util: use the KMS as DEKStore if it supports it

Signed-off-by: Niels de Vos <ndevos@redhat.com>

internal/util/crypto.go

@@ -66,15 +66,41 @@ var (
 
 type VolumeEncryption struct {
 	KMS EncryptionKMS
+
+	// dekStore that will be used, this can be the EncryptionKMS or a
+	// different object implementing the DEKStore interface.
+	dekStore DEKStore
 }
 
-// NewVolumeEncryption creates a new instance of VolumeEncryption.
+// NewVolumeEncryption creates a new instance of VolumeEncryption and
+// configures the DEKStore. If the KMS does not provide a DEKStore interface,
+// the VolumeEncryption will be created *and* a ErrDEKStoreNeeded is returned.
+// Callers that receive a ErrDEKStoreNeeded error, should use
+// VolumeEncryption.SetDEKStore() to configure an alternative storage for the
+// DEKs.
 func NewVolumeEncryption(kms EncryptionKMS) (*VolumeEncryption, error) {
 	ve := &VolumeEncryption{KMS: kms}
 
+	if kms.requiresDEKStore() == DEKStoreIntegrated {
+		dekStore, ok := kms.(DEKStore)
+		if !ok {
+			return nil, fmt.Errorf("KMS %T does not implement the "+
+				"DEKStore interface", kms)
+		}
+
+		ve.dekStore = dekStore
 		return ve, nil
 	}
 
+	return ve, ErrDEKStoreNeeded
+}
+
+// SetDEKStore sets the DEKStore for this VolumeEncryption instance. It will be
+// used when StoreNewCryptoPassphrase() or RemoveDEK() is called.
+func (ve *VolumeEncryption) SetDEKStore(dekStore DEKStore) {
+	ve.dekStore = dekStore
+}
+
 // Destroy frees any resources that the VolumeEncryption instance allocated.
 func (ve *VolumeEncryption) Destroy() {
 	ve.KMS.Destroy()

internal/util/secretskms.go

@@ -30,6 +30,8 @@ const (
 
 // SecretsKMS is default KMS implementation that means no KMS is in use.
 type SecretsKMS struct {
+	integratedDEK
+
 	passphrase string
 }
 

internal/util/vault.go

@@ -79,6 +79,7 @@ type vaultConnection struct {
 
 type VaultKMS struct {
 	vaultConnection
+	integratedDEK
 
 	// vaultPassphrasePath (VPP) used to be added before the "key" of the
 	// secret (like /v1/secret/data/<VPP>/key)

internal/util/vault_tokens.go

@@ -161,6 +161,7 @@ Example JSON structure in the KMS config is,
 */
 type VaultTokensKMS struct {
 	vaultConnection
+	integratedDEK
 
 	// Tenant is the name of the owner of the volume
 	Tenant string