How to Generate Bearer Token From Kubeconfig File Programmatically On Outside of Kubernetes With Golang

Question

I am trying to create a cli tool for kubernetes. I need to generate Bearer Token for communicating with kubernetes API. How can I generate the token from Kubeconfig File? I do not want to use external library or kubectl.

Here is example Kubeconfig File:

apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: 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
    server: https://192.168.1.18:6443
  name: kubernetes
contexts:
- context:
    cluster: kubernetes
    user: kubernetes-admin
  name: kubernetes-admin@kubernetes
current-context: kubernetes-admin@kubernetes
kind: Config
preferences: {}
users:
- name: kubernetes-admin
  user:
    client-certificate-data: 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
    client-key-data: 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

Answer 1

I need to generate Bearer Token for communicating with kubernetes API

You cannot ”generate” these tokens. They are issued by the control plane and signed with the private key that the control plane holds. It would be a security hole if you could generate these on the client side.