Hi,

In this article I would like share with you a new vulnerability against Azure Kubernetes.

Title: Privilege escalation from compromised node to cluster

CVE: CVE-2020-8559

Description:

If an attacker is able to intercept certain requests to the Kubelet within Azure Kubernetes Service (AKS), they can send a redirect response that may be followed by a client using the credentials from the original request. This can lead to compromise of other nodes.

If multiple clusters share the same certificate authority trusted by the client, and the same authentication credentials, this vulnerability may allow an attacker to redirect the client to another cluster. In this configuration, this vulnerability should be considered High severity.

Note that this vulnerability requires an attacker to first compromise a node through separate means.

Affected versions:

AKS patches all GA kubernetes versions control plane components automatically.

• kube-apiserver <v1.18.6
• kube-apiserver <v1.17.7
• kube-apiserver <v1.16.10
• and all kube-apiserver versions prior to v1.15.11

Fixed versions:

• kube-apiserver v1.18.6+
• kube-apiserver v1.17.7+
• kube-apiserver v1.16.10+

Maxime.

Hi,

In this article I would like share with you how you can enable host-based encryption on AKS. This feature is still in preview.

With host-based encryption, the data stored on the VM host of your AKS agent nodes’ VMs is encrypted at rest and flows encrypted to the Storage service. This means the temp disks are encrypted at rest with platform-managed keys. The cache of OS and data disks is encrypted at rest with either platform-managed keys or customer-managed keys depending on the encryption type set on those disks.

# Requirements
az feature register --namespace "Microsoft.Compute" --name "EncryptionAtHost"

az feature register --namespace "Microsoft.ContainerService" --name "EnableEncryptionAtHostPreview"

az feature list -o table --query "[?contains(name, 'Microsoft.Compute/EncryptionAtHost')].{Name:name,State:properties.state}"

az feature list -o table --query "[?contains(name, 'Microsoft.ContainerService/EnableEncryptionAtHostPreview')].{Name:name,State:properties.state}"

az provider register --namespace Microsoft.Compute

az provider register --namespace Microsoft.ContainerService

# Install the aks-preview extension
az extension add --name aks-preview

# Update the extension to make sure you have the latest version installed
az extension update --name aks-preview

# Create a new cluster to use host-based encryption
az aks create --name myAKSCluster --resource-group myResourceGroup -s Standard_DS2_v2 -l westus2 --aks-custom-headers EnableEncryptionAtHost=true

# Update an existing cluster to use host-based encryption
az aks nodepool add --name hostencrypt --cluster-name myAKSCluster --resource-group myResourceGroup -s Standard_DS2_v2 -l westus2 --aks-custom-headers EnableEncryptionAtHost=true

Maxime.

Hi,

In this article, I would like to share with you, how you can enable ephemeral os disk with your AKS cluster. This feature is still in public preview. Please don’t use use this feature with your production cluster.

By default, the operating system disk for an Azure virtual machine is automatically replicated to Azure storage to avoid data loss should the VM need to be relocated to another host. However, since containers aren’t designed to have local state persisted, this behavior offers limited value while providing some drawbacks, including slower node provisioning and higher read/write latency.

az feature register --name EnableEphemeralOSDiskPreview --namespace Microsoft.ContainerService

az feature list -o table --query "[?contains(name, 'Microsoft.ContainerService/EnableEphemeralOSDiskPreview')].{Name:name,State:properties.state}"

az provider register --namespace Microsoft.ContainerService

az extension add --name aks-preview

az extension update --name aks-preview

Configure the cluster to use Ephemeral OS disks when the cluster is created. Use the --aks-custom-headers flag to set Ephemeral OS as the OS disk type for the new cluster.

az aks create --name myAKSCluster --resource-group myResourceGroup -s Standard_DS3_v2 --aks-custom-headers EnableEphemeralOSDisk=true

Configure a new node pool to use Ephemeral OS disks. Use the --aks-custom-headers flag to set as the OS disk type as the OS disk type for that node pool.

az aks nodepool add --name ephemeral --cluster-name myAKSCluster --resource-group myResourceGroup -s Standard_DS3_v2 --aks-custom-headers EnableEphemeralOSDisk=true

Maxime.