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Pod API modify header

Pod API modify header is a Kubernetes pod-level chaos fault that overrides the header values of API requests and responses with the user-provided values for the given keys. This is achieved by starting the proxy server and redirecting the traffic through the proxy server.

A transient proxy (also known as helper pod) is brought up for a chaos duration to intercept the requests made from the target application to another service and elsewhere, and inject chaos accordingly. Target application refers to the application pods calling/sending egress traffic to an endpoint.

Pod API Modify Header

Use cases​

Pod API modify header:

  • Simulate different authentication states or test the behavior of your application when using invalid or expired credentials.
  • This fault can be utilized to validate the caching behavior of your API or client applications. By overriding cache-related headers, such as the "Cache-Control" or "ETag" headers, you can simulate cache validation scenarios.
  • It can be used to test content negotiation capabilities. By modifying the "Accept" header in the API request, you can simulate different content types or formats that the client application can accept.

Permissions required​

Below is a sample Kubernetes role that defines the permissions required to execute the fault.

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: hce
  name: pod-api-modify-header
spec:
  definition:
    scope: Cluster # Supports "Namespaced" mode too
permissions:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["create", "delete", "get", "list", "patch", "deletecollection", "update"]
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create", "get", "list", "patch", "update"]
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["deployments, statefulsets"]
    verbs: ["get", "list"]
  - apiGroups: [""]
    resources: ["replicasets, daemonsets"]
    verbs: ["get", "list"]
  - apiGroups: [""]
    resources: ["chaosEngines", "chaosExperiments", "chaosResults"]
    verbs: ["create", "delete", "get", "list", "patch", "update"]
  - apiGroups: ["batch"]
    resources: ["jobs"]
    verbs: ["create", "delete", "get", "list", "deletecollection"]

Prerequisites​

  • Kubernetes> 1.17
  • The application pods should be in the running state before and after injecting chaos.

Mandatory tunables​

Tunable Description Notes
TARGET_CONTAINER Name of the container subject to API header modification. None. For more information, go to target specific container
NODE_LABEL Node label used to filter the target node if TARGET_NODE environment variable is not set. It is mutually exclusive with the TARGET_NODE environment variable. If both are provided, the fault uses TARGET_NODE. For more information, go to node label.
TARGET_SERVICE_PORT Port of the target service. Defaults to port 80. For more information, go to target service port.
HEADERS_MAP Map of the headers to modify or add For example, {"X-Litmus-Test-Header": "X-Litmus-Test-Value"}. To remove a header, just set the value to ""; For example, {"X-Litmus-Test-Header": ""}. For more information, go to headers map.

Optional tunables​

Tunable Description Notes
PATH_FILTER API path or route used for the filtering. Targets all paths if not provided. For more information, go to path filter .
HEADERS_FILTERS Filters for HTTP request headers accept multiple comma-separated headers in the format key1:value1,key2:value2. For more information, go to header filters.
METHODS The HTTP request method type accepts comma-separated HTTP methods in upper cases, such as "GET,POST". For more information, go to methods.
QUERY_PARAMS HTTP request query parameter filters accept multiple comma-separated query parameters in the format of param1:value1,param2:value2. For more information, go to query params.
SOURCE_HOSTS Includes comma-separated source host names as filters, indicating the origin of the HTTP request. This is specifically relevant to the "ingress" type. For more information, go to source hosts.
SOURCE_IPS This includes comma-separated source IPs as filters, indicating the origin of the HTTP request. This is specifically relevant to the "ingress" type. For more information, go to source ips.
DESTINATION_HOSTS Comma-separated destination host names are used as filters, indicating the hosts on which you call the API. This specification applies exclusively to the "egress" type. For more information, go to destination hosts.
DESTINATION_IPS Comma-separated destination IPs are used as filters, indicating the hosts on which you call the API. This specification applies exclusively to the "egress" type. For more information, go to destination hosts.
PROXY_PORT Port where the proxy listens for requests. Default: 20000. For more information, go to proxy port.
LIB_IMAGE Image used to inject chaos. Default: harness/chaos-go-runner:main-latest. For more information, go to image used by the helper pod.
SERVICE_DIRECTION Direction of the flow of control, ingress or egress Default: ingress. For more information, go to service direction .
DATA_DIRECTION API payload type, request or response Default: both. For more information, go to data direction .
DESTINATION_PORTS comma-separated list of the destination service or host ports for which egress traffic should be affected Default: 80,443. For more information, go to destination ports
HTTPS_ENABLED facilitate HTTPS support for both incoming and outgoing traffic Default: false. For more information, go to https
CA_CERTIFICATES These CA certificates are used by the proxy server to generate the server certificates for the TLS handshake between the target application and the proxy server. These CA certificates must also be added to the target application's root certificate. For more information, go to CA certificates.
SERVER_CERTIFICATES These server certificates are used by the proxy server for the TLS handshake between the target application and the proxy server. The corresponding CA certificates should be loaded as root certificates inside the target application. For more information, go to server certificates.
HTTPS_ROOT_CERT_PATH Provide the root CA certificate directory path This setting must be configured if the root CA certificate directory differs from /etc/ssl/certs. Please refer to https://go.dev/src/crypto/x509/root_linux.go to understand the default certificate directory based on various Linux distributions. For more information, go to HTTPS
HTTPS_ROOT_CERT_FILE_NAME Provide the root CA certificate file name This setting must be configured if the root CA certificate file name differs from ca-certificates.crt. Please refer to https://go.dev/src/crypto/x509/root_linux.go to understand the default certificate file names based on various Linux distributions. For more information, go to HTTPS
NETWORK_INTERFACE Network interface used for the proxy. Default: eth0. For more information, go to network interface .
CONTAINER_RUNTIME Container runtime interface for the cluster Default: containerd. Support values: docker, containerd and crio. For more information, go to container runtime .
SOCKET_PATH Path of the containerd or crio or docker socket file. Default: /run/containerd/containerd.sock. For more information, go to socket path.
TOTAL_CHAOS_DURATION Duration of chaos injection (in seconds). Default: 60 s. For more information, go to duration of the chaos .
TARGET_PODS Comma-separated list of application pod names subject to pod HTTP modify body. If not provided, the fault selects target pods randomly based on provided appLabels. For more information, go to target specific pods.
PODS_AFFECTED_PERC Percentage of total pods to target. Provide numeric values. Default: 0 (corresponds to 1 replica). For more information, go to pod affected percentage
RAMP_TIME Period to wait before and after injecting chaos (in seconds). For example, 30 s. For more information, go to ramp time.
SEQUENCE Sequence of chaos execution for multiple target pods. Default: parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.

Target service port​

Port of the targeted service. Tune it by using the TARGET_SERVICE_PORT environment variable.

The following YAML snippet illustrates the use of this environment variable:

## provide the port of the targeted service
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-api-modify-header
      spec:
        components:
          env:
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            - name: PATH_FILTER
              value: '/status'

Headers map​

Map of the headers that need to be modified or added to the HTTP request or response. Tune it by using the HEADERS_MAP environment variable.

The following YAML snippet illustrates the use of this environment variable:

## provide the headers as a map
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-api-modify-header
      spec:
        components:
          env:
            # map of headers to modify/add; Eg: {"X-Litmus-Test-Header": "X-Litmus-Test-Value"}
            # to remove a header, just set the value to ""; Eg: {"X-Litmus-Test-Header": ""}
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: PATH_FILTER
              value: '/status'

Path filter​

API sub path (or route) to filter the API calls. Tune it by using the PATH_FILTER environment variable.

The following YAML snippet illustrates the use of this environment variable:

## provide api path filter
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-api-modify-header
      spec:
        components:
          env:
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

Destination ports​

A comma-separated list of the destination service or host ports for which egress traffic should be affected as a result of chaos testing on the target application. Tune it by using the DESTINATION_PORTS environment variable.

note

It is applicable only for the egress SERVICE_DIRECTION.

The following YAML snippet illustrates the use of this environment variable:

## provide destination ports
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-api-modify-header
      spec:
        components:
          env:
            # provide destination ports
            - name: DESTINATION_PORTS
              value: '80,443'
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

HTTPS​

To enable HTTPS support for both incoming and outgoing traffic between the target and the proxy, set the HTTPS_ENABLED field to true. The next step is to configure TLS, for which you can follow one of the ways: Using self-signed certificate or using trusted certificate.

Using Self-Signed Certificates​

To establish TLS communication between the target application and the proxy server, you can use one of the following.

  1. CA certificates

    The certificates provided by CA (or self-signed) to sign or validate the server certificates.

    • ca.key: The private key used to generate CA certificates.

    • ca.crt: The actual CA certificate.

    • Prerequisite: Load the ca.crt as the root CA certificate in the target application before experiment creation or execution.

    • Fault Configuration: Provide base64-encoded ca.key and ca.crt in the CA_CERTIFICATES environment variable.

      cat ca.key ca.crt > ca.pem
      cat ca.pem | base64  # Add this to the CA_CERTIFICATES environment variable

    In this setup, the proxy dynamically generates the server certificates with appropriate domain names during TLS handshake and sign them by the self-signed CA (provided in CA_CERTIFICATES environemtn variable) before sending them to the target application server.

  2. Server certificates

    The certificates used by the transient proxy server for TLS handshake with the target application.

    • server.key: The private key used to generate the server certificates.

    • server.crt: The actual Server certificate (signed by the CA).

    • Internal Domain: Domain in which the local (organization-managed) services are deployed. Typically, it contains the local upstream or soft microservice dependencies.

    • External Domain: Domain in which the third-party services are deployed (for example, AWS services like DynamoDB or S3). Typically, it comprises the hard dependencies.

    • SAN (Subject Alternative Names): List of domain names provided to the cert-generation command or within the config file (*.cnf) passed as args to the cert-generators while creating the CSR (Certificate Signing Request).

    • Prerequisites: Load the ca.crt as the root CA certificate in the target application before experiment creation or execution. Create a server.crt with the necessary domain names and sign it using CA certificates.

    • Fault Configuration: Provide base64-encoded server.key and server.crt in the SERVER_CERTIFICATES environment variable.

      cat server.key server.crt > server.pem
      cat server.pem | base64  # Add this to the SERVER_CERTIFICATES environment variable

    In this setup, the proxy sends the server certificates (provided in SERVER_CERTIFICATES environment variable) to the target application server as part of the TLS handshake.

note

Intermediate Certificates are the chain of certificates that are used to generate the eventual server certificate for security purposes.

Using Trusted Certificates​

You can use trusted server certificates for internal or external domains, both of which are described below.

  1. For Internal Domains

    • Prerequisites: Generate the server certificates with the internal domain names and sign them using a trusted CA. Since the CA is trusted, there is no need to load the CA certificate in the target application.

    • Fault Configuration: Provide the base64-encoded server.key, server.crt, and any intermediate certificates in the SERVER_CERTIFICATES environment variable.

      cat server.key server.crt <intermediate-certificates> > server.pem
      cat server.pem | base64  # Add this to the SERVER_CERTIFICATES env

  2. For External Domains

    • Prerequisites: Generate the server certificates that include both internal and external domain names, and sign them with the trusted CA. Since the CA is trusted, there is no need to load the CA certificates in the target application.

    • Fault Configuration: Provide the base64-encoded server.key, server.crt, and any intermediate certificates in the SERVER_CERTIFICATES environment variable.

      cat server.key server.crt <intermediate-certificates> > server.pem
      cat server.pem | base64  # Add this to the SERVER_CERTIFICATES env

Advanced fault tunables​

  • PROXY_PORT: Port where the proxy listens for requests and responses.
  • SERVICE_DIRECTION: Direction of the flow of control, either ingress or egress.
  • DATA_DIRECTION: API payload type, request, or response. It supports request, response, and both values.
  • NETWORK_INTERFACE: Network interface used for the proxy.

The following YAML snippet illustrates the use of this environment variable:

# it injects the api modify header fault
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-api-modify-header
      spec:
        components:
          env:
            # provide the proxy port
            - name: PROXY_PORT
              value: '20000'
            # provide the connection type
            - name: SERVICE_DIRECTION
              value: 'ingress'
            # provide the payload type
            - name: DATA_DIRECTION
              value: 'both'
            # provide the network interface
            - name: NETWORK_INTERFACE
              value: 'eth0'
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'

Advanced filters​

  • HEADERS_FILTERS: The HTTP request headers filters, that accept multiple comma-separated headers in the format of key1:value1,key2:value2.
  • METHODS: The HTTP request method type filters, that accept comma-separated HTTP methods in upper case, that is, GET,POST.
  • QUERY_PARAMS: The HTTP request query parameters filter, accepts multiple comma-separated query parameters in the format of param1:value1,param2:value2.
  • SOURCE_HOSTS: Comma-separated source host names filters, indicating the origin of the HTTP request. This is relevant to the ingress type, specified by SERVICE_DIRECTION environment variable.
  • SOURCE_IPS: Comma-separated source IPs filters, indicating the origin of the HTTP request. This is specifically relevant to the ingress type, specified by SERVICE_DIRECTION environment variable.
  • DESTINATION_HOSTS: Comma-separated destination host names filters, indicating the hosts on which you call the API. This specification applies exclusively to the egress type, specified by SERVICE_DIRECTION environment variable.
  • DESTINATION_IPS: Comma-separated destination IPs filters, indicating the hosts on which you call the API. This specification applies exclusively to the egress type, specified by SERVICE_DIRECTION environment variable.

The following YAML snippet illustrates the use of this environment variable:

# it injects the api modify header fault
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-api-modify-header
      spec:
        components:
          env:
            # provide the headers filters
            - name: HEADERS_FILTERS
              value: 'key1:value1,key2:value2'
            # provide the methods filters
            - name: METHODS
              value: 'GET,POST'
            # provide the query params filters
            - name: QUERY_PARAMS
              value: 'param1:value1,param2:value2'
            # provide the source hosts filters
            - name: SOURCE_HOSTS
              value: 'host1,host2'
            # provide the source ips filters
            - name: SOURCE_IPS
              value: 'ip1,ip2'
            # provide the connection type
            - name: SERVICE_DIRECTION
              value: 'ingress'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'

Container runtime and socket path​

The CONTAINER_RUNTIME and SOCKET_PATH environment variable to set the container runtime and socket file path, respectively.

  • CONTAINER_RUNTIME: It supports docker, containerd, and crio runtimes. The default value is containerd.
  • SOCKET_PATH: It contains path of containerd socket file by default(/run/containerd/containerd.sock). For docker, specify path as /var/run/docker.sock. For crio, specify path as /var/run/crio/crio.sock.

The following YAML snippet illustrates the use of these environment variables:

## provide the container runtime and socket file path
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
    - name: pod-api-modify-header
      spec:
        components:
          env:
            # runtime for the container
            # supports docker, containerd, crio
            - name: CONTAINER_RUNTIME
              value: "containerd"
            # path of the socket file
            - name: SOCKET_PATH
              value: "/run/containerd/containerd.sock"
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'