Keys and Certificates
To ensure trust between parties in a secure communication session, Palo Alto Networks firewalls and Panorama use digital certificates. Each certificate contains a cryptographic key to encrypt plaintext or decrypt ciphertext. Each certificate also includes a digital signature to authenticate the identity of the issuer. The issuer must be in the list of trusted certificate authorities (CAs) of the authenticating party. Optionally, the authenticating party verifies the issuer did not revoke the certificate (see Certificate Revocation).
Palo Alto Networks firewalls and Panorama use certificates in the following applications:
- User authentication for Captive Portal, multi-factor authentication (MFA), and web interface access to a firewall or Panorama.
- Device authentication for GlobalProtect VPN (remote user-to-site or large scale).
- Device authentication for IPSec site-to-site VPN with Internet Key Exchange (IKE).
- External dynamic list (EDL) validation.
- User-ID agent and TS agent access.
- Decrypting inbound and outbound SSL traffic.A firewall decrypts the traffic to apply policy rules, then re-encrypts it before forwarding the traffic to the final destination. For outbound traffic, the firewall acts as a forward proxy server, establishing an SSL/TLS connection to the destination server. To secure a connection between itself and the client, the firewall uses a signing certificate to automatically generate a copy of the destination server certificate.
The following table describes the keys and certificates that Palo Alto Networks firewalls and Panorama use. As a best practice, use different keys and certificates for each usage.
Secure access to firewall or Panorama administration interfaces (HTTPS access to the web interface) requires a server certificate for the MGT interface (or a designated interface on the dataplane if the firewall or Panorama does not use MGT) and, optionally, a certificate to authenticate the administrator.
In deployments where Authentication policy identifies users who access HTTPS resources, designate a server certificate for the Captive Portal interface. If you configure Captive Portal to use certificates for identifying users (instead of, or in addition to, interactive authentication), deploy client certificates also. For more information on Captive Portal, see Map IP Addresses to Usernames Using Captive Portal.
For outbound SSL/TLS traffic, if a firewall acting as a forward proxy trusts the CA that signed the certificate of the destination server, the firewall uses the forward trust CA certificate to generate a copy of the destination server certificate to present to the client. To set the private key size, see Configure the Key Size for SSL Forward Proxy Server Certificates. For added security, store the key on a hardware security module (for details, see Secure Keys with a Hardware Security Module).
For outbound SSL/TLS traffic, if a firewall acting as a forward proxy does not trust the CA that signed the certificate of the destination server, the firewall uses the forward untrust CA certificate to generate a copy of the destination server certificate to present to the client.
SSL Inbound Inspection
The keys that decrypt inbound SSL/TLS traffic for inspection and policy enforcement. For this application, import onto the firewall a private key for each server that is subject to SSL/TLS inbound inspection. See Configure SSL Inbound Inspection.
Beginning in PAN-OS 8.0, firewalls use the Elliptic-Curve Diffie-Hellman Ephemeral (ECDHE) algorithm to perform strict certificate checking. This means that if the firewall uses an intermediate certificate, you must reimport the certificate from your web server to the firewall after you upgrade to a PAN-OS 8.0 or later release and combine the server certificate with the intermediate certificate (install a chained certificate). Otherwise, SSL Inbound Inspection sessions that have an intermediate certificate in the chain will fail. To install a chained certificate:
SSL Exclude Certificate
Certificates for servers to exclude from SSL/TLS decryption. For example, if you enable SSL decryption but your network includes servers for which the firewall should not decrypt traffic (for example, web services for your HR systems), import the corresponding certificates onto the firewall and configure them as SSL Exclude Certificates. See Decryption Exclusions.
All interaction among GlobalProtect components occurs over SSL/TLS connections. Therefore, as part of the GlobalProtect deployment, deploy server certificates for all GlobalProtect portals, gateways, and Mobile Security Managers. Optionally, deploy certificates for authenticating users also.
Site-to-Site VPNs (IKE)
In a site-to-site IPSec VPN deployment, peer devices use Internet Key Exchange (IKE) gateways to establish a secure channel. IKE gateways use certificates or preshared keys to authenticate the peers to each other. You configure and assign the certificates or keys when defining an IKE gateway on a firewall. See Site-to-Site VPN Overview.
The firewall uses a master key to encrypt all private keys and passwords. If your network requires a secure location for storing private keys, you can use an encryption (wrapping) key stored on a hardware security module (HSM) to encrypt the master key. For details, see Encrypt a Master Key Using an HSM.
Trusted Root CA
The designation for a root certificate issued by a CA that the firewall trusts. The firewall can use a self-signed root CA certificate to automatically issue certificates for other applications (for example, SSL Forward Proxy).
Also, if a firewall must establish secure connections with other firewalls, the root CA that issues their certificates must be in the list of trusted root CAs on the firewall.
By default, Panorama, firewalls, and Log Collectors use a set of predefined certificates for the SSL/TLS connections used for management and log forwarding. However, you can enhance these connection by deploying custom certificates to the devices in your deployment. These certificates can also be used to secure the SSL/TLS connection between Panorama HA peers.
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