TLSv1.3 Decryption
Table of Contents
TLSv1.3 Decryption
Decrypt TLSv1.3 traffic to protect against threats in
encrypted traffic while benefiting from TLSv1.3 application security
and performance improvements.
You can decrypt, gain full visibility into, and prevent
known and unknown threats in TLSv1.3 traffic. TLSv1.3 is the latest
version of the TLS protocol, which provides application security
and performance improvements. To support TLSv1.3 decryption, you
must apply a Decryption profile to existing and new Decryption policy
rules with TLSv1.3 configured as the minimum protocol version or
with Max or TLSv1.3 configured as the maximum protocol version.
You can edit your existing profiles to support TLSv1.3. If you don’t
specify TLSv1.3 support in the Decryption profile, then PAN-OS defaults
to supporting TLSv1.2 as the maximum protocol version. The firewall
supports TLSv1.3 decryption for Forward Proxy, Inbound Inspection,
decrypted Network Packet Broker traffic, and Decryption Port Mirroring.
To use TLSv1.3, the client and server must be able to negotiate
TLSv1.3 ciphers. For websites that don’t support TLSv1.3, the firewall
selects an older version of the TLS protocol that the server supports.
The firewall supports the following decryption algorithms for
TLSv1.3:
- TLS13-AES-128-GCM-SHA256
- TLS13-AES-256-GCM-SHA384
- TLS13-CHACHA20-POLY1305-SHA256
If the Decryption profile you apply to decrypted traffic specifies
the protocol’s Max Version as Max,
then the profile supports TLSv1.3 and automatically uses TLSv1.3
with sites that support TLSv1.3. (You could set the Max
Version to TLSv1.3 to support
TLSv1.3, but when the next version of TLS is released, you will
need to update the profile. Setting the Max Version to Max future-proofs
the profile to automatically support new TLS versions as they are
released.) When you upgrade to PAN-OS 10.0, all Decryption profiles
with the Max Version set to Max are
reset to TLSv1.2 to provide automatic support
for mobile applications that use pinned certificates and prevent
that traffic from dropping.
Not all applications support the TLSv1.3 protocol. Follow decryption best practices, set the Min
Version of the TLS protocol to TLSv1.2,
and leave the Max Version setting as Max.
If business needs require allowing a weaker TLS protocol, create
a separate SSL Decryption profile with a Min Version that
allows the weaker protocol and attach it to a Decryption policy that
defines the traffic you need to allow with the weaker TLS protocol.
If your Decryption policy supports mobile applications, many
of which use pinned certificates, set the Max Version to TLSv1.2.
Because TLSv1.3 encrypts certificate information that was not encrypted
in previous TLS versions, the firewall can’t automatically add decryption
exclusions based on certificate information, which affects some
mobile applications. Therefore, if you enable TLSv1.3, the firewall
may drop some mobile application traffic unless you create a No
Decryption policy for that traffic. If you know the mobile applications
you use for business, consider creating a separate Decryption policy
and profile for those applications so that you can enable TLSv1.3
for all other traffic.
Do not attach a No Decryption profile to Decryption policies for
TLSv1.3 traffic that you don’t decrypt if you know that a particular
policy controls only TLSv1.3 traffic. A change from previous TLS
versions is that TLSv1.3 encrypts certificate information, so the
firewall no longer has visibility into that data and therefore cannot
block sessions with expired certificates or untrusted issuers, so
the profile has no effect. (The firewall can perform certificate
checks with TLSv1.2 and earlier because those protocols do not encrypt
certificate information and you should apply a No Decryption profile
to their traffic.) However, you can log undecrypted traffic of all
types by enabling logging successful and unsuccessful TLS handshakes
in the Decryption policy (logging unsuccessful TLS handshakes is
enabled by default).
When you allow unsupported modes in the SSL Protocol Settings Decryption Profile, the firewall
automatically adds the traffic to the Local Decryption Exclusion Cache. The firewall
still decrypts and inspects traffic that is downgraded from TLSv1.3
to TLSv1.2 and the Reason shown in the cache
for adding the server to the cache 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 would replace 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 specified TLSv1.3 as the Min
Version or the Max Version also changes to the
highest supported version.
- (PAN-OS 11.1 and earlier) For customers who use hardware security modules (HSMs), PAN-OS supports TLSv1.3 only for SSL Forward Proxy.
- (PAN-OS 11.2) For customers who use HSMs, PAN-OS supports TLSv1.3 for SSL Forward Proxy and SSL Inbound Inspection. To turn on this support, use the set ssl inbound-inspection tls1.3-with-hsm enable yes CLI command.If a client supports TLSv1.3 but not the server, then the first session is discarded and an entry for the session is added to the TLSv1.3 exclusion cache. In this case, future sessions will be supported with TLSv1.2. We recommend configuring SSL Inbound Inspection rules for servers that don't support TLSv1.3 and applying a Decryption profile that excludes TLSv1.3 to these rules.
You can configure an SSL Decryption profile that sets TLSv1.3
as the minimum allowed protocol version to achieve the tightest
security. However, some applications don’t support TLSv1.3 and may
not work if TLSv1.3 is the minimum allowed protocol. Apply a profile
that sets TLSv1.3 as the minimum version only to application traffic
that only supports TLSv1.3.
- Create a new SSL Decryption profile or edit an existing profile ().If the profile is new, specify a profile Name.
- Select SSL Protocol Settings.
- Change the Min Version to TLSv1.3.
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Using Max for the Max Version ensures that the traffic which the profile controls can use the strongest available protocol version. Min Version sets the weakest version of the protocol that the traffic can use. Setting the minimum version to TLSv1.3 means that the traffic must use TLSv1.3 (or greater) and that weaker protocol versions are blocked. (The Decryption Policy rule defines the traffic the profile controls.)When you configure TLSv1.3 as the Min Version, you must use Perfect Forward Secrecy (PFS) and the weaker key exchange, encryption, and authentication algorithms are not available. - Configure any other Decryption profile settings you need to set or change.
- Click OK to save the profile.
- Attach the profile to the appropriate Decryption Policy rule to apply it to the appropriate traffic.
