plugin/dnssec: check validityperiod of RRSIGs (#1385)

* plugin/dnssec: check validityperiod of RRSIGs

Somehow we missed implementing this. If a sig a retrieved from the
cache, but not valid anymore, regenerate it instead of server invalid
signatures.

Fixes #1378

* drop from cache after 3/4 validity

* six days means 6 days

plugin/dnssec/cache_test.go

@@ -32,3 +32,51 @@ func TestCacheSet(t *testing.T) {
 		t.Errorf("signature was not added to the cache")
 	}
 }
+
+func TestCacheNotValidExpired(t *testing.T) {
+	fPriv, rmPriv, _ := test.TempFile(".", privKey)
+	fPub, rmPub, _ := test.TempFile(".", pubKey)
+	defer rmPriv()
+	defer rmPub()
+
+	dnskey, err := ParseKeyFile(fPub, fPriv)
+	if err != nil {
+		t.Fatalf("failed to parse key: %v\n", err)
+	}
+
+	c := cache.New(defaultCap)
+	m := testMsg()
+	state := request.Request{Req: m, Zone: "miek.nl."}
+	k := hash(m.Answer) // calculate *before* we add the sig
+	d := New([]string{"miek.nl."}, []*DNSKEY{dnskey}, nil, c)
+	d.Sign(state, time.Now().UTC().AddDate(0, 0, -9))
+
+	_, ok := d.get(k)
+	if ok {
+		t.Errorf("signature was added to the cache even though not valid")
+	}
+}
+
+func TestCacheNotValidYet(t *testing.T) {
+	fPriv, rmPriv, _ := test.TempFile(".", privKey)
+	fPub, rmPub, _ := test.TempFile(".", pubKey)
+	defer rmPriv()
+	defer rmPub()
+
+	dnskey, err := ParseKeyFile(fPub, fPriv)
+	if err != nil {
+		t.Fatalf("failed to parse key: %v\n", err)
+	}
+
+	c := cache.New(defaultCap)
+	m := testMsg()
+	state := request.Request{Req: m, Zone: "miek.nl."}
+	k := hash(m.Answer) // calculate *before* we add the sig
+	d := New([]string{"miek.nl."}, []*DNSKEY{dnskey}, nil, c)
+	d.Sign(state, time.Now().UTC().AddDate(0, 0, +9))
+
+	_, ok := d.get(k)
+	if ok {
+		t.Errorf("signature was added to the cache even though not valid yet")
+	}
+}