how to retrieve password from within hook_user_presave()
It us not advised not to use the user's password as a raw value, however if you still want to access the password field value in unencrypted form than try the following:


&lt;?php
/**
 * Implements hook_form_alter().
 * Alters user_register_form.
 */
function MyModule_form_alter(&amp;$form, $form_state, $form_id) {
  // Add the additional validation callback for the user registration form.
  if ($form_id == 'user_register_form') {
    $form['#validate'][] = 'MyModule_user_register_form_validate';
  }
}

// Callback function for Validation handler of user_register_form.
function MyModule_user_register_form_validate($form, &amp;$form_state) {
  if (isset($form_state['values']['pass'])) {
    // Here you will get the value of password.
    $password = $form_state['values']['pass'];
  }
}
?&gt;