refactor: move ErrorWrapperTLSHandshaker to errorsx (#418)

Part of https://github.com/ooni/probe/issues/1505

internal/errorsx/tls.go

@@ -0,0 +1,31 @@
+package errorsx
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+)
+
+// TLSHandshaker is the generic TLS handshaker
+type TLSHandshaker interface {
+	Handshake(ctx context.Context, conn net.Conn, config *tls.Config) (
+		net.Conn, tls.ConnectionState, error)
+}
+
+// ErrorWrapperTLSHandshaker wraps the returned error to be an OONI error
+type ErrorWrapperTLSHandshaker struct {
+	TLSHandshaker
+}
+
+// Handshake implements TLSHandshaker.Handshake
+func (h *ErrorWrapperTLSHandshaker) Handshake(
+	ctx context.Context, conn net.Conn, config *tls.Config,
+) (net.Conn, tls.ConnectionState, error) {
+	tlsconn, state, err := h.TLSHandshaker.Handshake(ctx, conn, config)
+	err = SafeErrWrapperBuilder{
+		Classifier: ClassifyTLSFailure,
+		Error:      err,
+		Operation:  TLSHandshakeOperation,
+	}.MaybeBuild()
+	return tlsconn, state, err
+}

internal/errorsx/tls_test.go

@@ -0,0 +1,42 @@
+package errorsx
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"io"
+	"net"
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/netxmocks"
+)
+
+func TestErrorWrapperTLSHandshakerFailure(t *testing.T) {
+	th := ErrorWrapperTLSHandshaker{TLSHandshaker: &netxmocks.TLSHandshaker{
+		MockHandshake: func(ctx context.Context, conn net.Conn, config *tls.Config) (net.Conn, tls.ConnectionState, error) {
+			return nil, tls.ConnectionState{}, io.EOF
+		},
+	}}
+	conn, _, err := th.Handshake(
+		context.Background(), &netxmocks.Conn{
+			MockRead: func(b []byte) (int, error) {
+				return 0, io.EOF
+			},
+		}, new(tls.Config))
+	if !errors.Is(err, io.EOF) {
+		t.Fatal("not the error that we expected")
+	}
+	if conn != nil {
+		t.Fatal("expected nil con here")
+	}
+	var errWrapper *ErrWrapper
+	if !errors.As(err, &errWrapper) {
+		t.Fatal("cannot cast to ErrWrapper")
+	}
+	if errWrapper.Failure != FailureEOFError {
+		t.Fatal("unexpected Failure")
+	}
+	if errWrapper.Operation != TLSHandshakeOperation {
+		t.Fatal("unexpected Operation")
+	}
+}