This is an issue with IIS using Windows Authentication and Kerberos, not specific to One Identity Manager. As described by Microsoft here "HTTP 400 - Bad Request (Request Header too long)" error in Internet Information Services (IIS), the size of the WWW-Authenticate header field increases with group size and if a user is a member of more than 120 groups, exceeds the MaxFieldLength and MaxRequestBytes on IIS as configured on the server registry.
Please follow the resolution proposed by Microsoft here: "HTTP 400 - Bad Request (Request Header too long)" error in Internet Information Services (IIS) . As of writing, this means one and only one of the following:
- Decrease number of AD groups the user is a member of
- Configure MaxFieldLength and MaxRequestBytes according to the number of groups
- Change to NTLM authentication -- please note, this might not be acceptable depending on security requirements of your environment
One Identity does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 "Description of the Microsoft Windows registry" at Microsoft Support.