passwordallposts.php

<?   
// in functions.php
add_filter( 'the_password_form', 'ds_password_form' );
function ds_password_form() {
    global $post;
    $label = 'pwbox-'.( empty( $post->ID ) ? rand() : $post->ID );
    $link = esc_url( site_url( 'wp-login.php?action=postpass', 'login_post' ) );
    return "    
    <form action='{$link}' method='post' id='passwordForm'>
        <input name='post_password' id='{$label}' type='password' size='20' maxlength='20' placeholder='Password' />
        <input type='submit' name='Submit' value='Unlock' />
    </form>\n";
}


// above your main loop
if ( post_password_required() ) : ?>
<a href='#' data-featherlight='#passwordForm'>Unlock All Posts</a>
<div id='passwordInput' style='display:none'>
    <?= get_the_password_form(); ?>
</div>
<? endif;


// in your loop
//...
  if (post_password_required()) {
      echo "This is locked.. <a href='#' data-featherlight='#passwordForm'>unlock it</a>";
  } else {
    // unlocked post   
  }
//...
?>