One of the key feature provided by the WSO2 API Manager is its ability to secure the exposed API’s using OAuth 2.0 tokens. WSO2 API Manager supports all 4 grant types of OAuth 2.0 specification. OAuth 2.0 is a specification that is widely adapted especially in the mobile application space. However we still find the need for API’s to be accessed by web applications that still use standard username-password based credentials. Many of these web applications use SAML 2 based authentication and would prefer to use the same SAML assertion to access OAuth 2.0 protected API’s. This type of a scenario is supported by WSO2 API Manager which supports a SAML 2 Bearer grant type that can allow an application to exchange the SAML 2 bearer token with an OAuth 2.0 access token. This token exchange is transparent to the end-user hence it will not impact their user experience. This token exchange process can be depicted in the diagram below.
Step 1 – Application receives a SAML assertion from the SAML IdP after authenticating the user.
Step 2 – When the Application needs to invoke an API, it sends the SAML assertion to the token endpoint of the API Manager. SAML assertion is Base 64 encoded and sent as a SAML Bearer grant. Application will also need to send the consumer key and consumer secret which has to be obtained when subscribing to this API.
Step 3– API Manager will validate the request and exchange the SAML token with an OAuth 2.0 access token and a refresh token.
Step 4 – Application Access the API with the OAuth 2.0 access token (generated in the above step). This OAuth 2.0 token should be included as the Authorization header when invoking API’s via the API Manager.
The objective of this blog is to introduce the concept of token exchange, you would find detailed instructions on how to set this up in the following API Manager document.
WSO2 API Manager has the capability of restricting which grant types are enabled to a given application. This functionality is provided via the management console of the API Manager. Given below are the steps required
1. App developers should have the required permission in order to restrict the grant types available for an application. Permission given below should be set to a user role associate to the App developer.
2. Once this is done please log out and log into the API Manager’s admin console
3. Now you would see the OAuth URL available in the left navigation, click on this.
4. Here you would see all the applications that are created by the App developer, from this menu select the relevant application to which the grant types should be restricted.
5. Once you are inside the selected application you can define which grant types should be allowed to a given application. By default all grant types are ‘un-checked’ and all grant types are allowed. If you want to override this default configuration select on the required grant types that should be allowed to a given application.
6. Once you are done click on the update button and the configuration would be updated.
WSO2 API Manager provides a host of REST API’s that are capable of performing many operations in the API Manager. Given below are the steps to follow to retrieve token information such as the Consumer Key,Consumer Secret, and Access Token using the REST API. In order to perform this we assume that an instance of the API Manager is running(in port offset 0) and an application is already available in the API Store.
1. Initially you need to login to the API Store and create a cookie that can be used in subsequent REST calls. Login to the store using the following command. Replace the username and the password with the relavent value
curl -X POST -c cookies http://localhost:9763/store/site/blocks/user/login/ajax/login.jag -d "action=login&username=xxxx&password=xxxx"
2. Call the Generate Application Key API that would generate the required access keys. Use the below command to generate the application keys. The following command would generate keys for the default applications. Change the parameters accordingly based on your application.
curl -X POST -b cookies http://localhost:9763/store/site/blocks/subscription/subscription-add/ajax/subscription-add.jag -d "action=generateApplicationKey&application=DefaultApplication&keytype=PRODUCTION&provider=&tier=&version=&callbackUrl=&authorizedDomains="