TLS 1.3 is Coming - How to deal with it????

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TLS 1.3 is Coming - How to deal with it????

L6 Presenter

My security counter parts came to me letting me know that in Chrome version 70.X+ TLS 1.3 will be turned on by default.  This appears to be causing problems in our current firewall deployment:

 

A/P HA-par 5220s running 8.0.10 (soon to be 8.0.12).

 

It looks like Google has released an article describing what's going on:

 

https://www.chromium.org/Home/tls13

 

In this article it highlights how Cisco FirePower devices can be configured to avoid issue.  Does anyone know how to correct this in Palo?

 

 

Here is the error the users get (TLS1.3 Downgrade detected)

 

TLS_Error.png

 

 

 

This is the traffic log for the user traffic.  "Webmail" access is allowed, and we're doing SSL decryption.

 

TLS_1.3.PNG

 

25 REPLIES 25

L0 Member

We had the same issue.  The response we got from TAC was 1.3 won't be supported until at least 9.1.

 

However, Chrome Beta updated today to Version 70.0.3538.54 (Official Build) beta (64-bit).  Now the sites where we were experiencing the ERR_TL13_DOWNGRADE_DETECTED error are working correctly.  Has anyone else had the same results?

 

I'm not sure what changed from the Chrome side.  There was no update here https://www.chromium.org/Home/tls13

 

@Spachtholz wrote:

We had the same issue.  The response we got from TAC was 1.3 won't be supported until at least 9.1.

 

However, Chrome Beta updated today to Version 70.0.3538.54 (Official Build) beta (64-bit).  Now the sites where we were experiencing the ERR_TL13_DOWNGRADE_DETECTED error are working correctly.  Has anyone else had the same results?

 

I'm not sure what changed from the Chrome side.  There was no update here https://www.chromium.org/Home/tls13

 


 

Yes to both.  I heard that there might be some support in 9.0, but really nothing really until 9.1.

 

Also we've been trying to replicate on the same machine / user that reported the problem but we haven't had any issue with any sites.  So I'm not really sure what changed.

L2 Linker

We've got the same issue. Chrome has updated to Version 70.0.3538.67 (Official Build) (64-bit) and we are seeing the error ERR_TLS13_DOWNGRADE_DETECTED

 

We are trying to access pluralsight and schemeserve

L1 Bithead

I have the same issue with SSL Decrypt on PA-3020 PAN OS 8.1.3

 

While searching on this issue I found the following:

 

https://www.chromium.org/Home/tls13?tmpl=%2Fsystem%2Fapp%2Ftemplates%2Fprint%2F&showPrintDialog=1

 

Exerpt:

 

"The only Google service with TLS 1.3 enabled at this time is Gmail, thus Chrome 70 should successfully negotiate TLS 1.3 when connecting to Gmail. However, there is a possibility that bugs in software (such as anti-virus software), or hardware middleboxes, that are between Chrome 70 and a TLS 1.3-enabled service like Gmail will cause problems. We have worked hard to tweak TLS 1.3 in ways that workaround the middleware bugs that we're aware of, but there might be things that we don't know about. Thus, if you see the following situation, you might have some buggy software or hardware that we're not aware of and we would be very interested in the details: 1. Chrome 69 works without issues. 2. Chrome 70 works for most sites except Gmail. 3. Gmail fails to load with ERR_SSL_VERSION_INTERFERENCE or ERR_TLS13_DOWNGRADE_DETECTED."

 

This page also refered to an admin forum thread here:

https://productforums.google.com/forum/#!topic/chrome-admins/jRFqwLUh6YA;context-place=forum/chrome-...

 

 

Palo Alto decryption appears not to currently support TLS 1.3

If chrome is accessing sites using TLS 1.3 and our Firewalls are trying to decrypt it, we will see this error.

Hello All,

The link to the google groups article fixes the issue as it tells Chrome to disable the 1.3 variant.

 

Just paste the following into the chrome browser address field and it should bring it up, then change the setting to 'Disabled'. You will have to restart your browser.

 

chrome://flags/#tls13-variant

 

Cheers!

Desabling the 1.3 variant works on my PC, but i'm not sure how I would go about deploying this workaround.  

 

I don't have the option to disable 1.3 variant in my Chrome GPO, at least by that name.

 

Any ideas in that regard?

Update on this issue:

 

"We are aware of two vendors whose products have this bug: Cisco and Palo Alto Networks, although there may be more. We reported the issue to Cisco in December 2017. They released the fix this past August and have published an advisory. Palo Alto Networks recently discovered the issue on their devices and are planning to release PAN-OS 8.1.4, PAN-OS 8.0.14, and PAN-OS 7.1.21 to fix this, tentatively by Nov 30th."

 

Full link: 

 

https://www.ietf.org/mail-archive/web/tls/current/msg27066.html

 

I updated our firmware last night to 8.1.4 and the issue has gone away

PAN-OS 8.0.14 and 8.1.4 will support TLS 1.3.

 

 

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