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utm

Sophos UTM – An unsupported mechanism

I got some strange issues / problems while testing a Sophos UTM appliance with 9.004-34 software. The Web Security feature is filtering requests and using client authentication. The proxy is using Standard Mode with Active Directory SSO authentication. I testing the proxy by changing the proxy settings on a Citrix server. Everything was working without any problems. Next I tried some standalone workstations and laptops, including my own.

I wasn’t able to authenticate. I got an Authentication Failed in my browser and noticed the following entry in the Web Filter logging.

adir_auth_process_negotiate (auth_adir.c:311) gss_accept_sec_context: An unsupported mechanism was requestedNo error

I didn’t know where to look. I tried different things, like rejoining the Sophos UTM in Active Directory, rebooting the appliance and changing the proxy settings. When using the IP address of the Sophos UTM in the proxy settings the authentication mechanism NTLM is being used. When using the hostname or an DNS alias the authentication mechanism Kerberos is being used.

After some more testing I noticed that authentication failures only occurred when using Kerberos authentication. I did some more research on the internet and I found a lot of people complaining about this issues and blaming the “Windows Live ID Sign-In” component. My browser included this add-on. I disabled it in Internet Explorer, but that didn’t help. I stopped the service via msconfig, but that didn’t help either. Eventually I uninstalled the complete Windows Live Essentials suite from my laptop. This solved the problem!!!

Uninstalling the Windows Live Essentials component from the other laptops and workstations also resolved their problems. Till now I still don’t know why Windows Live Essentials “breaks” the Kerberos authentication process.

Sophos UTM – WebAdmin access via proxy and IE9

I just configured a Sophos UTM cluster based on software version 9. I was able to configure the appliance via WebAdmin and I could access the User Portal without any problems. The customer is using a Citrix based environment with Internet Explorer 9. IE9 is configured to use the Sophos UTM cluster as proxy server. The customer was able to access the User Portal, but he couldn’t access the WebAdmin page.

When they tried to access the WebAdmin page, the page isn’t shown correctly. The page is crippled and you don’t get the login options for entering username and password. We tried different settings, like adding the page to the trusted websites and to the proxy exemptions. Nothing seemed to help. We asked mighty Google for help and we found the following thread.

The following snippet from the thread solved the problem:

Had one of my guys have this problem already… remove the URL for the UTM from the Compatibility View list (in his case, he had to uncheck the “view intranet sites in compatibility view” checkbox in IE).

The customer changed this Group Policy Object in Active Directory and everybody was happy.