Content Security Policy (CSP.md)

Content Security Policy (CSP) is a layer of security to combat Cross-Site Scripting (XSS). For more information on CSP, please refer to this page.

Valtimo offers strongly typed CSP configuration through its environment files. In order to add this to your implementation, install version 11.2.0 or higher of the front-end libraries.

Defining your policy

It is advised to create a new folder in your implementation: src/environments/csp. In this folder, you will create a file defining a CSP policy for each environment your implementation is deployed to.

For a CSP for our development environment, we might define the following:

src/environments/csp/csp.dev.ts

// types imported from the 'csp-header' package, which is included in Valtimo FE libs 11.2.0 and up
import {CSPHeaderParams, DATA, SELF, UNSAFE_EVAL, UNSAFE_INLINE} from 'csp-header';
// optional import of utilities to manipulate URL strings
import {UrlUtils} from '@valtimo/config';
// the Keycloak configuration used on the development environment
import {authenticationKeycloak} from '../auth/keycloak-config.dev';

// in this object we define our CSP headers, which must conform to the type CSPHeaderParams (imported from 'csp-header')
export const cspHeaderParamsDev: CSPHeaderParams = {
    directives: {
        'default-src': [SELF],
        // DATA is needed because of use of inline images
        'img-src': [SELF, DATA],
        /*
        UNSAFE_EVAL is needed because of javascript in form.io forms (i.e. on summary page)
        Scripts loaded from https://cdn.form.io/ are allowed, otherwise Form.IO won't work in our app.
         */
        'script-src': [SELF, UNSAFE_EVAL, UNSAFE_INLINE, 'https://cdn.form.io/'],
        /* 
        DATA is needed because of use of inline fonts.
        Some external sources are allowed which are used in the Valtimo front-end libraries.
         */
        'font-src': [
            SELF,
            DATA,
            UNSAFE_INLINE,
            'https://cdnjs.cloudflare.com/ajax/libs/font-awesome/',
            'https://fonts.gstatic.com',
        ],
        'connect-src': [
            SELF,
            // connect-src must contain the root url of the keycloak instance the application uses to login
            UrlUtils.getUrlHost(authenticationKeycloak.options.keycloakOptions.config.url),
        ],
        'style-src': [
            SELF,
            // UNSAFE_INLINE is needed because of use of inline styles
            UNSAFE_INLINE,
            // external styles sources used by the Valtimo FE libs
            'https://cdnjs.cloudflare.com/ajax/libs/font-awesome/',
            'https://fonts.googleapis.com',
        ],
    },
};

Including your policy

After defining your policy in a separate file, import it in the environment file in which you want to use it. Next, add it under the key csp. After deploying your application, CSP headers should be added to the document head before app initialization.

src/environments/environment.ts

...
import {cspHeaderParamsDev} from './csp';

export const environment: ValtimoConfig = {
    ...
    csp: cspHeaderParamsDev
}

Extending your policy

The optional property csp in your environment file must refer to an object of type CSPHeaderParams, which is exported by the library csp-header. This library has many features which you can optionally use to add further flexibility to your CSP policy. Please refer to its NPM page to see what is possible.