2FA: Ability to see original QR code again

pkg/controller/account/two_factor.go

@@ -70,6 +70,9 @@ func Setup2FA() http.HandlerFunc {
 			}
 		}
 
+		// Are they (re)viewing their original QR code?
+		var isPairingSecondDevice bool
+
 		// POST form actions.
 		if r.Method == http.MethodPost {
 			var intent = r.PostFormValue("intent")
@@ -84,9 +87,16 @@ func Setup2FA() http.HandlerFunc {
 				// Valid?
 				if !valid {
 					session.FlashError(w, r, "The passcode you submitted didn't seem correct. Try a new six-digit code.")
+
+					// If they were reconfiguring a second device, go back to the re-setup screen.
+					if tf.Enabled {
+						isPairingSecondDevice = true
+						break
+					} else {
 						templates.Redirect(w, r.URL.Path)
 						return
 					}
+				}
 
 				// OK!
 				tf.Enabled = true
@@ -120,13 +130,25 @@ func Setup2FA() http.HandlerFunc {
 						session.Flash(w, r, "Your 2FA settings have been cleared and disabled.")
 					}
 				}
+			case "resetup":
+				// View the original QR code to set up a new device.
+				var password = r.PostFormValue("password")
+				if err := currentUser.CheckPassword(password); err != nil {
+					session.FlashError(w, r, "Couldn't access your 2FA QR code: the password you entered is incorrect.")
+				} else {
+					session.Flash(w, r, "Password accepted. Your 2FA QR code and setup steps will be displayed below.")
+					isPairingSecondDevice = true
+				}
 			default:
 				session.FlashError(w, r, "Unknown intent: %s", intent)
 			}
 
+			// All POST requests redirect away except resetup.
+			if !isPairingSecondDevice {
 				templates.Redirect(w, r.URL.Path)
 				return
 			}
+		}
 
 		// Generate the QR code.
 		qrCode, err := tf.QRCodeAsDataURL(key)
@@ -138,6 +160,7 @@ func Setup2FA() http.HandlerFunc {
 			"TwoFactor":             tf,
 			"Key":                   key,
 			"QRCode":                qrCode,
+			"IsPairingSecondDevice": isPairingSecondDevice,
 		}
 
 		if err := tmpl.Execute(w, r, vars); err != nil {

web/templates/account/dashboard.html

@@ -134,7 +134,7 @@
                 {{end}}
 
                 <!-- New Feature: Two Factor Auth -->
-                {{if not .TwoFactorEnabled}}
+                <!--
                 <div class="card block">
                     <header class="card-header has-background-success-dark">
                         <p class="card-header-title has-text-light">
@@ -162,7 +162,7 @@
                         </p>
                     </div>
                 </div>
-                {{end}}
+                -->
 
                 <div class="card block">
                     <header class="card-header has-background-link">

web/templates/account/two_factor_setup.html

@@ -38,7 +38,13 @@
                         the time-limited six-digit code to log in.
                     </p>
 
-                    <h4>Backup Codes</h4>
+                    <!-- Are they reconfiguring their 2FA app (viewing the barcode)? -->
+                    {{if .IsPairingSecondDevice}}
+                        {{template "2fa-setup" .}}
+                        <hr>
+                    {{end}}
+
+                    <h4 class="mt-4">Backup Codes</h4>
 
                     <p>
                         In case you lose access to your Authenticator App, please print off or write down these
@@ -72,7 +78,12 @@
                         </button>
                     </form>
 
-                    <h4 class="has-text-danger mt-4">Disable Two-Factor Auth</h4>
+                    <hr>
+
+                    <h4 class="has-text-danger mt-4">
+                        <i class="fa fa-exclamation-triangle mr-1"></i>
+                        Disable Two-Factor Auth
+                    </h4>
 
                     <p>
                         If you wish to <strong>disable</strong> two-factor authentication for your account, please enter
@@ -95,6 +106,43 @@
                             Disable Two-Factor Authentication
                         </button>
                     </form>
+
+                    <hr>
+
+                    <h4 class="has-text-warning mt-4">
+                        <i class="fa fa-qrcode mr-1"></i>
+                        Set Up Another Device
+                    </h4>
+
+                    <p>
+                        If you wish to <strong>set up another authenticator device</strong> and view your original
+                        QR code, you may do so by entering your current account password below. This may be useful
+                        if you have bought a new phone or want to migrate your authenticator to a different device,
+                        so that you may access the original QR code and configure the new authenticator.
+                    </p>
+
+                    <p>
+                        <strong>Note:</strong> this will not change your 2FA security key or backup codes. If you
+                        have lost your old authenticator, it will be more secure to <strong>disable and then set up
+                        2FA from scratch</strong>, which will generate a new secret key and backup codes.
+                    </p>
+
+                    <form action="{{.Request.URL.Path}}" method="POST">
+                        {{InputCSRF}}
+                        <input type="hidden" name="intent" value="resetup">
+
+                        <div class="field">
+                            <label class="label" for="password">Your account password:</label>
+                            <input type="password" class="input"
+                                name="password"
+                                placeholder="Password"
+                                required>
+                        </div>
+
+                        <button type="submit" class="button is-warning">
+                            View my original 2FA QR code
+                        </button>
+                    </form>
                 </div>
             </div>
         </div>
@@ -144,6 +192,16 @@
                         setting up your Authenticator App.
                     </p>
 
+                    {{template "2fa-setup" .}}
+                </div>
+            </div>
+        </div>
+    </div>
+    {{end}}<!-- Setup -->
+
+</div>
+{{end}}
+{{define "2fa-setup"}}
 <h2>Set up your Authenticator App</h2>
 
 <p>
@@ -233,13 +291,6 @@
 
     <button type="submit" class="button is-primary">Confirm &amp; Continue</button>
 </form>
-                </div>
-            </div>
-        </div>
-    </div>
-    {{end}}<!-- Setup -->
-
-</div>
 {{end}}
 {{define "scripts"}}
 <script>