Encryption: Fix DEKs cache (#43129)

* Encryption: Fix DEKs cache

* Clarify tests

pkg/server/backgroundsvcs/background_services.go

@@ -20,6 +20,7 @@ import (
 	"github.com/grafana/grafana/pkg/services/pluginsettings"
 	"github.com/grafana/grafana/pkg/services/provisioning"
 	"github.com/grafana/grafana/pkg/services/rendering"
+	secretsManager "github.com/grafana/grafana/pkg/services/secrets/manager"
 	"github.com/grafana/grafana/pkg/services/serviceaccounts"
 	"github.com/grafana/grafana/pkg/services/updatechecker"
 	"github.com/grafana/grafana/pkg/tsdb/azuremonitor"
@@ -45,7 +46,7 @@ func ProvideBackgroundServiceRegistry(
 	rendering *rendering.RenderingService, tokenService models.UserTokenBackgroundService,
 	provisioning *provisioning.ProvisioningServiceImpl, alerting *alerting.AlertEngine, pm *manager.PluginManager,
 	metrics *metrics.InternalMetricsService, usageStats *uss.UsageStats, updateChecker *updatechecker.Service,
-	tracing tracing.Tracer, remoteCache *remotecache.RemoteCache,
+	tracing tracing.Tracer, remoteCache *remotecache.RemoteCache, secretsService *secretsManager.SecretsService,
 	// Need to make sure these are initialized, is there a better place to put them?
 	_ *azuremonitor.Service, _ *cloudwatch.CloudWatchService, _ *elasticsearch.Service, _ *graphite.Service,
 	_ *influxdb.Service, _ *loki.Service, _ *opentsdb.Service, _ *prometheus.Service, _ *tempo.Service,
@@ -69,7 +70,8 @@ func ProvideBackgroundServiceRegistry(
 		metrics,
 		usageStats,
 		tracing,
-		remoteCache)
+		remoteCache,
+		secretsService)
 }
 
 // BackgroundServiceRegistry provides background services.

pkg/services/secrets/manager/manager.go

@@ -103,7 +103,7 @@ func (s *SecretsService) EncryptWithDBSession(ctx context.Context, payload []byt
 
 	// If encryption secrets.EnvelopeEncryptionFeatureToggle toggle is on, use envelope encryption
 	scope := opt()
-	keyName := fmt.Sprintf("%s/%s@%s", time.Now().Format("2006-01-02"), scope, s.currentProvider)
+	keyName := s.keyName(scope)
 
 	dataKey, err := s.dataKey(ctx, keyName)
 	if err != nil {
@@ -134,6 +134,10 @@ func (s *SecretsService) EncryptWithDBSession(ctx context.Context, payload []byt
 	return blob, nil
 }
 
+func (s *SecretsService) keyName(scope string) string {
+	return fmt.Sprintf("%s/%s@%s", now().Format("2006-01-02"), scope, s.currentProvider)
+}
+
 func (s *SecretsService) Decrypt(ctx context.Context, payload []byte) ([]byte, error) {
 	// Use legacy encryption service if secrets.EnvelopeEncryptionFeatureToggle toggle is off
 	if !s.settings.IsFeatureToggleEnabled(secrets.EnvelopeEncryptionFeatureToggle) {
@@ -265,7 +269,7 @@ func (s *SecretsService) newDataKey(ctx context.Context, name string, scope stri
 
 	// 4. Cache its unencrypted value and return it
 	s.dataKeyCache[name] = dataKeyCacheItem{
-		expiry:  time.Now().Add(15 * time.Minute),
+		expiry:  now().Add(dekTTL),
 		dataKey: dataKey,
 	}
 
@@ -275,11 +279,9 @@ func (s *SecretsService) newDataKey(ctx context.Context, name string, scope stri
 // dataKey looks up DEK in cache or database, and decrypts it
 func (s *SecretsService) dataKey(ctx context.Context, name string) ([]byte, error) {
 	if item, exists := s.dataKeyCache[name]; exists {
-		if item.expiry.Before(time.Now()) && !item.expiry.IsZero() {
-			delete(s.dataKeyCache, name)
-		} else {
-			return item.dataKey, nil
-		}
+		item.expiry = now().Add(dekTTL)
+		s.dataKeyCache[name] = item
+		return item.dataKey, nil
 	}
 
 	// 1. get encrypted data key from database
@@ -301,7 +303,7 @@ func (s *SecretsService) dataKey(ctx context.Context, name string) ([]byte, erro
 
 	// 3. cache data key
 	s.dataKeyCache[name] = dataKeyCacheItem{
-		expiry:  time.Now().Add(15 * time.Minute),
+		expiry:  now().Add(dekTTL),
 		dataKey: decrypted,
 	}
 
@@ -311,3 +313,37 @@ func (s *SecretsService) dataKey(ctx context.Context, name string) ([]byte, erro
 func (s *SecretsService) GetProviders() map[string]secrets.Provider {
 	return s.providers
 }
+
+// These variables are used to test the code
+// responsible for periodically cleaning up
+// data encryption keys cache.
+var (
+	now        = time.Now
+	dekTTL     = 15 * time.Minute
+	gcInterval = time.Minute
+)
+
+func (s *SecretsService) Run(ctx context.Context) error {
+	gc := time.NewTicker(gcInterval)
+
+	for {
+		select {
+		case <-gc.C:
+			s.log.Debug("removing expired data encryption keys from cache...")
+			s.removeExpiredItems()
+			s.log.Debug("done removing expired data encryption keys from cache")
+		case <-ctx.Done():
+			s.log.Debug("grafana is shutting down; stopping...")
+			gc.Stop()
+			return nil
+		}
+	}
+}
+
+func (s *SecretsService) removeExpiredItems() {
+	for id, dek := range s.dataKeyCache {
+		if dek.expiry.Before(now()) {
+			delete(s.dataKeyCache, id)
+		}
+	}
+}

pkg/services/secrets/manager/manager_test.go

@@ -3,6 +3,7 @@ package manager
 import (
 	"context"
 	"testing"
+	"time"
 
 	"github.com/grafana/grafana/pkg/infra/usagestats"
 	"github.com/grafana/grafana/pkg/services/encryption/ossencryption"
@@ -11,7 +12,6 @@ import (
 	"github.com/grafana/grafana/pkg/services/secrets/database"
 	"github.com/grafana/grafana/pkg/services/sqlstore"
 	"github.com/grafana/grafana/pkg/setting"
-
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"gopkg.in/ini.v1"
@@ -253,3 +253,63 @@ func (f *fakeKMS) Provide() (map[string]secrets.Provider, error) {
 	providers["fakeProvider.v1"] = f.fake
 	return providers, nil
 }
+
+func TestSecretsService_Run(t *testing.T) {
+	ctx := context.Background()
+	sql := sqlstore.InitTestDB(t)
+	store := database.ProvideSecretsStore(sql)
+	svc := SetupTestService(t, store)
+
+	t.Run("should stop with no error once the context's finished", func(t *testing.T) {
+		ctx, cancel := context.WithTimeout(ctx, time.Millisecond)
+		defer cancel()
+
+		err := svc.Run(ctx)
+		assert.NoError(t, err)
+	})
+
+	t.Run("should trigger cache clean up", func(t *testing.T) {
+		// Encrypt to ensure there's a data encryption key generated
+		_, err := svc.Encrypt(ctx, []byte("grafana"), secrets.WithoutScope())
+		require.NoError(t, err)
+
+		// Data encryption key cache should contain one element
+		require.Len(t, svc.dataKeyCache, 1)
+
+		// Execute background process after key's TTL, to force
+		// clean up process, during a millisecond with gc ticker
+		// configured on every nanosecond, to ensure the ticker
+		// is triggered.
+		gcInterval = time.Nanosecond
+
+		t.Cleanup(func() { now = time.Now })
+		now = func() time.Time { return time.Now().Add(dekTTL) }
+
+		ctx, cancel := context.WithTimeout(ctx, time.Millisecond)
+		defer cancel()
+
+		err = svc.Run(ctx)
+		require.NoError(t, err)
+
+		// Then, once the ticker has been triggered,
+		// the cleanup process should have happened,
+		// therefore the cache should be empty.
+		require.Len(t, svc.dataKeyCache, 0)
+	})
+
+	t.Run("should update data key expiry after every use", func(t *testing.T) {
+		// Encrypt to generate data encryption key
+		withoutScope := secrets.WithoutScope()
+		_, err := svc.Encrypt(ctx, []byte("grafana"), withoutScope)
+		require.NoError(t, err)
+
+		// New call to Encrypt one minute later should update cache entry's expiry
+		t.Cleanup(func() { now = time.Now })
+		now = func() time.Time { return time.Now().Add(time.Minute) }
+		_, err = svc.Encrypt(ctx, []byte("grafana"), withoutScope)
+		require.NoError(t, err)
+
+		dataKeyID := svc.keyName(withoutScope())
+		assert.True(t, svc.dataKeyCache[dataKeyID].expiry.After(time.Now().Add(dekTTL)))
+	})
+}