pid2pod

This is a small demo/experiment that shows how Linux process IDs (PIDs) can be mapped to Kubernetes pod metadata.

It works by looking up the target process's cgroup metadata in /proc/$PID/cgroup. This metadata contains the names of each cgroup assigned to the process. In the case of Docker containers created using the docker CLI or created by the kubelet, these cgroup names contain the Docker container ID. We can map this container ID to a Kubernetes pod by doing a lookup against the local kubelet API.

Thanks to the SPIRE implementation of SPIFFE, which inspired this method (see k8s.go).

Example Use Cases

• You want to enrich audit or other host-level events with pod-level metadata.

• You want to control access to a UNIX domain socket based on the calling pod.

Caveats

• Not well tested. Please use this as an example but don't run this in production.

• Only works for the Docker runtime. Other container runtimes may use a different scheme for cgroup names or may not even have workload PIDs visible from the host.

• Assumes the kubelet read-only API (--read-only-port) is running on http://localhost:10255/. We could add token/certificate authentication to move past this assumption.

• Has some inherent race conditions since a lookup from PID to pod metadata takes some time. The PID may correspond to a different process by the time the data is used.

  This may be avoided in some scenarios. For example, if you have a server holding an open UNIX domain socket you know the client has had the same PID for the whole connection.

Usage

The demo lists all processes on the system that it can map back to a pod. It must be run in privileged mode, in the host PID namespace, and in the host network namespace.

$ docker run --rm --privileged --pid=host --net=host pid2pod:latest
PID 4549 (kube-proxy): &pid2pod.ID{Namespace:"kube-system", PodName:"kube-proxy-mdnzr", PodUID:"6344523c-44b7-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"controller-revision-hash":"1193416634", "k8s-app":"kube-proxy", "pod-template-generation":"1"}, ContainerID:"7d6ca8ec4775491b941aeb9d55fe52fe14236575c26b395f36d0afa8717bdaae", ContainerName:"kube-proxy"}
PID 4992 (dashboard): &pid2pod.ID{Namespace:"kube-system", PodName:"kubernetes-dashboard-5498ccf677-xk55s", PodUID:"63fe5f9d-44b7-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"addonmanager.kubernetes.io/mode":"Reconcile", "app":"kubernetes-dashboard", "pod-template-hash":"1054779233", "version":"v1.8.1"}, ContainerID:"3d23b4ffce2f10bbcc10ffee5acc5bdb2446e48c9253bb51405d65ece5bf0dd2", ContainerName:"kubernetes-dashboard"}
PID 5079 (kube-dns): &pid2pod.ID{Namespace:"kube-system", PodName:"kube-dns-86f4d74b45-qfs6f", PodUID:"634ab7a3-44b7-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"k8s-app":"kube-dns", "pod-template-hash":"4290830601"}, ContainerID:"8ae06d9c2b923cad2a3fd8f1c5ebaad18483d6af369f968209cc940e7f501b1a", ContainerName:"kubedns"}
PID 5173 (storage-provisi): &pid2pod.ID{Namespace:"kube-system", PodName:"storage-provisioner", PodUID:"640b24b0-44b7-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"addonmanager.kubernetes.io/mode":"Reconcile", "integration-test":"storage-provisioner"}, ContainerID:"f22bff5ee043e33d952df17f9cf6d79d8b8de3b82d565566b0bef49d2a4fa809", ContainerName:"storage-provisioner"}
PID 5291 (dnsmasq-nanny): &pid2pod.ID{Namespace:"kube-system", PodName:"kube-dns-86f4d74b45-qfs6f", PodUID:"634ab7a3-44b7-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"k8s-app":"kube-dns", "pod-template-hash":"4290830601"}, ContainerID:"07567b209503648459d7e5bd5ef1e943355dc479ca68c629a30cc139810a95ae", ContainerName:"dnsmasq"}
PID 5339 (dnsmasq): &pid2pod.ID{Namespace:"kube-system", PodName:"kube-dns-86f4d74b45-qfs6f", PodUID:"634ab7a3-44b7-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"k8s-app":"kube-dns", "pod-template-hash":"4290830601"}, ContainerID:"07567b209503648459d7e5bd5ef1e943355dc479ca68c629a30cc139810a95ae", ContainerName:"dnsmasq"}
PID 5378 (sidecar): &pid2pod.ID{Namespace:"kube-system", PodName:"kube-dns-86f4d74b45-qfs6f", PodUID:"634ab7a3-44b7-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"k8s-app":"kube-dns", "pod-template-hash":"4290830601"}, ContainerID:"fa1685e9e27b95556313641bd6b4e7f3db7893a8dcb6d85f5cc369d895be17db", ContainerName:"sidecar"}
PID 16962 (sh): &pid2pod.ID{Namespace:"default", PodName:"testcli-5b8d779dfd-vpwkw", PodUID:"a8c810f7-44d3-11e8-b7fb-b2d1d7d0d428", PodLabels:map[string]string{"pod-template-hash":"1648335898", "run":"testcli"}, ContainerID:"8fe33943cbef5cdc741b265cad4c061e6232ec6187b9e00e2c2e800df7fce4aa", ContainerName:"testcli"}