[#1092] control: Move SignMessage to separate package

Signed-off-by: Alexander Chuprov <a.chuprov@yadro.com>

pkg/services/control/server/ctrlmessage/sign.go

@@ -0,0 +1,44 @@
+package ctrlmessage
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-api-go/v2/refs"
+	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/services/control"
+	frostfscrypto "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/crypto"
+	frostfsecdsa "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/crypto/ecdsa"
+)
+
+type SignedMessage interface {
+	ReadSignedData([]byte) ([]byte, error)
+	GetSignature() *control.Signature
+	SetSignature(*control.Signature)
+}
+
+// Sign signs Control service ctrlmessage with private key.
+func Sign(key *ecdsa.PrivateKey, msg SignedMessage) error {
+	binBody, err := msg.ReadSignedData(nil)
+	if err != nil {
+		return fmt.Errorf("marshal request body: %w", err)
+	}
+
+	var sig frostfscrypto.Signature
+
+	err = sig.Calculate(frostfsecdsa.Signer(*key), binBody)
+	if err != nil {
+		return fmt.Errorf("calculate signature: %w", err)
+	}
+
+	// TODO(@cthulhu-rider): #468 use Signature ctrlmessage from FrostFS API to avoid conversion
+	var sigV2 refs.Signature
+	sig.WriteToV2(&sigV2)
+
+	var sigControl control.Signature
+	sigControl.SetKey(sigV2.GetKey())
+	sigControl.SetSign(sigV2.GetSign())
+
+	msg.SetSignature(&sigControl)
+
+	return nil
+}