[#1216] neofs-cli: Reuse key retrieving code between modules

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

cmd/neofs-cli/internal/key/raw.go

@@ -0,0 +1,54 @@
+package key
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+	"os"
+
+	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+)
+
+// Get returns private key from the followind sources:
+// 1. WIF
+// 2. Raw binary key
+// 3. Wallet file
+// 4. NEP-2 encrypted WIF.
+// Ideally we want to touch file-system on the last step.
+// However, asking for NEP-2 password seems to be confusing if we provide a wallet.
+func Get(keyDesc string, address string) (*ecdsa.PrivateKey, error) {
+	priv, err := keys.NewPrivateKeyFromWIF(keyDesc)
+	if err == nil {
+		return &priv.PrivateKey, nil
+	}
+
+	p, err := getKeyFromFile(keyDesc)
+	if err == nil {
+		return p, nil
+	}
+
+	w, err := wallet.NewWalletFromFile(keyDesc)
+	if err == nil {
+		return FromWallet(w, address)
+	}
+
+	if len(keyDesc) == nep2Base58Length {
+		return FromNEP2(keyDesc)
+	}
+
+	return nil, ErrInvalidKey
+}
+
+func getKeyFromFile(keyPath string) (*ecdsa.PrivateKey, error) {
+	data, err := os.ReadFile(keyPath)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrInvalidKey, err)
+	}
+
+	priv, err := keys.NewPrivateKeyFromBytes(data)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrInvalidKey, err)
+	}
+
+	return &priv.PrivateKey, nil
+}