Authenticating from a Node.js client to Dynamics CRM via AD FS and OAuth2

Last week I decided to finally take a look at using OAuth2 as an authentication protocol with Dynamics CRM. I wanted to understand how it could enable non-Windows clients to consume CRM data. As it turns out, I was unable to find any documentation or comprehensive code samples for non-Windows clients, so I put together my own Node.js client, and I've added the code to my Crm-Sample-Code repository on GitHub here: Having endured a lot of frustration in getting this to work, I'd like to share some additional notes that might be helpful if you decide to start using OAuth2 with CRM.

If you're not already familiar with OAuth2, I suggest you take a look at this post on the Microsoft Dynamics CRM blog that explains how CRM uses OAuth at a high level: Although there's no code in that post, it will help you understand how OAuth authentication works.

Infrastructure and environment prep

I am running Dynamics CRM 2015 and Active Directory Federation Services (AD FS) on a single Windows Server 2012 R2 Azure VM. CRM and AD FS are configured for IFD. The CRM website is running on port 443. AD FS is running on port 444.

Before writing any code, I completed all the prep work outlined in this CRM SDK walkthrough - Specifically I enabled OAuth2 for CRM, and I registered an OAuth2 client application in AD FS. Although this was all done as part of an on-premise Dynamics CRM deployment, I don't see any reason that it won't work with CRM Online.

The code

Now, let's take a look at the Node.js application. I chose to write a Node.js client instead of something in C# for two main reasons. First, Node.js made it easy for me to inspect and modify all the HTTP headers that are required for getting OAuth2 to work. Second, Node.js is basically server-side JavaScript, so most of the work I've done can be easily ported to a client-side JavaScript implementation.

My Node.js application is written using the Express web framework, and it serves four web pages via routes. They are:

  1. / - This is the web application index page. It displays links to the login page and contacts display page.
  2. /auth/login - This page handles redirection of the browser to the AD FS login page.
  3. /auth/callback - This is the page to which AD FS redirects the user's browser after a successful login.
  4. /authenticated/contacts - This page queries the CRM OrganizationData service for contacts using an OAuth token for authentication.

The basic flow of the application is:

  1. A user starts on the index page. The page checks for an OAuth token in a session variable. If no token is present, a link to the login page is shown. If a token is present, a link to the contact display page is shown.
  2. When a user navigates to the login page, it makes a request to the CRM OrganizationData service to request the correct URL to use for authentication and redirects the browser to that page. The client id, resource name and redirect uri are all included in the query string of the request to AD FS. (See for more information on how this works.)
  3. The user authenticates with AD FS, and then AD FS redirects the user to the callback page with an authorization code in the query string.
  4. The callback page parses the authorization code from the query string and sends it to AD FS to request a token. The token is stored in a session cookie, and then the user is redirected to the index page, which should now show a link to the contact display page.
  5. The contact display page reads the token from the session cookie and makes an Odata request to CRM with the token supplied as the authorization header. The results are then parsed and displayed.

A few caveats:

  1. OAuth2 tokens eventually expire. The default AD FS OAuth2 token expiration value is 3600 seconds (one hour). It is possible to request a new token using a refresh token that is provided at the same time as the authorization token. Using the refresh token allows for reauthorization without needing to supply credentials again. My code sample does not demonstrate use of a refresh token.
  2. My sample application doesn't have much in the way of error handling, and it has not been extensively tested. If you plan to use OAuth with CRM, I highly recommend you don't just deploy my code in production without any further testing.
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