WordPress Role And Capability Checks For Plugin Development

The Importance of Capability Checks in WordPress Plugins

Implementing user capability checks is an essential part of developing secure, well-coded WordPress plugins. Capability checks help restrict access to sensitive plugin functions and data to only authorized users. This improves site security and prevents unauthorized changes that could introduce bugs or exploits.

Without proper capability checks, any logged-in user could potentially access powerful plugin settings and make changes that affect the entire site. This poses risks ranging from accidental mistakes that break functionality to malicious actions by untrusted users.

Capability checks also provide visible feedback to users on what they are able to access within the plugin. Users might otherwise encounter confusing error messages or seemingly broken features when attempting to access functions they lack permissions for.

Core WordPress User Roles and Capabilities

When coding capability checks, it helps to understand the core user roles and capabilities WordPress uses. These include:

• Administrators – The admin role has access to all plugin functions and site management features. Common caps include:
  • manage_options – Full admin access level
  • edit_others_posts – Edit any user’s content
  • publish_pages – Publish new pages
  • edit_themes – Update installed themes
• Editors – The editor role allows editing and publishing capabilities. Common caps include:
  • moderate_comments – Approve/remove comments
  • edit_published_posts – Edit existing posts
  • edit_others_pages – Edit other users’ pages
• Authors – Authors can publish their own content. Example caps:
  • upload files – Upload media
  • publish_posts – Publish new posts
• Contributors – Contributors can create content but not publish. Caps include:
  • edit_posts – Edit own draft content
• Subscribers – Subscribers have minimal capabilities:
  • read – Open published content

Plugins often use combinations of checks against both specific capabilities and broader user roles. For example, restricting access to a settings page to only admins.

Checking Capabilities with current_user_can()

The main WordPress function for checking user permissions is current_user_can(). This tests whether the current logged in user has the given capability.

Basic syntax:

  if ( current_user_can( 'manage_options' ) ) {
    
    // Admin level access code here
  
  }

We can also check against user roles directly like:

  if ( current_user_can( 'administrator' ) ) {

    // Code only admins can run

  }

When the user fails a capability check, we may want to provide visible feedback explaining the issue. For example:

  if ( ! current_user_can('manage_network') ) {

    wp_die( 'Sorry, you do not have permission to access this page' );

  } 

Wrapping sensitive code in capability checks guards against potential exploits while giving context to denied users.

Example: Restricting Access to Plugin Admin Pages

A common use case for granular capability checks is limiting which users can access a plugin’s admin settings pages. These often contain sensitive configuration data.

Without proper restrictions, subscriber-level members might be able to access settings they should not change. Or view data they shouldn’t have access to.

We can prevent this by checking capabilities on the admin page load. If the check fails, redirect to the WordPress dashboard:

  function myplugin_settings_checks() {

    // Only admins can access this page
    if ( ! current_user_can('manage_options') ) {
    
      wp_redirect( admin_url('/') );
      exit;
    
    }

  }
  
  add_action('load-myplugin_options', 'myplugin_settings_checks');

Now when a non-admin user tries to access the page, they will be redirected back to the dashboard with a “Not Authorized” type message. This gives feedback on why they cannot access a page protected for admins.

Additional Context Checks

Capability checks form the core of role restriction logic in plugins. We can supplement these with further context conditions as well.

For example, verifying the user is logged into the admin:

  if ( ! is_admin() || ! is_user_logged_in() ) {
  
    wp_redirect( wp_login_url() ); 
    exit;

  }

This doubles checks that:

1. The user is in the WordPress admin area
2. They are logged into an account

Before allowing access to update options.

Optimizing Permission Checks

There are a few best practices worth noting when implementing capability checks:

• Caching – Checking the user’s role on every page load can add overhead. In some cases, caching results can help.
• Limit DB queries – Try to call current_user_can() without forcing extra database lookups whenever possible.
• Check only once – No need to repeat the same capability check many times. Check once then store result in a variable.

Balancing security without impacting performance requires trading off these factors. But generally avoiding unnecessary queries helps plugins run faster.

Conclusion

Capability checks are crucial for controlling what WordPress users have access to within plugins. Checks like current_user_can() restrict unauthorized changes, improve security, and provide user feedback.

Common practices include checking against user roles and specific capabilities, providing error messages, adding context checks, and optimizing performance.

Taking the time to lock down plugin permissions ultimately leads to more secure, stable plugin operation.