Add aTLS endpoint to KMS (#236)

* Move file watcher and validator to internal

* Add aTLS endpoint to KMS for Kubernetes external requests

* Update Go version in Dockerfiles

* Move most KMS packages to internal

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

kms/internal/storage/memfsstorage.go

@@ -0,0 +1,32 @@
+package storage
+
+import "context"
+
+// MemMapStorage is the standard implementation of the Storage interface, storing keys in memory only.
+type MemMapStorage struct {
+	dekPool map[string][]byte
+}
+
+// NewMemMapStorage creates and initialises a new MemMapStorage object.
+func NewMemMapStorage() *MemMapStorage {
+	s := &MemMapStorage{
+		dekPool: make(map[string][]byte),
+	}
+
+	return s
+}
+
+// Get returns a DEK from MemMapStorage by key ID.
+func (s *MemMapStorage) Get(ctx context.Context, keyID string) ([]byte, error) {
+	encDEK, ok := s.dekPool[keyID]
+	if ok {
+		return encDEK, nil
+	}
+	return nil, ErrDEKUnset
+}
+
+// Put saves a DEK to MemMapStorage by key ID.
+func (s *MemMapStorage) Put(ctx context.Context, keyID string, encDEK []byte) error {
+	s.dekPool[keyID] = encDEK
+	return nil
+}