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NGINX WAF Investigation
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NGINX-WAF.md

NGINX WAF Ingress

Deploy NGINX Ingress Controller Operator

We are deploying via the certified NGINX Ingress Operator, therefore, create the ns, subs, and og for the operator.

kubectl create -f -<<EOF
apiVersion: v1
kind: Namespace
metadata:
  creationTimestamp: null
  name: nginx-ingress
spec: {}
status: {}
---
apiVersion: operators.coreos.com/v1
kind: OperatorGroup
metadata:
  name: nginx-ingress-tvj24
  namespace: nginx-ingress
spec:
  upgradeStrategy: Default
---
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  labels:
    operators.coreos.com/nginx-ingress-operator.nginx-ingress: ""
  name: nginx-ingress-operator
  namespace: nginx-ingress
spec:
  channel: alpha
  installPlanApproval: Automatic
  name: nginx-ingress-operator
  source: certified-operators
  sourceNamespace: openshift-marketplace
  startingCSV: nginx-ingress-operator.v1.3.1
EOF

Wait for the operator to be ready

kubectl wait --for=condition=Ready pod -l control-plane=controller-manager -n nginx-ingress

Create an instance of NginxIngress

Set current-context to the nginx-ingress namespace.

kubectl config set-context $(kubectl config current-context) --namespace=nginx-ingress

Create an instance of the NginxIngress:

kubectl create -f -<<EOF
apiVersion: charts.nginx.org/v1alpha1
kind: NginxIngress
metadata:
  name: starburst
  namespace: nginx-ingress
spec:
  controller:
    affinity: {}
    annotations: {}
    appprotect:
      enable: false # This enables WAF
      # F0307 23:14:59.281060       1 flags.go:222] NGINX App Protect support is for NGINX Plus # only
      # https://github.com/nginxinc/nginx-ingress-helm-operator/blob/b99d3cb9355458a55bac7d44b43ebe13c11e4ea2/helm-charts/nginx-ingress/README.md
    appprotectdos: # This is a nice to have too, protect against DOS
      debug: true
      enable: false
      maxDaemons: 0
      maxWorkers: 0
      memory: 0
    # autoscaling:
    #   annotations: {}
    #   enabled: false
    #   maxReplicas: 3
    #   minReplicas: 1
    #   targetCPUUtilizationPercentage: 50
    #   targetMemoryUtilizationPercentage: 50
    config:
      annotations: {}
      entries: {}
    customConfigMap: ''
    customPorts: []
    # If you do this, you have to manually create the secret
    # defaultTLS:
    #   secret: nginx-ingress/default-server-secret
    disableIPV6: false
    dnsPolicy: ClusterFirst
    enableCertManager: false
    enableCustomResources: true
    enableExternalDNS: false
    enableLatencyMetrics: false
    enableOIDC: false
    enablePreviewPolicies: false
    enableSnippets: false
    enableTLSPassthrough: false
    extraContainers: []
    globalConfiguration:
      create: false
      spec: {}
    healthStatus: false
    healthStatusURI: /nginx-health
    hostNetwork: false
    image:
      pullPolicy: IfNotPresent
      repository: nginx/nginx-ingress
      tag: 3.0.2-ubi
    includeYear: false
    ingressClass: nginx
    initContainers: []
    lifecycle: {}
    logLevel: 1
    minReadySeconds: 0
    nginxDebug: false
    nginxReloadTimeout: 60000
    nginxStatus:
      allowCidrs: 127.0.0.1
      enable: true
      port: 8080
    nginxplus: false
    pod:
      annotations: {}
      extraLabels: {}
    readyStatus:
      enable: true
      initialDelaySeconds: 0
      port: 8081
    replicaCount: 1
    reportIngressStatus:
      annotations: {}
      enable: true
      enableLeaderElection: true
      ingressLink: ''
    resources:
      requests:
        cpu: 100m
        memory: 128Mi
    service:
      annotations: {}
      create: true
      customPorts: []
      externalIPs: []
      externalTrafficPolicy: Local
      extraLabels: {}
      httpPort:
        enable: true
        port: 80
        targetPort: 80
      httpsPort:
        enable: true
        port: 443
        targetPort: 443
      loadBalancerIP: ''
      loadBalancerSourceRanges: []
      type: LoadBalancer
    serviceAccount:
      annotations: {}
      imagePullSecretName: ''

    serviceMonitor:
      create: false # not now
      endpoints: []
      labels: {}
      selectorMatchLabels: {}
    setAsDefaultIngress: false
    strategy: {}
    terminationGracePeriodSeconds: 30
    tolerations: []
    volumeMounts: []
    volumes: []
    watchNamespace: ''
    watchNamespaceLabel: ''
    watchSecretNamespace: ''
    kind: deployment
  nginxServiceMesh:
    enable: false
    enableEgress: false
  prometheus:
    create: false # not now
    port: 9113
    scheme: http
    secret: ''
  rbac:
    create: true
  serviceInsight:
    create: false
    port: 9114
    scheme: http
    secret: ''
EOF

If you had turned on App Protect support, you would get this error:

F0307 23:14:59.281060       1 flags.go:222] NGINX App Protect support is for NGINX Plus only

Catch the error around allowPriviledgeEscalation in the controller manager:

kubectl logs -f -l control-plane=controller-manager | egrep -A9 "allowPrivilegeEscalation|error"
# or 
kubectl get ev --sort-by='.lastTimestamp' | grep forbidden

output:

W0307 19:01:10.543082       1 warnings.go:70] would violate PodSecurity "restricted:v1.24": allowPrivilegeEscalation != false (container "starburst-nginx-ingress" must set securityContext.allowPrivilegeEscalation=false), seccompProfile (pod or container "starburst-nginx-ingress" must set securityContext.seccompProfile.type to "RuntimeDefault" or "Localhost")
{"level":"info","ts":1678215670.5483713,"logger":"helm.controller","msg":"Reconciled release","namespace":"nginx-ingress","name":"starburst","apiVersion":"charts.nginx.org/v1alpha1","kind":"NginxIngress","release":"starburst"}

If we go with this method of implementation for the WAF, this is an opportunity for us to contribute back upstream. This operator is a helm-operator and we need to expose the securityContext. UPDATE: THIS IS ALREADY A WIP.

Secondly, I don't think this error is very bad. This service account is localized to only one deployment. We can implement network policies in the cluster if we need to ease concern from prodsec

Fix this issue for now by adding a ClusterRole to the ServiceAccount nginx-ingress which allows it to create SecurityContext. Read more about SecurityContext:

kubectl create -f -<<EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  creationTimestamp: null
  name: nginx-privileged
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: system:openshift:scc:privileged
subjects:
- kind: ServiceAccount
  name: nginx-ingress
  namespace: nginx-ingress
EOF

This shows the securityContext used by the deployment:

kubectl get deploy starburst-nginx-ingress -ojsonpath='{.spec.template.spec.containers[0].securityContext}' | jq

output:

{
  "allowPrivilegeEscalation": true,
  "capabilities": {
    "add": [
      "NET_BIND_SERVICE"
    ],
    "drop": [
      "ALL"
    ]
  },
  "runAsNonRoot": true,
  "runAsUser": 101
}

Now we can finally go on to the ingress object after making sure the logs are reporting clean in the nginx instance

kubectl logs -l app=starburst-nginx-ingress

output

2023/03/07 23:32:14 [notice] 23#23: worker process 30 exited with code 0
2023/03/07 23:32:14 [notice] 23#23: worker process 33 exited with code 0
2023/03/07 23:32:14 [notice] 23#23: worker process 41 exited with code 0
2023/03/07 23:32:14 [notice] 23#23: signal 29 (SIGIO) received
2023/03/07 23:32:14 [notice] 23#23: signal 17 (SIGCHLD) received from 31
2023/03/07 23:32:14 [notice] 23#23: worker process 31 exited with code 0
2023/03/07 23:32:14 [notice] 23#23: signal 29 (SIGIO) received
2023/03/07 23:32:14 [notice] 23#23: signal 17 (SIGCHLD) received from 26
2023/03/07 23:32:14 [notice] 23#23: worker process 26 exited with code 0
2023/03/07 23:32:14 [notice] 23#23: signal 29 (SIGIO) received

Deploy an app and expose it at the Ingress

Deploy a sample app that we will route to, eventually this app will be Starburst, for now, it is a simple NGINX pod.

kubectl run backend --image=nginx --port=80 --expose

output

service/backend created
pod/backend created

Create an Ingress to route to the app.

kubectl create ing starburst --class=nginx --rule="redhat.com/=backend:80"

output

ingress.networking.k8s.io/starburst created

Test

curl -H "Host: redhat.com" $(k get svc starburst-nginx-ingress -ojsonpath='{.status.loadBalancer.ingress[0].hostname}')

output

<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

Deploy RateLimit and a WAF Policy

IGNORE THIS - You still must have nginx plus Skip to Clean Up

When we deployed the Nginx operator, we deployed a CRD called Policy, it has both WAF and RateLimit. Let's check it out:

k explain policies.spec --recursive

output

KIND:     Policy
VERSION:  k8s.nginx.org/v1

RESOURCE: spec <Object>

DESCRIPTION:
     PolicySpec is the spec of the Policy resource. The spec includes multiple
     fields, where each field represents a different policy. Only one policy
     (field) is allowed.

FIELDS:
   accessControl        <Object>
      allow     <[]string>
      deny      <[]string>
   basicAuth    <Object>
      realm     <string>
      secret    <string>
   egressMTLS   <Object>
      ciphers   <string>
      protocols <string>
      serverName        <boolean>
      sessionReuse      <boolean>
      sslName   <string>
      tlsSecret <string>
      trustedCertSecret <string>
      verifyDepth       <integer>
      verifyServer      <boolean>
   ingressClassName     <string>
   ingressMTLS  <Object>
      clientCertSecret  <string>
      verifyClient      <string>
      verifyDepth       <integer>
   jwt  <Object>
      jwksURI   <string>
      keyCache  <string>
      realm     <string>
      secret    <string>
      token     <string>
   oidc <Object>
      authEndpoint      <string>
      clientID  <string>
      clientSecret      <string>
      jwksURI   <string>
      redirectURI       <string>
      scope     <string>
      tokenEndpoint     <string>
      zoneSyncLeeway    <integer>
   rateLimit    <Object>
      burst     <integer>
      delay     <integer>
      dryRun    <boolean>
      key       <string>
      logLevel  <string>
      noDelay   <boolean>
      rate      <string>
      rejectCode        <integer>
      zoneSize  <string>
   waf  <Object>
      apPolicy  <string>
      enable    <boolean>
      securityLog       <Object>
         apLogConf      <string>
         enable <boolean>
         logDest        <string>
      securityLogs      <[]Object>
         apLogConf      <string>
         enable <boolean>
         logDest        <string>
kubectl apply -f -<<EOF
kind: Policy
version: k8s.nginx.org/v1
spec: 
  name: starburst
  namespace: nginx-ingress
spec:
  waf:
    enable: true
    securityLog:
      enable: true
      logDest: /tmp

Helpful Sites

Clean Up

kubectl delete nginxingress starburst --force
kubectl delete clusterrolebinding nginx-privileged
kubectl delete og,subs,csv --all --force

# clean up crds
kubectl get crd | grep nginx | awk '{print $1}' | xargs kubectl delete crd

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