apostrophe-cas

OBSOLETE — currently for Apostrophe 0.5.x only. If you need CAS support for 2.x, a pull request would be welcome. Or, consider using apostrophe-saml instead. That module can be used to integrate Apostrophe 2.x sites with Shibboleth, which may also be an available ID provider on your campus. Alternatively, use apostrophe-saml as a starting point to adapt this module to 2.x.

This module allows an Apostrophe site to act as a CAS client or server.

Client support means that you can send users to a third party site that supports CAS (Centralized Authentication Service) to log in, and then they will be logged into your Apostrophe site. This is known as "single sign-on."

Server support means that other sites can use your site as a CAS server. In this case your site is the authoritative one.

Installation

npm install --save apostrophe-cas

Configuration as a CAS Client

Add the module to the modules section of your app.js file:

    apostrophe-cas: {
      client: {
        protocol: 'https',
        host: 'cas.myschool.edu',
      },
    }

Next, make sure you shut off the regular authentication system. This is a top-level option in app.js (that is, it's not inside "modules," it's at the same level as "modules"):

  auth: false

Now your users will be redirected to the CAS login page at https://cas.myschool.edu/cas/login when they try to log in. After login they are directed back. Logout is also redirected.

Creating Users On the Fly

In some cases, any person who can log into the CAS server should also be a valid account on your site.

Here's how to automatically create new people on the fly:

    apostrophe-cas: {
      client: {
        protocol: 'https',
        host: 'cas.myschool.edu',
        createPerson: true
      },
    }

Adding New Users to a Group

By default, users created on the fly are not added to any group. You can change that, and also set default permissions for the group if it does not already exist:

    apostrophe-cas: {
      client: {
        protocol: 'https',
        host: 'cas.myschool.edu',
        createPerson: {
          group: {
            name: 'guests',
            permissions: [ 'guest' ]
          }
        }
      }
    }

Forcing an Admin User

You can use the admin option to set a username that always receives full admin permissions upon logging in. This is convenient for bootstrapping a new site that uses CAS login. First use the admin option to give your own CAS account full privileges, then log in and add groups and permissions for other CAS users.

    apostrophe-cas: {
      client: {
        protocol: 'https',
        host: 'cas.myschool.edu',
        createPerson: true,
        admin: 'jillrocks'
      }
    }

Setting First Names, Last Names and Other Metadata

Since CAS servers frequently don't provide any more information than a username, the default behavior is to set the user's first and last name based on their username, which isn't very satisfying.

As an alternative you can set the before option to a callback function that obtains additional information and populates the person object more completely, either from the cas object in the session or by some other means, such as an LDAP call or database call:

    apostrophe-cas: {
      client: {
        protocol: 'https',
        host: 'cas.myschool.edu',
        createPerson: {
          before: function(req, cas, person, callback) {
            // What did the cas server give us? Maybe extra
            // attributes are being passed and we can just
            // set person.firstName and person.lastName etc.
 
            console.log(cas);
 
            // No good? Try querying your LDAP or database server
            // with person.username
 
            // ...All done, invoke the callback
            return callback(null);
          }
        }
      }
      },
    }

There is also an after option, which takes the same arguments and is invoked after the person exists in the database.

Subclassing

If you prefer you can subclass the apostrophe-cas module and override the beforeCreatePerson and afterCreatePerson methods in your index.js file. You'll need to follow the same pattern used when subclassing apostrophe-snippets. If this is all new to you, just use the options.

Alternate sources for the unique username

By default this module expects a unique username in the user property returned by CAS. If this is not the right property for your needs, you can set the uniqueUsernameAttribute option of the module to a different property name. Unlike user, which is pulled directly from the CAS profile, this will be pulled from the attributes object included int he CAS profile. If you need even more control you can override the getCasUsername method of the module.

Alternate CAS URLs

In the client object above you may specify any of the fields below if needed. The defaults are shown. This is taken from the documentation of the connect-cas module, on which the client support in apostrophe-cas is built.

    protocol: 'https',
    host: undefined,
    hostname: undefined, // ex. google
    port: 443,
    paths: {
        validate: '/cas/validate',               // not implemented
        serviceValidate: '/cas/serviceValidate', // This is the one we use
        proxyValidate: '/cas/proxyValidate', // Not tested with Apostrophe
        proxy: '/cas/proxy', // Not tested with Apostrophe
        login: '/cas/login', // The user-visible login URL on the CAS server
        logout: '/cas/logout' // Ditto for logout
    }

Disabling Login

Occasionally you may need to temporarily disable login completely. To do so, set the disabled option to true:

    apostrophe-cas: {
      client: {
        disabled: true
      }
    }

This is useful during database migrations, content freezes and the like. The disabled.html page template will be rendered.

Configuration as a CAS Server

Configuring Apostrophe as a CAS server allows other sites to send users to Apostrophe to log in, and then redirects those users back to the other site, allowing that site to verify their username.

Here's the configuration to allow two sites to do this:

    'apostrophe-cas': {
      server: {
        services: [
          'https://www.site-we-are-allowing.com/',
          'https://www.another-ok-site.com/'
        ]
      }
    }

The CAS login, logout and serviceValidate URLs will be /cas/login, /cas/logout and /cas/serviceValidate. This is not currently configurable.

For security, the client site's URL must be in the services list. If the client site is lazy and sends people to both "www.foo.com" and plain old "foo.com", make sure you list both in services.

You may allow users to to come from an "http:" URL, but you really shouldn't, except for testing. https is necessary for secure use of CAS.

Security Notes

The CAS server does not check that incoming requests to the /cas/* routes are secured with https. Since Apostrophe is usually behind a reverse proxy like nginx, this isn't possible anyway. It is your responsibility to ensure that any non-https requests to /cas/* URLs are rejected by your proxy server in production.

Current Limitations

• The CAS client only obtains the username from the CAS server. No other fields are retrieved automatically. However, you can set callbacks to do more with the CAS data.
• The CAS server support is very basic and currently only provides the username to the other site. It was built as a convenient way to test the client support.
• There is no CAS proxy support. (Does anybody use that? What for?)

Changelog

0.5.9: the uniqueUsernameAttribute option can be used to specify a CAS attribute other than user to be used as the username.

0.5.8: if the client.disabled option is true, block existing login sessions, not just new logins.

0.5.7: do not allow users who are in the trash or do not have the login flag to log in. The Apostrophe unserialize mechanism also checks this, but it can't hurt to be thorough.