[#19] Add a version with no cdn-sdk deps

Signed-off-by: Pavel Korotkov <pavel@nspcc.ru>

neofs/credentials.go

@@ -0,0 +1,67 @@
+package neofs
+
+import (
+	"crypto/ecdsa"
+
+	"github.com/nspcc-dev/neofs-api-go/pkg/owner"
+	crypto "github.com/nspcc-dev/neofs-crypto"
+)
+
+type (
+	// Credentials contains methods that needed to work with NeoFS.
+	Credentials interface {
+		WIF() string
+		Owner() *owner.ID
+		PublicKey() *ecdsa.PublicKey
+		PrivateKey() *ecdsa.PrivateKey
+	}
+
+	cred struct {
+		key   *ecdsa.PrivateKey
+		owner *owner.ID
+		wif   string
+	}
+)
+
+// New creates an instance of Credentials through string representation of secret.
+//     It allows passing WIF, path, hex-encoded and others.
+func NewCredentials(secret string) (Credentials, error) {
+	key, err := crypto.LoadPrivateKey(secret)
+	if err != nil {
+		return nil, err
+	}
+	return setFromPrivateKey(key)
+}
+
+// PrivateKey returns ecdsa.PrivateKey.
+func (c *cred) PrivateKey() *ecdsa.PrivateKey {
+	return c.key
+}
+
+// PublicKey returns ecdsa.PublicKey.
+func (c *cred) PublicKey() *ecdsa.PublicKey {
+	return &c.key.PublicKey
+}
+
+// Owner returns owner.ID.
+func (c *cred) Owner() *owner.ID {
+	return c.owner
+}
+
+// WIF returns string representation of WIF.
+func (c *cred) WIF() string {
+	return c.wif
+}
+
+func setFromPrivateKey(key *ecdsa.PrivateKey) (*cred, error) {
+	wallet, err := owner.NEO3WalletFromPublicKey(&key.PublicKey)
+	if err != nil {
+		return nil, err
+	}
+	ownerID := owner.NewIDFromNeo3Wallet(wallet)
+	wif, err := crypto.WIFEncode(key)
+	if err != nil {
+		return nil, err
+	}
+	return &cred{key: key, owner: ownerID, wif: wif}, nil
+}