ACTIONS_RUNNER_CONTAINER_HOOK_TEMPLATE doesnt tolerate octal file modes in configmap volume declaration

Summary

I'm using the ACTIONS_RUNNER_CONTAINER_HOOK_TEMPLATE in ARC, and trying to mount a configmap with various file modes. Providing the file mode in octal results in a pipeline error during Initialize Containers part of my Job. Switching to decimal resolves the issue but is significantly more confusing.

BAD

    ---
    apiVersion: v1
    kind: PodTemplate
    metadata:
      name: runner-pod-template
      labels:
        app: github-actions-runner
        runnnerName: my-github-runner-test
      annotations:
        cluster-autoscaler.kubernetes.io/safe-to-evict: "false"
    spec:
      imagePullPolicy: Always
      containers:
      - name: $job
        securityContext:
          privileged: true
        env:
          - name: NODE_EXTRA_CA_CERTS
            value: /usr/local/share/ca-certificates/ca.crt
          - name: AWS_CONFIG_FILE
            value: /.aws/config
          - name: AWS_PROFILE
            value: target_role
        volumeMounts:
          - name: github-server-tls-cert
            mountPath: /usr/local/share/ca-certificates/ca.crt
            subPath: ca.crt
            readOnly: true
          - mountPath: /.aws
            name: aws-dir
          - name: iam-config
            mountPath: /.aws/config
            subPath: config
            readOnly: true
          - name: iam-config
            mountPath: /.aws/eks-credential-processrole.sh
            subPath: eks-credential-processrole.sh
        resources:
          requests:
            cpu: 100m
            memory: "4Gi"
      serviceAccountName: my-github-runner-test
      securityContext:
        fsGroup: 1001  # provides access to /home/runner/_work directory in ephemeral volume
      tolerations:
      - effect: NoSchedule
        key: dedicated
        operator: Equal
        value: gitlab
      volumes:
      - name: github-server-tls-cert
        configMap:
          name: my-cacert
          items:
            - key: ca.crt
              path: ca.crt
      - name: aws-dir
        emptyDir: {}
      - name: iam-config
        configMap:
          name: iam-config
          items:
          - key: config
            path: config
            # THIS DOESNT WORKS
            mode: 0777
          - key: eks-credential-processrole.sh
            path: eks-credential-processrole.sh
            # THIS DOESNT WORK
            mode: 0555

GOOD

    ---
    apiVersion: v1
    kind: PodTemplate
    metadata:
      name: runner-pod-template
      labels:
        app: github-actions-runner
        runnnerName: my-github-runner-test
      annotations:
        cluster-autoscaler.kubernetes.io/safe-to-evict: "false"
    spec:
      imagePullPolicy: Always
      containers:
      - name: $job
        securityContext:
          privileged: true
        env:
          - name: NODE_EXTRA_CA_CERTS
            value: /usr/local/share/ca-certificates/ca.crt
          - name: AWS_CONFIG_FILE
            value: /.aws/config
          - name: AWS_PROFILE
            value: target_role
        volumeMounts:
          - name: github-server-tls-cert
            mountPath: /usr/local/share/ca-certificates/ca.crt
            subPath: ca.crt
            readOnly: true
          - mountPath: /.aws
            name: aws-dir
          - name: iam-config
            mountPath: /.aws/config
            subPath: config
            readOnly: true
          - name: iam-config
            mountPath: /.aws/eks-credential-processrole.sh
            subPath: eks-credential-processrole.sh
        resources:
          requests:
            cpu: 100m
            memory: "4Gi"
      serviceAccountName: my-github-runner-test
      securityContext:
        fsGroup: 1001  # provides access to /home/runner/_work directory in ephemeral volume
      tolerations:
      - effect: NoSchedule
        key: dedicated
        operator: Equal
        value: gitlab
      volumes:
      - name: github-server-tls-cert
        configMap:
          name: my-cacert
          items:
            - key: ca.crt
              path: ca.crt
      - name: aws-dir
        emptyDir: {}
      - name: iam-config
        configMap:
          name: iam-config
          items:
          - key: config
            path: config
            # THIS WORKS
            mode: 292
          - key: eks-credential-processrole.sh
            path: eks-credential-processrole.sh
            # THIS WORKS
            mode: 365

Error Message

On the Initialize Containers step, i get the following error:

Error: Error: failed to create job pod: Pod "my-github-runner-test-s9klc-runner-96622-workflow" is invalid: [spec.volumes[4].configMap.items[1].mode: Invalid value: 555: must be a number between 0 and 0777 (octal), both inclusive, spec.containers[0].volumeMounts[6].name: Not found: "iam-config", spec.containers[0].volumeMounts[7].name: Not found: "iam-config"]
Error: Process completed with exit code 1.
Error: Executing the custom container implementation failed. Please contact your self hosted runner administrator.

I suspect the hook removes the 0 prefix in the octal notation causing the the actual pod yaml that the controller creates to provide an invalid value

Start by tracing how ACTIONS_RUNNER_CONTAINER_HOOK_TEMPLATE parses and emits ConfigMap volume item modes, then reproduce the provided PodTemplate with octal modes 0777 and 0555. Done means the generated pod accepts those modes as values between 0 and 0777, while the existing decimal-mode behavior remains valid.