"decrypt-unsupport-param" error on Inbound SSL Decryption

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"decrypt-unsupport-param" error on Inbound SSL Decryption

L3 Networker

I am trying to get inbound SSL decryption for our web server. I imported our web server's SSL certificate with private key to the Palo. It shows "Valid" and the "private key" checkbox is checked.

 

But the log shows it is not getting decrypted, and I'm seeing the session end "decrypt-unsupport-param" .

 

The certificate is signed by a CA, 2048-bit, SHA256

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L4 Transporter

it is right that DHE and ECDHE is not supported by PA for ssl-inbound-inspection. There ist a note in the Config which point to that. therefore you have to disable these algorithms like Rahman mentioned.

 

algo.PNG

 

you will find the algorithms below Objects - Decryption Profil. DHE and ECDHE is checked but they will be used only for ssl forward proxy.

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18 REPLIES 18

Cyber Elite
Cyber Elite

Hello,

According to the documetnation, here is what it means:

 

The session used an unsupported protocol version, cipher, or SSH algorithm. This session end reason is also displayed when the session produced a fatal error alert of type unsupported_extension, unexpected_message, or handshake_failure.

 

https://www.paloaltonetworks.com/documentation/71/pan-os/newfeaturesguide/networking-features/ssl-ss...

 

I however do not know howto resolve it. I'm sure a ticket into TAC could be a quicker answer?

 

Hope this helps.

L4 Transporter

Hi,

 

please take a look at "objects > decryption profile" and here the default profil or the your own configured profile. Take the tab "SSL-Decryption " and then "SSL Protocol Settings". Now you can choose the Protocol Version, Key Exchange Algorithms, Encryption Algorithms and Authentication Algorithms. Hope this helps.

 

Regards,

Klaus

Ok, I checked the decryption profile, and the default already has every option checked. Seems to be some other issue then

L4 Transporter

hi,

i think it is nessesary to debug. Maybe the it is an unsupport cipher.

 

Regards,

Klaus

 

L4 Transporter

another thing is to check the decryption policy for right Decryption Profil ...

It's a basic certificate aquired from Digicert.com. When I look at the certificate itself, it says its RSA SHA256, 2048-bit. But I don't see where it says the encryption algorithm, though (like AES-128CBC or AES-256GCM). I will ask the CA vendor

L4 Transporter

please check that the digicert-certificate is among the certificate authorities. this is necessary for trusted relationship and this to decrypt.

L4 Transporter

take a look on the picture i think it is the DHE or ECDHE. Both are support but not for the inbound direction. Just for SSL Forward Proxy.

L4 Transporter

Both algorithms (DHE and ECDHE) are only support for SSL Forward Proxy. Not for inbound direction. Take a look at the photo.

 

 

algo.PNG

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