service: implement a function for signing data

service/sign_test.go

@@ -0,0 +1,112 @@
+package service
+
+import (
+	"crypto/rand"
+	"errors"
+	"io"
+	"testing"
+
+	crypto "github.com/nspcc-dev/neofs-crypto"
+	"github.com/nspcc-dev/neofs-crypto/test"
+	"github.com/stretchr/testify/require"
+)
+
+type testSignedDataSrc struct {
+	e error
+	d []byte
+}
+
+type testSignedDataReader struct {
+	SignedDataSource
+
+	e error
+	d []byte
+}
+
+func testData(t *testing.T, sz int) []byte {
+	d := make([]byte, sz)
+	_, err := rand.Read(d)
+	require.NoError(t, err)
+	return d
+}
+
+func (s testSignedDataReader) SignedDataSize() int {
+	return len(s.d)
+}
+
+func (s testSignedDataReader) ReadSignedData(buf []byte) (int, error) {
+	if s.e != nil {
+		return 0, s.e
+	}
+
+	var err error
+	if len(buf) < len(s.d) {
+		err = io.ErrUnexpectedEOF
+	}
+	return copy(buf, s.d), err
+}
+
+func (s testSignedDataSrc) SignedData() ([]byte, error) {
+	return s.d, s.e
+}
+
+func TestDataSignature(t *testing.T) {
+	var err error
+
+	// nil data source
+	_, err = DataSignature(nil, nil)
+	require.EqualError(t, err, ErrNilSignedDataSource.Error())
+
+	// nil private key
+	_, err = DataSignature(new(testSignedDataSrc), nil)
+	require.EqualError(t, err, crypto.ErrEmptyPrivateKey.Error())
+
+	// create test private key
+	sk := test.DecodeKey(0)
+
+	t.Run("common signed data source", func(t *testing.T) {
+		// create test data source
+		src := &testSignedDataSrc{
+			d: testData(t, 10),
+		}
+
+		// create custom error for data source
+		src.e = errors.New("test error for data source")
+
+		_, err = DataSignature(src, sk)
+		require.EqualError(t, err, src.e.Error())
+
+		// reset error to nil
+		src.e = nil
+
+		// calculate data signature
+		sig, err := DataSignature(src, sk)
+		require.NoError(t, err)
+
+		// ascertain that the signature passes verification
+		require.NoError(t, crypto.Verify(&sk.PublicKey, src.d, sig))
+	})
+
+	t.Run("signed data reader", func(t *testing.T) {
+		// create test signed data reader
+		src := &testSignedDataReader{
+			d: testData(t, 10),
+		}
+
+		// create custom error for signed data reader
+		src.e = errors.New("test error for signed data reader")
+
+		sig, err := DataSignature(src, sk)
+		require.EqualError(t, err, src.e.Error())
+
+		// reset error to nil
+		src.e = nil
+
+		// calculate data signature
+		sig, err = DataSignature(src, sk)
+		require.NoError(t, err)
+
+		// ascertain that the signature passes verification
+		require.NoError(t, crypto.Verify(&sk.PublicKey, src.d, sig))
+	})
+}