Transparent Proxy and Filtering on Kubernetes with Initializers
This is a follow-on tutorial to the Transparent Proxy and Filtering on Kubernetes tutorial. It shows how to simplify the application of a transparent proxy for existing deployments using a Deployment Initializer. Initializers are one of the Dynamic Admission Control features of Kubernetes, and are available as an alpha feature in Kubernetes 1.7.
This tutorial uses the tproxy-initializer Kubernetes Initializer to inject the sidecar InitContainer, ConfigMap and environment variables into a deployment when the annotation "initializer.kubernetes.io/tproxy": "true" is present. This tutorial also demonstrates how to deploy the tproxy Helm chart with the optional Role Based Access Control support.
Just like in the previous tutorial, the purpose of the tproxy-sidecar container is to create firewall rules in the pod network to block egress traffic. The tproxy-podwatch controller watches for pod changes containing the annotation and automatically add/removes the local firewall REDIRECT rules to apply the transparent proxy to the pod.
Figure 1. transparent proxy with initializers architecture diagram
Objectives
- Create a Kubernetes cluster with initializer and RBAC support using Google Kubernetes Engine
- Deploy the tproxy, tproxy-initializer and the tproxy-podwatch pods using Helm
- Deploy example apps with annotations to test external access to a Google Cloud Storage bucket
Before you begin
This tutorial assumes you already have a Google Cloud Platform (GCP) account and are familiar with the high level concepts of Kubernetes Pods and Deployments.
Costs
This tutorial uses billable components of GCP, including:
Use the Pricing Calculator to estimate the costs for your environment.
Checkout the source repository
Open Cloud Shell
Clone the repository containing the code for this tutorial:
git clone https://github.com/danisla/kubernetes-tproxy cd kubernetes-tproxyThe remainder of this tutorial will be run from the root of the cloned repository directory.
Create Kubernetes Engine cluster and install Helm
Create Kubernetes Engine cluster with alpha features enabled, RBAC support, and a cluster version of at least 1.7 to support initializers:
gcloud container clusters create tproxy-example \ --zone us-central1-f \ --enable-kubernetes-alphaThis command also automatically configures the kubectl command to use the cluster.
Create a service account and cluster role binding for Helm to enable RBAC support:
kubectl create serviceaccount tiller --namespace kube-system kubectl create clusterrolebinding tiller-cluster-rule \ --clusterrole=cluster-admin \ --serviceaccount=kube-system:tillerInstall the Helm tool locally in your Cloud Shell instance:
curl -sL https://storage.googleapis.com/kubernetes-helm/helm-v2.5.1-linux-amd64.tar.gz | tar -xvf - && sudo mv linux-amd64/helm /usr/local/bin/ && rm -Rf linux-amd64Initialize Helm with the service account:
helm init --service-account=tillerThis installs the server side component of Helm, Tiller, in the Kubernetes cluster. The Tiller pod may take a minute to start, run the command below to verify it has been deployed:
helm versionYou should see the Client and Server versions in the output:
Client: &version.Version{SemVer:"v2.5.1", GitCommit:"7cf31e8d9a026287041bae077b09165be247ae66", GitTreeState:"clean"} Server: &version.Version{SemVer:"v2.5.1", GitCommit:"7cf31e8d9a026287041bae077b09165be247ae66", GitTreeState:"clean"}
Install the Helm chart
Before installing the chart, you must first extract the certificates generated by mitmproxy. The generated CA cert is used in the example pods to trust the proxy when making HTTPS requests.
Extract the generated certs using Docker:
cd charts/tproxy docker run --rm -v ${PWD}/certs/:/home/mitmproxy/.mitmproxy mitmproxy/mitmproxy >/dev/null 2>&1Install the chart with the initializer and RBAC enabled:
helm install -n tproxy --set tproxy.useInitializer=true,tproxy.useRBAC=true .The output of this command shows you how to augment your deployments to use the initializer. Example output below:
Add this metadata annotation to your deployment specs to apply the tproxy initializer: metadata: annotations: "initializer.kubernetes.io/tproxy": "true"Get the status of the DaemonSet pods:
kubectl get pods -o wideNotice in the example output below that there is a tproxy pod for each node:
NAME READY STATUS RESTARTS AGE IP NODE tproxy-tproxy-2h7lk 2/2 Running 0 21s 10.128.0.8 gke-tproxy-example-default-pool-1e70b38d-xchn tproxy-tproxy-4mvtf 2/2 Running 0 21s 10.128.0.7 gke-tproxy-example-default-pool-1e70b38d-hk89 tproxy-tproxy-ljfq9 2/2 Running 0 21s 10.128.0.6 gke-tproxy-example-default-pool-1e70b38d-jsqdA single instance of the initializer pod should be running in the kube-system namespace:
kubectl get pods -n kube-system --selector=app=tproxyExample output:
NAME READY STATUS RESTARTS AGE tproxy-tproxy-initializer-833731286-9kp84 1/1 Running 0 4m
Deploy example apps
Deploy the sample apps to demonstrate using and not using the annotation to trigger the initializer.
Change directories back to the repository root and deploy the example apps:
cd ../../ kubectl create -f examples/debian-app.yaml kubectl create -f examples/debian-app-locked.yamlNote that the second deployment is the one that contains the deployment annotation described in the chart post-install notes.
Get the logs for the pod without the tproxy annotation:
kubectl logs --selector=app=debian-app,variant=unlocked --tail=10Example output:
https://www.google.com: 200 https://storage.googleapis.com/solutions-public-assets/: 200 PING www.google.com (209.85.200.105): 56 data bytes 64 bytes from 209.85.200.105: icmp_seq=0 ttl=52 time=0.758 msThe output from the example app shows the status codes for the requests and the output of a ping command.
Notice the following:
- The request to https://www.google.com succeeds with status code 200.
- The request to the Cloud Storage bucket succeeds with status code 200.
- The the ping to www.google.com succeeds.
Get the logs for the pod with the tproxy annotation:
kubectl logs --selector=app=debian-app,variant=locked --tail=4Example output:
https://www.google.com: 418 https://storage.googleapis.com/solutions-public-assets/: 200 PING www.google.com (209.85.200.147): 56 data bytes ping: sending packet: Operation not permittedNotice the following:
- The proxy blocks the request to https://www.google.com with status code 418.
- The proxy allows the request to the Cloud Storage bucket with status code 200.
- The the ping to www.google.com is rejected.
Inspect the logs from the mitmproxy DaemonSet pod to show the intercepted requests and responses. Note that the logs have to be retrieved from the tproxy pod that is running on the same node as the example app.
kubectl logs $(kubectl get pods -o wide | awk '/tproxy.*'$(kubectl get pods --selector=app=debian-app,variant=locked -o=jsonpath={.items..spec.nodeName})'/ {print $1}') -c tproxy-tproxy-mode --tail=10Example output:
10.12.1.41:37380: clientconnect 10.12.1.41:37380: GET https://www.google.com/ HTTP/2.0 << 418 I'm a teapot 30b 10.12.1.41:37380: clientdisconnect 10.12.1.41:36496: clientconnect Streaming response from 64.233.191.128 10.12.1.41:36496: GET https://storage.googleapis.com/solutions-public-assets/adtech/dfp_networkimpressions.py HTTP/2.0 << 200 (content missing) 10.12.1.41:36496: clientdisconnectNotice that the proxy blocks the request to https://www.google.com with status code 418.
Cleanup
Delete the sample apps:
kubectl delete -f examples/debian-app.yaml kubectl delete -f examples/debian-app-locked.yamlDelete the tproxy helm release:
helm delete --purge tproxyDelete the Kubernetes Engine cluster:
gcloud container clusters delete tproxy-example --zone=us-central1-f
What's next?
- Transparent Proxy and Filtering on Kubernetes - Original tutorial that works without the initializer alpha feature. Also contains some of the additional chart configuration examples.
- tproxy helm chart - See all configuration options and deployment methods.
- Istio - A more broad approach to traffic filtering and network policy.
- Calico Egress NetworkPolicy - Another way to filter egress traffic at the pod level.
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