feat(resource): add Verifier.IssueDPoPNonce

resource/nonce.go

@@ -27,6 +27,24 @@ func generateDPoPNonce(random io.Reader) (string, error) {
 	return base64.RawURLEncoding.EncodeToString(buf), nil
 }
 
+// IssueDPoPNonce issues a fresh DPoP nonce this Verifier will accept, for
+// a resource server to hand out ahead of a request rather than in answer
+// to one: an OpenID4VCI 1.0 §7.2 Nonce Response's DPoP-Nonce header,
+// say, which the Wallet then uses at the Credential Endpoint this
+// Verifier guards. It returns "" and no error when Dependencies.Nonces is
+// nil: the Verifier doesn't use DPoP nonces, so there is none to give.
+//
+// Each call stores a nonce until Config.Limits.DPoPNonceLifetime has
+// passed. Called from an endpoint anyone may call (§7.1's Nonce Endpoint
+// is), it lets anyone add records, as that endpoint's own c_nonce does:
+// rate-limit it the same way.
+func (v *Verifier) IssueDPoPNonce(ctx context.Context) (string, error) {
+	if v.deps.Nonces == nil {
+		return "", nil
+	}
+	return v.issueDPoPNonce(ctx, v.deps.Clock.Now())
+}
+
 // issueDPoPNonce generates and persists a fresh nonce, valid from now
 // for v.cfg.Limits.DPoPNonceLifetime. Only ever called once v.deps.Nonces
 // is known to be non-nil.

resource/nonce_test.go

@@ -270,3 +270,25 @@ func TestInsufficientScopeCarriesNextNonce(t *testing.T) {
 		t.Fatalf("status = %d, want 403", rec.Code)
 	}
 }
+
+// TestIssueDPoPNonce: a nonce IssueDPoPNonce hands out ahead of a
+// request (as an OpenID4VCI Nonce Response does) is accepted by Verify,
+// once; a Verifier without Dependencies.Nonces has none to give.
+func TestIssueDPoPNonce(t *testing.T) {
+	ctx := context.Background()
+	first := newNonceFixture(t, "", nil)
+	issued, err := first.verifier.IssueDPoPNonce(ctx)
+	if err != nil || issued == "" {
+		t.Fatalf("IssueDPoPNonce = %q, %v; want a nonce", issued, err)
+	}
+	if _, err := newNonceFixture(t, issued, first.nonces).verify(t); err != nil {
+		t.Fatalf("Verify(issued nonce) = %v, want accepted", err)
+	}
+	if _, err := newNonceFixture(t, issued, first.nonces).verify(t); err == nil {
+		t.Fatal("Verify(issued nonce again) = nil error, want it refused as spent")
+	}
+
+	if nonce, err := newFixture(t).verifier.IssueDPoPNonce(ctx); nonce != "" || err != nil {
+		t.Errorf("IssueDPoPNonce without Nonces = %q, %v; want none and no error", nonce, err)
+	}
+}