kubelogin

This is a kubectl plugin for Kubernetes OpenID Connect (OIDC) authentication, also known as kubectl oidc-login.

Here is an example of Kubernetes authentication with the Google Identity Platform:

Kubelogin is designed to run as a client-go credential plugin. When you run kubectl, kubelogin opens the browser and you can log in to the provider. Then kubelogin gets a token from the provider and kubectl access Kubernetes APIs with the token. Take a look at the diagram:

Getting Started

Setup

Install the latest release from Homebrew, Krew or GitHub Releases.

# Homebrew (macOS and Linux)
brew install int128/kubelogin/kubelogin

# Krew (macOS, Linux, Windows and ARM)
kubectl krew install oidc-login

You need to set up the OIDC provider, cluster role binding, Kubernetes API server and kubeconfig. The kubeconfig looks like:

users:
- name: oidc
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1beta1
      command: kubectl
      args:
      - oidc-login
      - get-token
      - --oidc-issuer-url=ISSUER_URL
      - --oidc-client-id=YOUR_CLIENT_ID
      - --oidc-client-secret=YOUR_CLIENT_SECRET

See setup guide for more.

Run

Run kubectl.

kubectl get pods

Kubectl executes kubelogin before calling the Kubernetes APIs. Kubelogin automatically opens the browser and you can log in to the provider.

After authentication, kubelogin returns the credentials to kubectl and finally kubectl calls the Kubernetes APIs with the credential.

% kubectl get pods
Open http://localhost:8000 for authentication
NAME                          READY   STATUS    RESTARTS   AGE
echoserver-86c78fdccd-nzmd5   1/1     Running   0          26d

Kubelogin writes the ID token and refresh token to the token cache file.

If the cached ID token is valid, kubelogin just returns it. If the cached ID token has expired, kubelogin will refresh the token using the refresh token. If the refresh token has expired, kubelogin will perform reauthentication.

Troubleshoot

You can log out by removing the token cache directory (default ~/.kube/cache/oidc-login). Kubelogin will perform authentication if the token cache file does not exist.

You can dump claims of an ID token by setup command.

% kubectl oidc-login setup --oidc-issuer-url https://accounts.google.com --oidc-client-id REDACTED --oidc-client-secret REDACTED
authentication in progress...

## 2. Verify authentication

You got a token with the following claims:

{
  "sub": "********",
  "iss": "https://accounts.google.com",
  "aud": "********",
  ...
}

You can verify kubelogin works with your provider using acceptance test.

Usage

This document is for the development version. If you are looking for a specific version, see the release tags.

Kubelogin supports the following options:

Usage:
  kubelogin get-token [flags]

Flags:
      --oidc-issuer-url string                          Issuer URL of the provider (mandatory)
      --oidc-client-id string                           Client ID of the provider (mandatory)
      --oidc-client-secret string                       Client secret of the provider
      --oidc-extra-scope strings                        Scopes to request to the provider
      --token-cache-dir string                          Path to a directory for token cache (default "~/.kube/cache/oidc-login")
      --certificate-authority string                    Path to a cert file for the certificate authority
      --certificate-authority-data string               Base64 encoded cert for the certificate authority
      --insecure-skip-tls-verify                        If set, the server's certificate will not be checked for validity. This will make your HTTPS connections insecure
      --grant-type string                               Authorization grant type to use. One of (auto|authcode|authcode-keyboard|password) (default "auto")
      --listen-address strings                          [authcode] Address to bind to the local server. If multiple addresses are set, it will try binding in order (default [127.0.0.1:8000,127.0.0.1:18000])
      --skip-open-browser                               [authcode] Do not open the browser automatically
      --open-url-after-authentication string            [authcode] If set, open the URL in the browser after authentication
      --oidc-redirect-url-hostname string               [authcode] Hostname of the redirect URL (default "localhost")
      --oidc-auth-request-extra-params stringToString   [authcode, authcode-keyboard] Extra query parameters to send with an authentication request (default [])
      --username string                                 [password] Username for resource owner password credentials grant
      --password string                                 [password] Password for resource owner password credentials grant
  -h, --help                                            help for get-token

Global Flags:
      --add_dir_header                   If true, adds the file directory to the header
      --alsologtostderr                  log to standard error as well as files
      --log_backtrace_at traceLocation   when logging hits line file:N, emit a stack trace (default :0)
      --log_dir string                   If non-empty, write log files in this directory
      --log_file string                  If non-empty, use this log file
      --log_file_max_size uint           Defines the maximum size a log file can grow to. Unit is megabytes. If the value is 0, the maximum file size is unlimited. (default 1800)
      --logtostderr                      log to standard error instead of files (default true)
      --skip_headers                     If true, avoid header prefixes in the log messages
      --skip_log_headers                 If true, avoid headers when opening log files
      --stderrthreshold severity         logs at or above this threshold go to stderr (default 2)
  -v, --v Level                          number for the log level verbosity
      --vmodule moduleSpec               comma-separated list of pattern=N settings for file-filtered logging

See also the options of standalone mode.

Extra scopes

You can set the extra scopes to request to the provider by --oidc-extra-scope.

      - --oidc-extra-scope=email
      - --oidc-extra-scope=profile

CA Certificate

You can use your self-signed certificate for the provider.

      - --certificate-authority=/home/user/.kube/keycloak-ca.pem
      - --certificate-authority-data=LS0t...

HTTP Proxy

You can set the following environment variables if you are behind a proxy: HTTP_PROXY, HTTPS_PROXY and NO_PROXY. See also net/http#ProxyFromEnvironment.

Authentication flows

Authorization code flow

Kubelogin performs the authorization code flow by default.

It starts the local server at port 8000 or 18000 by default. You need to register the following redirect URIs to the provider:

• http://localhost:8000
• http://localhost:18000 (used if port 8000 is already in use)

You can change the listening address.

      - --listen-address=127.0.0.1:12345
      - --listen-address=127.0.0.1:23456

You can change the hostname of redirect URI from the default value localhost.

      - --oidc-redirect-url-hostname=127.0.0.1

You can add extra parameters to the authentication request.

      - --oidc-auth-request-extra-params=ttl=86400

When authentication completed, kubelogin shows a message to close the browser. You can change the URL to show after authentication.

      - --open-url-after-authentication=https://example.com/success.html

Authorization code flow with keyboard interactive

If you cannot access the browser, instead use the authorization code flow with keyboard interactive.

      - --grant-type=authcode-keyboard

Kubelogin will show the URL and prompt. Open the URL in the browser and then copy the code shown.

% kubectl get pods
Open https://accounts.google.com/o/oauth2/v2/auth?access_type=offline&client_id=...
Enter code: YOUR_CODE

Note that this flow uses the redirect URI urn:ietf:wg:oauth:2.0:oob and some OIDC providers do not support it.

You can add extra parameters to the authentication request.

      - --oidc-auth-request-extra-params=ttl=86400

Resource owner password credentials grant flow

Kubelogin performs the resource owner password credentials grant flow when --grant-type=password or --username is set.

Note that most OIDC providers do not support this flow. Keycloak supports this flow but you need to explicitly enable the "Direct Access Grants" feature in the client settings.

You can set the username and password.

      - --username=USERNAME
      - --password=PASSWORD

If the password is not set, kubelogin will show the prompt for the password.

      - --username=USERNAME

% kubectl get pods
Password:

If the username is not set, kubelogin will show the prompt for the username and password.

      - --grant-type=password

% kubectl get pods
Username: foo
Password:

Docker

You can run the Docker image instead of the binary. The kubeconfig looks like:

users:
- name: oidc
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1beta1
      command: docker
      args:
      - run
      - --rm
      - -v
      - /tmp/.token-cache:/.token-cache
      - -p
      - 8000:8000
      - quay.io/int128/kubelogin
      - get-token
      - --token-cache-dir=/.token-cache
      - --listen-address=0.0.0.0:8000
      - --oidc-issuer-url=ISSUER_URL
      - --oidc-client-id=YOUR_CLIENT_ID
      - --oidc-client-secret=YOUR_CLIENT_SECRET

Known limitations:

• It cannot open the browser automatically.
• The container port and listen port must be equal for consistency of the redirect URI.

Related works

Kubernetes Dashboard

You can access the Kubernetes Dashboard using kubelogin and kauthproxy.

Contributions

This is an open source software licensed under Apache License 2.0. Feel free to open issues and pull requests for improving code and documents.

Development

Go 1.13 or later is required.

# Run lint and tests
make check

# Compile and run the command
make
./kubelogin

See also the system test.