Support priv/unpriv image extraction

Optionally add back privileged extraction which can be enabled with
LUET_PRIVILEGED_EXTRACT=true

Signed-off-by: Ettore Di Giacinto <mudler@sabayon.org>

vendor/github.com/moby/buildkit/session/testutil/testutil.go

@@ -0,0 +1,70 @@
+package testutil
+
+import (
+	"context"
+	"io"
+	"net"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+// Handler is function called to handle incoming connection
+type Handler func(ctx context.Context, conn net.Conn, meta map[string][]string) error
+
+// Dialer is a function for dialing an outgoing connection
+type Dialer func(ctx context.Context, proto string, meta map[string][]string) (net.Conn, error)
+
+// TestStream creates an in memory session dialer for a handler function
+func TestStream(handler Handler) Dialer {
+	s1, s2 := sockPair()
+	return func(ctx context.Context, proto string, meta map[string][]string) (net.Conn, error) {
+		go func() {
+			err := handler(context.TODO(), s1, meta)
+			if err != nil {
+				logrus.Error(err)
+			}
+			s1.Close()
+		}()
+		return s2, nil
+	}
+}
+
+func sockPair() (*sock, *sock) {
+	pr1, pw1 := io.Pipe()
+	pr2, pw2 := io.Pipe()
+	return &sock{pw1, pr2, pw1}, &sock{pw2, pr1, pw2}
+}
+
+type sock struct {
+	io.Writer
+	io.Reader
+	io.Closer
+}
+
+func (s *sock) LocalAddr() net.Addr {
+	return dummyAddr{}
+}
+func (s *sock) RemoteAddr() net.Addr {
+	return dummyAddr{}
+}
+func (s *sock) SetDeadline(t time.Time) error {
+	return nil
+}
+func (s *sock) SetReadDeadline(t time.Time) error {
+	return nil
+}
+func (s *sock) SetWriteDeadline(t time.Time) error {
+	return nil
+}
+
+type dummyAddr struct {
+}
+
+func (d dummyAddr) Network() string {
+	return "tcp"
+}
+
+func (d dummyAddr) String() string {
+	return "localhost"
+}