The world's most useless 2FA

foo.diff

diff --git a/mysite/code/CustomAuthenticator.php b/mysite/code/CustomAuthenticator.php
new file mode 100644
index 0000000..141a9f1
--- /dev/null
+++ b/mysite/code/CustomAuthenticator.php
@@ -0,0 +1,14 @@
+<?php
+
+use SilverStripe\Security\MemberAuthenticator\Authenticator;
+
+class CustomAuthenticator extends Authenticator
+{
+    /**
+     * @inherit
+     */
+    public function getLoginHandler($link)
+    {
+        return CustomLoginHandler::create($link, $this);
+    }
+}
diff --git a/mysite/code/CustomLoginHandler.php b/mysite/code/CustomLoginHandler.php
new file mode 100644
index 0000000..dbfbca3
--- /dev/null
+++ b/mysite/code/CustomLoginHandler.php
@@ -0,0 +1,76 @@
+<?php
+
+use SilverStripe\Security\MemberAuthenticator\LoginHandler;
+use SilverStripe\Security\Member;
+use SilverStripe\Control\Session;
+use SilverStripe\Forms\Form;
+use SilverStripe\Forms\FormAction;
+use SilverStripe\Forms\FieldList;
+use SilverStripe\Forms\TextField;
+
+use SilverStripe\Dev\Debug;
+
+class CustomLoginHandler extends LoginHandler
+{
+
+    private static $allowed_actions = [
+        'step2',
+        'secondStepForm',
+    ];
+
+    public function doLogin($data, $formHandler)
+    {
+        if ($member = $this->checkLogin($data)) {
+            Session::set('CustomLoginHandler.MemberID', $member->ID);
+            Session::set('CustomLoginHandler.Data', $data);
+            return $this->redirect($this->link('step2'));
+        }
+
+        // Fail to login redirects back to form
+        return $this->redirectBack();
+    }
+
+    public function step2()
+    {
+        return [
+            "Form" => $this->secondStepForm()
+        ];
+    }
+
+    public function secondStepForm()
+    {
+        return new Form(
+            $this,
+            "secondStepForm",
+            new FieldList(
+                new TextField('SecondFactor', 'Your 2FA (12345)')
+            ),
+            new FieldList(
+                new FormAction('completeSecondStep', 'Login in')
+            )
+        );
+    }
+
+    public function completeSecondStep($data)
+    {
+        if ($this->checkSecondFactor($data)) {
+            $memberID = Session::get('CustomLoginHandler.MemberID');
+            $member = Member::get()->byID($memberID);
+            $data = Session::get('CustomLoginHandler.Data');
+            if (!$member) {
+                return $this->redirectBack();
+            }
+            $this->performLogin($member, $data);
+            return $this->redirectAfterSuccessfulLogin();
+        }
+
+
+        // Fail to login redirects back to form
+        return $this->redirectBack();
+    }
+
+    protected function checkSecondFactor($data)
+    {
+        return $data['SecondFactor'] === '12345';
+    }
+}

It's actually quite useful as an example multi-step login for the documentation, so it's not entirely useless ;)