Types of authentication
FortiOS supports two different types of authentication based on your situation and needs.
Security policy authentication is easily applied to all users logging on to a network, or network service. For example if a group of users on your network such as the accounting department who have access to sensitive data need to access the Internet, it is a good idea to make sure the user is a valid user and not someone trying to send company secrets to the Internet. Security policy authentication can be applied to as many or as few users as needed, and it supports a number of authentication protocols to easily fit with your existing network.
Virtual Private Network (VPN) authentication enables secure communication with hosts located outside the company network, making them part of the company network while the VPN tunnel is operating. Authentication applies to the devices at both ends of the VPN and optionally VPN users can be authenticated as well.
Security policy authentication
Security policies enable traffic to flow between networks. Optionally, the policy can allow access only to specific originating addresses, device types, users or user groups. Where access is controlled by user or user group, users must authenticate by entering valid username and password credentials.
The user’s authentication expires if the connection is idle for too long, 5 minutes by default but that can be customized.
Security policies are the mechanism for FSSO, NTLM, certificate based, and RADIUS SSO authentication.
FSSO
Fortinet Single Sign on (FSSO) provides seamless authentication support for Microsoft Windows Active Directory (AD) and Novell eDirectory users in a FortiGate environment.
On a Microsoft Windows or Novell network, users authenticate with the Active Directory or Novell eDirectory at logon. FSSO provides authentication information to the FortiGate unit so that users automatically get access to permitted resources. See Introduction to agent-based FSSO on page 553.
NTLM
The NT LAN Manager (NTLM) protocol is used when the MS Windows Active Directory (AD) domain controller can not be contacted. NTLM is a browser-based method of authentication.
The FSSO software is installed on each AD server and the FortiGate unit is configured to communicate with each FSSO client. When a user successfully logs into their Windows PC (and is authenticated by the AD Server), the FSSO client communicates the user’s name, IP address, and group login information to the FortiGate unit. The FortiGate unit sets up a temporary access policy for the user, so when they attempt access through the firewall they do not need to re-authenticate. This model works well in environments where the FSSO client can be installed on all AD servers.
In system configurations where it is not possible to install FSSO clients on all AD servers, the FortiGate unit must be able to query the AD servers to find out if a user has been properly authenticated. This is achieved using the NTLM messaging features of Active Directory and Internet Explorer.
Even when NTLM authentication is used, the user is not asked again for their username and password. Internet Explorer stores the user’s credentials and the FortiGate unit uses NTLM messaging to validate them in the Windows AD environment.
Note that if the authentication reaches the timeout period, the NTLM message exchange restarts. For more information on NTLM, see NTLM authentication on page 508 and FSSO NTLM authentication support on page 559.
Certificates
Certificates can be used as part of a policy. All users being authenticated against the policy are required to have the proper certificate. See Certificate-based authentication on page 522
RADIUS SSO
RADIUS Single Sign-On (RSSO) is a remote authentication method that does not require any local users to be configured, and relies on RADIUS Start records to provide the FortiGate unit with authentication information.
That information identifies the user and user group, which is then matched using a security policy. See SSO using RADIUS accounting records on page 596.