TLS 1.3 Decryption
Decrypt TLSv1.3 traffic to protect against threats in encrypted traffic while
benefiting from TLSv1.3 application security and performance improvements.
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To support TLSv1.3 decryption, apply a decryption profile with TLSv1.3 configured as the
minimum or maximum protocol version to existing and new decryption policy rules. You can
edit existing decryption profiles to support TLSv1.3. If you don’t enable TLSv1.3,
PAN-OS defaults to TLSv1.2 as the maximum protocol version. If a website or application
doesn't support TLSv1.3, the Next-Generation Firewall (NGFW) automatically selects a TLS
protocol version that the server supports.
To establish a TLSv1.3 connection, both client and server must support negotiation with
TLSv1.3 ciphers. The following decryption algorithms are supported for TLSv1.3
connections:
If the Max Version a decryption profile supports is
Max, then the profile supports TLSv1.3 and automatically uses
TLSv1.3 with sites supporting this protocol. The Max option
ensures that the traffic that the profile controls uses the strongest available protocol
version. It also future-proofs the decryption profile as it provides automatic support
for new TLS versions as they are released.
You can configure TLSv1.3 as the
Max Version instead of Max. However,
when the next TLS version releases, you'll need to update the decryption
profile.
Min Version specifies the weakest version of the protocol that the
traffic can use. Setting the minimum protocol version to
TLSv1.3
achieves the tightest security because it requires traffic to use TLSv1.3 or greater
protocol versions. This blocks weaker protocols and makes weaker key exchange,
encryption, and authentication algorithms unavailable. Further, TLSv1.3 requires the use
of
Perfect Forward Secrecy (PFS). Apply a profile
that sets TLSv1.3 as the minimum version only to application traffic that only supports
TLSv1.3.If
As not all applications support TLSv1.3, follow
decryption best practices and set the
Min Version of the TLS protocol to
TLSv1.2 and the
Max Version to
Max. If access to websites or applications with weaker TLS
protocols is a business requirement, create separate decryption profiles with a
Min Version that allows the weaker protocol and attach it to
a decryption policy rule that specifies the traffic you need to allow with the weaker
TLS protocol.
For decryption policy rules that support mobile applications, many of which use pinned
certificates, set the Max Version to
TLSv1.2. TLSv1.3 encrypts certificate information that was
not encrypted in previous TLS versions, preventing NGFWs from
automatically adding decryption exclusions based on certificate information. As a
result, if you enable TLSv1.3, the NGFW may drop some mobile application
traffic. To mitigate potential issues, create a No Decryption policy rule for this
traffic. If you know the specific mobile applications required for business, consider
creating a separate decryption policy rule and decryption profile for those
applications. This approach allows you to enable TLSv1.3 for all other traffic.
Avoid attaching
No-decryption profiles to
decryption policy rules that exclusively
handle TLSv1.3 traffic. TLSv1.3 encrypts certificate information, so the
NGFW doesn't have visibility into this information and therefore
can’t block sessions with expired certificates or untrusted issuers, making the
profile ineffective. (The
NGFW can perform certificate checks with
TLSv1.2 and earlier protocols because those protocols don’t encrypt certificate
information. You should apply No Decryption profiles to decryption policy rules
handling TLSv1.2 and earlier traffic.) However, you can log undecrypted traffic of
all types by selecting the options to log successful and unsuccessful TLS handshakes
in decryption policy rules. Unsuccessful TLS handshakes are logged by default.
If you allow unsupported modes in the
SSL Protocol Settings of a decryption profile, the
NGFW and
Prisma Access automatically adds this traffic to its
Local SSL Decryption Exclusion Cache.The
NGFW and
Prisma Access still decrypts and
inspects traffic that is downgraded from TLSv1.3 to TLSv1.2. The
Reason shown in the cache for the added servers is
TLS13_UNSUPPORTED.
If you downgrade from PAN-OS 11.1 to a previous version, any decryption profile that
specifies TLSv1.3 as the Min Version or the Max
Version changes to the highest supported version. For example,
downgrading from PAN-OS 11.1 to PAN-OS 9.1 replaces TLSv1.3 with TLSv1.2. If a Panorama
device on PAN-OS 11.1 pushes the configuration to devices that run older versions of
PAN-OS, any decryption profile that specifies TLSv1.3 as the Min
Version or the Max Version also changes to the
highest supported version.
