[#207] sdk/client: Implement GetEACLWithSignature method

GetEACL method of Client receives eACL table with signature, verifies the
signature and return the table. In some cases we need to receive table and
signature regardless of their correctness. New method GetEACLWithSignature
provides such an opportunity.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/client/container.go

@@ -3,6 +3,7 @@ package client
 import (
 	"context"
 
+	"github.com/nspcc-dev/neofs-api-go/pkg"
 	"github.com/nspcc-dev/neofs-api-go/pkg/acl/eacl"
 	"github.com/nspcc-dev/neofs-api-go/pkg/container"
 	"github.com/nspcc-dev/neofs-api-go/pkg/owner"
@@ -18,6 +19,13 @@ type delContainerSignWrapper struct {
 	body *v2container.DeleteRequestBody
 }
 
+// EACLWithSignature represents eACL table/signature pair.
+type EACLWithSignature struct {
+	table *eacl.Table
+
+	sig *pkg.Signature
+}
+
 var errNilReponseBody = errors.New("response body is nil")
 
 func (c delContainerSignWrapper) ReadSignedData(bytes []byte) ([]byte, error) {
@@ -28,6 +36,16 @@ func (c delContainerSignWrapper) SignedDataSize() int {
 	return len(c.body.GetContainerID().GetValue())
 }
 
+// EACL returns eACL table.
+func (e EACLWithSignature) EACL() *eacl.Table {
+	return e.table
+}
+
+// Signature returns table signature.
+func (e EACLWithSignature) Signature() *pkg.Signature {
+	return e.sig
+}
+
 func (c Client) PutContainer(ctx context.Context, cnr *container.Container, opts ...CallOption) (*container.ID, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
@@ -77,9 +95,30 @@ func (c Client) DeleteContainer(ctx context.Context, id *container.ID, opts ...C
 }
 
 func (c Client) GetEACL(ctx context.Context, id *container.ID, opts ...CallOption) (*eacl.Table, error) {
+	v, err := c.getEACL(ctx, id, true, opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	return v.table, nil
+}
+
+func (c Client) GetEACLWithSignature(ctx context.Context, id *container.ID, opts ...CallOption) (*EACLWithSignature, error) {
+	return c.getEACL(ctx, id, false, opts...)
+}
+
+func (c Client) getEACL(ctx context.Context, id *container.ID, verify bool, opts ...CallOption) (*EACLWithSignature, error) {
 	switch c.remoteNode.Version.Major() {
 	case 2:
-		return c.getEACLV2(ctx, id, opts...)
+		resp, err := c.getEACLV2(ctx, id, verify, opts...)
+		if err != nil {
+			return nil, err
+		}
+
+		return &EACLWithSignature{
+			table: eacl.NewTableFromV2(resp.GetEACL()),
+			sig:   pkg.NewSignatureFromV2(resp.GetSignature()),
+		}, nil
 	default:
 		return nil, errUnsupportedProtocol
 	}
@@ -316,7 +355,7 @@ func (c Client) delContainerV2(ctx context.Context, id *container.ID, opts ...Ca
 	}
 }
 
-func (c Client) getEACLV2(ctx context.Context, id *container.ID, opts ...CallOption) (*eacl.Table, error) {
+func (c Client) getEACLV2(ctx context.Context, id *container.ID, verify bool, opts ...CallOption) (*v2container.GetExtendedACLResponseBody, error) {
 	// apply all available options
 	callOptions := c.defaultCallOptions()
 
@@ -358,23 +397,23 @@ func (c Client) getEACLV2(ctx context.Context, id *container.ID, opts ...CallOpt
 			return nil, errNilReponseBody
 		}
 
-		if err := signature.VerifyDataWithSource(
+		if verify {
-			v2signature.StableMarshalerWrapper{
+			if err := signature.VerifyDataWithSource(
-				SM: body.GetEACL(),
+				v2signature.StableMarshalerWrapper{
-			},
+					SM: body.GetEACL(),
-			func() (key, sig []byte) {
+				},
-				s := body.GetSignature()
+				func() (key, sig []byte) {
+					s := body.GetSignature()
 
-				return s.GetKey(), s.GetSign()
+					return s.GetKey(), s.GetSign()
-			},
+				},
-			signature.SignWithRFC6979(),
+				signature.SignWithRFC6979(),
-		); err != nil {
+			); err != nil {
-			return nil, errors.Wrap(err, "incorrect signature")
+				return nil, errors.Wrap(err, "incorrect signature")
+			}
 		}
 
-		result := eacl.NewTableFromV2(body.GetEACL())
+		return body, nil
-
-		return result, nil
 	default:
 		return nil, errUnsupportedProtocol
 	}