Manual Chapter : SSL Traffic Management

Applies To:

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BIG-IP DNS

  • 14.0.0

BIG-IP AFM

  • 14.0.0

BIG-IP Analytics

  • 14.0.0

BIG-IP PEM

  • 14.0.0

BIG-IP ASM

  • 14.0.0

BIG-IP AAM

  • 14.0.0

BIG-IP Link Controller

  • 14.0.0

BIG-IP APM

  • 14.0.0

BIG-IP LTM

  • 14.0.0
Manual Chapter

SSL Traffic Management

About SSL offload

When you want the BIG-IP system to process application traffic over SSL, you can configure the system to perform the SSL handshake that destination servers normally perform. This ability for the BIG-IP system to offload SSL processing from a destination server is an important feature of the BIG-IP system.

The most common way to configure the BIG-IP system is to create a Client SSL profile, which makes it possible for the BIG-IP system to decrypt client requests before sending them on to a server, and encrypt server responses before sending them back to the client.

Within a Client SSL profile specifically, you can specify multiple certificate/key pairs, one per key type. This enables the system to accept all types of cipher suites that a client might support as part of creating a secure connection. The system then decrypts the client data, manipulates any headers or payload according to the way that you configured the Client SSL profile, and by default, sends the request in clear text to the target server for processing.

For those sites that require enhanced security on their internal network, you can configure a Server SSL profile. With a Server SSL profile, the BIG-IP system re-encrypts the request before sending it to the destination server. When the server returns an encrypted response, the BIG-IP system decrypts and then re-encrypts the response, before sending the response back to the client.

About client-side and server-side SSL profiles

You can manage the way that the BIG-IP system processes SSL application traffic by configuring two types of SSL profiles: A Client SSL profile, a Server SSL profile, or both. These profiles affect the way that the system manages SSL traffic passing through the system.

When you configure Client SSL or Server SSL profiles and assign them to a virtual server, the BIG-IP system offloads SSL processing from the destination server. This offloading not only conserves resource on destination servers, but enables the BIG-IP system to customize SSL traffic processing according to your configuration specifications.

Create a custom Client SSL profile

You create a custom Client SSL profile when you want the BIG-IP® system to terminate client-side SSL traffic for the purpose of decrypting client-side ingress traffic and encrypting client-side egress traffic. By terminating client-side SSL traffic, the BIG-IP system offloads these decryption/encryption functions from the destination server. When you perform this task, you can specify multiple certificate key chains, one for each key type (RSA, DSA, and ECDSA). This allows the BIG-IP system to negotiate secure client connections using different cipher suites based on the client's preference.
Note: At a minimum, you must specify a certificate key chain that includes an RSA key pair. Specifying certificate key chains for DSA and ECDSA key pairs is optional, although highly recommended.
  1. On the Main tab, click Local Traffic > Profiles > SSL > Client .
    The Client SSL profile list screen opens.
  2. Click Create.
    The New Client SSL Profile screen opens.
  3. In the Name field, type a unique name for the profile.
  4. From the Parent Profile list, select clientssl.
  5. Select the Custom check box.
    The settings become available for change.
  6. From the Configuration list, select Advanced.
  7. For the Mode setting, select the Enabled check box.
  8. For the Certificate Key Chain setting, click Add.
    1. From the Certificate list, select a certificate name.
      This is the name of a certificate that you installed on the BIG-IP system. If you have not generated a certificate request nor installed a certificate on the BIG-IP system, and the BIG-IP system is not part of a device service clustering (DSC) configuration, you can specify the name of the existing certificate named default.
      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.
    2. From the Key list, select the name of the key associated with the certificate specified in the previous step.
      This is the name of a key that you installed on the BIG-IP system. If you have not installed a key on the BIG-IP system, and the BIG-IP system is not part of a device service clustering (DSC) configuration, you can specify the name of the existing key named default.
      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.
    3. From the Chain list, select the chain that you want to include in the certificate key chain.
      A certificate chain can contain either a series of public key certificates in Privacy Enhanced Mail (PEM) format or a series of one or more PEM files. A certificate chain can contain certificates for Intermediate certificate Authorities (CAs).
      Note: The default self-signed certificate and the default CA bundle certificate are not appropriate for use as a certificate chain.
    4. For the Passphrase field, type a string that enables access to SSL certificate/key pairs that are stored on the BIG-IP system with password protection.
      This setting is optional. For added security, the BIG-IP system automatically encrypts the pass phrase itself. This pass phrase encryption process is invisible to BIG-IP system administrative users.
    5. Click Add.
  9. In the Certificate Key Chain setting, click Add again, and repeat the process for all certificate key chains that you want to specify.
    At a minimum, you must specify an RSA certificate key chain.
    The result is that all specified key chains appear in the text box.
  10. To enable OCSP stapling, select theOCSP Stapling check box.
    To enable OCSP stapling, you must first create an OCSP Stapling profile. See Creating an OCSP stapling profile for detailed steps.
  11. If you want to Notify Certificate Status to Virtual Server, select the check box.
  12. 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:

  13. Configure any other settings as needed.
  14. Click Finished.
After performing this task, you can see the custom Client SSL profile in the list of Client SSL profiles on the system.
Note: By default, TLSv1.3 is disabled in this configuration.
To use this profile, you must assign it to a virtual server. See Assigning SSL profiles to a virtual server for detailed information.

Create a custom Server SSL profile

With a Server SSL profile, the BIG-IP® system can perform decryption and encryption for server-side SSL traffic.
  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. Configure any other settings as needed.
  13. Click Finished.
After performing this task, you can see the custom Server SSL profile in the list of Server SSL profiles on the system.
Note: By default, TLSv1.3 is disabled in this configuration.
To use this profile, you must assign it to a virtual server. See the Assigning SSL profiles to a virtual server section for detailed information.

Create a custom Client SSL profile that supports C3D

You create a custom Client SSL profile when you want the BIG-IP® system to terminate client-side SSL traffic for the purpose of decrypting client-side ingress traffic and encrypting client-side egress traffic. By terminating client-side SSL traffic, the BIG-IP system offloads these decryption/encryption functions from the destination server. When you perform this task, you can specify multiple certificate key chains, one for each key type (RSA, DSA, and ECDSA). This allows the BIG-IP system to negotiate secure client connections using different cipher suites based on the client's preference.
Note: At a minimum, you must specify a certificate key chain that includes an RSA key pair. Specifying certificate key chains for DSA and ECDSA key pairs is optional, although highly recommended.
Note: For detailed information on how to complete the client certificate constrained delegation (C3D) configuration and ensure that your custom client SSL profile is set up properly, see About client certificate constrained delegation before completing your custom profile setup.
  1. On the Main tab, click Local Traffic > Profiles > SSL > Client .
    The Client SSL profile list screen opens.
  2. Click Create.
    The New Client SSL Profile screen opens.
  3. In the Name field, type a unique name for the profile.
  4. From the Parent Profile list, select clientssl.
  5. Select the Custom check box.
    The settings become available for change.
  6. From the Configuration list, select Advanced.
  7. For the Mode setting, select the Enabled check box.
  8. For the Certificate Key Chain setting, click Add.
    1. From the Certificate list, select a certificate name.
      This is the name of a certificate that you installed on the BIG-IP system. If you have not generated a certificate request nor installed a certificate on the BIG-IP system, and the BIG-IP system is not part of a device service clustering (DSC) configuration, you can specify the name of the existing certificate named default.
      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.
    2. From the Key list, select the name of the key associated with the certificate specified in the previous step.
      This is the name of a key that you installed on the BIG-IP system. If you have not installed a key on the BIG-IP system, and the BIG-IP system is not part of a device service clustering (DSC) configuration, you can specify the name of the existing key named default.
      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.
    3. From the Chain list, select the chain that you want to include in the certificate key chain.
      A certificate chain can contain either a series of public key certificates in Privacy Enhanced Mail (PEM) format or a series of one or more PEM files. A certificate chain can contain certificates for Intermediate certificate Authorities (CAs).
      Note: The default self-signed certificate and the default CA bundle certificate are not appropriate for use as a certificate chain.
    4. For the Passphrase field, type a string that enables access to SSL certificate/key pairs that are stored on the BIG-IP system with password protection.
      This setting is optional. For added security, the BIG-IP system automatically encrypts the pass phrase itself. This pass phrase encryption process is invisible to BIG-IP system administrative users.
    5. Click Add.
  9. In the Certificate Key Chain setting, click Add again, and repeat the process for all certificate key chains that you want to specify.
    At a minimum, you must specify an RSA certificate key chain.
    The result is that all specified key chains appear in the text box.
  10. To enable OCSP stapling, select theOCSP Stapling check box.
    To enable OCSP stapling, you must first create an OCSP Stapling profile. See Creating an OCSP stapling profile for detailed steps.
  11. If you want to Notify Certificate Status to Virtual Server, select the check box.
  12. 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:

  13. For the Client Authentication area, select the Custom check box.
  14. For Client Certificate list, specify whether you want to ignore, require, or request the client certificate authentication.
  15. If you are enabling C3D, from the Trusted Certificate Authorities list, you must select a trusted CA bundle.
  16. Select the Custom check box for the Client Certificate Constrained Delegation area.
    The settings become available for change.
    Note: See About client certificate constrained delegation prior to enabling C3D.
  17. For the Client Certificate Constrained Delegation setting, select Enabled.
  18. From the OCSP list, select the object that the BIG-IP system's SSL should use to connect to the OCSP responder and check the client certificate status.
    You can click the + icon to open the create-new OCSP object screen. See Creating an OCSP stapling profile for detailed steps.
  19. For the Unknown OCSP Response Control list, specify the action the system takes when the OCSP object returns an unknown status:
    • If you want the connection to be dropped, retain the default value Drop.
    • If you want the connection to ignore the unknown status and continue, Select Ignore.
  20. Click Finished.
After performing this task, you can see the custom Client SSL profile in the list of Client SSL profiles on the system.
Note: By default, TLSv1.3 is disabled in this configuration.
To use this profile, you must assign it to a virtual server. See Assigning SSL profiles to a virtual server for detailed information.

Create a custom Server SSL profile that supports C3D

With a Server SSL profile, the BIG-IP® system can perform decryption and encryption for server-side SSL traffic.
Note: For detailed information on how to complete the client certificate constrained delegation (C3D) configuration and ensure that your custom server SSL profile is set up properly, see About client certificate constrained delegation before completing your custom profile setup.
  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. If you intend to use OCSP stapling, then from the OCSP list, select the OCSP object that the BIG-IP system's SSL should use to connect to the OCSP responder and to check the server certificate status. You can click the + icon to open the create-new OCSP object screen.
    The OCSP stapling object can be added in both forward and reverse proxy configurations. When the server SSL Forward Proxy property is set to Enabled, the forward proxy OCSP object is used to validate and staple the web server's certificate status. When the server SSL Forward Proxy property is set to Disabled, the reverse proxy OCSP object is used to reset the client connection if the web server certificate has been revoked.
  16. Select the Custom check box for the Client Certificate Constrained Delegation section.
    The settings become available for change.
    Note: See About client certificate constrained delegation prior to enabling C3D.
  17. From the Client Certificate Constrained Delegation setting, select Advanced.
  18. From the Client Certificate Constrained Delegation list, select Enabled.
  19. From the CA Certificate list, select the name of the certificate file that is used as the certification authority certificate.
  20. From the CA Key list, select the name of the key file that is used as the certification authority key.
  21. In the CA Passphrase field, type the passphrase of the key file that is used as the certification authority key.
    Note: This should be the passphrase corresponding to the specified CA Key.
  22. For the Confirm CA Passphrase field, type the identical passphrase.
  23. For the Certificate Lifespan fields, type the lifespan of the certificate generated that is using the SSL client certificate constrained delegation.
    The default is 1 day, 0 hours.
  24. To define the extensions of the client certificates to be included in the generated certificates, from the Certificate Extensions list, select Extensions List.
  25. For the Certificate Extensions List setting, click Disable or Enable to add or remove available extensions.
    • Basic Constraints: Uses basic constraints to indicate whether the certificate belongs to a CA.
    • Extended Key Usage: Uses Extended Key Usage, typically on a leaf certificate, to indicate the purpose of the public key contained in the certificate.
    • Key Usage: Provides a bitmap specifying the cryptographic operations that may be performed using the public key contained in the certificate; for example, it could indicate that the key should be used for signature but not for enciphering.
    • Subject Alternative Name: Allows identities to be bound to the subject of the certificate. These identities may be included in addition to, or in place of, the identity in the subject field of the certificate.

    You can also add extensions in the Custom extension field. Type in the extension name and click Add.

  26. Click Finished.
To use this profile, you must assign it to a virtual server. See the Assigning SSL profiles to a virtual server section for detailed information.

Assign SSL profiles to a virtual server

The final task in the process of implementing SSL profiles is to assign the SSL profile to a virtual server. If the relevant virtual server does not yet exist, you can assign the SSL profile (or profiles) to the virtual server when you create it.
Note: For a reverse proxy Virtual Server, ensure you attach both the created client and server SSL profiles. You will not be able to enable Client Certificate Constrained Delegation (C3D) if this step is not completed. See the About client certificate constrained delegation section for more detailed information on enabling C3D.
  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of a virtual server.
  3. From the Configuration list, select Advanced.
  4. For the SSL Profile (Client) setting, from the Available list, select the name of the Client SSL profile you previously created and move the name to the Selected list.
  5. For the SSL Profile (Server) setting, from the Available list, select the name of the Server SSL profile you previously created and move the name to the Selected list.
  6. Click Update to save the changes.

About BIG-IP cipher support

The BIG-IP system includes a default cipher string named DEFAULT, which contains a subset of the cipher suites that the BIG-IP system supports.

The full set of cipher suites that the BIG-IP system supports are contained in the NATIVE cipher string. The cipher suites contained in both the DEFAULT and NATIVE cipher string are eligible for hardware acceleration.

The BIG-IP system supports a large set of cryptographic parameters that you can use to modify how the BIG-IP manages SSL/TLS connections.

With TLS 1.2, modifications to cipher suites can be made using the following cryptographic parameters:

  • Key exchange algorithms, for example RSA or ECDHE.
  • Authentication algorithms, for example RSA or ECDSA.
  • Encryption ciphers, for example AES256 or CAMELLIA.
  • Message authentication codes, for example SHA256 or SHA384.

Glossary of cipher-related terms

The BIG-IP system supports many cryptographic parameters used to negotiate SSL/TLS connections. The following list will help you understand how these parameters are organized on the BIG-IP system.

Cipher Group
A BIG-IP configuration object that specifies a list of cipher rules. The BIG-IP system offers several pre-built cipher groups, such as f5-default, f5-ecc, and f5-secure. You can use a pre-built cipher group or create a new custom cipher group. Cipher Groups can be associated with a Client or Server SSL profile's Cipher option to specify the allowed cryptographic parameters.
Cipher rule
A BIG-IP configuration object that specifies a list of cipher suites used to negotiate SSL/TLS connections. The BIG-IP system offers several pre-built cipher rules, such as f5-default, f5-ecc, and f5-secure. You can use a pre-built cipher rule or create a custom cipher rule. Cipher Rules are applied to Cipher Groups.
Cipher string
A BIG-IP named object that specifies a list of one or more cipher suites, for example DEFAULT or NATIVE. You can combine cipher strings to create the final cipher string that the BIG-IP system uses to negotiate SSL security parameters with another system. Cipher Strings can be associated with a Client or Server profile's Cipher option to specify the allowed cryptographic parameters.
Cipher Suites
A cipher suite is a combination of a key exchange method, authentication method, bulk encryption algorithm, and a message authentication code (MAC). The BIG-IP system uses cipher suites to negotiate the security parameters used to create SSL/TLS connections.
Rule Audit
The Rule Audit can be used when creating a custom Cipher Rule to display list of cipher suites contained in the cipher rule.
Group Audit
The Group Audit can be used when creating a custom Cipher Group, to display the list of cipher suites that will make up the final Cipher Group.

What is a cipher group?

A cipher group contains a list of cipher rules, and the instructions that the BIG-IP® system needs for building the cipher string it will use for security negotiation. The instructions tell the system which cipher rules to include in the string, and how to apply them (allow, restrict, or exclude, and in what order).

Pre-built cipher groups

The BIG-IP system offers a few pre-built cipher groups that you can choose from to use as is to build your final cipher string, However, it's common to create your own custom cipher group instead.

Custom cipher groups

This illustration shows an example of a custom cipher group. Using this cipher group, the BIG-IP system builds the final cipher string using a user-created custom cipher rule named /Common/my_ecdhe_rsa and the pre-built cipher rule /Common/f5-default.

Notice that the system will exclude from the string any cipher suites defined in the pre-built cipher rule /Common/f5-hw_keys.

Also notice that the cipher group displays a preview of the final cipher string after the instructions are applied.

About pre-built cipher groups

The BIG-IP system offers a set of pre-built cipher groups, with names containing the prefix f5-. Note that in general, a cipher group contains the cipher suites that you want to allow, restrict, or exclude when the system builds the cipher string used for SSL negotiation.

A pre-built cipher group allows all cipher suites specified in a corresponding pre-built cipher rule to be included in the final cipher string that the BIG-IP system builds for SSL negotiation. A prebuilt cipher group does not restrict the allowed cipher suites in any way, nor does it exclude any cipher suites.

This table lists and describes the pre-built cipher groups on the system.

Table 1. Descriptions of the pre-built cipher groups
Cipher group name Description
f5-aes Allows all cipher suites specified in the pre-built cipher rule f5-aes.
f5-default Allows all cipher suites specified in the pre-built cipher rule f5-default.
f5-ecc Allows all cipher suites specified in the pre-built cipher rule f5-ecc.
f5-hw_keys Allows all cipher suites specified in the pre-built cipher rule f5-hw_keys.
f5-secure Allows all cipher suites specified in the pre-built cipher rule f5-secure.

About custom cipher groups

This illustration shows an example of a custom cipher group. Using this cipher group, the BIG-IP system builds the final cipher string using a user-created custom cipher rule named /Common/my_ecdhe_rsa and the pre-built cipher rule /Common/f5-default.

Notice that the system will exclude from the string any cipher suites defined in the pre-built cipher rule /Common/f5-hw_keys.

Also notice that the cipher group displays a preview of the final cipher string after the instructions are applied.

Building a custom Cipher Group

Before starting this task, make sure you've confirmed the need to create a custom cipher string instead of using a pre-built cipher group.

You build a final, custom cipher string by creating a cipher group. A cipher group contains the cipher rules and instructions that the BIG-IP system needs for building the cipher string it will use for security negotiation with a client or server system.

  1. On the Main tab, click Local Traffic > Ciphers > Groups .
    The screen displays a list of pre-built cipher groups.
  2. Click Create.
  3. In the Name field, type a name for the cipher group.
    Note: Never include the prefix f5- in a cipher rule name. This prefix is reserved for pre-built cipher groups only.
  4. If you created any custom rules, then in the Cipher Creation area of the screen in the Available Cipher Rules list, verify that the custom rules appear in the list.
  5. For each cipher rule in the Available Cipher Rules list, click the plus sign to view the cipher suites included in the rule.

    For example, this shows the cipher suites included in the pre-built cipher rule named /Common/f5-ecc.

  6. In the Available Cipher Rules list, select the boxes for the cipher rules you want to allow for negotiating security for SSL connections.
    Important: We strongly recommend that you select the cipher rule /Common/f5-default, and for added security, select other cipher rules, too.

    Here's an example of a list of available cipher rules that you might see within a cipher group. Notice that we've selected both a pre-built cipher rule and a custom cipher rule:

  7. In the Group Details setting, move the selected cipher rules to the Allow the following box.

    Here we see that we're instructing the BIG-IP system to allow, during security negotiation, the cipher suites contained in the selected cipher rules:

  8. Again from the Available Cipher Rules list, select the boxes for the cipher rules you want to restrict the allowed cipher rules to when negotiating security for SSL connections.
  9. Move the selected cipher rules to the Restrict the Allowed list to the following box.
  10. If you want to exclude any cipher rules from the allowed list, then from the Available Cipher Rules list, select the boxes for the rules you want to exclude.
  11. Move the selected cipher rules to the Exclude the following from the Allowed list box.
  12. From the Order list, select the order that you want the BIG-IP system to use when negotiating SSL connections.
    The choices are: Default, Speed, Strength, FIPS, and Hardware.
  13. In the Cryptographic Parameters box, view the cipher suites that the BIG-IP system will use to construct the final cipher string, based on the selections you made in the previous steps.
  14. Click Finished.
After you complete this task, the BIG-IP system has a custom cipher group that the BIG-IP system will use to build the final cipher string.

What is a cipher rule?

A cipher rule is an object that contains a list of cipher suites. After you create a cipher rule, you specify it within a cipher group. A cipher group is the object that builds the actual cipher string that the system will use during SSL negotiation.

You can use pre-defined cipher rules that the BIG-IP system provides, or you can create your own.

An example of a cipher rule might be one that specifies only cipher suites that use a particular bulk encryption algorithm and key exchange method.

Note: DH Groups and Signature Algorithms allow modification of TLS 1.3 key agreements and signature algorithms respectively. At this time, the TLS1.3 protocol RFC is in draft status. BIG-IP version 14.0 implements RFC draft version 26 only and is considered to be in beta phase and therefore not meant to be deployed in production environments.

About pre-built cipher rules

Pre-built cipher rules

The BIG-IP system offers a set of pre-built cipher rules, with names containing the prefix f5-. This table lists these cipher rules and the cipher strings they represent.

Table 2. Pre-built cipher rules and their contents
Cipher rule name Associated cipher string
f5-aes AES
f5-default DEFAULT
f5-ecc ECDHE:ECDHE_ECDSA
f5-hw_keys ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES256-CBC-SHA:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDH-RSA-AES256-GCM-SHA384:ECDH-RSA-AES256-SHA384:ECDH
f5-secure ECDHE:RSA:!SSLV3:!RC4:!EXP:!DES

About custom cipher rules

You can use the following cryptographic parameters to create custom cipher rules:

Cipher suites
These represent the bulk encryption and hash algorithms used to negotiate SSL/TLS connections. An example of a cipher suite is ECDHE-RSA-AES128-CBC-SHA.
DH groups
In TLS1.3, these are the Elliptic Curve Diffie Hellman (ECDH) key agreement algorithms used to negotiate SSL/TLS connections. The available key agreement curves are: P256, P384, and X25519.
Signature algorithms
In TLS1.3, these are the digital signature algorithms for authentication. Examples of signature algorithms are rsa_pkcs1_sha256 and ecdsa_secp256r1_sha256.

Create a custom cipher rule

When you create your own cipher rules for inclusion in a custom cipher group, the BIG-IP system builds a cipher string that includes or excludes the cipher suites and algorithms needed for negotiating SSL connections.

  1. On the Main tab, click Local Traffic > Ciphers > Rules .
    The screen displays a list of pre-built cipher rules.
  2. Click Create.
  3. In the Name field, type a name for the cipher rule.
    Note: Never include the prefix f5- in a cipher rule name. This prefix is reserved for pre-built cipher rules only.

    For example:

  4. In the Cipher Suites field, type one or more cipher suites.

    For example:

  5. In the DH Groups field, type one or more Elliptic Curve Diffie-Hellman key exchange algorithms, separated by commas (:).
    Note: The available named groups (formerly known as curves) are: secp256r1, secp384r1, and X25519. You can also type a special keyword, DEFAULT, which represents the recommended set of named groups.
    For example, you can specify secp256r1:X25519.
  6. In the Signature Algorithms field, type one or more signature algorithms, separated by commas (:), that you want to include in the cipher rule. You can also type a special keyword, DEFAULT, which represents the recommended set of signature algorithms.
    Note: The available signature algorithms are: DSA-SHA1, DSA-SHA256, DSA-SHA384, DSA-SHA512, ECDSA-SHA1, ECDSA-SHA256, ECDSA-SHA384, ECDSA-SHA512, RSA-PKCS1-SHA1, RSA-PKCS1-SHA256, RSA-PKCS1-SHA384, RCS-PKCS1-SHA512, RSA-PSS-SHA256, RSA-PSS-SHA384, and RSA-PSS-SHA512 .
    For example, you can specify RSA_PKCS1_SHA256:ECDSA_P256_SHA256.
  7. Click Finished.
The cipher rule now appears within any custom cipher group, in the list of available cipher rules.

About the DEFAULT and NATIVE cipher strings

The DEFAULT cipher string appears as the default value in the Ciphers setting of the Client SSL and Server SSL profiles and represents a subset of the cipher suites found in the NATIVE cipher suite.

The NATIVE cipher string represents the full set of BIG-IP supported cipher suites.

Both the DEFAULT and NATIVE cipher strings represent cipher suites that are eligible for hardware acceleration.

Important: We strongly recommend that you use the default cipher string and, for added security, append other cipher suites to it.

Viewing cipher suites in the DEFAULT and NATIVE cipher strings

Before you use this command, confirm that your BIG-IP user account grants you access to the advanced shell.

Follow these steps to display the cipher suites associated with the DEFAULT cipher string. This list of cipher suites is also included in the pre-built cipher rule f5-default.

  1. Using an SSH client application such as PuTTY, access the advanced shell on the BIG-IP system.
  2. At the system prompt, to view the DEFAULT cipher suites used for client-side negotiation, type the command tmm --clientciphers DEFAULT.
  3. At the system prompt, to view the DEFAULT cipher suites used for server-side negotiation, type the command tmm --serverciphers DEFAULT.

Best practices for BIG-IP cipher strings

For security and performance reasons, consider the following recommendations:

  • When modifying cipher suites, F5 strongly recommends that you append cipher suite modifications to the DEFAULT cipher string.
  • Include a cipher string that specifies the ECC key type. Due to their smaller size, ECC keys reduce computing costs while maintaining a similar 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 perfect forward secracy, which creates an ephemeral private key for each new secure connection. This ensures the same private key is never 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. And by the way, diagnostic tools like ssldump won't work when you're using Forward Secrecy.

About Diffie-Hellman Ephemeral key exchange

The BIG-IP system supports the Diffie-Hellman Ephemeral key exchange method, as well as other Diffie-Hellman variations. A Diffie–Hellman key exchange method is an alternative to RSA key exchange and allows the client and the BIG-IP system to establish a shared secret session key to use for communication.

About DHE key exchange

Because Diffie-Hellman key exchange methods do not include authentication, use of Diffie-Hellman Ephemeral (DHE) requires that it be paired with an authentication mechanism. The DHE key exchange/authentication pairs that the BIG-IP system supports are:

  • DHE-RSA-* (Diffie-Hellman Ephemeral-RSA)
  • DHE-DSS-* (Diffie-Hellman Ephemeral-DSS)
  • ECDHE-RSA-* (Elliptic Curve Diffie-Hellman Ephemeral-RSA)
  • ECDHE-ECDSA-* (Elliptic Curve Diffie-Hellman Ephemeral-DSA)
Note: DHE key exchange methods, when paired with RSA and DSS authentication, are not included in the cipher rule f5-default nor in the cipher keyword DEFAULT.

About Perfect-Forward-Privacy

The Diffie-Hellman Ephemeral (DHE) key exchange method provides Perfect Forward Privacy (PFP). With standard Diffie-Hellman, multiple key exchanges all use the same session key, which can compromise security. By contrast, DHE uses PFP, which generates a disposable key per session and thereby ensures that the same session key is never used twice. No key remains to be disclosed, and if the private key of the server is discovered, past communication remains secure.

Supported Diffie-Hellman variations

The BIG-IP system supports all three Diffie-Hellman key exchange methods. They are:

Diffie-Hellman Ephemeral (DHE)
Diffie-Hellman Ephemeral uses temporary public keys. The authenticity of a temporary key can be verified by checking the digital signature included in the key exchange messages. The key exchange messages are signed using either the RSA or DSA algorithms, depending on the cipher being used. For example, DHE-RSA uses RSA to sign the key exchange messages. DHE includes Perfect Forward Secrecy (PFS), which means that a compromise of the system's long-term signing key does not affect the privacy of past sessions. Like FIPS, DHE prevents private key disclosure.
Diffie-Hellman (DH)
Diffie-Hellman embeds the system's public parameter in the certificate, and the CA then signs the certificate. That is, the certificate contains the Diffie-Hellman public-key parameters, and those parameters never change.
Anonymous Diffie-Hellman (ADH)
Anonymous Diffie-Hellman uses DH, but without authentication. The keys used in the exchange are not authenticated, resulting in keys being susceptible to security attacks.

Viewing a list of supported DHE ciphers

Before using this command, confirm that your user account grants you access to the advanced shell.
You perform this task when you want to display a specific set of ciphers that the BIG-IP system supports.
  1. Access the advanced shell on the BIG-IP system.
  2. At the system prompt, type the command tmm --clientciphers ciphers .
    For example, to see a list of DHE+DES ciphers, type tmm --clientciphers DHE:DHE_DSS. To see a list of ECDHE ciphers, type tmm --clientciphers ECDHE:ECDHE_ECDSA.

Specifying a Diffie-Hellman key exchange method

Use this task to modify an existing Client SSL profile to enable support for Diffie-Hellman key exchange.
  1. On the Main tab, click Local Traffic > Profiles > SSL > Client or Local Traffic > Profiles > SSL > Server .
    The Client SSL or Server SSL profile list screen opens.
  2. In the Name column, click the name of the profile you want to modify.
  3. Select the Custom check box.
    The settings become available for change.
  4. To specify DHE ciphers:
    1. From the Configuration list, select Advanced.
    2. For the Ciphers setting, click Cipher String and type DHE:DHE_DSS.
  5. Click Update.
After you perform this task and assign the profile to a virtual server, the BIG-IP uses the DHE key exchange method to establish secure communication with the relevant client or server.

Viewing DHE key exchange statistics

You can use the Traffic Management Shell (tmsh) to view statistics about the use of Diffie-Hellman ciphers in SSL negotiation.
  1. Access the system prompt on the BIG-IP system.
  2. From the BIG-IP system prompt, type tmsh show ltm profile client-ssl profile_name .
    An example of a name for a profile that specifies DHE ciphers is my_dhe_profile.
After you type this command, the BIG-IP system displays output such as the following. In this example, the profile statistics show that Diffie-Hellman Ephemeral (DHE) with RSA certificates has been used once:
Sample profile statistics for key exchange method

Sample profile statistics for key exchange method

About Elliptic Curve encryption

The BIG-IP system supports Elliptic Curve Cryptography (ECC). Because Elliptic Curve key sizes are significantly smaller than those of other key types, ECC is ideally suited for smaller, mobile devices for which key storage is an issue. On the BIG-IP system, ECC works with the SSL offload feature.

About Elliptic Curve cipher support

The BIG-IP system supports multiple ciphers that use Elliptic Curve Cryptography (ECC) encryption with Diffie-Hellman key exchange. On the BIG-IP system, EC is used with DHE to establish the shared secret; however, the subsequent bulk encryption of data cannot be done with any ECC-based algorithm and must be done using conventional crypto algorithms such as AES and 3DES. For example, a typical Elliptic Curve cipher is: ECDHE-RSA-AES128-CBC-SHA.

The specific ECC ciphers that the BIG-IP system supports are:

  • ECDHE-RSA-*
  • ECDHE-ECDSA-*
  • ECDH-ECDSA-*

Because ECC with Diffie-Hellman does not include a mechanism for digitally signing handshake messages, the RSA or DSA algorithms are used to digitally sign the handshake messages to thwart Man-in-the-Middle attacks. For example, an ECDHE-ECDSA-* cipher suite uses the ECC DSA certificate specified in the Client SSL profile to digitally sign the handshake messages.

Note: Elliptic Curve ciphers with DSA are not included in the DEFAULT cipher suite.

Viewing ECDH key exchange statistics

You can use the Traffic Management Shell (tmsh) to view statistics about the use of Elliptic Curve Diffie-Hellman ciphers in SSL negotiation.
  1. Access the system prompt on the BIG-IP system.
  2. From the BIG-IP system prompt, type tmsh show ltm profile client-ssl profile_name | grep ECDH.
    An example of a name for a profile that specifies DHE ciphers is my_ecdh_profile.
After you type this command, the BIG-IP system displays output such as the following. In this example, the profile statistics show that ECDH with RSA certificates has been used six times:
Sample profile statistics for key exchange method

Sample profile statistics for key exchange method

Specifying an Elliptic Curve Diffie-Hellman key exchange method

Use this task to modify an existing Client SSL profile to enable support for Elliptic Curve Diffie-Hellman Ephemeral (ECDHE) key exchange.
  1. On the Main tab, click Local Traffic > Profiles > SSL > Client or Local Traffic > Profiles > SSL > Server .
    The Client SSL or Server SSL profile list screen opens.
  2. In the Name column, click the name of the profile you want to modify.
  3. Select the Custom check box.
    The settings become available for change.
  4. For the Ciphers setting, click Cipher String and type DEFAULT:ECDHE.
  5. Click Update.
After you perform this task and assign the profile to a virtual server, the BIG-IP system uses the ECDHE key exchange method to establish secure communication with the relevant client or server.

Unsupported cipher suites on the BIG-IP system

For security reasons, these cipher suites are unavailable in the BIG-IP system:

  • EXP-EDH-RSA-DES-CBC-SHA
  • EXP-ADH-DES-CBC-SHA
  • EXP-RC2-CBC-MD5
  • EXP-ADH-RC4-MD5

About cipher keywords on the BIG-IP system

There are a few things you should know when specifying keywords to create a BIG-IP cipher string. These things apply whether or not you are creating a cipher string using cipher rules and groups or typing a raw cipher string into an SSL profile.

About the COMPAT cipher string

In previous BIG-IP releases, cipher support included the COMPAT cipher string, allowing the use of OpenSSL cipher suites not natively supported by the BIG-IP. In this release, the COMPAT cipher string has been removed.

If your configuration includes the COMPAT cipher string, it will be replaced with NONE and secure connections relying on these cipher suites will fail.

This change:

  • Optimizes the security of your cipher configuration by preventing any OpenSSL cipher suite vulnerabilities from being introduced into the BIG-IP system.
  • Changes the meaning of the NATIVE keyword; this keyword now equivalent to the keyword ALL.

Invalid keywords for BIG-IP cipher strings

When you manually configure a cipher string on the BIG-IP system (as opposed to using a cipher group), these keywords are invalid:

  • COMPAT
  • SSLV2 (a subset of COMPAT)
  • RC2 (a subset of COMPAT)
  • Any other subsets of COMPAT or SSLv2

If you attempt to specify these keywords within a cipher string, the system displays an error message and prevents you from creating the relevant SSL profile.

Important: If you have an SSL profile in a previous BIG-IP version and then upgrade to version 14.0 or higher, the system automatically resolves the issue for you.

Changes to BIG-IP cipher keywords during a system upgrade

During a BIG-IP software upgrade to version 14.0 or higher, the system takes these actions:

  • If the system detects the keywords COMPAT, SSLv2, RC2, or any subset of these in an existing cipher string, the system logs a message in the file /var/log/ltm and changes any of these keywords to None.
  • The system treats the keyword NATIVE as being equivalent to keyword ALL.
  • If a cipher string evaluates to an empty set, the system remaps the string to the default cipher string, represented by the keyword DEFAULT. The default cipher string contains a subset of the cipher suites that are suitable for most SSL connections.