Require authenticator code every 24 hours

2 files changed, 66 insertions, 69 deletions

diff --git a/roseh.moe.go b/roseh.moe.go
index 063a08a..180ce5f 100644
--- a/roseh.moe.go
+++ b/roseh.moe.go
@@ -347,13 +347,8 @@ func sharedFileHandler(w http.ResponseWriter, r *http.Request) {
 }
 
 func qrHandler(w http.ResponseWriter, r *http.Request) {
-	sig, err := base64.RawURLEncoding.DecodeString(r.FormValue("s"))
-	if err != nil {
-		http.Error(w, fmt.Sprintf("Bad signature: %s", err), http.StatusBadRequest)
-		return
-	}
-	text := r.FormValue("t")
-	if !verify([]byte(text), sig, "qr") {
+	text, ok := verify(r.FormValue("t"), "qr")
+	if !ok {
 		http.Error(w, "Bad signature", http.StatusBadRequest)
 		return
 	}
@@ -610,7 +605,7 @@ 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) + "&s=" + base64.RawURLEncoding.EncodeToString(mac([]byte(downloadURL), "qr")),
+		QR:  "/qr.png?t=" + url.QueryEscape(downloadURL) + mac(downloadURL, "qr"),
 	}); err != nil {
 		log.Printf("Warning: wormholeSend: %s", err)
 	}
@@ -690,19 +685,25 @@ func cleanHole() error {
 	}
 }
 
-const macSize = sha256.Size
-
-func mac(msg []byte, purpose string) []byte {
+func mac(msg string, purpose string) string {
 	mac := hmac.New(sha256.New, secretKey)
 	io.WriteString(mac, purpose)
 	io.WriteString(mac, ":")
-	mac.Write(msg)
-	return mac.Sum(nil)
+	io.WriteString(mac, msg)
+	return base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
 }
 
-func verify(msg, messageMAC []byte, purpose string) bool {
+func verify(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)
-	return hmac.Equal(messageMAC, expectedMAC)
+	if !hmac.Equal([]byte(msgMAC), []byte(expectedMAC)) {
+		return "", false
+	}
+	return msg, true
 }
 
 func marshalInt(x int64) []byte {
@@ -722,11 +723,10 @@ func unmarshalInt(b []byte) (int64, bool) {
 	return int64(binary.BigEndian.Uint64(buf)), true
 }
 
-const yearOffset = 2025
+var myUnixEpoch = time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC)
 
 func marshalTime(t time.Time) []byte {
-	year, month, day := t.UTC().Date()
-	return marshalInt((int64(year)-yearOffset)<<9 | int64(month)<<5 | int64(day))
+	return marshalInt(int64(t.Sub(myUnixEpoch) / time.Second))
 }
 
 func unmarshalTime(b []byte) (time.Time, bool) {
@@ -734,15 +734,14 @@ func unmarshalTime(b []byte) (time.Time, bool) {
 	if !ok {
 		return time.Time{}, false
 	}
-	return time.Date(int(n>>9+yearOffset), time.Month(n>>5&0xf), int(n&0x1f), 0, 0, 0, 0, time.UTC), true
+	return myUnixEpoch.Add(time.Duration(n) * time.Second), true
 }
 
 func makeToken() string {
-	t := marshalTime(time.Now())
-	return base64.RawURLEncoding.EncodeToString(append(t, mac(t, "auth")...))
+	t := base64.RawURLEncoding.EncodeToString(marshalTime(time.Now()))
+	return t + mac(t, "auth")
 }
 
-const cookieExpiration = 300 * 24 * time.Hour
 const authCookieName = "a"
 
 func attachCookie(w http.ResponseWriter) {
@@ -751,7 +750,7 @@ func attachCookie(w http.ResponseWriter) {
 		Value:       makeToken(),
 		Path:        "/",
 		Domain:      selfURL.Hostname(),
-		Expires:     time.Now().Add(cookieExpiration),
+		Expires:     time.Now().Add(longLoginTimeout),
 		Secure:      true,
 		HttpOnly:    true,
 		SameSite:    http.SameSiteStrictMode,
@@ -759,34 +758,28 @@ func attachCookie(w http.ResponseWriter) {
 	})
 }
 
-func cookieAuth(w http.ResponseWriter, r *http.Request) bool {
+func cookieAuth(r *http.Request) (time.Duration, bool) {
 	cookie, err := r.Cookie(authCookieName)
 	if err != nil {
-		return false
-	}
-	authCookie, err := base64.RawURLEncoding.DecodeString(cookie.Value)
-	if err != nil {
-		return false
+		return 0, false
 	}
-	if len(authCookie) < macSize {
-		return false
+	msg, ok := verify(cookie.Value, "auth")
+	if !ok {
+		return 0, false
 	}
-	msg, mac := authCookie[:len(authCookie)-macSize], authCookie[len(authCookie)-macSize:]
-	if !verify(msg, mac, "auth") {
-		return false
+	msgBytes, err := base64.RawURLEncoding.DecodeString(msg)
+	if err != nil {
+		return 0, false
 	}
-	t, ok := unmarshalTime(msg)
+	t, ok := unmarshalTime(msgBytes)
 	if !ok {
-		return false
-	}
-	cookieAge := time.Since(t)
-	if cookieAge > cookieExpiration {
-		return false
+		return 0, false
 	}
-	if cookieAge > 24*time.Hour {
-		attachCookie(w)
+	age := time.Since(t)
+	if age > longLoginTimeout {
+		return 0, false
 	}
-	return true
+	return age, true
 }
 
 func totp(t int64) []byte {
@@ -808,13 +801,12 @@ func checkOTP(auth string) int {
 	return subtle.ConstantTimeCompare([]byte(auth), totp(now)) | subtle.ConstantTimeCompare([]byte(auth), totp(now-1))
 }
 
-func checkPassword(password, auth string) bool {
-	otpMatches := checkOTP(auth)
+func checkPassword(password string) int {
 	hash, err := pwhash.Hash(password, notepadPassword[:pwhash.SaltSize])
 	if err != nil {
-		return false
+		return 0
 	}
-	return subtle.ConstantTimeCompare(hash, notepadPassword[pwhash.SaltSize:])&otpMatches != 0
+	return subtle.ConstantTimeCompare(hash, notepadPassword[pwhash.SaltSize:])
 }
 
 var (
@@ -824,45 +816,47 @@ var (
 )
 
 type loginTemplateArgs struct {
+	Quick bool
 	Error bool
 }
 
 func redirectLogin(w http.ResponseWriter, r *http.Request, redirect string) {
-	redirect += base64.RawURLEncoding.EncodeToString(mac([]byte(redirect), "redirect"))
+	redirect += mac(redirect, "redirect")
 	http.Redirect(w, r, "//"+selfURL.Host+"/login?redirect="+url.QueryEscape(redirect), http.StatusSeeOther)
 }
 
+const (
+	quickLoginTimeout = 24 * time.Hour
+	longLoginTimeout  = 300 * 24 * time.Hour
+)
+
 func serveLogin(w http.ResponseWriter, r *http.Request) {
-	if err := loginTemplate.Execute(w, loginTemplateArgs{}); err != nil {
+	_, cookieOK := cookieAuth(r)
+	if err := loginTemplate.Execute(w, loginTemplateArgs{
+		Quick: cookieOK,
+	}); err != nil {
 		log.Printf("Warning: login: %s", err)
 	}
 }
 
-func verifyRedirect(redirect string) (string, bool) {
-	base64MacSize := base64.RawURLEncoding.EncodedLen(macSize)
-	if len(redirect) < base64MacSize {
-		return "", false
-	}
-	redirect, macBase64 := redirect[:len(redirect)-base64MacSize], redirect[len(redirect)-base64MacSize:]
-	mac, err := base64.RawURLEncoding.DecodeString(macBase64)
-	if err != nil {
-		return "", false
-	}
-	if !verify([]byte(redirect), mac, "redirect") {
-		return "", false
-	}
-	return redirect, true
-}
-
 func login(w http.ResponseWriter, r *http.Request) {
-	if !checkPassword(r.FormValue("password"), r.FormValue("auth")) {
-		if err := loginTemplate.Execute(w, loginTemplateArgs{Error: true}); err != nil {
+	otpMatches := checkOTP(r.FormValue("auth"))
+	passwordMatches := 1
+	_, cookieOK := cookieAuth(r)
+	if !cookieOK {
+		passwordMatches = checkPassword(r.FormValue("password"))
+	}
+	if otpMatches&passwordMatches == 0 {
+		if err := loginTemplate.Execute(w, loginTemplateArgs{
+			Quick: cookieOK,
+			Error: true,
+		}); err != nil {
 			log.Printf("Warning: login: %s", err)
 		}
 		return
 	}
 	attachCookie(w)
-	redirect, ok := verifyRedirect(r.FormValue("redirect"))
+	redirect, ok := verify(r.FormValue("redirect"), "redirect")
 	if !ok {
 		redirect = "/"
 	}
@@ -1119,7 +1113,8 @@ type authHandler struct {
 }
 
 func (h *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
-	if !cookieAuth(w, r) {
+	if age, ok := cookieAuth(r); !ok || age > quickLoginTimeout {
+		log.Printf("Warning: ok age = %v %v", ok, age)
 		if h.noRedirect {
 			http.Error(w, "not logged in", http.StatusUnauthorized)
 		} else {
diff --git a/templates/login.html.template b/templates/login.html.template
index a64f3c6..43f91fd 100644
--- a/templates/login.html.template
+++ b/templates/login.html.template
@@ -25,9 +25,11 @@
 {{- 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">