How to customise Azure AD OIDC user ID token for APM integration
Overview A Service Provider (SP) such as the F5 APM can integrate with Azure AD (AAD) as an Identity Provider (IDP) for federated authentication using OpenID Connect (OIDC). Through this process, a user visiting APM (e.g., https://myapps.acme.corp ) is immediately redirected to AAD for authentication, once authenticated, AAD returns a code to the APM via the user browser. The APM grabs that code, adds additional information, sends them together to AAD, and finally receives an ‘access_token’ and ‘id_token’. This article takes a special focus around what is included in ‘id_token’ that AAD returns, as it is used by APM, and broadly speaking by any relying party SP, for the purpose of session creation. ‘id_token’ (part of OIDC) contains user identity information and is highly customizable. The customization of ‘id_token’ is completely done within AAD. The concept is simple, but not until it is well understood in my experience; especially with the AAD having a bunch of configuration items in the mix, such as ‘Token configuration’, ‘API permissions’ and ‘Expose an API’. This article hopes to cut all the clutter and un-muddy the water so to speak, around this topic. OIDC As a refresher, the difference between oAuth and OIDC lies in that OIDC is an identity piece laying on top of oAuth. Specifically, with oAuth, ‘access_token’ alone is returned, whereas with OIDC, ‘id_token’ is returned in addition to ‘access_token’. Scope To tell AAD we are using OIDC, the APM needs to include a scope named ‘openid’ in its outbound request to the AAD. This is achieved via the following setting. Within AAD, your application must include ‘openid’, as shown below. By default, the ‘openid’ scope comes with a list of claims that will be included in ‘id_token’. However, for certain claims to be available, additional scopes are also required. For example, if you want to have ‘preferred_username’and ‘name’ claims included, ‘profile’ scope needs to be added as well, as is depicted in the following. AAD also lets you add optional claims via ‘Token configuration’ as shown below. If these optional claims need additional scopes, AAD will add those scopes in for you under ‘API permissions’. On the APM ‘OAuth Client’ configuration, make sure to add those scopes in as highlighted below. Once the APM matches scope with AAD, AAD will include all claims in ‘id_token’ it sends back to the APM. The APM is then able to consume those claims based on the use case (e.g., create a session using email) I am hoping that this short article sheds some light around your integration work around this space.
APM Cookbook: SAML IdP Chaining
As an APM subject mater expert at F5 I often find myself in situations where a customer or colleague needs an example of a particular configuration. While most of these requests are easily handled with a call or WebEx I'm a firm believer in sharing knowledge through documentation.. and I don't like getting calls at 3 AM. If you're like me you grew up with the O'Reilly Cookbook series which served as a great reference document for various development or server configuration tasks. My goal is to create a similar reference resource here on DevCentral for those one-off scenarios where a visual example may help your complete your task. For the first APM Cookbook series I'll discuss SAML IdP chaining. Overview Security Assertion Markup Language, more commonly known as SAML, is a popular federated authentication method that provides web based single sign-on. One of the key security advantages to SAML is the reduction in username/password combinations that a user has remember... or in my experience as a security engineer the number of passwords written on a post-it note stuck to their monitor. There are two major services in a SAML environment: IdP - Identity Provider SP - Service Provider The identity provider is the SAML service that authenticates the user and passes an assertion to then service providers proving the user's identity. F5's APM performs both IdP and SP services and allows customers to easily deploy federated authentication in their environment. In more complex scenarios you may run across a requirement where multiple SAML IdPs need to be chained together. This comes up from time to time when customers have contractors that utilize federated authentication for authorization to corporate resources. Example For our configuration we have the Globex Corporation that uses APM to authenticate uses to Office 365. Globex hire contractors from Acme Corp. who authenticate using the Acme Corp. ADFS environment. However, since Office 365 is configured to authenticate against the Globex APM we need to convert the Acme Corp. SAML assertion into a Globex SAML assertion, which is known as IdP chaining. The step ladder for this process is shown below: 1. User requests https://outlook.com/globex.com 2 - 3. Office 365 redirects user to idp.globex.com 3 - 4. idp.globex.com determines user is a contractor and redirect user to sts.acme.com 5 - 8. User authenticates using Acme credentials and is then redirect back to idp.globex.com 9. idp.globex.com consumes the Acme SAML assertion and creates a Globex SAML assertion 10. User is redirected back to Office 365 11 - 12. Office 365 consumes the Globex SAML assertion and displays the user's mail Configuration To configure your APM SAML IdP to accept incoming assertion from sts.acme.com we need to create an external SP connector. Under the Access Policy -> SAML -> BIG-IP as SP configuration section: 1. Create a new SAML SP Service 2. Export the SP metadata and configure sts.acme.com accordingly (follow your IdP vendor's documentation) 3. Click the External IdP Connectors menu at the top 4. Click the dropdown arrow on the create button and choose From Metadata (import the metadata from sts.acme.com) 5. Bind the Local SP service to the external IdP connector Now that idp.globex.com and sts.acme.com are configured to trust one another we need to configure the APM IdP to consume the sts.acme.com SAML assertion. The IdP's Visual Policy Editor should look similar to the image below: 1. The Decision Box asks the user what company they're with. This is a simple example but more elaborate home realm discovery techniques can be used. 2. The SAML Auth box is configured to consume the sts.acme.com assertion 3. Since we no longer have a login form on the IdP we need to set a few APM session variables: session.logon.last.username = Session Variable session.saml.last.identity session.logon.last.logonname = Session Variable session.saml.last.identity 4. Create an Advanced Resource Assign that matches your existing IdP Advance Resource Assign. Conclusion This particular post was a little longwinded due to the steps required but overall is a fairly simple configuration. So the next time someone asks if your F5 can do IdP chaining you can confidently reply "Yes and I know how to do that".
