Hi paloalto community,
we're currently still testing ssl decryption and discovered a new error, which I can't google to find a solution.
If we're visiting the following site, we get an "ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY" error. Site: https://www.1erforum.de/
See attached our configuration and ssl information without decryption enabled.
Firmware and Specs:
PA 850 - FW 9.0.5
IE doesn't care if you are using a weak cipher suite, which is why it's working in IE but not Firefox or Chrome. The bigger issue is why the decryption process isn't negotiating to the strongest available cipher unless the site has been configured with a cipher preference that makes it utilize the strongest cipher suites by default (such as Chrome). It appears through additional troubleshooting that the firewall is using the first matching cipher, which in the case of these example sites isn't strong enough to meet the requirements of the browser.
In fairness to PAN, the HTTP/2 connection shouldn't be attempting to use a questionable cipher suite such as in the di.fm example. The vast majority of the HTTP/2 enabled websites will work perfectly fine, because the site owner is specifying the preferred order with strong to weak ciphers. In the examples listed so far the server is providing no preference order, which could be causing the firewall to negotiate to one of the weaker cipher suites being offered by the server.
Sounds like a feature which the PA team should consider? For my point of view it's more like a bug. If browsers can view the page, the PA should do it too.
For our users the current state is very bad - they will assume the page (e.g. of a customer) is not working, but instdead we have to whitelist it to exclude it from decryption.
Same issue on PA-850 with FW 9.1.2-h1
Tested with https://microsoft.com
I tried the workaround (Objects - Decryption - Decryption Profile - ENABLE/CHECK 'Strip ALPN')
BUT to disable HTTP/2 inspection wouldn't/shouldn't be the solution I think. In future HTTP/2 sites will increase - so Palo Alto should get a solution in the software.
Palo - is there any roadmap when this issue is solved without workaround?
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