FortiGate
FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
FrankY1
Staff
Staff
Article Id 292054
Description This article describes that when using the proxy option 'Restrict Google account usage to specific domains', it is working as expected, as only the specified domains are allowed while all other domains are rejected.  But there is no blocked traffic in the logs, all traffic is showing as accepted. 
Scope FortiGate.
Solution

This is the expected behavior, traffic is not getting blocked by FortiGate. 

Google makes this restriction possible by inspecting the 'X-GoogApps-Allowed-Domains' header in HTTP.

When this header is used in conjunction with a list of domains, Google can determine which domains are allowed and then block all others. Acting as a web proxy, Fortigate can intercept the HTTP requests, and add this header with the allowed domain list.

This is why FortiGate does not block any domains. Instead, it simply inserts the 'X-GoogApps-Allowed-Domains' header and passes the packets to Google who will then take action to allow or reject the requests.

 

Example:

In the Web Filter profile, only 'fortinet.com' is the allowed domain: 

 

chrome_7lAfC0h2dX.png

 

This is blocking other domains as per the test result on the client machine trying to log to Gmail using a personal Gmail account:

 

mstsc_3C21HaWzex.png

 

In the logs, the traffic is accepted, and there is no block happening on the firewall:

 

chrome_9kGZeYImM0.png

 

In the packet capture, the 'X-GoogApps-Allowed-Domains' header is inserted with the permitted domain 'fortinet.com':

 

mstsc_XsHi7CqAtp.png

 

 

Related documents:
https://support.google.com/a/answer/1668854?hl=en#zippy=%2Cstep-choose-a-web-proxy-server%2Cstep-con...
Technical Tip: How to enable access only to internal domains hosted on Google while web filter categ...

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