CORS Filter

Overview

CORS Filter is an implementation of the W3C's Cross-Origin Resource Sharing (CORS) specification.

The CORS Filter works by adding required Access-Control-* headers to the HttpServletResponse object. The filter also protects against HTTP response splitting. If a request is invalid or not permitted, the request is rejected with HTTP status code 403 (Forbidden).

The minimal configuration required to use the CORS Filter is shown below, and is already added to the web.xml in jans-auth.war. The filter name is io.jans.as.server.filter.CorsFilter.

    <filter-mapping>
        <filter-name>CorsFilter</filter-name>
        <url-pattern />
    </filter-mapping>

Configure CORS

CORS can be configured in Jans Server using Jans TUI. Follow these steps:

1. Open Jans TUI using /opt/jans/jans-cli/jans_cli_tui.py command.
2. Go to Auth Server > Properties and select corsConfigurationFilters
3. This will display the CORS Configuration Filter parameters, as shown below:

1. Define and configure the parameters.
2. Click save at the bottom of the page.

Parameters supported by CORS Filters

CORS Filter supports the following initialization parameters:

Attribute	Description
corsAllowedOrigins	A list of origins that are allowed to access the resource. A * can be specified to enable access to resource from any origin. Otherwise, a whitelist of comma separated origins can be provided. Eg: http://www.w3.org, https://www.apache.org. Defaults: * (Any origin is allowed to access the resource).
corsAllowedMethods	A comma separated list of HTTP methods that can be used to access the resource, using cross-origin requests. These are the methods which will also be included as part of Access-Control-Allow-Methods header in pre-flight response. Eg: GET, POST. Defaults: GET, POST, HEAD, OPTIONS
corsExposedHeaders	A comma separated list of request headers that can be used when making an actual request. These headers will also be returned as part of Access-Control-Allow-Headers header in a pre-flight response. Eg: Origin, Accept. Defaults: Origin, Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-Headers
corsSupportCredentials	A flag that indicates whether the resource supports user credentials. This flag is exposed as part of Access-Control-Allow-Credentials header in a pre-flight response. It helps browser determine whether or not an actual request can be made using credentials. Defaults: true
corsLoggingEnabled	Value to enable logging, Setting the value to False will disable logging. Defaults: true
corsPreflightMaxAge	The duration in seconds the browser is allowed to cache the result of the pre-flight request. This will be included as part of the Access-Control-Max-Age header in the pre-flight response. A negative value will prevent the CORS Filter from adding this response header to the pre-flight response. Defaults: 1800
corsRequestDecorate	A flag to control if CORS specific attributes should be added to the HttpServletRequest object. Defaults: true

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Last update: 2023-12-11
Created: 2022-05-18