Add Image as Environment Variable

 1apiVersion: kyverno.io/v1
 2kind: ClusterPolicy
 3metadata:
 4  name: add-image-as-env-var
 5  # env array needs to exist (least one env var is present)
 6  annotations:
 7    pod-policies.kyverno.io/autogen-controllers: None
 8    policies.kyverno.io/title: Add Image as Environment Variable
 9    policies.kyverno.io/category: Other
10    policies.kyverno.io/severity: medium
11    policies.kyverno.io/minversion: 1.6.0
12    kyverno.io/kyverno-version: 1.6.2
13    kyverno.io/kubernetes-version: "1.23"
14    policies.kyverno.io/subject: Pod
15    policies.kyverno.io/description: >-
16      The Kubernetes downward API only has the ability to express so many
17      options as environment variables. The image consumed in a Pod is commonly
18      needed to make the application aware of some logic it must take. This policy
19      takes the value of the `image` field and adds it as an environment variable
20      to bare Pods and Deployments having no more than two containers. The `env` array must already exist for the policy
21      to operate correctly. This policy may be easily extended to support other higher-level
22      Pod controllers as well as more containers by following the established rules.      
23spec:
24  background: false
25  schemaValidation: false
26  rules:
27  # One Pod
28  - name: pod-containers-1-inject-image
29    match:
30      any:
31      - resources:
32          kinds:
33          - Pod
34    preconditions:
35      all:
36      - key: "{{request.object.spec.containers[] | length(@)}}"
37        operator: GreaterThanOrEquals
38        value: 1
39    mutate:
40      patchesJson6902: |-
41        - op: add
42          path: "/spec/containers/0/env/-"
43          value: {"name":"K8S_IMAGE","value":"{{request.object.spec.containers[0].image}}"}        
44  # Two or more Pods
45  - name: pod-containers-2-inject-image
46    match:
47      any:
48      - resources:
49          kinds:
50          - Pod
51    preconditions:
52      all:
53      - key: "{{request.object.spec.containers[] | length(@)}}"
54        operator: GreaterThanOrEquals
55        value: 2
56    mutate:
57      patchesJson6902: |-
58        - op: add
59          path: "/spec/containers/1/env/-"
60          value: {"name":"K8S_IMAGE","value":"{{request.object.spec.containers[1].image}}"}        
61  # Deployment with one Pod
62  - name: deploy-containers-1-inject-image
63    match:
64      any:
65      - resources:
66          kinds:
67          - Deployment
68    preconditions:
69      all:
70      - key: "{{request.object.spec.template.spec.containers[] | length(@)}}"
71        operator: GreaterThanOrEquals
72        value: 1
73    mutate:
74      patchesJson6902: |-
75        - op: add
76          path: "/spec/template/spec/containers/0/env/-"
77          value: {"name":"K8S_IMAGE","value":"{{request.object.spec.template.spec.containers[0].image}}"}        
78  # Deployment with two or more Pods
79  - name: deploy-containers-2-inject-image
80    match:
81      any:
82      - resources:
83          kinds:
84          - Deployment
85    preconditions:
86      all:
87      - key: "{{request.object.spec.template.spec.containers[] | length(@)}}"
88        operator: GreaterThanOrEquals
89        value: 2
90    mutate:
91      patchesJson6902: |-
92        - op: add
93          path: "/spec/template/spec/containers/1/env/-"
94          value: {"name":"K8S_IMAGE","value":"{{request.object.spec.template.spec.containers[1].image}}"}