Configure SSL Forward Proxy

SSL Forward Proxy decryption enables the firewall to see potential threats in outbound encrypted traffic and apply security protections against those threats.
To enable the firewall to perform SSL Forward Proxy decryption, you must set up the certificates required to establish the firewall as a trusted third party (proxy) to the session between the client and the server. The firewall can use certificates signed by an enterprise certificate authority (CA) or self-signed certificates generated on the firewall as
Forward Trust certificates
to authenticate the SSL session with the client.
  • (
    Recommended Best Practice
    )
    Enterprise CA-signed Certificates
    —An enterprise CA can issue a signing certificate that the firewall can use to sign the certificates for sites which require SSL decryption. When the firewall trusts the CA that signed the certificate of the destination server, the firewall can send a copy of the destination server certificate to the client, signed by the enterprise CA. This is a best practice because usually all network devices already trust the Enterprise CA (it is usually already installed in the devices’ CA Trust storage), so you don’t need to deploy the certificate on the endpoints, so the rollout process is smoother.
  • Self-signed Certificates
    —The firewall can act as a CA and generate self-signed certificates that the firewall can use to sign the certificates for sites which require SSL decryption. The firewall can sign a copy of the server certificate to present to the client and establish the SSL session. This method requires that you need to install the self-signed certificates on all of your network devices so that those devices recognize the firewall’s self-signed certificates. Because the certificates must be deployed to all devices, this method is better for small deployments and proof-of-concept (POC) trials than for large deployments.
Additionally, set up a
Forward Untrust certificate
for the firewall to present to clients when the server certificate is signed by a CA that the firewall does not trust. This ensures that clients are prompted with a certificate warning when attempting to access sites with untrusted certificates.
Regardless of whether you generate Forward Trust certificates from your Enterprise Root CA or use a self-signed certificate generated on the firewall, generate a separate subordinate Forward Trust CA certificate for each firewall. The flexibility of using separate subordinate CAs enables you to revoke one certificate when you decommission a device (or device pair) without affecting the rest of the deployment and reduces the impact in any situation in which you need to revoke a certificate. Separate Forward Trust CAs on each firewall also helps troubleshoot issues because the CA error message the user sees includes information about the firewall the traffic is traversing. If you use the same Forward Trust CA on every firewall, you lose the granularity of that information.
After setting up the Forward Trust and Forward Untrust certificates required for SSL Forward Proxy decryption, create a Decryption policy rule to define the traffic you want the firewall to decrypt and create a Decryption profile to apply SSL controls and checks to the traffic. The Decryption policy decrypts SSL tunneled traffic that matches the rule into clear text traffic. The firewall blocks and restricts traffic based on the Decryption profile attached to the Decryption policy and on the firewall Security policy. The firewall re-encrypts traffic as it exits the firewall.
  1. Ensure that the appropriate interfaces are configured as either virtual wire, Layer 2, or Layer 3 interfaces.
    View configured interfaces on the
    Network
    Interfaces
    Ethernet
    tab. The
    Interface Type
    column displays if an interface is configured to be a
    Virtual Wire
    or
    Layer 2
    , or
    Layer 3
    interface. You can select an interface to modify its configuration, including what type of interface it is.
  2. Configure the Forward Trust certificate for the firewall to present to clients when a trusted CA has signed the server certificate. You can use an enterprise CA-signed certificate or a self-signed certificate as the forward trust certificate.
    (
    Recommended Best Practice
    ) Use an enterprise CA-signed certificate as the Forward Trust certificate. Create a uniquely named Forward Trust certificate on each firewall:
    1. Generate a Certificate Signing Request (CSR) for the enterprise CA to sign and validate:
      1. Select
        Device
        Certificate Management
        Certificates
        and click
        Generate
        .
      2. Enter a
        Certificate Name
        . Use a unique name for each firewall.
      3. In the
        Signed By
        drop-down, select
        External Authority (CSR)
        .
      4. (
        Optional
        ) If your enterprise CA requires it, add
        Certificate Attributes
        to further identify the firewall details, such as Country or Department.
      5. Click
        Generate
        to save the CSR. The pending certificate is now displayed on the
        Device Certificates
        tab.
    2. Export the CSR:
      1. Select the pending certificate displayed on the
        Device Certificates
        tab.
      2. Click
        Export
        to download and save the certificate file.
        Leave
        Export private key
        unselected in order to ensure that the private key remains securely on the firewall.
      3. Click
        OK
        .
    3. Provide the certificate file to your enterprise CA. When you receive the enterprise CA-signed certificate from your enterprise CA, save the enterprise CA-signed certificate to import onto the firewall.
    4. Import the enterprise CA-signed certificate onto the firewall:
      1. Select
        Device
        Certificate Management
        Certificates
        and click
        Import
        .
      2. Enter the pending
        Certificate Name
        exactly. The
        Certificate Name
        that you enter must exactly match the pending certificate name in order for the pending certificate to be validated.
      3. Select the signed
        Certificate File
        that you received from your enterprise CA.
      4. Click
        OK
        . The certificate is displayed as valid with the Key and CA check boxes selected.
    5. Select the validated certificate to enable it as a
      Forward Trust Certificate
      to be used for SSL Forward Proxy decryption.
    6. Click
      OK
      to save the enterprise CA-signed forward trust certificate.
    Use a self-signed certificate as the Forward Trust certificate:
    1. Click the self-signed root CA certificate (
      Device
      Certificate Management
      Certificates
      Device Certificates
      ) to open
      Certificate information
      and then click the
      Trusted Root CA
      checkbox.
    2. Click
      OK
      .
    3. Generate new subordinate CA certificates for each firewall:
      1. Select
        Device
        Certificate Management
        Certificates
        .
      2. Click
        Generate
        at the bottom of the window.
      3. Enter a
        Certificate Name
        .
      4. Enter a
        Common Name
        , such as 192.168.2.1. This should be the IP or FQDN that will appear in the certificate. In this case, we are using the IP of the trust interface. Avoid using spaces in this field.
      5. In the
        Signed By
        field, select the self-signed Root CA certificate that you created.
      6. Click the
        Certificate Authority
        check box to enable the firewall to issue the certificate. Selecting this check box creates a certificate authority (CA) on the firewall that is imported to the client browsers, so clients trust the firewall as a CA.
      7. Generate
        the certificate.
    4. Click the new certificate to modify it and click the
      Forward Trust Certificate
      checkbox to configure the certificate as the Forward Trust Certificate.
    5. Click
      OK
      to save the self-signed forward trust certificate.
    6. Repeat this procedure to generate a unique subordinate CA certificate on each firewall.
  3. Distribute the forward trust certificate to client system certificate stores.
    If you are using an enterprise-CA signed certificate as the forward trust certificate for SSL Forward Proxy decryption, and the client systems already have the enterprise CA installed in the local trusted root CA list, you can skip this step. (The client systems trust the subordinate CA certificates you generate on the firewall because the Enterprise Trusted Root CA has signed them.)
    If you do not install the forward trust certificate on client systems, users see certificate warnings for each SSL site they visit.
    On a firewall configured as a GlobalProtect portal:
    This option is supported with Windows and Mac client OS versions, and requires GlobalProtect agent 3.0.0 or later to be installed on the client systems.
    1. Select
      Network
      GlobalProtect
      Portals
      and then select an existing portal configuration or
      Add
      a new one.
    2. Select
      Agent
      and then select an existing agent configuration or
      Add
      a new one.
    3. Add
      the self-signed firewall Trusted Root CA certificate to the Trusted Root CA section. After GlobalProtect distributes the firewall’s Trusted Root CA certificate to client systems, the client systems trust the firewall’s subordinate CA certificates because the clients trust the firewall’s Root CA certificate.
    4. Install in Local Root Certificate Store
      so that the GlobalProtect portal automatically distributes the certificate and installs it in the certificate store on GlobalProtect client systems.
    5. Click
      OK
      twice.
    Without GlobalProtect:
    Export the firewall Trusted Root CA certificate so that you can import it into client systems. Highlight the certificate and click
    Export
    at the bottom of the window. Choose PEM format.
    Do not select the
    Export private key
    checkbox! The private key should remain on the firewall and should not be exported to client systems.
    Import the firewall’s Trusted Root CA certificate into the browser Trusted Root CA list on the client systems in order for the clients to trust it. When importing into the client browser, ensure that you add the certificate to the Trusted Root Certification Authorities certificate store. On Windows systems, the default import location is the Personal certificate store. You can also simplify this process by using a centralized deployment option, such as an Active Directory Group Policy Object (GPO).
  4. Configure the Forward Untrust certificate (use the same Forward Untrust certificate for all firewalls).
    1. Click
      Generate
      at the bottom of the certificates page.
    2. Enter a
      Certificate Name
      , such as my-ssl-fwd-untrust.
    3. Set the
      Common Name
      , for example 192.168.2.1. Leave
      Signed By
      blank.
    4. Click the
      Certificate Authority
      check box to enable the firewall to issue the certificate.
    5. Click
      Generate
      to generate the certificate.
    6. Click
      OK
      to save.
    7. Click the new my-ssl-fwd-untrust certificate to modify it and enable the
      Forward Untrust Certificate
      option.
      Do not export the Forward Untrust certificate to the Certificate Trust Lists of your network devices! Do not install the Forward Untrust certificate on client systems. This is critical because installing the Untrust certificate in the Trust List results in devices trusting websites that the firewall does not trust. In addition, users won’t see certificate warnings for untrusted sites, so they won’t know the sites are untrusted and may access those sites, which could expose your network to threats.
    8. Click
      OK
      to save.
  5. (
    Optional
    ) Configure the Key Size for SSL Forward Proxy Server Certificates that the firewall presents to clients. By default, the firewall determines the key size to use based on the key size of the destination server certificate.
  6. Create a Decryption Policy Rule to define traffic for the firewall to decrypt and Create a Decryption Profile to apply SSL controls to the traffic.
    Although Decryption profiles are optional, it is a best practice to include a Decryption profile with each Decryption policy rule to prevent weak, vulnerable protocols and algorithms from allowing questionable traffic on your network.
    1. Select
      Policies
      Decryption
      , Add or modify an existing rule, and define traffic to be decrypted.
    2. Select
      Options
      and:
      • Set the rule
        Action
        to
        Decrypt
        matching traffic.
      • Set the rule
        Type
        to
        SSL Forward Proxy
        .
      • (
        Optional but a best practice
        ) Configure or select an existing
        Decryption Profile
        to block and control various aspects of the decrypted traffic (for example, create a decryption profile to perform certificate checks and enforce strong cipher suites and protocol versions).
    3. Click
      OK
      to save.
  7. This option requires an active WildFire license and is a WildFire best practice.
  8. Commit
    the configuration.
  9. Choose your next step:

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