neofs: Sign multipart objects in the gate

Closes #975.

Signed-off-by: Evgenii Baidakov <[email protected]>

internal/neofs/neofs.go

@@ -26,6 +26,7 @@ import (
 	"github.com/nspcc-dev/neofs-sdk-go/container"
 	"github.com/nspcc-dev/neofs-sdk-go/container/acl"
 	cid "github.com/nspcc-dev/neofs-sdk-go/container/id"
+	neofscrypto "github.com/nspcc-dev/neofs-sdk-go/crypto"
 	"github.com/nspcc-dev/neofs-sdk-go/eacl"
 	"github.com/nspcc-dev/neofs-sdk-go/object"
 	oid "github.com/nspcc-dev/neofs-sdk-go/object/id"
@@ -246,6 +247,37 @@ func (x *NeoFS) DeleteContainer(ctx context.Context, id cid.ID, token *session.C
 	return nil
 }
 
+func (x *NeoFS) signMultipartObject(header *object.Object, signer neofscrypto.Signer) error {
+	var (
+		payloadChecksum = sha256.New()
+		sig             neofscrypto.Signature
+	)
+
+	payloadChecksum.Write(header.Payload())
+	header.SetPayloadChecksum(checksum.NewFromHash(checksum.SHA256, payloadChecksum))
+
+	if x.IsHomomorphicHashingEnabled() {
+		var homoChecksum = tz.New()
+
+		homoChecksum.Write(header.Payload())
+		header.SetPayloadHomomorphicHash(checksum.NewFromHash(checksum.TillichZemor, homoChecksum))
+	}
+
+	id, err := header.CalculateID()
+	if err != nil {
+		return fmt.Errorf("calculate ID: %w", err)
+	}
+	header.SetID(id)
+
+	if err = sig.Calculate(signer, id.Marshal()); err != nil {
+		return fmt.Errorf("sign object ID: %w", err)
+	}
+
+	header.SetSignature(&sig)
+
+	return nil
+}
+
 // CreateObject implements neofs.NeoFS interface method.
 func (x *NeoFS) CreateObject(ctx context.Context, prm layer.PrmObjectCreate) (oid.ID, error) {
 	attrNum := len(prm.Attributes) + 1 // + creation time
@@ -310,6 +342,10 @@ func (x *NeoFS) CreateObject(ctx context.Context, prm layer.PrmObjectCreate) (oi
 			prm.Payload = bytes.NewReader(obj.Payload())
 			obj.SetPayloadSize(uint64(len(obj.Payload())))
 
+			if err := x.signMultipartObject(&obj, x.signer(ctx)); err != nil {
+				return oid.ID{}, errors.New("object sign failed")
+			}
+
 			// Link object should never have a previous one.
 			obj.ResetPreviousID()
 		}