Manual Chapter : Create a custom Server SSL profile that supports CRL

Applies To:

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BIG-IP DNS

  • 14.1.2, 14.1.0

BIG-IP Analytics

  • 14.1.2, 14.1.0

BIG-IP AFM

  • 14.1.2, 14.1.0

BIG-IP PEM

  • 14.1.2, 14.1.0

BIG-IP ASM

  • 14.1.2, 14.1.0

BIG-IP AAM

  • 14.1.2, 14.1.0

BIG-IP Link Controller

  • 14.1.2, 14.1.0

BIG-IP APM

  • 14.1.2, 14.1.0

BIG-IP LTM

  • 14.1.2, 14.1.0
Manual Chapter

Create a custom Server SSL profile that supports CRL

With a Server SSL profile, the BIG-IP® system can perform decryption and encryption for server-side SSL traffic.

A certificate revocation list (CRL) is a published list of revoked certificates issued and updated by the certificate authority who signed them. Clients like your internet browser, will check the certificate's CRL URI to find out if the certificate is valid. When a certificate is revoked, the CRL is updated to reflect the revokation and published accordingly. Lists are not the most efficient way to maintain a record of revocation in high volume scenarios so some application vendors have deprecated their use in favor of online certificate status protcol (OCSP). However, you still need a CRL configuraiton as it is still a common scenario and recommended for backward compatibility.

Note:

Before you create a customer Server SSL profile that supports CRL, you must create either a configured DNS resolver or a configured BIG-IP LTM pool.

Create an internal proxy

  1. On the Main tab, click System > Services > Internal Proxies .
    The Internal Proxies screen opens.
  2. Click Create.
    The New Internal Proxy screen opens.
  3. In the Name field, type a unique name for your internal proxy.
  4. Select the Use Proxy Server check box if you want to use the Proxy Server Pool instead of DNS Resolver. The Proxy Server Pool is the LTM pool with one or multiple proxies for forwarding the CRL request to the CRL server. The DNS Resolver is the internal DNS resolver the BIG-IP system uses to fetch the internal proxy response.
    1. From the DNS Resolver list, select the internal DNS resolver the BIG-IP system uses to fetch the internal proxy response. This involves specifying one or more DNS servers in the DNS resolver configuration. Use this option when:
      • There is a DNS server that can do the name-resolution of the internal proxy.
      • The internal proxy can be reached on one of BIG-IP system's interfaces.

      If you are not selecting a pre-existing DNS Resolver you can create one. Click + to define a new internal DNS resolver and then return to this screen.

    2. From the Proxy Server Pool list, select the LTM pool for forwarding the CRL request to the CRL server.
  5. From the Route Domain list, select the route domain for fetching an internal proxy using HTTP explicit proxy. It is common to have the Route Domain set to 0. Click + to define a new route domain.
    You have now created an internal proxy and are ready to create a CRL configuration object.

Create a CRL configuration object

  1. On the Main tab, click System > Certificate Management > Traffic Certificate Management > CRL .
    The CRL screen opens.
  2. Click Create.
    The New CRL screen opens.
  3. In the Name field, type a name that specifies the certificate revocation list.
  4. Specify if you want to select Strict Revocation Check to protect your configuration from accidental future changes. The Strict Revocation Check specifies whether the strict revocation check for the certificate revocation list is enable or disabled. If the check box is selected it enables the strict revocation check and keymgmtd waits for the c fetching/caching to complete. If it is disabled, keymgmtd immediately replies with certificate status that is unknown and starts to download/cache the certificate revocation list file.
  5. For the Internal Proxy section, select Internal Proxy List to define the CRL list that specifies the internal DNS resolver or a proxy server pool. Select either New Internal Proxy or Internal Proxy List to specify the internal proxy.
  6. Click Update.
    You are now ready to create your custom Server SSL profile that supports CRL.

Create a Custom Server SSL Profile that supports CRL

  1. On the Main tab, click Local Traffic > Profiles > SSL > Server .
    The Server SSL profile list screen opens.
  2. Click Create.
    The New Server SSL Profile screen opens.
  3. In the Name field, type a unique name for the profile.
  4. From the Parent Profile list, select serverssl.
  5. From the Configuration list, select Advanced.
  6. Select the Custom check box.
    The settings become available for change.
  7. From the Certificate list, select the name of an SSL certificate on the BIG-IP system.
    Important: If the BIG-IP system is part of a DSC Sync-Failover group, always select a non-default certificate name, and ensure that this same certificate name is specified in every instance of this SSL profile in the device group. Taking these actions helps to ensure that SSL handshakes are successful after a failover event.
  8. From the Key list, select the name of an SSL key on the BIG-IP system.
    Important: If the BIG-IP system is part of a DSC Sync-Failover group, always select a non-default key name, and ensure that this same key name is specified in every instance of this SSL profile in the device group. Taking these actions helps to ensure that SSL handshakes are successful after a failover event.
  9. In the Pass Phrase field, type a pass phrase that enables access to the certificate/key pair on the BIG-IP system.
  10. From the Chain list, select the name of an SSL chain on the BIG-IP system.
  11. For the Ciphers setting, specify a cipher group or cipher string by choosing one of these options.
    Note: If you specified an ECDSA certificate key chain in the Certificate Key Chain setting, you must include the cipher string ECDHE_ECDSA in the cipher group or cipher string that you specify in the Ciphers setting. (At a minimum, you should specify a cipher group or string such as DEFAULT:ECDHE_ECDSA.) This is necessary to ensure successful cipher negotiation when the BIG-IP system is offered an ECDSA-based certificate only.
    Option Description
    Cipher Group

    Select an existing cipher group from the list when you want to use a system-defined or custom cipher group to define the ciphers that the BIG-IP system uses for negotiating SSL connections. Here's an example of the Ciphers setting where we've selected a custom cipher group that we created earlier.

    Cipher String

    Type a cipher string in the box if you want to manually specify a cipher string instead of selecting a cipher group. For security and performance reasons, consider following these recommendations:

    • Always append ciphers to the DEFAULT cipher string.
    • Type a cipher string that includes the ECC key type, because its shorter length speeds up encryption and decryption while still offering virtually the same level of security.
    • Disable ADH ciphers but also include the keyword HIGH. To do this, just include both !ADH and :HIGH in your cipher string.
    • For AES, DES, and RC4 encryption types, make sure you specify the DHE key exchange method. DHE uses Forward Privacy, which creates a key that it throws away after each session so that the same session key never gets used twice. When you use DHE, make sure that the SSL private key isn't being shared with a monitoring system or a security device like an intrusion detection or prevention system. Also, diagnostic tools like ssldump won't work when you're using Forward Secrecy.
    • Disable EXPORT ciphers by including !EXPORT in the cipher string.
    • If you can live with removing support for the SSLv3 protocol version, do it. This protocol version is not secure. Simply include :!SSLv3 in any cipher string you type.

    Here's an example of the Ciphers setting where we have opted to manually type the cipher string DEFAULT:ECDHE-RSA-AES-128-GCM-SHA256:!ADH:!EXPORT:HIGH:

  12. In the same area of the screen, configure any other settings as needed.
  13. Select the Custom check box for the Server Authentication area of the screen.
    The settings become available for change.
  14. Change or retain the values for all Server Authentication settings as needed.
  15. From the CRL list, select the CRL object that specifies the SSL client certificate constrained delegation CRL object that the BIG-IP system's SSL should use. You can click the + icon to open the create-new CRL object screen.
  16. From the CRL File list, select the name of a file containing a list of revoked server certificates.
  17. In the Allow Expired CRL File field, select the check box to instruct the system to use the specified CRL file even if it has expired. The default is disabled.
  18. Complete any other settings and click Finished.
After performing this task, you can see the custom Server SSL profile that supports CRL in the list of Server SSL profiles on the system.