Fortigate running 6.2.4 keeps switching to SSL decryption

[DerekWSmall]

I have a Fortigate 60E, running 6.2.4 (build 1112).  It works great most of the time. However occasionally it will start doing SSL decryption, and anyone hitting any SSL site through it will start getting traffic encrypted with the Fortigate's cert, not the public site's cert.  I can't figure out why the Fortigate just starts doing this apparently out-of-the-blue.  A reboot fixes the problem, but I can't explain it.  Anyone have any ideas where to start? Are there any known exploits that could be causing this to occur?  I believe I have the outside interface pretty well locked down, but of course it could something on the inside triggering it.

[Markus]

Same here with 61F and 6.2.4 Nothing found so far, only reboot helps.

[DerekWSmall]

Happened again. Can anyone from Fortinet offer any advice?  Hello. Bueller, Bueller, Bueller....

[poundy]

ok, while there are Fortinet staff here, I wouldn't ever treat this as an official support channel. Raise a support case if it is that big a concern

[emnoc]

Do you have any policy with ssl inspection enable is the 1st question? I 'm running 6.2.4 on dozen devices form a 51 up to a 900 and we do not see that issue.

Ken Felix

[Markus]

Hi Ken Yes, I have policies with SSL Inspection enabled (flow and deep). Best regards, Markus

[emnoc]

You need to investigate those policies and traffic flow. The fortigate does not have a brain of it own but does what you configure it to do.

So the traffic your getting ssl-decrytion is matching that policy. It could be anything but  you have to look. Can you recreate the issue? Is it the same src/dst, protocol, web,etc........?

Ken Felix

[Markus]

Thank you for the reply. I wasn't able to reproduce. As I can see, there are a lot of DNS sessions open when it hits. The strange thing is, that also traffic FROM internet, hitting policies with full inspection (e.g. owa) stop responding. The session count increase to 3-4x than "normal" and then this behaviour occurs. No attack or something, dns sessions are from my internal server to my provider dns servers.

[Markus]

coming back - 6.2.5 solved this problem for me