Certificate Authority Verification

The elemental-register and elemental-system-agent rely on the Rancher's Certificate Authority configuration to verify the MachineRegistration URL, and to remotely watch plans.

Depending on whether the Certificate Authority is private or public, you may want to instruct the agent to enforce strict CA verification, or to use the system trust store instead.

From Rancher 2.9, the agent-tls-mode global setting will also apply to the installation of Elemental agents.
Note that if the agent-tls-mode setting changes, Elemental machines will need to be reset in order for the setting to apply.

Private CA certificate lifecycle

When using a private CA, the recommendation is to always make sure that the same CA is also used for Rancher.
Elemental will make use of the cacerts, when including the CA cert to be trusted by agents. This is the same value as it appears on the https://my.rancher.example/cacerts URL.

Note however that it will not be possible to update this value after an Elemental machine has been installed.
Replacing the CA certificate on Rancher may lead to Elemental machines not being able to re-connect to Rancher and operating normally, when the agent-tls-mode is set to strict.

For this reason the recommendation is to use the agent-tls-mode: system-store setting instead and manage the lifecycle of CA certs on Elemental machines directly, when a private Certificate Authority is in use.

The CA cert can be installed in custom OS images directly, or passed as a cloud-init configuration in Elemental resources.
For example the initial CA certificate can be included in the MachineRegistration cloud-config:

apiVersion: elemental.cattle.io/v1beta1
kind: MachineRegistration
metadata:
  name: fire-nodes
  namespace: fleet-default
spec:
  config:
    cloud-config:
      write_files:
        - path: /etc/pki/trust/anchors/rancher-ca.pem
          permission: 0444
          content: |-
            -----BEGIN CERTIFICATE-----
            MIIDETCCAfmgAwIBAgIRAK0J3NrgPllXUiGYrA9sTlUwDQYJKoZIhvcNAQELBQAw
            IjEgMB4GA1UEAxMXZWxlbWVudGFsLXNlbGZzaWduZWQtY2EwHhcNMjQxMDA3MTEw
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            Af8wHQYDVR0OBBYEFIv2OZVFAhh8HzoEwjlf5GivNf6IMA0GCSqGSIb3DQEBCwUA
            A4IBAQAfNUNQKZ02oTo9q+/nbS8kIuhwzSTtNzKflQU5oibpDSAxYlx2gsYqppb/
            w7voj+GiONQR22PrCFh+Kr7aGr/GZh6oXg47dK4Es2dVeE8qdqW3WtZ8oj/OJxmP
            7TqWZdGf7TAxfgNzIpGjWFw/coJ7dcYbDrcZFWG5oQpTbLHK/ECMPWytGVRjrqE6
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            OUkPxQ15e+3tUnDLUDnkTk3xMVRvJehnk/I75auqlUra55KLqfd6SUEbGP3MU9ZI
            12xVJHQTSN8XWh0++9jNG0eSMe75
            -----END CERTIFICATE-----
      runcmd:
        - update-ca-certificates

Before the CA cert is replaced on Rancher, the new CA cert can be included on Elemental machines by upgrading them.
The new CA cert can be configured in the ManagedOSImage cloudConfig:

apiVersion: elemental.cattle.io/v1beta1
kind: ManagedOSImage
metadata:
  name: ca-cert-upgrade
  namespace: fleet-default
spec:
  # The cloudConfig will be applied after node reboot
  cloudConfig:
    write_files:
      - path: /etc/pki/trust/anchors/rancher-ca-new.pem
        permission: 0444
        content: |-
          -----BEGIN CERTIFICATE-----
          MIIDEDCCAfigAwIBAgIQVgcMnY4HFB5+bZ9yhLaFkTANBgkqhkiG9w0BAQsFADAi
          MSAwHgYDVQQDExdlbGVtZW50YWwtc2VsZnNpZ25lZC1jYTAeFw0yNDEwMDcxMjUx
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          +v/ObqPOOyYszL/Nyv8/BomPgBia/GXGe8mkQHEWUXFS4P6KdMGQQU3X6Pm071qG
          QEWEIy95szy1H/q1DgZQCM5fjYPcfFJMopQ28vJEk58/9PePr/GZRWAeAhmMKZeg
          HP/wpuUMEdEh7vGYjKjVuIJiFgT2lVDKqrtRIon+L1iIP3IRmVa49UzmdW2wM79W
          a1nv52+EZaw3UDSLPonvs29AZG8M+NuENlefHWEwYVpDEwF9lXinfL3wMw36gIo4
          X4LmStP9WU4mvglrR8Zwj1M9COMrYbBYQ86jUGM0L0eNG52Uflsn+0ttLRhgkpba
          wAl8jAZWdQIDAQABo0IwQDAOBgNVHQ8BAf8EBAMCAqQwDwYDVR0TAQH/BAUwAwEB
          /zAdBgNVHQ4EFgQUmOGv0AwumUlwQDdULL2dLik/6FUwDQYJKoZIhvcNAQELBQAD
          ggEBACMmDLbKOgz5Zo1pSLTYc08Nb5sRTK/bW24IZ67cfdPstvTQBDAH5+obAjus
          N2Linl/IAsN8K2cnoBq1gM3sST+YDVOBdItZXwe8jybk3IoJPdzE63l//ReTyTSg
          OamwUR6qHcLZ9XNwS4z8WYNy3mDLO6dgq7udb2DHm/0mvyi3Q0oRvsrI+9JCCrgz
          YTFWEWhbpfUzH+dheISMYJx3l/iIFJajaASWKtGBMnp9G+RC2HhDcDwBnW/4JT1h
          wqvat7kdRIxcWHtW482JKRyfa58QidqA7nIBblZJuWqpo4etAVZTCV/caFKbn/Ek
          FrT88MNiy5xsimgQSdt9vptOvJc=
          -----END CERTIFICATE-----
    runcmd:
      - update-ca-certificates
  osImage: "registry.suse.com/suse/sl-micro/6.0/baremetal-os-container:2.1.2-3.59"
  clusterTargets:
    - clusterName: volcano
  upgradeContainer:
    envs:
      # Use FORCE to force an upgrade. 
      # This is convenient when the `osImage` is the same, and only the `cloudConfig` changed.
      - name: FORCE
        value: "false"