cmd/litcli: add super macaroon helper commands

In this commit, a `supermacrootkey` helper command is added which lets a
user generate a random root key ID for a super macaroon along with an
`issupermacaroon` command that allows a users to easily confirm if a
macaroon is considered a super macaroon or not. Neither of these
commands require a connection to LiTd.

cmd/litcli/helpers.go

@@ -0,0 +1,125 @@
+package main
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"os"
+
+	"github.com/lightninglabs/lightning-terminal/session"
+	"github.com/urfave/cli"
+)
+
+// helperCommands are commands that do not require a connection to LiTd to
+// return a response.
+var helperCommands = cli.Command{
+	Name:     "helper",
+	Usage:    "helper commands",
+	Category: "Helper",
+	Subcommands: []cli.Command{
+		generateSuperMacRootIDCmd,
+		isSuperMacaroonCmd,
+	},
+}
+
+// generateSuperMacRootIDCmd is a command that can be used to generate a root
+// key ID for a super macaroon. A suffix may be specified.
+var generateSuperMacRootIDCmd = cli.Command{
+	Name: "supermacrootkey",
+	Usage: "Generate a valid super macaroon root key ID from scratch " +
+		"or from a given root key ID suffix",
+	Description: `
+	This command can be used to generate a valid super macaroon root key ID
+	from scratch or from a given root key ID suffix.
+	`,
+	Action: superMacRootKey,
+	Flags: []cli.Flag{
+		cli.StringFlag{
+			Name: "root_key_suffix",
+			Usage: "A 4-byte suffix to use in the construction " +
+				"of the root key ID. If not provided, then a " +
+				"random one will be generated. This must be " +
+				"specified as a hex string using a maximum of " +
+				"8 characters.",
+		},
+	},
+}
+
+// superMacRootKey generates a super macaroon root key ID.
+func superMacRootKey(ctx *cli.Context) error {
+	var suffix [4]byte
+
+	if ctx.IsSet("root_key_suffix") {
+		suffixBytes, err := hex.DecodeString(
+			ctx.String("root_key_suffix"),
+		)
+		if err != nil {
+			return err
+		}
+
+		copy(suffix[:], suffixBytes)
+	} else {
+		_, err := rand.Read(suffix[:])
+		if err != nil {
+			return err
+		}
+	}
+
+	id := session.NewSuperMacaroonRootKeyID(suffix)
+
+	printJSON(struct {
+		RootKeyID uint64 `json:"root_key_id"`
+	}{
+		RootKeyID: id,
+	})
+
+	return nil
+}
+
+// isSuperMacaronoCmd is a command that a user can run in order to check if
+// a macaroon is a super macaroon.
+var isSuperMacaroonCmd = cli.Command{
+	Name:  "issupermacaroon",
+	Usage: "Prints 'true' if the given macaroon is a super macaroon",
+	Description: `
+	This command can be used to verify if a macaroon is considered a 
+	super macaroon.
+	`,
+	Action: isSuperMacaroon,
+	Flags: []cli.Flag{
+		cli.StringFlag{
+			Name:     "mac",
+			Usage:    "The hex-encoded macaroon",
+			Required: true,
+		},
+	},
+}
+
+// isSuperMacaroon checks if the users given macaroon is considered a super
+// macaroon.
+func isSuperMacaroon(ctx *cli.Context) error {
+	isSuperMac := session.IsSuperMacaroon(ctx.String("mac"))
+
+	printJSON(struct {
+		IsSuperMacaroon bool `json:"is_super_macaroon"`
+	}{
+		IsSuperMacaroon: isSuperMac,
+	})
+
+	return nil
+}
+
+// printJSON marshals the given interface as a json byte slice, formats it to
+// use easy to read indentation and writes it as a string to standard out.
+func printJSON(resp interface{}) {
+	b, err := json.Marshal(resp)
+	if err != nil {
+		fatal(err)
+	}
+
+	var out bytes.Buffer
+	json.Indent(&out, b, "", "\t")
+	out.WriteString("\n")
+	out.WriteTo(os.Stdout)
+}

cmd/litcli/main.go

@@ -76,6 +76,7 @@ func main() {
 	app.Commands = append(app.Commands, privacyMapCommands)
 	app.Commands = append(app.Commands, autopilotCommands)
 	app.Commands = append(app.Commands, litCommands...)
+	app.Commands = append(app.Commands, helperCommands)
 
 	err := app.Run(os.Args)
 	if err != nil {