HTTP proxy support in Azure Kubernetes Service

Azure Kubernetes Service (AKS) clusters, whether deployed into a managed or custom virtual network, have certain outbound dependencies necessary to function properly. Previously, in environments requiring internet access to be routed through HTTP proxies, this was a problem. Nodes had no way of bootstrapping the configuration, environment variables, and certificates necessary to access internet services.

This feature adds HTTP proxy support to AKS clusters, exposing a straightforward interface that cluster operators can use to secure AKS-required network traffic in proxy-dependent environments.

Both AKS nodes and Pods will be configured to use the HTTP proxy.

Some more complex solutions may require creating a chain of trust to establish secure communications across the network. The feature also enables installation of a trusted certificate authority onto the nodes as part of bootstrapping a cluster.

Limitations and other details

The following scenarios are not supported:

• Different proxy configurations per node pool
• User/Password authentication
• Custom CAs for API server communication
• Windows-based clusters
• Node pools using Virtual Machine Availability Sets (VMAS)
• Using * as wildcard attached to a domain suffix for noProxy

By default, httpProxy, httpsProxy, and trustedCa have no value.

The Pods will be injected with the following environment variables:

• HTTP_PROXY
• http_proxy
• HTTPS_PROXY
• https_proxy
• NO_PROXY
• no_proxy

To disable the injection of the proxy environment variables the Pod should be annotated with: "kubernetes.azure.com/no-http-proxy-vars":"true"

Prerequisites

The latest version of the Azure CLI. Run az --version to find the version, and run az upgrade to upgrade the version. If you need to install or upgrade, see Install Azure CLI.

Configuring an HTTP proxy using the Azure CLI

Using AKS with an HTTP proxy is done at cluster creation, using the az aks create command and passing in configuration as a JSON file.

The schema for the config file looks like this:

{
  "httpProxy": "string",
  "httpsProxy": "string",
  "noProxy": [
    "string"
  ],
  "trustedCa": "string"
}

• httpProxy: A proxy URL to use for creating HTTP connections outside the cluster. The URL scheme must be http.
• httpsProxy: A proxy URL to use for creating HTTPS connections outside the cluster. If this isn't specified, then httpProxy is used for both HTTP and HTTPS connections.
• noProxy: A list of destination domain names, domains, IP addresses or other network CIDRs to exclude proxying.
• trustedCa: A string containing the base64 encoded alternative CA certificate content. Currently only the PEM format is supported.

Example input:

{
  "httpProxy": "http://myproxy.server.com:8080/", 
  "httpsProxy": "https://myproxy.server.com:8080/", 
  "noProxy": [
    "localhost",
    "127.0.0.1"
  ],
  "trustedCA": "LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUgvVENDQmVXZ0F3SUJB...b3Rpbk15RGszaWFyCkYxMFlscWNPbWVYMXVGbUtiZGkvWG9yR2xrQ29NRjNURHg4cm1wOURCaUIvCi0tLS0tRU5EIENFUlRJRklDQVRFLS0tLS0="
}

Create a file and provide values for httpProxy, httpsProxy, and noProxy. If your environment requires it, provide a value for trustedCa. Next, deploy a cluster, passing in your filename using the http-proxy-config flag.

az aks create -n $clusterName -g $resourceGroup --http-proxy-config aks-proxy-config.json

Your cluster will initialize with the HTTP proxy configured on the nodes.

Configuring an HTTP proxy using Azure Resource Manager (ARM) templates

Deploying an AKS cluster with an HTTP proxy configured using an ARM template is straightforward. The same schema used for CLI deployment exists in the Microsoft.ContainerService/managedClusters definition under properties:

"properties": {
    ...,
    "httpProxyConfig": {
        "httpProxy": "string",
        "httpsProxy": "string",
        "noProxy": [
            "string"
        ],
        "trustedCa": "string"
    }
}

In your template, provide values for httpProxy, httpsProxy, and noProxy. If necessary, provide a value for trustedCa. Deploy the template, and your cluster should initialize with your HTTP proxy configured on the nodes.

Updating Proxy configurations

Values for httpProxy, httpsProxy, trustedCa and NoProxy can be changed and applied to the cluster with the az aks update command. An aks update for httpProxy, httpsProxy, and/or NoProxy will automatically inject new environment variables into pods with the new httpProxy, httpsProxy, or NoProxy values. Pods must be rotated for the apps to pick it up, because the environment variable values are injected at the Pod creating by a mutating admission webhook. For components under kubernetes, like containerd and the node itself, this won't take effect until a node image upgrade is performed.

For example, assuming a new file has been created with the base64 encoded string of the new CA cert called aks-proxy-config-2.json, the following action updates the cluster. Or, you need to add new endpoint urls for your applications to No Proxy:

az aks update -n $clusterName -g $resourceGroup --http-proxy-config aks-proxy-config-2.json

Monitoring add-on configuration

The HTTP proxy with the Monitoring add-on supports the following configurations:

• Outbound proxy without authentication
• Outbound proxy with username & password authentication
• Outbound proxy with trusted cert for Log Analytics endpoint

The following configurations aren't supported:

• The Custom Metrics and Recommended Alerts features aren't supported when you use a proxy with trusted certificates

Next steps

For more information regarding the network requirements of AKS clusters, see control egress traffic for cluster nodes in AKS.