SSL Inbound Inspection
SSL Inbound Inspection decryption decrypts inbound traffic
so the firewall can protect against threats in the encrypted traffic
destined for your servers.
Use SSL Inbound Inspection to decrypt and inspect inbound
SSL/TLS traffic from a client to a targeted network server (any
server you have the certificate for and can import it onto the firewall)
and block suspicious sessions. For example, suppose a malicious
actor wants to exploit a known vulnerability in your web server.
Inbound SSL/TLS decryption provides visibility into the traffic,
allowing the firewall to respond to the threat proactively.
SSL Inbound Inspection works similarly to
SSL Forward Proxy, except
that the firewall decrypts inbound traffic to servers instead of
decrypting outbound traffic from internal clients. The firewall
acts as a man-in-the-middle proxy between the external client and
the internal server and must generate a new session key for each
secure session. The firewall creates a secure session between the
client and the firewall and another secure session between the firewall
and the server to decrypt and inspect the traffic.
Because the firewall is a proxy device, SSL Inbound Inspection
cannot decrypt some sessions, such as sessions with client authentication
or pinned certificates. Being a proxy also means that the firewall
does not support High Availability (HA) sync for decrypted SSL sessions.
On the firewall, you must
install the certificate and private key
for each server for which you want to perform SSL Inbound Inspection.
The TLS versions that your web server supports determine how you
should install the server certificate and key on the firewall. If
your web server supports TLS 1.2 and Rivest, Shamir, Adleman (RSA)
or Perfect Forward Secrecy (
PFS) key exchange algorithms
and your
end-entity (leaf) certificate is signed by intermediate certificates,
we recommend
uploading a certificate chain (a
single file) to the firewall. Uploading the chain avoids client-side
server certificate authentication issues.
TLS 1.3 removes support for the RSA key exchange algorithm.
The firewall handles TLS 1.3 connections differently than TLS
1.2 connections. During TLS 1.3 handshakes, the firewall sends the
client the same certificate or certificate chain that it receives
from the server. As a result, uploading the server certificate and
private key to the firewall is sufficient if you correctly set up
your web server. For example, if your server’s leaf certificate
is signed by intermediate certificates, the chain of certificates
needs to be installed on the server to avoid client-side server
authentication issues.
When you configure the
SSL Protocol Settings Decryption
Profile for SSL Inbound Inspection traffic, create separate profiles
for servers with different security capabilities. For example, if
one set of servers supports only RSA, the SSL Protocol Settings
only need to support RSA. However, the SSL Protocol Settings for
servers that support PFS should support PFS. Configure SSL Protocol
Settings for the highest level of security that the server supports,
but check performance to ensure that the firewall resources can
handle the higher processing load that higher security protocols
and algorithms require.
When you configure SSL Inbound Inspection and use a PFS
cipher, session resumption is not supported.
When you configure SSL Inbound Inspection, the proxied
traffic does not support DSCP code points or QoS.
