Computer-based authentication / authorization fails with Integrated Web Authentication (IWA)

Products

ProxySG Software - SGOS

Issue/Introduction

Certain applications / User-Agents will perform authentication with their computer accounts. This is generally observed with Windows Vista and Windows 7. Computer accounts are similar to user accounts in several ways – they have a password, and they can belong to groups. However, by default, computer accounts belong only to the 'Domain Computers' group.

For example, the Windows Update agent may authenticate with the computer's account and result in forbidden/denied access :

Hypertext Transfer Protocol
                HEAD http://download.windowsupdate.com/v9/windowsupdate/redir/muv4wuredir.cab?xxxxxxxxxx HTTP/1.1\r\n
                Accept: */*\r\n
                User-Agent: Windows-Update-Agent\r\n
                Proxy-Connection: Keep-Alive\r\n
                Host: download.windowsupdate.com\r\n
                [truncated] Proxy-Authorization: NTLM         NTLM Secure Service Provider
                        NTLMSSP identifier: NTLMSSP
                        NTLM Message Type: NTLMSSP_AUTH (0x00000003)
                        Lan Manager Response: 000000000000000000000000000000000000000000000000
                        NTLM Client Challenge: 0000000000000000
                        NTLM Response: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...
                        NTLM Client Challenge: xxxxxxxxxxxxxxxx
                        Domain name: KLDEV
                        User name: BLUECOAT1$           <<<<< Computer Account / Host name is sent as the username
                        Host name: BLUECOAT1            <<<<< Computer hostname
                        Session Key: Empty
                        Flags: 0xa2888205
                        Version 6.1 (Build 7600); NTLM Current Revision 15
                        MIC: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
                Cookie: BCSI-CS-XXXXXXXXXXXXXXXX=X\r\n
                \r\n
            
            HTTP/1.1 403 Forbidden
            Cache-Control: no-cache
            Pragma: no-cache
            Content-Type: text/html; charset=utf-8
            Proxy-Connection: Keep-Alive
            Connection: Keep-Alive
            Content-Length: 572

Resolution

If your organization's security policy allows computer authenticated accounts to access the Internet, the following policy should address the problem.

<Proxy>
                    realm="IWA_Realm_Name" group="DOMAIN\Domain Computers" ALLOW

or

<Proxy>
                    realm="IWA_Realm_Name" group="DOMAIN\Domain Computers" user.login.log_out(yes)

The 'Domain Computers' is available as a source Group object in the VPM's Web Access Layer, similar as other group objects. Hence, the CPL above can also be applied fom the VPM.

Important

Do not use any IP-based surrogate such as Proxy-IP for authentication because the ProxySG may not reauthenticate user traffic within the cached duration. If you need to use an IP-based surrogate, use the user.login.log_out(yes) policy above.