SSL decryption( Some traffic is not decrypted)

Jafar_Hussain · ‎02-07-2020

Dear All,

I have applied SSL forward decryption in my Paloalto, then i observed some traffic are decrypted and some traffic not decrypt.

Example:- I have applied the decryption in social-networking (Facebook traffic is decrypted but Snapchat traffic is not decrypted,however, both are falling under the social-networking category.)

Why it's strange behaviour.

OtakarKlier · ‎02-07-2020

Hello,

Unfortunately there is some traffic that cannot be decrypted or it will break the connection. Snapchat is one of these as it uses a pinned certificate.

To view the automatically bypassed domains, click the Device tab -> Certificate Management -> SSL Decryption Exclusion

https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClEzCAK

Hope that helps.

Jafar_Hussain · ‎02-07-2020

@OtakarKlier

Ok, thanks for the information. it means all the URL/Application which are already in exclusion, will not decrypt?

Apart from this if any traffic is not decrypted so what is the issue?

BPry · ‎02-07-2020

@Jafar_Hussain,

Correct; if the domain is listed in the SSL Decryption Exclusion list, the firewall is going to let that through without going through the decryption process so that it doesn't break anything.

@Jafar_Hussain wrote:
Apart from this if any traffic is not decrypted so what is the issue?

Can you provide one of the domains that you are running into an issue with that isn't covered by an exclusion? Keep in mind, depending on how you have things configured if the firewall detects that it isn't able to decrypt certain traffic without causing an issue, it will put that into a cache to skip decryption going forward so it doesn't continue to break the site for users.

Jafar_Hussain · ‎02-07-2020

@BPry Thanks for the information.

I will keep is in observation. if i found something I will let you know.

Thanks once again.

Jafar_Hussain · ‎02-10-2020

@BPry @OtakarKlier

I am facing a problem with the certificate(When I enabled the decryption and tried to open the website in Mozilla and internet explorer it is working as expected means it is taking the same self-sign certificate which I have generated).

However, when I tried to access the website in chrome, the browser is not accepting the certificate which is generated by FW. it is taking its own google certificate.

Can you help me with this?

Jafar_Hussain · ‎02-10-2020

any one can give me reply........

BPry · ‎02-10-2020

@Jafar_Hussain,

Can you post the actual website so we can actually take a look at it.

Jafar_Hussain · ‎02-10-2020

@BPry

Example:- For testing, I have created a custom URL category only for (youtube+facebook+netflix). this is policy i mention in decryption rule with decrypt SSL forward proxy. and I have an import certificate already in my machine. when i try to open this URL in Mozilla and Internet explorer it is working as expected both browsers are taking a certificate which i have import however in chrome i can't see the same certificate this browser is taking its own google certificate why ?????

Remo · ‎02-10-2020

How do these connecrions look in the traffic log? Could it be possible that they use port 443/udp?

BPry · ‎02-10-2020

@Jafar_Hussain,

Right off the bat I would look at if you are allowing QUIC traffic when you are utilizing Chrome.

Jafar_Hussain · ‎02-10-2020

@BPry I am not getting your point.

@Remo I can see in the traffic log when I open the chrome browser there is no decryption showing in traffic log however when I open in Mozilla traffic log showing as decrypted.

BPry · ‎02-10-2020

@Jafar_Hussain,

Chrome will default to using the QUIC protocol, which to @Remo's point will come across on udp/443. Best practices would have you disallowing QUIC connections so that traffic is forced to fail-back to standard SSL/TLS connections over tcp/443. Then your decryption will actually work.