[#1255] node/session: Add persistent session storage

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

pkg/services/session/storage/persistent/util.go

@@ -0,0 +1,59 @@
+package persistent
+
+import (
+	"crypto/ecdsa"
+	"crypto/x509"
+	"encoding/binary"
+	"fmt"
+
+	"github.com/nspcc-dev/neofs-node/pkg/services/session/storage"
+	"go.etcd.io/bbolt"
+)
+
+const expOffset = 8
+
+func packToken(exp uint64, key *ecdsa.PrivateKey) ([]byte, error) {
+	rawKey, err := x509.MarshalECPrivateKey(key)
+	if err != nil {
+		return nil, fmt.Errorf("could not marshal private key: %w", err)
+	}
+
+	res := make([]byte, expOffset, expOffset+len(rawKey))
+	binary.LittleEndian.PutUint64(res, exp)
+
+	res = append(res, rawKey...)
+
+	return res, nil
+}
+
+func unpackToken(raw []byte) (*storage.PrivateToken, error) {
+	epoch := binary.LittleEndian.Uint64(raw[:expOffset])
+
+	key, err := x509.ParseECPrivateKey(raw[expOffset:])
+	if err != nil {
+		return nil, fmt.Errorf("could not unmarshal private key: %w", err)
+	}
+
+	return storage.NewPrivateToken(key, epoch), nil
+}
+
+func epochFromToken(rawToken []byte) uint64 {
+	return binary.LittleEndian.Uint64(rawToken)
+}
+
+func iterateNestedBuckets(b *bbolt.Bucket, fn func(b *bbolt.Bucket) error) error {
+	c := b.Cursor()
+
+	for k, v := c.First(); k != nil; k, v = c.Next() {
+		// nil value is a hallmark
+		// of the nested buckets
+		if v == nil {
+			err := fn(b.Bucket(k))
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}