License Key Registration with ECDSA JWT Tokens

* New command-line tool: doodle-admin for signing license keys for
  users. Includes functions to initialize a keypair, sign license keys
  and validate existing keys.
* The Main Menu screen shows a blue "Register Game" button in the bottom
  right corner of the screen, for unregistered users only.
* In Edit Mode, there is a "Help -> Register" menu item that opens the
  License Window.
* The License UI Window lets the user select the license.key file to
  register the game with. If registered, a copy of the key is placed in
  Doodle's profile directory and the licensee name/email is shown in the
  License UI window.
* Unregistered games will show the word "(shareware)" next to the title
  screen version number and Edit Mode status bar.
* No restrictions are yet placed on free versions of the game.

cmd/doodad/main.go

@@ -9,8 +9,8 @@ import (
 	"time"
 
 	"git.kirsle.net/apps/doodle/cmd/doodad/commands"
-	"git.kirsle.net/apps/doodle/pkg/balance"
 	"git.kirsle.net/apps/doodle/pkg/branding"
+	"git.kirsle.net/apps/doodle/pkg/license"
 	"github.com/urfave/cli/v2"
 )
 
@@ -32,7 +32,7 @@ func main() {
 	app.Usage = "command line interface for Doodle"
 
 	var freeLabel string
-	if balance.FreeVersion {
+	if !license.IsRegistered() {
 		freeLabel = " (shareware)"
 	}
 

cmd/doodle-admin/command/key.go

@@ -0,0 +1,44 @@
+package command
+
+import (
+	"git.kirsle.net/apps/doodle/pkg/license"
+	"git.kirsle.net/apps/doodle/pkg/log"
+	"github.com/urfave/cli/v2"
+)
+
+// Key a license key for Sketchy Maze.
+var Key *cli.Command
+
+func init() {
+	Key = &cli.Command{
+		Name:  "key",
+		Usage: "generate an admin ECDSA signing key",
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:     "public",
+				Usage:    "Filename to write the public key to (.pem)",
+				Required: true,
+			},
+			&cli.StringFlag{
+				Name:     "private",
+				Usage:    "Filename to write the private key to (.pem)",
+				Required: true,
+			},
+		},
+		Action: func(c *cli.Context) error {
+			key, err := license.AdminGenerateKeys()
+			if err != nil {
+				return cli.Exit(err.Error(), 1)
+			}
+
+			err = license.AdminWriteKeys(key, c.String("private"), c.String("public"))
+			if err != nil {
+				return cli.Exit(err.Error(), 1)
+			}
+
+			log.Info("Written private key: %s", c.String("private"))
+			log.Info("Written public key: %s", c.String("public"))
+			return nil
+		},
+	}
+}

cmd/doodle-admin/command/sign.go

@@ -0,0 +1,73 @@
+package command
+
+import (
+	"fmt"
+	"io/ioutil"
+
+	"git.kirsle.net/apps/doodle/pkg/license"
+	"git.kirsle.net/apps/doodle/pkg/log"
+	"github.com/urfave/cli/v2"
+)
+
+// Sign a license key for Sketchy Maze.
+var Sign *cli.Command
+
+func init() {
+	Sign = &cli.Command{
+		Name:  "sign",
+		Usage: "sign a license key for the paid version of Sketchy Maze.",
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:     "key",
+				Aliases:  []string{"k"},
+				Usage:    "Private key .pem file for signing",
+				Required: true,
+			},
+			&cli.StringFlag{
+				Name:     "name",
+				Aliases:  []string{"n"},
+				Usage:    "User name for certificate",
+				Required: true,
+			},
+			&cli.StringFlag{
+				Name:     "email",
+				Aliases:  []string{"e"},
+				Usage:    "User email address",
+				Required: true,
+			},
+			&cli.StringFlag{
+				Name:    "output",
+				Aliases: []string{"o"},
+				Usage:   "Output file, default outputs to console",
+			},
+		},
+		Action: func(c *cli.Context) error {
+			key, err := license.AdminLoadPrivateKey(c.String("key"))
+			if err != nil {
+				return cli.Exit(err.Error(), 1)
+			}
+
+			reg := license.Registration{
+				Name:  c.String("name"),
+				Email: c.String("email"),
+			}
+
+			result, err := license.AdminSignRegistration(key, reg)
+			if err != nil {
+				return cli.Exit(err.Error(), 1)
+			}
+
+			// Writing to an output file?
+			if output := c.String("output"); output != "" {
+				log.Info("Write to: %s", output)
+				if err := ioutil.WriteFile(output, []byte(result), 0644); err != nil {
+					return cli.Exit(err, 1)
+				}
+			} else {
+				fmt.Println(result)
+			}
+
+			return nil
+		},
+	}
+}

cmd/doodle-admin/command/verify.go

@@ -0,0 +1,59 @@
+package command
+
+import (
+	"io/ioutil"
+	"time"
+
+	"git.kirsle.net/apps/doodle/pkg/license"
+	"git.kirsle.net/apps/doodle/pkg/log"
+	"github.com/urfave/cli/v2"
+)
+
+// Verify a license key for Sketchy Maze.
+var Verify *cli.Command
+
+func init() {
+	Verify = &cli.Command{
+		Name:  "verify",
+		Usage: "check the signature on a license key",
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:     "key",
+				Aliases:  []string{"k"},
+				Usage:    "Public key .pem file that signed the JWT",
+				Required: true,
+			},
+			&cli.StringFlag{
+				Name:     "filename",
+				Aliases:  []string{"f"},
+				Usage:    "File name of the license file to validate",
+				Required: true,
+			},
+		},
+		Action: func(c *cli.Context) error {
+			key, err := license.AdminLoadPublicKey(c.String("key"))
+			if err != nil {
+				return cli.Exit(err.Error(), 1)
+			}
+
+			jwt, err := ioutil.ReadFile(c.String("filename"))
+			if err != nil {
+				return cli.Exit(err.Error(), 1)
+			}
+
+			reg, err := license.Validate(key, string(jwt))
+			if err != nil {
+				return cli.Exit(err.Error(), 1)
+			}
+
+			log.Info("Registration valid")
+			log.Info("      Name: %s", reg.Name)
+			log.Info("     Email: %s", reg.Email)
+			log.Info("    Issued: %s", time.Unix(reg.IssuedAt, 0))
+			log.Info("       NBF: %s", time.Unix(reg.NotBefore, 0))
+			log.Info("Raw:\n%+v", reg)
+
+			return nil
+		},
+	}
+}

cmd/doodle-admin/main.go

@@ -0,0 +1,59 @@
+// doodle-admin performs secret admin tasks like generating license keys.
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"sort"
+	"time"
+
+	"git.kirsle.net/apps/doodle/cmd/doodle-admin/command"
+	"git.kirsle.net/apps/doodle/pkg/branding"
+	"github.com/urfave/cli/v2"
+)
+
+// Build variables.
+var (
+	Build     = "N/A"
+	BuildDate string
+)
+
+func init() {
+	if BuildDate == "" {
+		BuildDate = time.Now().Format(time.RFC3339)
+	}
+}
+
+func main() {
+	app := cli.NewApp()
+	app.Name = "doodle-admin"
+	app.Usage = "Admin tasks for Sketchy Maze."
+
+	app.Version = fmt.Sprintf("%s build %s. Built on %s",
+		branding.Version,
+		Build,
+		BuildDate,
+	)
+
+	app.Flags = []cli.Flag{
+		&cli.BoolFlag{
+			Name:  "debug, d",
+			Usage: "enable debug level logging",
+		},
+	}
+
+	app.Commands = []*cli.Command{
+		command.Key,
+		command.Sign,
+		command.Verify,
+	}
+
+	sort.Sort(cli.FlagsByName(app.Flags))
+	sort.Sort(cli.CommandsByName(app.Commands))
+
+	err := app.Run(os.Args)
+	if err != nil {
+		log.Fatal(err)
+	}
+}

cmd/doodle/main.go

@@ -15,6 +15,7 @@ import (
 	"git.kirsle.net/apps/doodle/pkg/balance"
 	"git.kirsle.net/apps/doodle/pkg/bindata"
 	"git.kirsle.net/apps/doodle/pkg/branding"
+	"git.kirsle.net/apps/doodle/pkg/license"
 	"git.kirsle.net/apps/doodle/pkg/log"
 	"git.kirsle.net/apps/doodle/pkg/shmem"
 	"git.kirsle.net/apps/doodle/pkg/sound"
@@ -51,7 +52,7 @@ func main() {
 	app.Usage = fmt.Sprintf("%s - %s", branding.AppName, branding.Summary)
 
 	var freeLabel string
-	if balance.FreeVersion {
+	if !license.IsRegistered() {
 		freeLabel = " (shareware)"
 	}
 

pkg/balance/theme.go

@@ -127,7 +127,9 @@ func init() {
 	ButtonDanger.HoverForeground = ButtonPrimary.Foreground
 
 	ButtonBabyBlue.Background = render.RGBA(0, 153, 255, 255)
+	ButtonBabyBlue.Foreground = render.White
 	ButtonBabyBlue.HoverBackground = render.RGBA(0, 220, 255, 255)
+	ButtonBabyBlue.HoverForeground = render.White
 
 	ButtonPink.Background = render.RGBA(255, 153, 255, 255)
 	ButtonPink.HoverBackground = render.RGBA(255, 220, 255, 255)

pkg/branding/branding.go

@@ -4,7 +4,7 @@ package branding
 const (
 	AppName   = "Sketchy Maze"
 	Summary   = "A drawing-based maze game"
-	Version   = "0.6.1-alpha"
+	Version   = "0.6.1"
 	Website   = "https://www.sketchymaze.com"
 	Copyright = "2021 Noah Petherbridge"
 

pkg/doodle.go

@@ -233,11 +233,6 @@ func (d *Doodle) NewMap() {
 
 // NewDoodad loads a new Doodad in Edit Mode.
 func (d *Doodle) NewDoodad(size int) {
-	if balance.FreeVersion {
-		d.Flash("Doodad editor is not available in your version of the game.")
-		return
-	}
-
 	log.Info("Starting a new doodad")
 	scene := &EditorScene{
 		DrawingType: enum.DoodadDrawing,
@@ -262,9 +257,6 @@ func (d *Doodle) EditDrawing(filename string) error {
 		log.Info("is a Level type")
 		scene.DrawingType = enum.LevelDrawing
 	case ".doodad":
-		if balance.FreeVersion {
-			return fmt.Errorf("Doodad editor not supported in your version of the game")
-		}
 		scene.DrawingType = enum.DoodadDrawing
 	default:
 		return fmt.Errorf("file extension '%s' doesn't indicate its drawing type", ext)

pkg/editor_ui.go

@@ -10,6 +10,7 @@ import (
 	"git.kirsle.net/apps/doodle/pkg/drawtool"
 	"git.kirsle.net/apps/doodle/pkg/enum"
 	"git.kirsle.net/apps/doodle/pkg/level"
+	"git.kirsle.net/apps/doodle/pkg/license"
 	"git.kirsle.net/apps/doodle/pkg/log"
 	"git.kirsle.net/apps/doodle/pkg/native"
 	"git.kirsle.net/apps/doodle/pkg/uix"
@@ -51,6 +52,7 @@ type EditorUI struct {
 	layersWindow        *ui.Window
 	publishWindow       *ui.Window
 	filesystemWindow    *ui.Window
+	licenseWindow       *ui.Window
 
 	// Palette window.
 	Palette    *ui.Window
@@ -508,24 +510,22 @@ func (u *EditorUI) SetupMenuBar(d *Doodle) *ui.MenuBar {
 			d.GotoNewMenu()
 		})
 	})
-	if !balance.FreeVersion {
+	fileMenu.AddItem("New doodad", func() {
-		fileMenu.AddItem("New doodad", func() {
+		u.Scene.ConfirmUnload(func() {
-			u.Scene.ConfirmUnload(func() {
+			d.Prompt("Doodad size [100]>", func(answer string) {
-				d.Prompt("Doodad size [100]>", func(answer string) {
+				size := balance.DoodadSize
-					size := balance.DoodadSize
+				if answer != "" {
-					if answer != "" {
+					i, err := strconv.Atoi(answer)
-						i, err := strconv.Atoi(answer)
+					if err != nil {
-						if err != nil {
+						d.Flash("Error: Doodad size must be a number.")
-							d.Flash("Error: Doodad size must be a number.")
+						return
-							return
-						}
-						size = i
 					}
-					d.NewDoodad(size)
+					size = i
-				})
+				}
+				d.NewDoodad(size)
 			})
 		})
-	}
+	})
 	fileMenu.AddItemAccel("Save", "Ctrl-S*", func() {
 		if u.Scene.filename != "" {
 			saveFunc(u.Scene.filename)
@@ -688,6 +688,27 @@ func (u *EditorUI) SetupMenuBar(d *Doodle) *ui.MenuBar {
 	helpMenu.AddItemAccel("User Manual", "F1", func() {
 		native.OpenLocalURL(balance.GuidebookPath)
 	})
+	helpMenu.AddItem("Register", func() {
+		if u.licenseWindow == nil {
+			cfg := windows.License{
+				Supervisor: u.Supervisor,
+				Engine:     d.Engine,
+				OnCancel: func() {
+					u.licenseWindow.Hide()
+				},
+			}
+			cfg.OnLicensed = func() {
+				// License status has changed, reload the window!
+				if u.licenseWindow != nil {
+					u.licenseWindow.Hide()
+				}
+				u.licenseWindow = windows.MakeLicenseWindow(d.width, d.height, cfg)
+			}
+
+			cfg.OnLicensed()
+		}
+		u.licenseWindow.Show()
+	})
 	helpMenu.AddItem("About", func() {
 		if u.aboutWindow == nil {
 			u.aboutWindow = windows.NewAboutWindow(windows.About{
@@ -747,7 +768,7 @@ func (u *EditorUI) SetupStatusBar(d *Doodle) *ui.Frame {
 	}
 
 	var shareware string
-	if balance.FreeVersion {
+	if !license.IsRegistered() {
 		shareware = " (shareware)"
 	}
 	extraLabel := ui.NewLabel(ui.Label{

pkg/license/admin.go

@@ -0,0 +1,100 @@
+package license
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"encoding/pem"
+	"io/ioutil"
+	"time"
+
+	"github.com/dgrijalva/jwt-go"
+)
+
+// AdminGenerateKeys generates the ECDSA public and private key pair for the admin
+// side of creating signed license files.
+func AdminGenerateKeys() (*ecdsa.PrivateKey, error) {
+	privateKey, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
+	return privateKey, err
+}
+
+// AdminWriteKeys writes the admin signing key to .pem files on disk.
+func AdminWriteKeys(key *ecdsa.PrivateKey, privateFile, publicFile string) error {
+	// Encode the private key to PEM format.
+	x509Encoded, err := x509.MarshalECPrivateKey(key)
+	if err != nil {
+		return err
+	}
+	pemEncoded := pem.EncodeToMemory(&pem.Block{
+		Type:  "PRIVATE KEY",
+		Bytes: x509Encoded,
+	})
+
+	// Encode the public key to PEM format.
+	x509EncodedPub, err := x509.MarshalPKIXPublicKey(key.Public())
+	if err != nil {
+		return err
+	}
+	pemEncodedPub := pem.EncodeToMemory(&pem.Block{
+		Type:  "PUBLIC KEY",
+		Bytes: x509EncodedPub,
+	})
+
+	// Write the files.
+	if err := ioutil.WriteFile(privateFile, pemEncoded, 0600); err != nil {
+		return err
+	}
+	if err := ioutil.WriteFile(publicFile, pemEncodedPub, 0644); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// AdminLoadPrivateKey loads the private key from disk.
+func AdminLoadPrivateKey(privateFile string) (*ecdsa.PrivateKey, error) {
+	// Read the private key file.
+	pemEncoded, err := ioutil.ReadFile(privateFile)
+	if err != nil {
+		return nil, err
+	}
+
+	// Decode the private key.
+	block, _ := pem.Decode([]byte(pemEncoded))
+	x509Encoded := block.Bytes
+	privateKey, _ := x509.ParseECPrivateKey(x509Encoded)
+	return privateKey, nil
+}
+
+// AdminLoadPublicKey loads the private key from disk.
+func AdminLoadPublicKey(publicFile string) (*ecdsa.PublicKey, error) {
+	pemEncodedPub, err := ioutil.ReadFile(publicFile)
+	if err != nil {
+		return nil, err
+	}
+
+	// Decode the public key.
+	blockPub, _ := pem.Decode([]byte(pemEncodedPub))
+	x509EncodedPub := blockPub.Bytes
+	genericPublicKey, _ := x509.ParsePKIXPublicKey(x509EncodedPub)
+	publicKey := genericPublicKey.(*ecdsa.PublicKey)
+
+	return publicKey, nil
+}
+
+// AdminSignRegistration signs the registration object.
+func AdminSignRegistration(key *ecdsa.PrivateKey, reg Registration) (string, error) {
+	reg.StandardClaims = jwt.StandardClaims{
+		Issuer:    "Maze Admin",
+		IssuedAt:  time.Now().Unix(),
+		NotBefore: time.Now().Unix(),
+	}
+
+	token := jwt.NewWithClaims(jwt.SigningMethodES384, reg)
+	signed, err := token.SignedString(key)
+	if err != nil {
+		return "", err
+	}
+	return signed, nil
+}

pkg/license/config.go

@@ -0,0 +1,25 @@
+package license
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+)
+
+// Run-time configuration variables provided by the application.
+const pemSigningKey = `-----BEGIN PUBLIC KEY-----
+MHYwEAYHKoZIzj0CAQYFK4EEACIDYgAEMrqAMHjZ1dPlKwDOsiCSr5N3OSvnYKLM
+efe2xD+5hJYrpvparRFnaMbMuqde4M6d6sCCKO8BHtfAzmyiQ/CD38zs9MiDsamy
+FDYEEJu+Fqx482I7fIa5ZEE770+wWJ3k
+-----END PUBLIC KEY-----`
+
+var Signer *ecdsa.PublicKey
+
+func init() {
+	key, err := ParsePublicKeyPEM(pemSigningKey)
+	if err != nil {
+		fmt.Printf("license: failed to parse app keys: %s\n", err)
+		return
+	}
+
+	Signer = key
+}

pkg/license/license.go

@@ -0,0 +1,103 @@
+// Package license holds functions related to paid product activation.
+package license
+
+import (
+	"crypto/ecdsa"
+	"crypto/x509"
+	"encoding/pem"
+	"errors"
+	"io/ioutil"
+	"path/filepath"
+
+	"git.kirsle.net/apps/doodle/pkg/userdir"
+	"github.com/dgrijalva/jwt-go"
+)
+
+// Registration object encoded into a license key file.
+type Registration struct {
+	Name  string `json:"name"`
+	Email string `json:"email"`
+	jwt.StandardClaims
+}
+
+// IsRegistered returns a boolean answer: is the product registered?
+func IsRegistered() bool {
+	if _, err := GetRegistration(); err == nil {
+		return true
+	}
+	return false
+}
+
+// GetRegistration returns the currently registered user, by checking
+// for the license.key file in the profile folder.
+func GetRegistration() (Registration, error) {
+	if Signer == nil {
+		return Registration{}, errors.New("signer not ready")
+	}
+
+	filename := filepath.Join(userdir.ProfileDirectory, "license.key")
+	jwt, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return Registration{}, err
+	}
+
+	// Check if the JWT is valid.
+	reg, err := Validate(Signer, string(jwt))
+	if err != nil {
+		return Registration{}, err
+	}
+
+	return reg, err
+}
+
+// UploadLicenseFile handles the user selecting the license key file, and it is
+// validated and ingested.
+func UploadLicenseFile(filename string) (Registration, error) {
+	if Signer == nil {
+		return Registration{}, errors.New("signer not ready")
+	}
+
+	jwt, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return Registration{}, err
+	}
+
+	// Check if the JWT is valid.
+	reg, err := Validate(Signer, string(jwt))
+	if err != nil {
+		return Registration{}, err
+	}
+
+	// Upload the license to Doodle's profile directory.
+	outfile := filepath.Join(userdir.ProfileDirectory, "license.key")
+	if err := ioutil.WriteFile(outfile, jwt, 0644); err != nil {
+		return Registration{}, err
+	}
+
+	return reg, nil
+}
+
+// Validate the registration is signed by the appropriate public key.
+func Validate(publicKey *ecdsa.PublicKey, tokenString string) (Registration, error) {
+	var reg Registration
+	token, err := jwt.ParseWithClaims(tokenString, &reg, func(token *jwt.Token) (interface{}, error) {
+		return publicKey, nil
+	})
+	if err != nil {
+		return reg, err
+	}
+
+	if !token.Valid {
+		return reg, errors.New("token not valid")
+	}
+	return reg, nil
+}
+
+// ParsePublicKeyPEM loads a public key from PEM format.
+func ParsePublicKeyPEM(keytext string) (*ecdsa.PublicKey, error) {
+	blockPub, _ := pem.Decode([]byte(keytext))
+	x509EncodedPub := blockPub.Bytes
+	genericPublicKey, _ := x509.ParsePKIXPublicKey(x509EncodedPub)
+	publicKey := genericPublicKey.(*ecdsa.PublicKey)
+	return publicKey, nil
+}

pkg/main_scene.go

@@ -6,12 +6,14 @@ import (
 	"git.kirsle.net/apps/doodle/pkg/balance"
 	"git.kirsle.net/apps/doodle/pkg/branding"
 	"git.kirsle.net/apps/doodle/pkg/level"
+	"git.kirsle.net/apps/doodle/pkg/license"
 	"git.kirsle.net/apps/doodle/pkg/log"
 	"git.kirsle.net/apps/doodle/pkg/native"
 	"git.kirsle.net/apps/doodle/pkg/scripting"
 	"git.kirsle.net/apps/doodle/pkg/shmem"
 	"git.kirsle.net/apps/doodle/pkg/uix"
 	"git.kirsle.net/apps/doodle/pkg/updater"
+	"git.kirsle.net/apps/doodle/pkg/windows"
 	"git.kirsle.net/go/render"
 	"git.kirsle.net/go/render/event"
 	"git.kirsle.net/go/ui"
@@ -30,6 +32,8 @@ type MainScene struct {
 	labelVersion *ui.Label
 	labelHint    *ui.Label
 	frame        *ui.Frame // Main button frame
+	btnRegister  *ui.Button
+	winRegister  *ui.Window
 
 	// Update check variables.
 	updateButton *ui.Button
@@ -63,7 +67,7 @@ func (s *MainScene) Setup(d *Doodle) error {
 
 	// Version label.
 	var shareware string
-	if balance.FreeVersion {
+	if !license.IsRegistered() {
 		shareware = " (shareware)"
 	}
 	ver := ui.NewLabel(ui.Label{
@@ -106,6 +110,41 @@ func (s *MainScene) Setup(d *Doodle) error {
 	s.updateButton.Hide()
 	s.Supervisor.Add(s.updateButton)
 
+	// Register button.
+	s.btnRegister = ui.NewButton("Register", ui.NewLabel(ui.Label{
+		Text: "Register Game",
+		Font: balance.LabelFont,
+	}))
+	s.btnRegister.SetStyle(&balance.ButtonPrimary)
+	s.btnRegister.Handle(ui.Click, func(ed ui.EventData) error {
+		if s.winRegister == nil {
+			cfg := windows.License{
+				Supervisor: s.Supervisor,
+				Engine:     d.Engine,
+				OnCancel: func() {
+					s.winRegister.Hide()
+				},
+			}
+			cfg.OnLicensed = func() {
+				// License status has changed, reload the window!
+				if s.winRegister != nil {
+					s.winRegister.Hide()
+				}
+				s.winRegister = windows.MakeLicenseWindow(d.width, d.height, cfg)
+			}
+
+			cfg.OnLicensed()
+		}
+		s.winRegister.Show()
+		return nil
+	})
+	s.btnRegister.Compute(d.Engine)
+	s.Supervisor.Add(s.btnRegister)
+
+	if license.IsRegistered() {
+		s.btnRegister.Hide()
+	}
+
 	// Main UI button frame.
 	frame := ui.NewFrame("frame")
 	s.frame = frame
@@ -329,7 +368,7 @@ func (s *MainScene) Draw(d *Doodle) error {
 
 	// Hint label.
 	s.labelHint.MoveTo(render.Point{
-		X: d.width - s.labelHint.Size().W - 32,
+		X: (d.width / 2) - (s.labelHint.Size().W / 2),
 		Y: d.height - s.labelHint.Size().H - 32,
 	})
 	s.labelHint.Present(d.Engine, s.labelHint.Point())
@@ -348,6 +387,16 @@ func (s *MainScene) Draw(d *Doodle) error {
 	})
 	s.frame.Present(d.Engine, s.frame.Point())
 
+	// Register button.
+	s.btnRegister.MoveTo(render.Point{
+		X: d.width - s.btnRegister.Size().W - 24,
+		Y: d.height - s.btnRegister.Size().H - 24,
+	})
+	s.btnRegister.Present(d.Engine, s.btnRegister.Point())
+
+	// Present supervised windows.
+	s.Supervisor.Present(d.Engine)
+
 	return nil
 }
 

pkg/windows/license_key.go

@@ -0,0 +1,275 @@
+package windows
+
+import (
+	"fmt"
+	"time"
+
+	"git.kirsle.net/apps/doodle/pkg/balance"
+	"git.kirsle.net/apps/doodle/pkg/branding"
+	"git.kirsle.net/apps/doodle/pkg/license"
+	"git.kirsle.net/apps/doodle/pkg/modal"
+	"git.kirsle.net/apps/doodle/pkg/native"
+	"git.kirsle.net/go/render"
+	"git.kirsle.net/go/ui"
+	"git.kirsle.net/go/ui/style"
+)
+
+// License window.
+type License struct {
+	// Settings passed in by doodle
+	Supervisor *ui.Supervisor
+	Engine     render.Engine
+
+	OnLicensed func()
+	OnCancel   func()
+}
+
+// MakeLicenseWindow initializes a license window for any scene.
+// The window width/height are the actual SDL2 window dimensions.
+func MakeLicenseWindow(windowWidth, windowHeight int, cfg License) *ui.Window {
+	win := NewLicenseWindow(cfg)
+	win.Compute(cfg.Engine)
+	win.Supervise(cfg.Supervisor)
+
+	// Center the window.
+	size := win.Size()
+	win.MoveTo(render.Point{
+		X: (windowWidth / 2) - (size.W / 2),
+		Y: (windowHeight / 2) - (size.H / 2),
+	})
+
+	return win
+}
+
+// NewLicenseWindow initializes the window.
+func NewLicenseWindow(cfg License) *ui.Window {
+	var (
+		windowWidth  = 340
+		windowHeight = 320
+		labelSize    = render.NewRect(100, 16)
+		valueSize    = render.NewRect(windowWidth-labelSize.W-4, labelSize.H)
+		isRegistered bool
+		registration license.Registration
+		summary      = "Unregistered (shareware)"
+	)
+
+	// Get our current registration status.
+	if reg, err := license.GetRegistration(); err == nil {
+		isRegistered = true
+		registration = reg
+		windowHeight = 200
+		summary = "Registered"
+	}
+
+	window := ui.NewWindow("Registration")
+	window.SetButtons(ui.CloseButton)
+	window.Configure(ui.Config{
+		Width:      windowWidth,
+		Height:     windowHeight,
+		Background: render.RGBA(200, 200, 255, 255),
+	})
+
+	var rows = []struct {
+		IfRegistered   bool
+		IfUnregistered bool
+
+		Label       string
+		Text        string
+		Button      *ui.Button
+		ButtonStyle *style.Button
+		Func        func()
+		PadY        int
+		PadX        int
+	}{
+		{
+			Label: "Version:",
+			Text:  fmt.Sprintf("%s v%s", branding.AppName, branding.Version),
+		},
+		{
+			Label: "Status:",
+			Text:  summary,
+		},
+		{
+			IfRegistered: true,
+			Label:        "Name:",
+			Text:         registration.Name,
+		},
+		{
+			IfRegistered: true,
+			Label:        "Email:",
+			Text:         registration.Email,
+		},
+		{
+			IfRegistered: true,
+			Label:        "Issued:",
+			Text:         time.Unix(registration.IssuedAt, 0).Format("Jan 2, 2006 15:04:05 MST"),
+		},
+		{
+			IfUnregistered: true,
+			Text: "Register your game today! By purchasing the full\n" +
+				"version of Sketchy Maze, you will unlock additional\n" +
+				"features including improved support for custom\n" +
+				"doodads that attach with your level files for easy\n" +
+				"sharing between multiple computers.\n\n" +
+				"When you purchase the game you will receive a\n" +
+				"license key file; click the button below to browse\n" +
+				"and select the key file to register this copy of\n" +
+				branding.AppName + ".",
+			PadY: 8,
+			PadX: 2,
+		},
+		{
+			IfRegistered: true,
+			Text:         "Thank you for your support!",
+			PadY:         8,
+			PadX:         2,
+		},
+		{
+			IfUnregistered: true,
+			Button: ui.NewButton("Key Browse", ui.NewLabel(ui.Label{
+				Text: "Upload License Key File",
+				Font: balance.UIFont,
+			})),
+			ButtonStyle: &balance.ButtonPrimary,
+			Func: func() {
+				filename, err := native.OpenFile("Select License File", "*.key *.txt")
+				if err != nil {
+					modal.Alert(err.Error())
+					return
+				}
+
+				// Upload and validate the license key.
+				reg, err := license.UploadLicenseFile(filename)
+				if err != nil {
+					modal.Alert(err.Error())
+					return
+				}
+
+				modal.Alert("Thank you, %s!", reg.Name).WithTitle("Registration OK!")
+				if cfg.OnLicensed != nil {
+					cfg.OnLicensed()
+				}
+			},
+		},
+	}
+	for _, row := range rows {
+		row := row
+
+		// It has a conditional?
+		if (row.IfRegistered && !isRegistered) ||
+			(row.IfUnregistered && isRegistered) {
+			continue
+		}
+
+		frame := ui.NewFrame("Frame")
+		if row.Label != "" {
+			lf := ui.NewFrame("LabelFrame")
+			lf.Resize(labelSize)
+			label := ui.NewLabel(ui.Label{
+				Text: row.Label,
+				Font: balance.LabelFont,
+			})
+			lf.Pack(label, ui.Pack{
+				Side: ui.E,
+			})
+			frame.Pack(lf, ui.Pack{
+				Side: ui.W,
+			})
+		}
+
+		if row.Text != "" {
+			tf := ui.NewFrame("TextFrame")
+			if row.Label != "" {
+				tf.Resize(valueSize)
+			}
+			label := ui.NewLabel(ui.Label{
+				Text: row.Text,
+				Font: balance.UIFont,
+			})
+			tf.Pack(label, ui.Pack{
+				Side: ui.W,
+			})
+			frame.Pack(tf, ui.Pack{
+				Side: ui.W,
+			})
+		}
+
+		if row.Button != nil {
+			btn := row.Button
+			if row.ButtonStyle != nil {
+				btn.SetStyle(row.ButtonStyle)
+			}
+			btn.Handle(ui.Click, func(ed ui.EventData) error {
+				if row.Func != nil {
+					row.Func()
+				}
+				return nil
+			})
+			btn.Compute(cfg.Engine)
+			cfg.Supervisor.Add(btn)
+			frame.Pack(btn, ui.Pack{
+				Side: ui.N,
+			})
+		}
+		window.Pack(frame, ui.Pack{
+			Side:  ui.N,
+			FillX: true,
+			PadY:  row.PadY,
+			PadX:  row.PadX,
+		})
+	}
+
+	/////////////
+	// Buttons at bottom of window
+
+	bottomFrame := ui.NewFrame("Button Frame")
+	window.Pack(bottomFrame, ui.Pack{
+		Side:  ui.N,
+		FillX: true,
+	})
+
+	frame := ui.NewFrame("Button frame")
+	buttons := []struct {
+		label string
+		f     func()
+	}{
+		{"Website", func() {
+			native.OpenURL(branding.Website)
+		}},
+		{"Close", func() {
+			if cfg.OnCancel != nil {
+				cfg.OnCancel()
+			}
+		}},
+	}
+	for _, button := range buttons {
+		button := button
+
+		btn := ui.NewButton(button.label, ui.NewLabel(ui.Label{
+			Text: button.label,
+			Font: balance.MenuFont,
+		}))
+
+		btn.Handle(ui.Click, func(ed ui.EventData) error {
+			button.f()
+			return nil
+		})
+
+		btn.Compute(cfg.Engine)
+		cfg.Supervisor.Add(btn)
+
+		frame.Pack(btn, ui.Pack{
+			Side:   ui.W,
+			PadX:   4,
+			Expand: true,
+			Fill:   true,
+		})
+	}
+	bottomFrame.Pack(frame, ui.Pack{
+		Side: ui.N,
+		PadX: 8,
+		PadY: 12,
+	})
+
+	return window
+}