11 @@ type Env struct {
 	// Kept is the resources the node last applied for a module from the declaration it kept before the switch (ADR 0539
 	// §9), as JSON, and whether it held the module. Nil when the node kept none.
 	Kept func(module string) ([]json.RawMessage, bool)
-	// Verify judges a composition's bytes before anything of it is read: a composition whose signer is not trusted is
-	// refused (ADR 0539 §3). Nil trusts the bucket, which only the controller and the operator can write.
-	Verify func(key string, raw []byte) error
-	Say    func(string)
+	// Trusted is the public keys a composition may be signed by: the controller's and the operator's (ADR 0539 §3). A
+	// composition unsigned, signed by another key, or changed after it was signed is refused and nothing of it is
+	// applied. Nil trusts no key, so nothing is applied.
+	Trusted func() []ed25519.PublicKey
+	Say     func(string)
 }
 
 // Agent follows the wants.
@@ -281,23 +283,24 @@ func (a *Agent) takeComposition(u Update) string {
 		return module
 	}
 	now := compNow{Raw: u.Value, Rev: u.Revision}
-	if a.env.Verify != nil {
-		if err := a.env.Verify(u.Key, u.Value); err != nil {
-			now.Err = fmt.Errorf("refused: %w", err)
-			a.comps[u.Key] = now
-			a.sayOnce("verify:"+u.Key, fmt.Sprintf("the composition %s is refused and nothing of it is applied: %v", u.Key, err))
-			return module
-		}
-	}
 	c, err := delivery.DecodeComposed(u.Value)
 	if err == nil {
+		var trusted []ed25519.PublicKey
+		if a.env.Trusted != nil {
+			trusted = a.env.Trusted()
+		}
+		// The signature before anything of the composition is used: its digest is what the want names.
 		now.C = c
-		now.Dig, err = delivery.ComposedDigestOf(c)
-	}
-	now.Err = err
-	if err != nil {
+		now.Dig, err = delivery.VerifyComposed(c, trusted)
+		if err != nil {
+			now.C = delivery.Composed{}
+			a.sayOnce("verify:"+u.Key, fmt.Sprintf("the composition %s is refused and nothing of it is applied: %v", u.Key, err))
+			err = fmt.Errorf("refused: %w", err)
+		}
+	} else {
 		a.sayOnce("decode:"+u.Key, fmt.Sprintf("the composition %s cannot be read, and nothing of it is applied: %v", u.Key, err))
 	}
+	now.Err = err
 	a.comps[u.Key] = now
 	return module
 }