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Invoking an Endpoint from a Different Domain¶

This topic provides instructions on invoking an endpoint in an OAuth2 .war file from the JavaScript of a web application that is located in a different domain than the WSO2 Identity Server domain.

Tip

This is relevant for any REST endpoint in WSO2 Identity Server.

When attempting this, you will typically see a "No 'Access-Control-Allow-Origin' header that is present on the requested resource. Therefore, your web application is not allowed access. The issue occurs as the script on your page is running from a specific domain and would try to request the resource via an XmlHttpRequest or XDomainRequest from a different domain as this is a cross-origin request.

In order to get rid of this issue, you must enable this by sending the following CORS (Cross-Origin Resource Sharing) header using a custom filter.

Access-Control-Allow-Origin: http://example.com

In the above example, http://example.com is the domain name of the location of the page where that script is hosted.

Invoking the UserInfo endpoint through JavaScript¶

There are two possible solutions to apply the CORS header.

Customizing OpenIDConnectUserEndpoint.java as indicated below and replacing the oauth2.war file. Introduce the following header to the getUserClaims() method. By applying this filter, it allows to invoke OpenIDConnectUserEndpoint from the ' http://example.com ' domain. If you add a '*' instead of ' http://example.com ', it allows you to invoke this endpoint from any domain. However, this approach leads to some security risks.
```
respBuilder.header("Access-Control-Allow-origin", 'http://example.com')
```
Tip

Customizing the endpoint to allow cross origin communication and replacing the .war is not actually recommended.
Applying a CORS filter. A CORS filter is already used in the OAuth web application of the WSO2 Identity Server and you can do the following configuration changes to the web.xml file located in the <IS_HOME>/repository/deployment/server/webapps/oauth2/WEB-INF directory in order to add above mentioned header. Enable the CORS filter for the OAuth web application by adding the filter configuration to the web.xml file as indicated below.
```
<filter>
    <filter-name>CORS</filter-name>
    <filter-class>com.thetransactioncompany.cors.CORSFilter</filter-class>
    <init-param>
        <param-name>cors.allowOrigin</param-name>
        <param-value>http://example.com</param-value>
    </init-param>
</filter>


<filter-mapping>
    <filter-name>CORS</filter-name>
    <url-pattern>/example.html</url-pattern>
</filter-mapping>
```
For configuration details of a CORS filter, see here.

Tip

You can provide whitespace-separated list of origins that the CORS filter must allow like cors.allowOrigin . However, you must make sure not to use wildcards like * since it allows any origin and it may lead to some security vulnerabilities.

The dependency is already included in the oauth2.war. Thus, it is not necessary to separately add it to the pom.xml file. However, if you are using another endpoint you need to add the dependency as shown below.

Applying CORS filter to another web application¶

Add the following module to the dependencies section of the pom.xml file.

<dependency>
    <groupId>com.thetransactioncompany.wso2</groupId>
    <artifactId>cors-filter</artifactId>
    <version>1.7.0.wso2v1</version>
</dependency>

Enable the CORS filter for the web application by adding the filter configuration to the web.xml in the <SAMPLE_WEB_APP>/src/main/webapps/WEB-INF directory as mentioned above in the second approach.

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