Kubernetes Audit Log Collection¶

Kubernetes Audit provides security-related time series operation records (including time, source, operation results, users initiating the operation, operated resources, and detailed information about requests/responses).

Configuration¶

Prerequisites¶

Install K8S environment
Install DataKit

Enable Audit Log Policy¶

❗ If already enabled, please ignore

Taking Kubernetes 1.24 as an example, enabling the audit log policy

Log in to the master node server

cd /etc/kubernetes

Add audit-policy.yml

audit-policy.yml

# Copyright © 2022 sealos.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

apiVersion: audit.k8s.io/v1 # This is required.
kind: Policy
# Don't generate audit events for all requests in RequestReceived stage.
omitStages:
- "RequestReceived"
rules:
# The following requests were manually identified as high-volume and low-risk,
# so drop them.
- level: None
    users: [ "system:kube-proxy" ]
    verbs: [ "watch" ]
    resources:
    - group: "" # core
        resources: [ "endpoints", "services" ]
- level: None
    users: [ "system:unsecured" ]
    namespaces: [ "kube-system" ]
    verbs: [ "get" ]
    resources:
    - group: "" # core
        resources: [ "configmaps" ]
- level: None
    users: [ "kubelet" ] # legacy kubelet identity
    verbs: [ "get" ]
    resources:
    - group: "" # core
        resources: [ "nodes" ]
- level: None
    userGroups: [ "system:nodes" ]
    verbs: [ "get" ]
    resources:
    - group: "" # core
        resources: [ "nodes" ]
- level: None
    users:
    - system:kube-controller-manager
    - system:kube-scheduler
    - system:serviceaccount:kube-system:endpoint-controller
    verbs: [ "get", "update" ]
    namespaces: [ "kube-system" ]
    resources:
    - group: "" # core
        resources: [ "endpoints" ]
- level: None
    users: [ "system:apiserver" ]
    verbs: [ "get" ]
    resources:
    - group: "" # core
        resources: [ "namespaces" ]
# Don't log these read-only URLs.
- level: None
    nonResourceURLs:
    - /healthz*
    - /version
    - /swagger*
# Don't log events requests.
- level: None
    resources:
    - group: "" # core
        resources: [ "events" ]
# Secrets, ConfigMaps, and TokenReviews can contain sensitive & binary data,
# so only log at the Metadata level.
- level: Metadata
    resources:
    - group: "" # core
        resources: [ "secrets", "configmaps" ]
    - group: authentication.k8s.io
        resources: [ "tokenreviews" ]
# Get repsonses can be large; skip them.
- level: Request
    verbs: [ "get", "list", "watch" ]
    resources:
    - group: "" # core
    - group: "admissionregistration.k8s.io"
    - group: "apps"
    - group: "authentication.k8s.io"
    - group: "authorization.k8s.io"
    - group: "autoscaling"
    - group: "batch"
    - group: "certificates.k8s.io"
    - group: "extensions"
    - group: "networking.k8s.io"
    - group: "policy"
    - group: "rbac.authorization.k8s.io"
    - group: "settings.k8s.io"
    - group: "storage.k8s.io"
# Default level for known APIs
- level: RequestResponse
    resources:
    - group: "" # core
    - group: "admissionregistration.k8s.io"
    - group: "apps"
    - group: "authentication.k8s.io"
    - group: "authorization.k8s.io"
    - group: "autoscaling"
    - group: "batch"
    - group: "certificates.k8s.io"
    - group: "extensions"
    - group: "networking.k8s.io"
    - group: "policy"
    - group: "rbac.authorization.k8s.io"
    - group: "settings.k8s.io"
    - group: "storage.k8s.io"
    - group: "autoscaling.alibabacloud.com"
# Default level for all other requests.
- level: Metadata

💡 Corresponding policy information can be adjusted according to actual needs.

API Server Enable Audit Log¶

❗ If already enabled, please ignore

Enter the directory /etc/kubernetes/manifests, first back up the kube-apiserver.yaml file, and the backed-up file should not be placed under /etc/kubernetes/manifests/. Adjust the content of the file.

Add commands under spec.containers.command:

  - command:
    - kube-apiserver
    - --advertise-address=10.0.16.204
    - --allow-privileged=true
    - --audit-log-format=json
    - --audit-log-maxage=7
    - --audit-log-maxbackup=10
    - --audit-log-maxsize=100
    - --audit-log-path=/var/log/kubernetes/audit.log
    - --audit-policy-file=/etc/kubernetes/audit-policy.yml

Add under spec.containers.volumeMounts:

    - mountPath: /etc/kubernetes
      name: audit
    - mountPath: /var/log/kubernetes
      name: audit-log

Add under spec.volumes:

  - hostPath:
      path: /etc/kubernetes
      type: DirectoryOrCreate
    name: audit
  - hostPath:
      path: /var/log/kubernetes
      type: DirectoryOrCreate
    name: audit-log

Take effect

After modifying the API Server, it will automatically restart. Wait patiently for a few minutes.

Verify

Run the following command to check if the audit.log file is generated. If it exists, it proves that the configuration has taken effect.

ls /var/log/kubernetes

Collect K8S Audit Logs¶

K8S audit logs are stored in the /var/log/kubernetes directory of the corresponding master node. Here, we use the annotation method for collection.

Create pod: k8s-audit-log.yaml

apiVersion: v1
kind: Pod
metadata:
  name: kube-audit-log
  annotations:
        datakit/logs: |
          [
            {
              "disable": false,
              "type": "file",
              "path":"/var/log/kubernetes/audit.log",
              "source":  "k8s-audit",
              "tags" : {
                "atype": "kube-audit-log"
              }
            }
          ]

spec:
  containers:
  - name: kube-audit-log
    image: busybox
#    command: ["sleep", "1"]
    args:
    - /bin/sh
    - -c
    - >
      i=0;
      while true;
      do
        i=$((i+1));
        sleep 10;
      done
    volumeMounts:
    - mountPath: /var/log/kubernetes
      name: datakit-vol-opt
  volumes:
  - name: datakit-vol-opt
    hostPath: 
      path: /var/log/kubernetes
  nodeSelector:
     kubernetes.io/hostname: k8s-master
  tolerations:
  - key: "node-role.kubernetes.io/master"
    operator: "Exists"
    effect: "NoSchedule"
  - key: "node-role.kubernetes.io/control-plane"
    operator: "Exists"
    effect: "NoSchedule"

❗ Note that this pod can only run on the master node.

Execute

kubectl apply -f k8s-audit-log.yaml

View

After a few minutes, you can view the corresponding logs on Guance. Since they are in json format, Guance supports searching via the @+json field name, such as @verb:update.

Audit Log Field Extraction¶

After collecting audit logs, through Guance's pipeline capabilities, key fields from the audit logs can be extracted for further analysis.

On Guance, Logs - Pipeline - Create
Select the corresponding log source k8s-audit
Pipeline Name: kubelet-audit
Define parsing rules

abc = load_json(_)

add_key(kind, abc["kind"])
add_key(level, abc["level"])
add_key(stage, abc["stage"])
add_key(verb, abc["verb"])
add_key(auditID, abc["auditID"])
add_key(username, abc["user"]["username"])
add_key(responseCode, abc["responseStatus"]["code"])
if abc["responseStatus"]["code"]==200 {
  add_key(status, "OK")
}else{
  add_key(status, "FAIL")
}
add_key(sourceIP_0,abc["sourceIPs"][0])

add_key(namespace,abc["objectRef"]["namespace"])
add_key(node,abc["objectRef"]["name"])

Click to test the script
Save