Fortigate user permissions peculiarities

While working with a customer on their Fortigate firewalls, I was introduced to a peculiarity of how FortiOS interprets user’s diag commands. I suspect this affects multiple versions, but I don’t have the ability to test this.

  • FortiOS: 4.2.x
  • User: wild-card (TACACS)
  • Profile: super_admin_readonly

TACACS users whose permissions elevate them to the super_admin profile are unaffected. They can run diag commands unrestricted as they have full access.

TACACS users whose permissions remain at super_admin_readonly were finding that they could not run diag commands that accessed an interface, such as diag sniff packet any “icmp”. Upon further investigation, the issue was related to the IP the user connected to and the interface (“any” in the example) used in the command. As a readonly user, the any interface is off-limits. The interfaces configured for the VDOM that the user connected to are available to the readonly users.

In other words, if a firewall had two VDOMs, Common and DMZ, and the user connected to any interface connected to the Common interface, only those interfaces would be useable. For instance, diag sniff packet common-outside “icmp” would work, as well as common-inside. Interfaces connected to other VDOMs are off-limits, so diag sniff packet dmz-outside “icmp would fail. By providing the end user a list of the IP addresses and interface names, and the VDOM they belonged to, the user was able to perform all required diagnostic commands.

I hope this is fixed in more recent versions, but at least there’s a workaround that makes some logical sense.

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