Completely overhaul the auth again

Now we're all in on passkeys (ooh fancy)

5 files changed, 386 insertions, 173 deletions

diff --git a/roseh.moe.go b/roseh.moe.go
index 0369740..8e2c999 100644
--- a/roseh.moe.go
+++ b/roseh.moe.go
@@ -24,12 +24,15 @@ import (
 	"cmp"
 	"compress/gzip"
 	"context"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/ed25519"
 	"crypto/hkdf"
 	"crypto/hmac"
 	"crypto/rand"
-	"crypto/sha1"
+	"crypto/rsa"
 	"crypto/sha256"
-	"crypto/subtle"
+	"crypto/x509"
 	"embed"
 	"encoding/base64"
 	"encoding/binary"
@@ -58,7 +61,6 @@ import (
 
 	"github.com/skip2/go-qrcode"
 	"roseh.moe/pkg/oae2"
-	"roseh.moe/pkg/roseh.moe/internal/pwhash"
 	"roseh.moe/pkg/wordlist"
 )
 
@@ -104,7 +106,43 @@ func urlFlag(name, def, doc string) *url.URL {
 	return u
 }
 
-var notepadPassword, secretKey, authenticatorKey []byte
+func sigVerifier(keyBytes []byte) (func(msg, sig []byte) bool, error) {
+	key, err := x509.ParsePKIXPublicKey(keyBytes)
+	if err != nil {
+		return nil, err
+	}
+	switch key := key.(type) {
+	case *ecdsa.PublicKey:
+		return func(msg, sig []byte) bool {
+			hash := sha256.Sum256(msg)
+			return ecdsa.VerifyASN1(key, hash[:], sig)
+		}, nil
+	case *rsa.PublicKey:
+		return func(msg, sig []byte) bool {
+			hash := sha256.Sum256(msg)
+			return rsa.VerifyPKCS1v15(key, crypto.SHA256, hash[:], sig) == nil
+		}, nil
+	case ed25519.PublicKey:
+		return func(msg, sig []byte) bool {
+			return ed25519.Verify(key, msg, sig)
+		}, nil
+	default:
+		return nil, fmt.Errorf("unsupported key type")
+	}
+}
+
+func verifyPubKey(pubKey, msg, sig []byte) error {
+	verify, err := sigVerifier(pubKey)
+	if err != nil {
+		return err
+	}
+	if !verify(msg, sig) {
+		return fmt.Errorf("message failed validation")
+	}
+	return nil
+}
+
+var secretKey []byte
 
 func loadSecrets() error {
 	fileBytes, err := os.ReadFile(*secretsFile)
@@ -112,31 +150,17 @@ func loadSecrets() error {
 		return err
 	}
 	var secretsConfig struct {
-		NotepadPassword string `xml:",attr"`
-		SecretKey       string `xml:",attr"`
-		AuthKey         string `xml:",attr"`
+		SecretKey string `xml:",attr"`
 	}
 	if err := xml.Unmarshal(fileBytes, &secretsConfig); err != nil {
 		return fmt.Errorf("%s: %s", *secretsFile, err)
 	}
-	if secretsConfig.NotepadPassword == "" {
-		return fmt.Errorf("%s: missing NotepadPassword", *secretsFile)
-	}
 	if secretsConfig.SecretKey == "" {
 		return fmt.Errorf("%s: missing SecretKey", *secretsFile)
 	}
-	if secretsConfig.AuthKey == "" {
-		return fmt.Errorf("%s: missing AuthKey", *secretsFile)
-	}
-	if notepadPassword, err = base64.StdEncoding.DecodeString(secretsConfig.NotepadPassword); err != nil {
-		return fmt.Errorf("%s: bad NotepadPassword (try base64)", *secretsFile)
-	}
 	if secretKey, err = base64.StdEncoding.DecodeString(secretsConfig.SecretKey); err != nil {
 		return fmt.Errorf("%s: bad SecretKey (try base64)", *secretsFile)
 	}
-	if authenticatorKey, err = base64.StdEncoding.DecodeString(secretsConfig.AuthKey); err != nil {
-		return fmt.Errorf("%s: bad AuthKey (try base64)", *secretsFile)
-	}
 	return nil
 }
 
@@ -155,9 +179,16 @@ type commandConfig struct {
 	Multi       bool   `xml:",attr"`
 }
 
+type passkey struct {
+	ID  string `xml:",attr"`
+	Key string `xml:",attr"`
+}
+
 type serviceConfiguration struct {
 	PackageRedirects []packageConfig `xml:"Redirects>Package"`
 	CommandRedirects []commandConfig `xml:"Redirects>Command"`
+	Passkey          []passkey
+	passkeys         map[int64][]byte
 }
 
 var (
@@ -188,6 +219,32 @@ func loadConfig() (*serviceConfiguration, error) {
 	if err := xml.Unmarshal(fileBytes, config); err != nil {
 		return nil, err
 	}
+	names := make(map[string]bool)
+	config.passkeys = make(map[int64][]byte)
+	namesByID := make(map[int64]string)
+	for _, passkey := range config.Passkey {
+		if names[passkey.ID] {
+			return nil, fmt.Errorf("%s: duplicate name %q", *configFile, passkey.ID)
+		}
+		names[passkey.ID] = true
+		keyBytes, err := base64.RawURLEncoding.DecodeString(passkey.Key)
+		if err != nil {
+			return nil, fmt.Errorf("%s: invalid key for device %q: %s", *configFile, passkey.ID, err)
+		}
+		id, n := binary.Varint(keyBytes)
+		if n <= 0 {
+			return nil, fmt.Errorf("%s: invalid key for device %q: bad device ID", *configFile, passkey.ID)
+		}
+		key := keyBytes[n:]
+		if _, err := sigVerifier(key); err != nil {
+			return nil, fmt.Errorf("%s: invalid key for device %q: %s", *configFile, passkey.ID, err)
+		}
+		if _, ok := config.passkeys[id]; ok {
+			return nil, fmt.Errorf("%s: passkeys %q and %q have duplicate ID %d", *configFile, namesByID[id], passkey.ID, id)
+		}
+		config.passkeys[id] = key
+		namesByID[id] = passkey.ID
+	}
 	slices.SortFunc(config.PackageRedirects, func(x, y packageConfig) int { return strings.Compare(x.Name, y.Name) })
 	slices.SortFunc(config.CommandRedirects, func(x, y commandConfig) int { return strings.Compare(x.Name, y.Name) })
 	serviceConfigMu.Lock()
@@ -212,6 +269,11 @@ var (
 		"host": func() string {
 			return selfURL.Host
 		},
+		"xmlEscape": func(s string) string {
+			buf := new(strings.Builder)
+			xml.EscapeText(buf, []byte(s))
+			return buf.String()
+		},
 	}).Parse(outlineString))
 )
 
@@ -347,7 +409,7 @@ func sharedFileHandler(w http.ResponseWriter, r *http.Request) {
 }
 
 func qrHandler(w http.ResponseWriter, r *http.Request) {
-	text, ok := verify(r.FormValue("t"), "qr")
+	text, ok := verifyHMAC(r.FormValue("t"), "qr")
 	if !ok {
 		http.Error(w, "Bad signature", http.StatusBadRequest)
 		return
@@ -605,7 +667,7 @@ func wormholeUpload(w http.ResponseWriter, r *http.Request) {
 	downloadURL := selfURL.String() + "/wormhole/" + hole
 	if err := wormholeSuccessTemplate.Execute(w, wormholeSuccessTemplateArgs{
 		URL: downloadURL,
-		QR:  "/qr.png?t=" + url.QueryEscape(downloadURL) + mac(downloadURL, "qr"),
+		QR:  "/qr.png?t=" + url.QueryEscape(signMsg(downloadURL, "qr")),
 	}); err != nil {
 		log.Printf("Warning: wormholeSend: %s", err)
 	}
@@ -685,87 +747,44 @@ func cleanHole() error {
 	}
 }
 
-func mac(msg string, purpose string) string {
+func mac(msg []byte, purpose string) []byte {
 	mac := hmac.New(sha256.New, secretKey)
 	io.WriteString(mac, purpose)
 	io.WriteString(mac, ":")
-	io.WriteString(mac, msg)
-	return base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
+	mac.Write(msg)
+	return mac.Sum(nil)
+}
+
+func signMsg(msg, purpose string) string {
+	return msg + base64.RawURLEncoding.EncodeToString(mac([]byte(msg), purpose))
 }
 
-func verify(signedMsg, purpose string) (string, bool) {
+func verifyHMAC(signedMsg, purpose string) (string, bool) {
 	macSize := base64.RawURLEncoding.EncodedLen(sha256.Size)
 	if len(signedMsg) < macSize {
 		return "", false
 	}
 	msg, msgMAC := signedMsg[:len(signedMsg)-macSize], signedMsg[len(signedMsg)-macSize:]
-	expectedMAC := mac(msg, purpose)
+	expectedMAC := base64.RawURLEncoding.EncodeToString(mac([]byte(msg), purpose))
 	if !hmac.Equal([]byte(msgMAC), []byte(expectedMAC)) {
 		return "", false
 	}
 	return msg, true
 }
 
-func marshalInt(x uint64) []byte {
-	buf := make([]byte, 8)
-	binary.BigEndian.PutUint64(buf, x)
-	for ; len(buf) > 0 && buf[0] == 0; buf = buf[1:] {
-	}
-	return buf
-}
-
-func unmarshalInt(b []byte) (uint64, bool) {
-	if len(b) > 8 {
-		return 0, false
-	}
-	buf := make([]byte, 8)
-	copy(buf[8-len(b):], b)
-	return binary.BigEndian.Uint64(buf), true
-}
-
-func marshalTime(t time.Time) []byte {
-	t = t.UTC()
-	year, month, day := t.Date()
-	hour, minute, second := t.Clock()
-	u := uint64(year)
-	u = u<<4 | uint64(month)
-	u = u<<5 | uint64(day)
-	u = u<<5 | uint64(hour)
-	u = u<<6 | uint64(minute)
-	u = u<<6 | uint64(second)
-	return marshalInt(u)
-}
-
-func unmarshalTime(b []byte) (time.Time, bool) {
-	u, ok := unmarshalInt(b)
-	if !ok {
-		return time.Time{}, false
-	}
-	second, u := int(u&0x3f), u>>6
-	minute, u := int(u&0x3f), u>>6
-	hour, u := int(u&0x1f), u>>5
-	day, u := int(u&0x1f), u>>5
-	month, u := time.Month(u&0xf), u>>4
-	year := int(u)
-	return time.Date(year, month, day, hour, minute, second, 0, time.UTC), true
-}
-
-const authVersion = "authv2"
-
-func makeToken() string {
-	t := base64.RawURLEncoding.EncodeToString(marshalTime(time.Now()))
-	return t + mac(t, authVersion)
-}
-
-const authCookieName = "a"
+const (
+	authVersion    = "authv3"
+	authCookieName = "a"
+)
 
-func attachCookie(w http.ResponseWriter) {
+func attachCookie(w http.ResponseWriter, expiry time.Time) {
+	token := signMsg(base64.RawURLEncoding.EncodeToString(binary.AppendVarint(nil, expiry.Unix())), authVersion)
 	http.SetCookie(w, &http.Cookie{
 		Name:        authCookieName,
-		Value:       makeToken(),
+		Value:       token,
 		Path:        "/",
 		Domain:      selfURL.Hostname(),
-		Expires:     time.Now().Add(longLoginTimeout),
+		Expires:     expiry,
 		Secure:      true,
 		HttpOnly:    true,
 		SameSite:    http.SameSiteStrictMode,
@@ -773,105 +792,122 @@ func attachCookie(w http.ResponseWriter) {
 	})
 }
 
-func cookieAuth(r *http.Request) (time.Duration, bool) {
+func cookieAuth(r *http.Request) bool {
 	cookie, err := r.Cookie(authCookieName)
 	if err != nil {
-		return 0, false
+		return false
 	}
-	msg, ok := verify(cookie.Value, authVersion)
+	msg, ok := verifyHMAC(cookie.Value, authVersion)
 	if !ok {
-		return 0, false
+		return false
 	}
 	msgBytes, err := base64.RawURLEncoding.DecodeString(msg)
 	if err != nil {
-		return 0, false
+		return false
 	}
-	t, ok := unmarshalTime(msgBytes)
-	if !ok {
-		return 0, false
+	expiryUnix, n := binary.Varint(msgBytes)
+	if n <= 0 {
+		return false
 	}
-	age := time.Since(t)
-	if age > longLoginTimeout {
-		return 0, false
+	expiry := time.Unix(expiryUnix, 0)
+	if time.Now().After(expiry) {
+		return false
 	}
-	return age, true
-}
-
-func totp(t int64) []byte {
-	ts := make([]byte, 8)
-	binary.BigEndian.PutUint64(ts, uint64(t))
-	hash := hmac.New(sha1.New, authenticatorKey)
-	hash.Write(ts)
-	mac := hash.Sum(nil)
-	offset := mac[len(mac)-1] & 0xf
-	n := int32(mac[offset])&0x7f<<24 |
-		int32(mac[offset+1])<<16 |
-		int32(mac[offset+2])<<8 |
-		int32(mac[offset+3])
-	return strconv.AppendInt(nil, int64(n%1_000_000), 10)
+	return true
 }
 
-func checkOTP(auth string) int {
-	now := time.Now().Unix() / 30
-	return subtle.ConstantTimeCompare([]byte(auth), totp(now-1)) | subtle.ConstantTimeCompare([]byte(auth), totp(now)) | subtle.ConstantTimeCompare([]byte(auth), totp(now+1))
-}
-
-func checkPassword(password string) int {
-	hash, err := pwhash.Hash(password, notepadPassword[:pwhash.SaltSize])
-	if err != nil {
-		return 0
-	}
-	return subtle.ConstantTimeCompare(hash, notepadPassword[pwhash.SaltSize:])
-}
+var (
+	challengeMu    sync.Mutex
+	challenge      []byte
+	challengePosed time.Time
+)
 
 var (
 	//go:embed templates/login.html.template
 	loginTemplateString string
-	loginTemplate       = template.Must(outlinedTemplate(loginTemplateString))
+	loginTemplate       = template.Must(template.New("login").Parse(loginTemplateString))
 )
 
 type loginTemplateArgs struct {
-	Quick bool
-	Error bool
-}
-
-func redirectLogin(w http.ResponseWriter, r *http.Request, redirect string) {
-	redirect += mac(redirect, "redirect")
-	http.Redirect(w, r, "//"+selfURL.Host+"/login?redirect="+url.QueryEscape(redirect), http.StatusSeeOther)
+	Challenge string
 }
 
-const (
-	quickLoginTimeout = 24 * time.Hour
-	longLoginTimeout  = 300 * 24 * time.Hour
-)
-
 func serveLogin(w http.ResponseWriter, r *http.Request) {
-	_, cookieOK := cookieAuth(r)
+	buf := make([]byte, 32)
+	rand.Read(buf)
+	challengeMu.Lock()
+	challenge = buf
+	challengePosed = time.Now()
+	challengeMu.Unlock()
 	if err := loginTemplate.Execute(w, loginTemplateArgs{
-		Quick: cookieOK,
+		Challenge: base64.StdEncoding.EncodeToString(buf),
 	}); err != nil {
 		log.Printf("Warning: login: %s", err)
 	}
 }
 
 func login(w http.ResponseWriter, r *http.Request) {
-	otpMatches := checkOTP(r.FormValue("auth"))
-	passwordMatches := 1
-	_, cookieOK := cookieAuth(r)
-	if !cookieOK {
-		passwordMatches = checkPassword(r.FormValue("password"))
+	challengeMu.Lock()
+	myChallenge := challenge
+	challenge = nil
+	posed := challengePosed
+	challengeMu.Unlock()
+	if len(myChallenge) == 0 {
+		http.Error(w, "Request already consumed", http.StatusConflict)
+		return
 	}
-	if otpMatches&passwordMatches == 0 {
-		if err := loginTemplate.Execute(w, loginTemplateArgs{
-			Quick: cookieOK,
-			Error: true,
-		}); err != nil {
-			log.Printf("Warning: login: %s", err)
-		}
+	if time.Since(posed) > 10*time.Minute {
+		http.Error(w, "Challenge is too old. Please try again", http.StatusConflict)
 		return
 	}
-	attachCookie(w)
-	redirect, ok := verify(r.FormValue("redirect"), "redirect")
+	userBytes, err := base64.StdEncoding.DecodeString(r.FormValue("user"))
+	if err != nil {
+		http.Error(w, "Bad user", http.StatusBadRequest)
+		return
+	}
+	user, n := binary.Varint(userBytes)
+	if n <= 0 {
+		http.Error(w, "Bad user", http.StatusBadRequest)
+		return
+	}
+	authData, err := base64.StdEncoding.DecodeString(r.FormValue("auth-data"))
+	if err != nil {
+		http.Error(w, "Bad auth data", http.StatusBadRequest)
+		return
+	}
+	clientData, err := base64.StdEncoding.DecodeString(r.FormValue("client-data"))
+	if err != nil {
+		http.Error(w, "Bad client data: invalid base64", http.StatusBadRequest)
+		return
+	}
+	challengeBase64 := base64.RawURLEncoding.EncodeToString(myChallenge)
+	if !strings.Contains(string(clientData), challengeBase64) {
+		http.Error(w, "Bad client data: bad challenge", http.StatusBadRequest)
+		return
+	}
+	sig, err := base64.StdEncoding.DecodeString(r.FormValue("sig"))
+	if err != nil {
+		http.Error(w, "Bad sig", http.StatusBadRequest)
+		return
+	}
+	config, err := loadConfig()
+	if err != nil {
+		log.Printf("Error: failed to load config: %s", err)
+		http.Error(w, "Internal error", http.StatusInternalServerError)
+		return
+	}
+	pubKey, ok := config.passkeys[user]
+	if !ok {
+		http.Error(w, "No user with the given ID", http.StatusBadRequest)
+		return
+	}
+	clientDataHash := sha256.Sum256(clientData)
+	if err := verifyPubKey(pubKey, slices.Concat(authData, clientDataHash[:]), sig); err != nil {
+		http.Error(w, "Challenge failed", http.StatusBadRequest)
+		return
+	}
+	attachCookie(w, time.Now().Add(30*24*time.Hour))
+	redirect, ok := verifyHMAC(r.FormValue("redirect"), "redirect")
 	if !ok {
 		redirect = "/"
 	}
@@ -879,6 +915,86 @@ func login(w http.ResponseWriter, r *http.Request) {
 }
 
 var (
+	//go:embed templates/register/register.html.template
+	registerTemplateString string
+	registerTemplate       = template.Must(outlinedTemplate(registerTemplateString))
+)
+
+type registerTemplateArgs struct {
+	ID        string
+	Challenge string
+}
+
+func serveRegister(w http.ResponseWriter, r *http.Request) {
+	serviceConfig, err := loadConfig()
+	if err != nil {
+		log.Printf("Error: failed to load service config: %s", err)
+		http.Error(w, "Internal error", http.StatusInternalServerError)
+		return
+	}
+	var maxID int64
+	for id := range serviceConfig.passkeys {
+		maxID = max(maxID, id)
+	}
+	myID := maxID + 1
+	buf := make([]byte, 32)
+	rand.Read(buf)
+	if err := registerTemplate.Execute(w, registerTemplateArgs{
+		ID:        base64.StdEncoding.EncodeToString(binary.AppendVarint(nil, myID)),
+		Challenge: base64.StdEncoding.EncodeToString(buf),
+	}); err != nil {
+		log.Printf("Warning: serveRegister: %s", err)
+	}
+}
+
+var (
+	//go:embed templates/register/register-success.html.template
+	registerSuccessTemplateString string
+	registerSuccessTemplate       = template.Must(outlinedTemplate(registerSuccessTemplateString))
+)
+
+type registerSuccessTemplateArgs struct {
+	ID  string
+	Key string
+}
+
+func register(w http.ResponseWriter, r *http.Request) {
+	username := r.FormValue("name")
+	if username == "" {
+		http.Error(w, "Passkey name is required", http.StatusBadRequest)
+		return
+	}
+	config, err := loadConfig()
+	if err != nil {
+		log.Printf("Error: failed to load config: %s", err)
+		http.Error(w, "Internal error", http.StatusInternalServerError)
+		return
+	}
+	for _, passkey := range config.Passkey {
+		if passkey.ID == username {
+			http.Error(w, "Passkey name already used", http.StatusBadRequest)
+			return
+		}
+	}
+	userID, err := base64.StdEncoding.DecodeString(r.FormValue("id"))
+	if err != nil {
+		http.Error(w, "Invalid user ID", http.StatusBadRequest)
+		return
+	}
+	key, err := base64.StdEncoding.DecodeString(r.FormValue("key"))
+	if err != nil {
+		http.Error(w, "Invalid key", http.StatusBadRequest)
+		return
+	}
+	if err := registerSuccessTemplate.Execute(w, registerSuccessTemplateArgs{
+		ID:  r.FormValue("name"),
+		Key: base64.RawURLEncoding.EncodeToString(slices.Concat(userID, key)),
+	}); err != nil {
+		log.Printf("Warning: register: %s", err)
+	}
+}
+
+var (
 	//go:embed templates/note.html.template
 	notepadString   string
 	notepadTemplate = template.Must(outlinedTemplate(notepadString))
@@ -1128,8 +1244,7 @@ type authHandler struct {
 }
 
 func (h *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	if age, ok := cookieAuth(r); !ok || age > quickLoginTimeout {
-		log.Printf("Warning: ok age = %v %v", ok, age)
+	if !cookieAuth(r) {
 		if h.noRedirect {
 			http.Error(w, "not logged in", http.StatusUnauthorized)
 		} else {
@@ -1139,7 +1254,8 @@ func (h *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			if *https != "" {
 				u.Scheme = "https"
 			}
-			redirectLogin(w, r, u.String())
+			redirect := signMsg(u.String(), "redirect")
+			http.Redirect(w, r, "//"+selfURL.Host+"/login?redirect="+url.QueryEscape(redirect), http.StatusSeeOther)
 		}
 		return
 	}
@@ -1241,6 +1357,8 @@ func main() {
 	mux.HandleFunc("GET /wormhole/{hole}", wormholeDownload)
 	mux.Handle("GET /login", &timeoutHandler{h: http.HandlerFunc(serveLogin), timeout: 5 * time.Minute})
 	mux.Handle("POST /login", &timeoutHandler{h: http.HandlerFunc(login), timeout: 5 * time.Minute})
+	mux.Handle("GET /register", &timeoutHandler{h: http.HandlerFunc(serveRegister), timeout: 5 * time.Minute})
+	mux.Handle("POST /register", &timeoutHandler{h: http.HandlerFunc(register), timeout: 5 * time.Minute})
 	mux.Handle("GET /notepad", &timeoutHandler{h: &authHandler{h: http.HandlerFunc(notepad)}, timeout: 5 * time.Minute})
 	mux.Handle("POST /notepad", &timeoutHandler{h: &authHandler{h: http.HandlerFunc(autosave), noRedirect: true}, timeout: 5 * time.Minute})
 	mux.Handle("GET /cmd/{$}", &timeoutHandler{h: http.HandlerFunc(cmdIndex), timeout: 5 * time.Minute})
diff --git a/static/styles.css b/static/styles.css
index 3f8ad7d..c0ffb2e 100644
--- a/static/styles.css
+++ b/static/styles.css
@@ -119,7 +119,7 @@ input.password {
 	font-size: 18px;
 }
 
-input.submit {
+img.submit {
 	margin-top: 20px;
 	padding: 0;
 	background: #f5f5f5;
@@ -128,6 +128,7 @@ input.submit {
 	border-radius: 15px;
 	box-shadow: 0 0 10px rgba(255, 105, 180, 0.5);
 	font-size: 25px;
+	cursor: pointer;
 }
 
 form.wormhole {
diff --git a/templates/login.html.template b/templates/login.html.template
index 279927b..ae0874a 100644
--- a/templates/login.html.template
+++ b/templates/login.html.template
@@ -17,25 +17,29 @@
   -- <https://www.gnu.org/licenses/>.
   -->
 
-<title>Login</title>
+<!doctype html>
 
-<section>
-{{- if .Error}}
-	<p class="login-error"><img class="inline" width="150" height="163" src="/static/angry.webp">Incorrect password
-{{- end}}
-	<form class="password-form" method="post">
-		<table>
-		{{- if not .Quick}}
-			<tr class="password-form-row">
-				<td><label class="password-label" for="password">Enter password</label>
-				<td><input id="password" class="password" type="password" name="password" autofocus>
-		{{- end}}
-			<tr class="password-form-row">
-				<td><label class="password-label" for="auth">Google authenticator code</label>
-				<td><input id="auth" class="password" name="auth">
-			<tr>
-				<td>
-				<td><input type="image" width="100" height="71" class="submit" src="/static/point.webp" alt="Submit">
-		</table>
-	</form>
-</section>
+<form id="form" method="post">
+	<input id="user"        type="hidden" name="user">
+	<input id="auth-data"   type="hidden" name="auth-data">
+	<input id="client-data" type="hidden" name="client-data">
+	<input id="sig"         type="hidden" name="sig">
+</form>
+
+<script>
+async function main() {
+	const publicKeyCredential = await navigator.credentials.get({publicKey: {
+		challenge: Uint8Array.fromBase64("{{.Challenge}}").buffer,
+	}});
+	const rsp = publicKeyCredential.response;
+	document.getElementById("user").value = new Uint8Array(rsp.userHandle).toBase64();
+	document.getElementById("auth-data").value = new Uint8Array(rsp.authenticatorData).toBase64();
+	document.getElementById("client-data").value = new Uint8Array(rsp.clientDataJSON).toBase64();
+	document.getElementById("sig").value = new Uint8Array(rsp.signature).toBase64();
+	document.getElementById("form").submit();
+}
+
+main();
+</script>
+
+This page requires JavaScript™ to be enabled
diff --git a/templates/register/register-success.html.template b/templates/register/register-success.html.template
new file mode 100644
index 0000000..847f97a
--- /dev/null
+++ b/templates/register/register-success.html.template
@@ -0,0 +1,28 @@
+<!-- Copyright 2026 Rose Hogenson <r@roseh.moe>
+  --
+  -- This file is part of roseh.moe.
+  --
+  -- roseh.moe is free software: you can redistribute it and/or modify
+  -- it under the terms of the GNU Affero General Public License
+  -- as published by the Free Software Foundation, either version 3 of
+  -- the License, or (at your option) any later version.
+  --
+  -- roseh.moe is distributed in the hope that it will be useful,
+  -- but WITHOUT ANY WARRANTY; without even the implied warranty
+  -- of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+  -- GNU Affero General Public License for more details.
+  --
+  -- You should have received a copy of the GNU Affero General Public
+  -- License along with roseh.moe. If not, see
+  -- <https://www.gnu.org/licenses/>.
+  -->
+
+<title>Registered</title>
+
+<section>
+	<h1>Registered!</h1>
+	<p>A device key has been generated, but it must be authorized on
+	the server:</p>
+	<pre>	&lt;Passkey ID="{{.ID | xmlEscape}}"
+	         Key="{{.Key | xmlEscape}}"/&gt;</pre>
+</section>
diff --git a/templates/register/register.html.template b/templates/register/register.html.template
new file mode 100644
index 0000000..3b4d959
--- /dev/null
+++ b/templates/register/register.html.template
@@ -0,0 +1,62 @@
+<!-- Copyright 2026 Rose Hogenson <r@roseh.moe>
+  --
+  -- This file is part of roseh.moe.
+  --
+  -- roseh.moe is free software: you can redistribute it and/or modify
+  -- it under the terms of the GNU Affero General Public License
+  -- as published by the Free Software Foundation, either version 3 of
+  -- the License, or (at your option) any later version.
+  --
+  -- roseh.moe is distributed in the hope that it will be useful,
+  -- but WITHOUT ANY WARRANTY; without even the implied warranty
+  -- of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+  -- GNU Affero General Public License for more details.
+  --
+  -- You should have received a copy of the GNU Affero General Public
+  -- License along with roseh.moe. If not, see
+  -- <https://www.gnu.org/licenses/>.
+  -->
+
+<title>Register</title>
+
+<section>
+	<form id="form" class="password-form" method="post">
+		<input id="id" type="hidden" name="id" value="{{.ID}}">
+		<input id="key" type="hidden" name="key">
+		<table>
+			<tr class="password-form-row">
+				<td><label class="password-label" for="name">Enter a name for this passkey</label>
+				<td><input id="name" class="password" name="name">
+			<tr>
+				<td>
+				<td>
+					<img width="100" height="71" class="submit" src="/static/point.webp" alt="Submit"
+							onClick="generateKey()">
+		</table>
+	</form>
+</section>
+
+<script>
+async function generateKey() {
+	const name = document.getElementById("name").value;
+	const publicKeyCredential = await navigator.credentials.create({publicKey: {
+		challenge: Uint8Array.fromBase64("{{.Challenge}}").buffer,
+		pubKeyCredParams: [
+			{alg: -9,   type: "public-key"},
+			{alg: -257, type: "public-key"},
+			{alg: -7,   type: "public-key"},
+			{alg: -8,   type: "public-key"},
+		],
+		rp: {
+			name: "roseh.moe",
+		},
+		user: {
+			displayName: name,
+			id: Uint8Array.fromBase64(document.getElementById("id").value).buffer,
+			name: name,
+		},
+	}});
+	document.getElementById("key").value = new Uint8Array(publicKeyCredential.response.getPublicKey()).toBase64();
+	document.getElementById("form").submit();
+}
+</script>