Wordpress - Password protect a custom post type programmatically

functions.php

<?php
/**
 * Password protects a custom post type programmatically.
 *
 * @param $post
 */
add_action( 'the_post', function( $post ){
	if ( $post->post_type != 'post' ) {
		return;
	}	
	$post->post_password = 'your_password';
} );
?>

Thanks pablo, works great and super useful - we were looking for keeping the same password for all posts to simplify for users and this makes it very easy and programmable.