I recently started using the Facebook C# SDK from CodePlex in my efforts to link SharePoint 2010, Claims-Based Identity, Azure ACS, and Facebook into one killer demo for my presentation on Claims-Based Identity that I will be giving at SharePoint Saturday Virginia Beach next month.

Without giving too much away, I intend to leverage the AccessToken input claim type provided by Facebook through Azure ACS to reach back into the user’s Facebook profile and obtain more information about the user who has just logged in to SharePoint from Facebook.

After rushing into coding a new web part (as any good developer would), I immediately encountered the following exception upon deployment:

The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.
at FluentHttp.HttpHelper.OpenRead()
at Facebook.FacebookClient.Api(String path, IDictionary`2 parameters, HttpMethod httpMethod, Type resultType)
…

This error was met with the following corresponding entry in the Event Viewer:

In order to resolve this error, it is important to remember that SharePoint 2010 maintains its own certificate store, where separate trusts must be configured and maintained. Even though the root of the certificate chain may already be trusted everywhere else, you will receive this error unless an explicit trust is configured for SharePoint in Central Administration (or through PowerShell).

After much trial and error, I discovered that two trusts must be configured to support Facebook. First, go to the DigiCert Root Certificate site and download the following certificates as .cer files:

• Under Root Certificates: DigiCert High Assurance EV Root CA
• Under Intermediate Certificates: DigiCert High Assurance CA-3

Now that you are armed with these two .cer files, go to Central Administration. Go to Security, then under “General Security,” choose Manage Trust.

For each of the two .cer files, perform the following steps:

1. From the ribbon, select New.
2. In the “Establish Trust Relationship” dialog that appears, give each certificate a friendly name. In the “Root Authority Certificate” section, press Browse… and navigate to each .cer file.
3. Press OK.

Perform an IISRESET after adding both certificates, and you should be ready to leverage the Facebook C# SDK from SharePoint 2010. Happy coding, and I hope to see you at SPSVB on January 7th!