pkg/chrootarchive: Skip privileged tests when non-root

These tests fail when run by a non-root user

  === RUN   TestUntarWithMaliciousSymlinks
      archive_unix_test.go:63: assertion failed: expected error to contain "open /safe/host-file: no such file or directory", got "Error processing tar file(exit status 1): Error creating mount namespace before pivot: operation not permitted"
  --- FAIL: TestUntarWithMaliciousSymlinks (0.00s)
  === RUN   TestTarWithMaliciousSymlinks
      archive_unix_test.go:90: /tmp/TestTarWithMaliciousSymlinks400408188
  === RUN   TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe_host-file
      archive_unix_test.go:155: assertion failed: error is not nil: error processing tar file: Error after fallback to chroot: operation not permitted: exit status 1
  === RUN   TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe/_host-file
      archive_unix_test.go:155: assertion failed: error is not nil: error processing tar file: Error after fallback to chroot: operation not permitted: exit status 1
  === RUN   TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe_
      archive_unix_test.go:155: assertion failed: error is not nil: error processing tar file: Error after fallback to chroot: operation not permitted: exit status 1
  === RUN   TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe/_
      archive_unix_test.go:155: assertion failed: error is not nil: error processing tar file: Error after fallback to chroot: operation not permitted: exit status 1
  === RUN   TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root_safe/host-file
      archive_unix_test.go:155: assertion failed: error is not nil: error processing tar file: Error after fallback to chroot: operation not permitted: exit status 1
  === RUN   TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root_/safe/host-file
      archive_unix_test.go:155: assertion failed: error is not nil: error processing tar file: Error after fallback to chroot: operation not permitted: exit status 1
  === RUN   TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root_
      archive_unix_test.go:155: assertion failed: error is not nil: error processing tar file: Error after fallback to chroot: operation not permitted: exit status 1
  --- FAIL: TestTarWithMaliciousSymlinks (0.02s)
      --- FAIL: TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe_host-file (0.00s)
      --- FAIL: TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe/_host-file (0.00s)
      --- FAIL: TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe_ (0.00s)
      --- FAIL: TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root/safe/_ (0.00s)
      --- FAIL: TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root_safe/host-file (0.00s)
      --- FAIL: TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root_/safe/host-file (0.00s)
      --- FAIL: TestTarWithMaliciousSymlinks//tmp/TestTarWithMaliciousSymlinks400408188/root_ (0.00s)
  FAIL
  FAIL	github.com/docker/docker/pkg/chrootarchive	0.042s

Signed-off-by: Arnaud Rebillout <elboulangero@gmail.com>

pkg/chrootarchive/archive_unix_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/docker/docker/pkg/archive"
 	"golang.org/x/sys/unix"
 	"gotest.tools/v3/assert"
+	"gotest.tools/v3/skip"
 )
 
 // Test for CVE-2018-15664
@@ -23,6 +24,7 @@ import (
 // some path outside of a container's rootfs that we do not copy data to a
 // container path that will actually overwrite data on the host
 func TestUntarWithMaliciousSymlinks(t *testing.T) {
+	skip.If(t, os.Getuid() != 0, "skipping test that requires root")
 	dir, err := ioutil.TempDir("", t.Name())
 	assert.NilError(t, err)
 	defer os.RemoveAll(dir)
@@ -84,6 +86,7 @@ func TestUntarWithMaliciousSymlinks(t *testing.T) {
 // some path outside of a container's rootfs that we do not unwittingly leak
 // host data into the archive.
 func TestTarWithMaliciousSymlinks(t *testing.T) {
+	skip.If(t, os.Getuid() != 0, "skipping test that requires root")
 	dir, err := ioutil.TempDir("", t.Name())
 	assert.NilError(t, err)
 	// defer os.RemoveAll(dir)