Update: In November 2019 AWS introduced support for integration between Azure AD and AWS SSO.  The integration offers a ton more features, including out of the box support for multiple AWS accounts.  I highly recommend you go that route if you’re looking to integrate the two platforms.  Check out my series on the new integration here.

Hi everyone.  After being slammed with work from the real job over the past few months, I’m back with a new deep dive into the integration between Azure Active Directory (AAD) and Amazon Web Services (AWS).  I enjoyed the heck out of this one because I finally got some playtime in AWS and got to integrate two of the big cloud providers together to make some cool stuff happen.  There are a lot of blogs and articles out there (including Microsoft’s and Amazon’s *cough cough*) which provide the steps to accomplish this integration, but either the steps are incomplete, outdated, or wrong and none of them give a great explanation of the why or the how.  I can’t complain though, what else would I blog about?

Before we jump into the technologies that power the integration, let me first answer the question as to why we’d want to do the integration in the first place.

Let’s face it, managing digital identities is hard and it’s only getting harder with the introduction of cloud technology to the mix.  The tens of thousands of identities you’re managing for your users on-premises data center can quickly grow into the millions when SaaS comes into the mix. The operational overhead or supporting those millions of identities can eat up a large part of your IT budget and make your user experience miserable.  Beyond the cost issue, saddling your users with hundreds of credentials means users are going to re-use passwords and store them in whatever ways are convenient for them (under the keyboard anyone?) which introduces the risk of the credentials being compromised and sensitive data getting leaked.

Now more than ever you need to put a strong focus on centralized identity management and modern authentication and authorization.  Historically this was very challenging to do because of the lack of application programming interfaces (APIs) that allowed for create read update delete (CRUD) operations against the individual user records represented in an application database such as a SQL backend.  Beyond the lack of good APIs, you also were stuck using complicated and limiting legacy authentication and authorization protocols such as Kerberos, NTLM, LDAP, and the like.

Thankfully the industry has made a dramatic shift towards providing robust web-based APIs and support for modern authentication and authorization such as SAML, WS-Fed, Open ID Connect, and OAuth.  This presents a unique opportunity for organizations to shift towards a centralized identity management model where one authoritative store drives the lifecycle of an identity across all applications.  With the introduction of the modern protocols, users aren’t required to maintain thousands of credentials and can instead rely upon a singular trusted credential service provider (CSP) to act as the primary authentication point allowing users to then assert their identities to applications.  This frees the application from having to be saddled with storing and managing user credentials as well as improving the user experience, not to mention using these modern protocols is far simpler for your average developer.

Integrating AAD and AWS allow you to take advantage of centralized identity and modern authentication and authorization.  AAD specifically allows you to leverage all the cool features of a modern Identity-as-a-Service (IDaaS) offering such as behavioral analytics, multifactor authentication, adaptive authentication, and contextual-based authorization.  The short of it is you get a rock solid IDaaS to back the industry leading PaaS and IaaS offerings of AWS.  The best of both worlds right?

Now that you understand why you’d want to integrate the two solutions, let’s look at the technology powering the solution. In this integration the vendors are leveraging the concepts of modern APIs and modern authentication and authorization I touched upon above.  First up is authentication.

In this integration SAML, specifically the identity provider-initiated single sign-on POST binding, is being used to assert the user’s identity to the service provider (SP) after the user successfully authenticates with the identity provider (IdP).  Azure AD plays the role of IdP and AWS plays the role of SP.  The sequence of events plays out as follows:

1. The user navigates to AAD and authenticates using either a credential or an asserted identity from a federated identity store.  The user then selects AWS from the listing of applications exposed through a method like the MyApps portal.  AAD generates an assertion containing a claim of the user’s identity and the AWS Identity and Access Management (IAM) role(s) the user is authorized to use and redirects the user to an endpoint at AWS.
2. The user’s browser posts the assertion to the endpoint at AWS.
3. The assertion is passed to the AWS security token service (STS) which checks the assertion to ensure it is from an identity provider that has been configured to be trusted for the AWS account, verifies the roles can be granted to a federated user, and completes the authentication process granting the user access to the AWS management console.(Don’t worry, we’ll dig into this process much more deeply using Fiddler in the next post.)

For provisioning, the AWS API is used.  AAD queries the AWS API using credentials for an AWS security principal that is associated with a role that has the IAMReadOnlyAccess permissions policy or greater.  It queries for the IAM roles configured for the account and synchronizes those roles back to AAD.  When the synchronization is complete, AAD users can then be added to the relevant roles from within AAD creating a one stop shop for doing your identity lifecycle management, authentication, and authorization.  Nice right?

At a high level that is the why and the what. In my upcoming posts in this series I’ll be digging deep into the how.  This will include how to do the integration, the pitfalls of the Microsoft tutorial, and of course Fiddler captures showing the conversations between the web browser, AAD, and AWS.

The journey continues in my second entry.