Inbound SSL decryption

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Inbound SSL decryption

L3 Networker

I am trying to set up a TLSv1.3 / TLSv1.2 webserver behind a palo firewall with ssl inbound decryption.

However i seem to get a lot of ssl errors and the website does not work if specific ciphers are not listed first...

For one I would like to understand why that is and even ciphers listed here have issues: https://docs.paloaltonetworks.com/compatibility-matrix/supported-cipher-suites/cipher-suites-support...

 

Basically, what should the apache config look like for the palo to be able to decrypt the traffic, yet still have the highest possible security (e.g. as rated by https://www.ssllabs.com/ssltest/) ?

1 ACCEPTED SOLUTION

Accepted Solutions

That wont fully work with TLSv1.2 and TLSv1.3 at the same time, I figured out how to do this a while back and gave an example config to TAC but here it is as reference for everyone...

To support both TLSv1.2 and TLSv1.3 at the same time and use secure ciphers, I found the following to work the best:

Apache:

 

Spoiler

SSLOpenSSLConfCmd ECDHParameters brainpoolP256r1

SSLOpenSSLConfCmd Curves secp521r1:secp384r1:prime256v1
SSLOpenSSLConfCmd SignatureAlgorithms ECDSA+SHA512:ECDSA+SHA384:ECDSA+SHA256:RSA+SHA512:RSA+SHA384:RSA+SHA256:rsa_pss_rsae_sha512:rsa_pss_rsae_sha256

SSLCipherSuite "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384"

 

nginx:

 

Spoiler

ssl_conf_command ECDHParameters brainpoolP256r1

ssl_conf_command Curves secp521r1:secp384r1:prime256v1
ssl_conf_command SignatureAlgorithms ECDSA+SHA512:ECDSA+SHA384:ECDSA+SHA256:RSA+SHA512:RSA+SHA384:RSA+SHA256:rsa_pss_rsae_sha512:rsa_pss_rsae_sha256

ssl_ciphers ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384

this needs a certain minimum version of openssl and apache/nginx 🙂

a bit cumbersome but oh well...

it fulfills palos restrictions/requirements while still offering all compatible and secure ciphers and being compatible to modern browsers (I checked this for TLSv1.2 and TLSv1.3 only as those were the only secure ones).
if anyone does the same in other flavors like lighttpd, haproxy or any other platform that might need customization, please be so kind and post an example here as well so others can adapt it into their configs 🙂

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9 REPLIES 9

L2 Linker

Hi,

 

which PANOS version are you running? Some logs might be helpful as well.

 

Thanks.

 

 

 

 

Kind regards,
René
// If you like my answer force commit it.

running PANOS 10.0.1, log only shows "General TLS protocol error" together with the ciphers that were used

any specific debug or log i should show?

@Rene_Boehme or anyone know working ciphers for apache with TLSv1.2 and which ones work TLSv1.3?

There is nothing in the sslmgr.log and nothing but the General errors in the UI

the only ciphers that seem to work with Palo decryption on TLSv1.2 and Chrome/Firefox are these two:

AES256-GCM-SHA384:AES128-GCM-SHA256

all others error out even if those ciphers above are also available but not listed first (SSLHonorCipherOrder is set to off)

but with these ciphers which are considered weak, i dont even get forward secrecy and therefore the rating is down to B...

I wonder why the following ciphers dont work:
ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-CHCHA20-POLY1305-SHA256:CHACHA20-POLY1305-SHA256 or the ECDHE-ECDSA ones which are listed as supported but not shown in the decryption profile settings

 

anyone have an idea or even just an idea how to troubleshoot this further?

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