BUG - SSL/TLS Inspection seems to break Honeywell smart devices

1) There is a known issue with "Use proxy instead of DPI mode" not being respected when Web Filter=None. This is being worked on for GA.

2) There is a known issue with handling and logging of unscannable traffic. This is also being looked at, post-GA

The traffic is on port 443 and matches a Firewall Rule for DPI mode and matches an TLS Rule Do Not decrypt rule.
The sslx system does not recognize it as an TLS handshake, or there is something invalid about it.
The sslx system, not being able to handle it, passes it to the HTTP parser hoping it can.
The HTTP parser does not recognize it as plaintext HTTP and logs an error "HTTP parsing error encountered"

Therefore it might appear to an administrator that the "Do not decrypt" was ignored, that it was decrypted and had trouble with the data after. In fact, what occurs is that neither the SSL system nor the HTTP system could parse the packets.

Therefore some/most "HTTP parsing error encountered" in the log is actually a failure in handling the SSL handshake.

In v18.0 EAP3 and most likely in v18 GA if you are in this scenario:
proxy mode - In Web > General Settings > turn Block Unrecognized SSL Protocols off.
DPI mode - In the command line (not ssh) use 'set http relay_invalid_http traffic on'

This may change post-GA.

1) There is a known issue with "Use proxy instead of DPI mode" not being respected when Web Filter=None. This is being worked on for GA.

2) There is a known issue with handling and logging of unscannable traffic. This is also being looked at, post-GA

The traffic is on port 443 and matches a Firewall Rule for DPI mode and matches an TLS Rule Do Not decrypt rule.
The sslx system does not recognize it as an TLS handshake, or there is something invalid about it.
The sslx system, not being able to handle it, passes it to the HTTP parser hoping it can.
The HTTP parser does not recognize it as plaintext HTTP and logs an error "HTTP parsing error encountered"

Therefore it might appear to an administrator that the "Do not decrypt" was ignored, that it was decrypted and had trouble with the data after. In fact, what occurs is that neither the SSL system nor the HTTP system could parse the packets.

Therefore some/most "HTTP parsing error encountered" in the log is actually a failure in handling the SSL handshake.

In v18.0 EAP3 and most likely in v18 GA if you are in this scenario:
proxy mode - In Web > General Settings > turn Block Unrecognized SSL Protocols off.
DPI mode - In the command line (not ssh) use 'set http relay_invalid_http traffic on'

This may change post-GA.

1) Has not changed for GA. Please use "Allow All".
2) We have done several fixes for related defects, but we do not think that this particular problem is resolved. However we would like someone who was previously experiencing this problem to report whether it is working in GA.

Specifically for the Honeywell smart thermostat, as far as I know:
In 17.5 (proxy) it fails with "Block unrecognized protocols" Checked
In 17.5 (proxy) it works with "Block unrecognized protocols" unchecked
In 18.0 GA (proxy) it fails with "Block unrecognized protocols" Checked
In 18.0 GA (proxy) it works with "Block unrecognized protocols" unchecked
In 18.0 GA (DPI) it fails with "relay_invalid_http_traffic" off
In 18.0 GA (DPI) it works with "relay_invalid_http_traffic" on

Please confirm if this is true.

Block unrecognized protocols can be changed in Web > General Settings.
relay_invalid_http_traffic can be changed in command line (no ssh/advanced shell) with 'set http_proxy relay_invalid_http_traffic on/off'.

Hi Michael,

so what you are advising is there is no way to stop a firewall rule from being scanned eg LAN to LAN rules?

Ian

rfcat_vk said:

so what you are advising is there is no way to stop a firewall rule from being scanned eg LAN to LAN rules?

Ian, I love you man and I like all the bug reports you are giving us.  I'm a QA tester - I love testing, I love bugs.  But please do not hijack threads.

This thread is about Honeywell smart devices in a LAN contacting to a server on the Internet.

Hi Michael,

I could not find my original thread on the subject and this one has lots of explanations about the same issue, so I added a question because I have a device which has similar issues with DPI?

Ian

Your question is answered by Rich Baldry in this thread:

https://community.sophos.com/products/xg-firewall/sfos-eap/sfos-v18-early-access-program/f/feedback-and-issues/117987/question---bug---dpi-appears-to-be-on-by-default

Hi Michael,

that answer was about the display when you click on the field on the firewall rule not about turning off DPI.

Ian

rfcat_vk said:

So how do I turn off inspection of internal rules only?

RichBaldry said:

Hi Ian,

Our intent is for it not to be necessary to turn this off, so that the DPI Engine has no impact on traffic if there are no scanning or inspection policies applicable to it, but so that we can still include information about it in our overall accounting of traffic.

There are still a couple of outstanding situations that we've come across in the EAP that we are aiming to fix before the GA release of v18, including a few relating to our handling of traffic that is not recognized as TLS or HTTP on port 443. One of the major impacts of this right now is OpenVPN SSL VPN connections, which send a few packets of custom handshake protocol before beginning a TLS handshake. We've had reports of a few IoT devices that use OpenVPN to tunnel traffic to the cloud - is it possible that's what's going on with your camera?

So to be clear on your question "so what you are advising is there is no way to stop a firewall rule from being scanned eg LAN to LAN rules" the answer from the program manager is "the intent is for it not to be necessary to turn this off".

Therein lies the issue, you cannot use the http proxy on internal traffic (which does not break the application). but DPI does, so how do you overcome this because there is no log to show what needs to be exempted.

Ian

I will test out the original issue and get back to you Mike.

As far as what Ian said, I know it is off topic but it is also part of this issue overall. If I could have disabled any scanning whatsoever on a firewall rule, I could have bypassed this issue all together.

If what Ian is saying is true and the DPI is scanning even LAN to LAN traffic, how in the world can XG meet the performance numbers that are posted for the firewall itself? Snort can't put up those numbers with any of the hardware appliances. 20 GBPS throughout on an XG230? Yeah right. If DPI wasn't involved maybe. Sorry I continued off topic but it is related.

Off topic, but currently in v18 GA if you create a Rule without any Security profile on it, It will bypass Snort. The issue of DPI scanning LAN to LAN Traffic in my believe has only present on v18 EAP.

I've just tested it out with HTTP(s)-Download/SFTP/SMB and all of them bypassed Snort/AV/DPI using a Rule without any Security profile being applied.

So it's pretty much working as expected right now in v18 GA.

Thanks!