cmd/fscrypt: add metadata command

This command adds in the "fscrypt metadata" command. This command allows
advanced users to manipulate the metadata directly instead of just
creating a policy or protector as an option when encrypting a directory.

As some of these methods will require certain flags, error handling for
this case is also added. As the change passphrase method must indicate
when a old vs new password is necessary, additional KeyFuncs are added
which add this indicator.

Change-Id: Ibc92872088fae078df3c0eebd4f0cfcb7252d781

1 files changed, 12 insertions, 0 deletions

diff --git a/cmd/fscrypt/errors.go b/cmd/fscrypt/errors.go
index aa2f2ab..272160a 100644
--- a/cmd/fscrypt/errors.go
+++ b/cmd/fscrypt/errors.go
@@ -186,3 +186,15 @@ func expectedArgsErr(c *cli.Context, expectedArgs int, atMost bool) error {
 func onUsageError(c *cli.Context, err error, _ bool) error {
 	return &usageError{c, err.Error()}
 }
+
+// checkRequiredFlags makes sure that all of the specified string flags have
+// been given nonempty values. Returns a usage error on failure.
+func checkRequiredFlags(c *cli.Context, flags []*stringFlag) error {
+	for _, flag := range flags {
+		if flag.Value == "" {
+			message := fmt.Sprintf("required flag %s not provided", shortDisplay(flag))
+			return &usageError{c, message}
+		}
+	}
+	return nil
+}