Problem:

When connecting K2 server (on-premise in this case) to Sharepoint Online, there is an error when retrieving users from azure AD (claims issuer, AAD). 

The only error in K2 log: The input is not a valid Base-64 string as it contains a non-base 64 character

The problem appears in workspace when adding users, in smartobject tester, in people picker and so on.

Resolution:

If account that is used for retrieving AAD info has special characters in AD profile it wont work.  WARNING: The username did not have special characters (č, š, ž, ü, ä...) I am talking about additional fields e.g. Name, Surname. These are included in the token! 

Sincerely,

Benny

Keywords: Sharepoint Online, Azure, AAD, AD, Base-64, claims, issuer