Decryption Profile for No Decryption

The No Decryption profile blocks risky sessions for traffic that you choose not to decrypt by policy rule.
The No Decryption profile (
Objects
Decryption Profile
No Decryption
) controls server verification checks for traffic that you choose not to decrypt as defined in “No Decryption” Decryption policies to which you attach the profile. (Don’t exclude traffic that you can’t decrypt because a site breaks decryption for technical reasons such as a pinned certificate or mutual authentication by policy. Instead, add the hostname to the Decryption Exclusion List.) The following figure shows the general best practice recommendations for the No Decryption profile settings, but the settings you use also depend on your company’s security compliance rules and local laws and regulations.
no-decryption-best-practice-decryption-profile.png
  • Block sessions with expired certificates
    —Always check this box to block sessions with servers that have expired certificates and prevent access to potentially insecure sites. If you don’t check this box, users can connect with and transact with potentially malicious sites and see warning messages when they attempt to connect, but the connection is not prevented.
  • Block sessions with untrusted issuers
    —Always check this box to block sessions with servers that have untrusted certificate issuers. An untrusted issuer may indicate a man-in-the-middle attack, a replay attack, or other attack.
(Applies to PAN-OS 9.0.9 and later for TLSv1.2 and earlier) If you choose to allow sessions with untrusted issuers (not recommended) and only
Block sessions with expired certificates
, there is a scenario in which a session with a trusted, expired issuer may be blocked inadvertently. When the firewall’s certificate store contains a valid, self-signed Trusted CA and the server sends an expired CA in the certificate chain, the firewall does not check its certificate store. Instead, the firewall blocks the session based on the expired CA when it should find the trusted, valid alternative trust anchor and allow the session based on that trusted self-signed certificate.
To avoid this scenario, in addition to
Block sessions with expired certificates
, enable
Block sessions with untrusted issuers
. This forces the firewall to check its certificate store, find the self-signed Trusted CA, and allow the session.

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