cmd/fscrypt: Add --user flag for running as root

The --user flag can now be used to have the targe user (the one whose
keyring and password will be used in fscrypt) be different than the
calling user. Very usefull for things like

	sudo fscrypt purge /media/joerichey/usb --user=joerichey

which will now have privileges to drop caches, but will properly clear
the keys from the user's keyring.

1 files changed, 3 insertions, 2 deletions

diff --git a/cmd/fscrypt/setup.go b/cmd/fscrypt/setup.go
index 6433b0c..72dfbdb 100644
--- a/cmd/fscrypt/setup.go
+++ b/cmd/fscrypt/setup.go
@@ -26,11 +26,12 @@ import (
 	"os"
 
 	"github.com/google/fscrypt/actions"
+	"github.com/google/fscrypt/util"
 )
 
 // createGlobalConfig creates (or overwrites) the global config file
 func createGlobalConfig(w io.Writer, path string) error {
-	if os.Getuid() != 0 {
+	if !util.IsUserRoot() {
 		return ErrMustBeRoot
 	}
 
@@ -61,7 +62,7 @@ func createGlobalConfig(w io.Writer, path string) error {
 
 // setupFilesystem creates the directories for a filesystem to use fscrypt.
 func setupFilesystem(w io.Writer, path string) error {
-	ctx, err := actions.NewContextFromMountpoint(path)
+	ctx, err := actions.NewContextFromMountpoint(path, nil)
 	if err != nil {
 		return err
 	}