Refresh HA1 SSH Keys and Configure Key Options

If you enable encryption over the HA1 control link, you can refresh the SSH host keys and change various key options.
When you configure Configure Active/Passive HA or Configure Active/Active HA, you can enable encryption for the HA1 (control link) connection between HA firewalls. You may want to secure the HA1 traffic between HA firewalls with encryption if the firewalls aren’t located in the same site.
All Palo Alto Networks firewalls come with Secure Shell (SSH) preconfigured on them, and the HA firewalls can act as both SSH server and SSH client simultaneously. If you have enabled encryption on the HA1 control link, use the CLI commands that follow to secure the connection between the HA firewalls. You can change the default host key type, generate a new pair of public and private SSH host keys for the HA1 control link, and configure other HA1 encryption settings.
The following examples show how to refresh (regenerate) your HA1 SSH keys, and change and display various SSH settings for the HA1 control link after you enable encryption and Access the CLI.
If you are configuring the HA1 control link with encryption in FIPS-CC mode, you must set automatic rekeying parameters for session keys.
  • (Optional) Set the default host key type.
    If you enable encryption on the HA1 control link, the firewall uses a default host key type of RSA 2048 unless you change it. The HA1 SSH connection uses only the default host key type to authenticate the HA peers (before an encrypted session is established between them). You can change the default host key type; the choices are ECDSA 256, 384, or 521, or RSA 2048, 3072, or 4096. Change the default host key type if you prefer a longer RSA key length, or if you prefer ECDSA rather than RSA. This example sets the default host key type to an ECDSA key of 256 bits. It also re-establishes the HA1 connection using the new host key without restarting the HA peers.
    1. admin@PA-3060> configure
    2. admin@PA-3060# set deviceconfig system ssh default-hostkey ha key-type ECDSA key-length 256
    3. admin@PA-3060# commit
    4. admin@PA-3060# exit
    5. admin@PA-3060> request high-availability sync-to-remote ssh-key
      An HA connection must already be established between the HA firewalls. If the firewalls have not yet established an HA connection, you must enable encryption on the control link connection, export the HA key to a network location and import the HA key on the peer. See Configure Active/Passive HA or Configure Active/Active HA.
    6. admin@PA-3060> set ssh service-restart ha
    7. admin@PA-3060> configure
    8. admin@PA-3060# show deviceconfig system ssh default-hostkey
  • Establish when automatic rekeying of the session keys occurs for SSH over the HA1 control link by setting parameters.
    The session keys are used for encrypting the traffic between the HA peers. After any one rekeying parameter reaches its configured value, SSH uses the new session encryption keys. The parameters are data, interval (seconds), and packet count. If you set more than one parameter, rekeying occurs when the first parameter reaches its configured value, and then the firewall resets all rekeying parameters. You can set a second or third parameter in case you aren’t sure that one parameter you configured will reach its value as fast as you want rekeying to occur.
    1. admin@PA-3060> configure
    2. admin@PA-3060# set deviceconfig system ssh session-rekey ha data 32
      Rekeying occurs after the volume of data (in megabytes) is transmitted following the previous rekeying. The default is based on the type of cipher you use, and ranges from 1GB to 4GB. The range is 10 to 4000 MB. Alternatively, you can enter set deviceconfig system ssh session-rekey ha data default, which sets the data parameter to the default value of the individual cipher you are using.
    3. admin@PA-3060# set deviceconfig system ssh session-rekey ha interval 3600
      Rekeying occurs after the specified time interval (in seconds) passes following the previous rekeying. By default, time-based rekeying is disabled (set to none). The range is 10 to 3600.
      If you are configuring the HA1 control link with encryption in FIPS-CC mode, you must set a time interval within the range; you cannot leave it disabled.
    4. admin@PA-3060# set deviceconfig system ssh session-rekey ha packets 27
      Rekeying occurs after the defined number of packets (2n) are transmitted following the previous rekeying. Enter the exponent to which 2 is raised; for example, 14 configures that a maximum of 214 packets are transmitted before a rekeying occurs. The default is 228; the range is 12 to 27 (212 to 227). Alternatively, you can enter set deviceconfig system ssh session-rekey ha packets default, which sets the value to 228.
      Choose rekeying parameters based on your type of traffic and network speeds (in addition to FIPS-CC requirements if they apply to you). Don’t set the parameters so low that they affect SSH performance.
    5. admin@PA-3060# commit
    6. admin@PA-3060# exit
    7. admin@PA-3060> set ssh service-restart ha
    8. admin@PA-3060> configure
    9. admin@PA-3060# show deviceconfig system ssh session-rekey ha
  • (Optional) Set the SSH server to use the specified encryption ciphers for the HA1 sessions.
    HA1 SSH allows all supported ciphers by default. When you set one or more ciphers, the SSH server advertises only those ciphers while connecting, and if the SSH client (HA peer) tries to connect using a different cipher, the server terminates the connection.
    1. admin@PA-3060> configure
    2. admin@PA-3060# set deviceconfig system ssh ciphers ha cipher
      aes128-cbc—AES 128-bit cipher with Cipher Block Chaining
      aes128-ctr—AES 128-bit cipher with Counter Mode
      aes128-gcm—AES 128-bit cipher with GCM (Galois/Counter Mode)
      aes192-cbc—AES 192-bit cipher with Cipher Block Chaining
      aes192-ctr—AES 192-bit cipher with Counter Mode
      aes256-cbc—AES 256-bit cipher with Cipher Block Chaining
      aes256-ctr—AES 256-bit cipher with Counter Mode
      aes256-gcm—AES 256-bit cipher with GCM
    3. admin@PA-3060# commit
    4. admin@PA-3060# exit
    5. admin@PA-3060> set ssh service-restart ha
    6. admin@PA-3060> configure
    7. admin@PA-3060# show deviceconfig system ssh ciphers ha
  • (Optional) Delete a cipher from the set of ciphers you selected for SSH over the HA1 control link.
    This example deletes the AES CBC cipher with 128-bit key.
    1. admin@PA-3060> configure
    2. admin@PA-3060# delete deviceconfig system ssh ciphers ha aes128-cbc
    3. admin@PA-3060# commit
    4. admin@PA-3060# exit
    5. admin@PA-3060> set ssh service-restart ha
    6. admin@PA-3060> configure
    7. admin@PA-3060# show deviceconfig system ssh ciphers ha
  • (Optional) Set the message authentication code (MAC) for HA1 SSH.
    By default the server advertises all of the MAC algorithms to the client.
    1. admin@PA-3060> configure
    2. admin@PA-3060# set deviceconfig system ssh mac ha value
      hmac-sha1—MAC with SHA1 cryptographic hash
      hmac-sha2-256—MAC with SHA2-256 cryptographic hash
      hmac-sha2-512—MAC with SHA2-512 cryptographic hash
    3. admin@PA-3060# commit
    4. admin@PA-3060# exit
    5. admin@PA-3060> set ssh service-restart ha
  • Regenerate ECDSA or RSA host keys for HA1 SSH to replace the existing keys.
    The HA peers use the host keys to authenticate each other. This example regenerates the ECDSA 256 default host key.
    Regenerating a host key does not change your default host key type. To regenerate the default host key you are using, you must specify your default host key type and length when you regenerate. Regenerating a host key that isn’t your default host key type simply regenerates a key that you aren’t using and therefore has no effect.
    1. admin@PA-3060> configure
    2. admin@PA-3060# set deviceconfig system ssh regenerate-hostkeys ha key-type ECDSA key-length 256
    3. admin@PA-3060# commit
    4. admin@PA-3060# exit
    5. admin@PA-3060> request high-availability sync-to-remote ssh-key
      An HA connection must already be established between the HA firewalls. If the firewalls have not yet established an HA connection, you must enable encryption on the control link connection, export the HA key to a network location, and import the HA key on the peer. See Configure Active/Passive HA or Configure Active/Active HA.
    6. admin@PA-3060> set ssh service-restart ha

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