How device identity is established through client certificates, and how device trust context is established between FortiClient, FortiClient EMS, and the FortiGate, are integral to ZTNA.
FortiClient endpoints provide the following information to FortiClient EMS when they register to the EMS:
Device information (network details, operating system, model, and others)
Logged on user information
Security posture (On-net/Off-net, antivirus software, vulnerability status, and others)
It also requests and obtains a client device certificate from the EMS ZTNA Certificate Authority (CA) when it registers to FortiClient EMS. The client uses this certificate to identify itself to the FortiGate.
FortiClient EMS issues and signs the client certificate with the FortiClient UID, certificate serial number, and EMS serial number. The certificate is then synchronized to the FortiGate. EMS also shares its EMS ZTNA CA certificate with the FortiGate, so that the FortiGate can use it to authenticate the clients.
FortiClient EMS uses zero trust tagging rules to tag endpoints based on the information that it has on each endpoint. The tags are also shared with the FortiGate.
The FortiGate maintains a continuous connection to the EMS server to synchronize endpoint device information, including primarily:
Client certificate SN
Device credentials (user/domain)
Network details (IP and MAC address and routing to the FortiGate)
When a device's information changes, such as when a client moves from on-net to off-net, or their security posture changes, EMS is updated with the new device information and then updates the FortiGate. The FortiGate's WAD daemon can use this information when processing ZTNA traffic.
FortiClient EMS has a default_ZTNARootCA certificate generated by default that the ZTNA CA uses to sign CSRs from the FortiClient endpoints. Clicking the refresh button revokes and updates the root CA, forcing updates to the FortiGate and FortiClient endpoints by generating new certificates for each client.