在CakePHP中实现安全的LDAP登录，可以按照以下步骤进行：

1. 安装LDAP插件：首先需要安装CakePHP的LDAP插件。可以通过Composer运行以下命令来安装插件：

composer require vdechenaud/cakephp-ldap

2. 配置LDAP连接：在config/app.php文件中添加LDAP连接的配置信息：

'Ldap' => [
    'host' => 'ldap.example.com',
    'port' => 389,
    'basedn' => 'dc=example,dc=com',
    'binddn' => 'cn=admin,dc=example,dc=com',
    'bindpw' => 'password',
    'users' => [
        'model' => 'Users',
        'filter' => '(&(objectClass=inetOrgPerson)(uid={0}))',
        'fields' => [
            'username' => 'uid',
            'password' => 'userpassword',
            'email' => 'mail',
            'name' => 'cn',
        ],
    ],
],

这里的配置信息需要根据你的LDAP服务器进行相应的修改。

3. 创建用户模型：在src/Model目录下创建UsersTable.php文件，定义UsersTable类来处理用户相关操作。可以参考以下示例代码：

addBehavior('Ldap.Ldap', ['userModel' => 'Users']);
    }

    public function findLdapAuth(\Cake\ORM\Query $query, array $options)
    {
        $query
            ->select(['username', 'password'])
            ->where(['Users.username' => $options['username']])
            ->contain([]);

        return $query;
    }

    public function beforeSave(\Cake\Event\EventInterface $event, \Cake\ORM\EntityInterface $entity, \ArrayObject $options)
    {
        if ($entity->isNew() && !$entity->get('password')) {
            $entity->set('password', $this->generatePassword());
        }

        return true;
    }

    public function generatePassword()
    {
        $password = '';

        // 生成随机密码的逻辑

        return $password;
    }

    public function setPassword($password)
    {
        $hasher = new DefaultPasswordHasher();

        return $hasher->hash($password);
    }
}

4. 创建登录控制器：在src/Controller目录下创建UsersController.php文件，定义UsersController类来处理用户登录逻辑。可以参考以下示例代码：

loadComponent('Auth', [
            'authenticate' => [
                'Ldap',
            ],
            'loginAction' => [
                'controller' => 'Users',
                'action' => 'login',
            ],
            'loginRedirect' => [
                'controller' => 'Users',
                'action' => 'index',
            ],
            'logoutRedirect' => [
                'controller' => 'Users',
                'action' => 'login',
            ],
            'authError' => 'You are not authorized to access that location.',
            'unauthorizedRedirect' => [
                'controller' => 'Users',
                'action' => 'login',
            ],
        ]);
    }

    public function login()
    {
        if ($this->request->is('post')) {
            $user = $this->Auth->identify();
            if ($user) {
                $this->Auth->setUser($user);
                return $this->redirect($this->Auth->redirectUrl());
            } else {
                $this->Flash->error('Invalid username or password, try again');
            }
        }
    }

    public function logout()
    {
        return $this->redirect($this->Auth->logout());
    }
}

5. 创建登录视图：在src/Template/Users目录下创建login.ctp文件，用于显示登录表单。可以参考以下示例代码：

Login
Form->create() ?>
Form->control('username', ['required' => true]) ?>
Form->control('password', ['required' => true]) ?>