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    5. Decryption Exclusions

    Decryption Exclusions

    Some applications can’t be decrypted for technical reasons and some traffic can’t be decrypted for business, compliance, or regulatory reasons. Make decryption exceptions only when you must.
    You can exclude two types of traffic from decryption:
    • Traffic that breaks decryption for
      technical reasons
      , such as using a pinned certificate, an incomplete certificate chain, unsupported ciphers, or mutual authentication (decrypting blocks the traffic). Palo Alto Networks provides a predefined SSL Decryption Exclusion list (
      Device
      Certificate management
      SSL Decryption Exclusion
      ) that excludes hosts with applications and services that are known to break decryption technically from SSL Decryption by default. If you encounter sites that break decryption technically and are not on the SSL Decryption Exclusion list, you can add them to list manually by server hostname. The firewall blocks sites whose applications and services break decryption technically unless you add them to the SSL Decryption Exclusion list.
    • Traffic that you
      choose
       not to decrypt because of business, regulatory, personal, or other reasons, such as financial-services, health-and-medicine, or government traffic. You can choose to exclude traffic based on source, destination, URL category, and service.
    You can use asterisks (*) as wildcards to create decryption exclusions for multiple hostnames associated with a domain. Asterisks behave the same way that carets (^) behave for URL category exceptions—each asterisk controls one variable subdomain (label) in the hostname. This enables you to create both very specific and very general exclusions. For example:
    • mail.*.com matches mail.company.com but does not match mail.company.sso.com.
    • *.company.com matches tools.company.com but does not match eng.tools.company.com.
    • *.*.company.com matches eng.tools.company.com but does not match eng.company.com.
    • *.*.*.company.com matches corp.exec.mail.company.com, but does not match corp.mail.company.com.
    • mail.google.* matches mail.google.com, but does not match mail.google.uk.com.
    • mail.google.*.* matches mail.google.co.uk, but does not match mail.google.com.
    For example, to use wildcards to exclude video-stats.video.google.com from decryption but not to exclude video.google.com from decryption, exclude *.*.google.com.
    Regardless of the number of asterisk wildcards that precede a hostname (without a non-wildcard label preceding the hostname), the hostname matches the entry. For example, *.google.com, *.*.google.com, and *.*.*.google.com all match google.com. However, *.dev.*.google.com does not match google.com because one label (dev) is not a wildcard.
    To increase visibility into traffic and reduce the attack surface as much as possible, don’t make decryption exceptions unless you must.

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