Technical Tip: How to enable access only to internal domains hosted on Google while the web filter category 'Web-based Email' is set to block

[gmanea]

Description

This article describes how to enable access to internal domains hosted on Google while web filter category 'Webmail' is set to block. 

Example.

'company.com' is hosted on Gmail and to restrict access only to these accounts any other webmail service (Google or not) should be disabled.  

Scope

FortiGate.

Solution

• If these options are not visible, check if the proxy-based web filter profile is used since this feature is only supported in a proxy-based profile.
• Deep inspection is necessary to restrict a Google account for a specific domain.

1. Create a web filter profile called 'test' using the GUI.

2. Enable 'URL Filter' under the static filter and create a dummy entry, like 'example.com'. Make sure that under 'Fortiguard Category Based Filter', the 'Web-based Email' under 'General Interest - Personal' is 'Allow'.
   
   
3. Enable 'Restrict Google account for the specific domain' and define the domain that is hosted on Google Mail services. 

4. Go to the CLI and the following entries and verify if they look like the following:

config web-proxy profile

    edit "Auto-web-proxy-profile_ff0ygfu3d"

        config headers

            edit 1

                set name "X-GoogApps-Allowed-Domains"

                set content "company.com"       <----- The company domain hosted in Google mail services.

            next

        end

    next

end

show config webfilter urlfilter .                         

    edit 1

        set name "Auto-webfilter-urlfilter_gkkqnfrif"

        # config entries

            edit 1

                set url "example.com"

                set action block

            next

        end

    next

end

Change it with the following entries in the same order.

config webfilter urlfilter

    edit 1

        set name "Auto-webfilter-urlfilter_gkkqnfrif"

        config entries

            delete 1                                <----- This will delete the 'example.com' entry created from GUI.

            edit 1

                set url "*.google.com"

                set type wildcard

                set web-proxy-profile "Auto-web-proxy-profile_ff0ygfu3d"

            next

            edit 2

                set url "gmail.com"

            next

            edit 3

                set url "google.com"

            next

        end

    next

end

Sometimes the Google suite uses URLs outside the *.google.com wildcard, such as to upload/download and/or send/receive files via email.

To allow uploading and downloading files from Gmail without any restrictions conditioned to the 'Web-based Email' category being blocked, add the URLs in charge of this process in webfilter urlfilter. In this case, the one known so far is 'mail-attachment.googleusercontent.com' which also belongs to the blocked category.

This URL must be allowed or exempted to allow uploading and downloading files from the email:

    config webfilter urlfilter
        edit 2
            set name "Auto-webfilter-urlfilter_2ge7ltkpd"
            config entries
                edit 1
                    set url "*mail-attachment.googleusercontent.com*" <---
                    set type wildcard
                next
            end
        next
     end

Identify the URL that allows the upload and download of files to configure it in the URL filter in case there are any more through webfilter profile logs.

Outcome: 

• Access to any email service will be denied (according to the webmail Category)
• Access to personal Gmail Accounts on any other domain hosted on Gmail will be denied.
• Access only from addresses containing @company.com will be allowed. 
  
• Access only from addresses containing @company.com will be allowed. 
• Access to File uploads and downloads will be allowed from the @company.com domain even if the 'Web-based Email' category is being blocked.