179 lines
6.1 KiB
Plaintext
179 lines
6.1 KiB
Plaintext
---
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layout: docs
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page_title: Kubernetes - Auth Methods
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description: |-
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The Kubernetes auth method allows automated authentication of Kubernetes
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Service Accounts.
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---
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# Kubernetes Auth Method
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The `kubernetes` auth method can be used to authenticate with Vault using a
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Kubernetes Service Account Token. This method of authentication makes it easy to
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introduce a Vault token into a Kubernetes Pod.
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## Authentication
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### Via the CLI
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The default path is `/kubernetes`. If this auth method was enabled at a
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different path, specify `-path=/my-path` in the CLI.
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```shell-session
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$ vault write auth/kubernetes/login role=demo jwt=...
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```
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### Via the API
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The default endpoint is `auth/kubernetes/login`. If this auth method was enabled
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at a different path, use that value instead of `kubernetes`.
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```shell-session
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$ curl \
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--request POST \
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--data '{"jwt": "<your service account jwt>", "role": "demo"}' \
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http://127.0.0.1:8200/v1/auth/kubernetes/login
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```
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The response will contain a token at `auth.client_token`:
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```json
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{
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"auth": {
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"client_token": "38fe9691-e623-7238-f618-c94d4e7bc674",
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"accessor": "78e87a38-84ed-2692-538f-ca8b9f400ab3",
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"policies": ["default"],
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"metadata": {
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"role": "demo",
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"service_account_name": "vault-auth",
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"service_account_namespace": "default",
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"service_account_secret_name": "vault-auth-token-pd21c",
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"service_account_uid": "aa9aa8ff-98d0-11e7-9bb7-0800276d99bf"
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},
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"lease_duration": 2764800,
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"renewable": true
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}
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}
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```
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## Configuration
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Auth methods must be configured in advance before users or machines can
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authenticate. These steps are usually completed by an operator or configuration
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management tool.
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1. Enable the Kubernetes auth method:
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```text
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$ vault auth enable kubernetes
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```
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1. Use the `/config` endpoint to configure Vault to talk to Kubernetes. Use `kubectl cluster-info` to validate the Kubernetes host address and TCP port. Kubernetes 1.21+ clusters may require setting the service account `issuer`, [as described here](/docs/auth/kubernetes#discovering-the-service-account-issuer). For the list of available configuration options, please see the [API documentation](/api/auth/kubernetes).
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```text
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$ vault write auth/kubernetes/config \
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token_reviewer_jwt="<your reviewer service account JWT>" \
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kubernetes_host=https://192.168.99.100:<your TCP port or blank for 443> \
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kubernetes_ca_cert=@ca.crt
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```
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!> **NOTE:** The pattern Vault uses to authenticate Pods depends on sharing
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the JWT token over the network. Given the [security model of
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Vault](/docs/internals/security), this is allowable because Vault is
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part of the trusted compute base. In general, Kubernetes applications should
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**not** share this JWT with other applications, as it allows API calls to be
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made on behalf of the Pod and can result in unintended access being granted
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to 3rd parties.
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1. Create a named role:
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```text
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vault write auth/kubernetes/role/demo \
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bound_service_account_names=vault-auth \
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bound_service_account_namespaces=default \
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policies=default \
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ttl=1h
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```
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This role authorizes the "vault-auth" service account in the default
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namespace and it gives it the default policy.
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For the complete list of configuration options, please see the [API
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documentation](/api/auth/kubernetes).
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### Discovering the service account `issuer`
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Kubernetes 1.21+ clusters may require setting the service account
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[`issuer`](/api-docs/auth/kubernetes#issuer) to the same value as
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`kube-apiserver`'s `--service-account-issuer` flag. This is because the service
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account JWTs for these clusters may have an issuer specific to the cluster
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itself, instead of the old default of `kubernetes/serviceaccount`. If you are
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unable to check this value directly, you can run the following and look for the
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`"iss"` field to find the required value:
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```bash
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kubectl proxy &
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curl --silent http://127.0.0.1:8001/api/v1/namespaces/default/serviceaccounts/default/token \
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-H "Content-Type: application/json" \
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-X POST \
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-d '{"apiVersion": "authentication.k8s.io/v1", "kind": "TokenRequest"}' \
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| jq -r '.status.token' \
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| cut -d. -f2 \
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| base64 -D
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```
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Most clusters will also have that information available at the
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`.well-known/openid-configuration` endpoint:
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```bash
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kubectl proxy &
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curl --silent http://127.0.0.1:8001/.well-known/openid-configuration | jq -r .issuer
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```
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This value is then used when configuring Kubernetes auth, e.g.:
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```bash
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vault write auth/kubernetes/config \
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token_reviewer_jwt="$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)" \
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kubernetes_host="https://$KUBERNETES_PORT_443_TCP_ADDR:443" \
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kubernetes_ca_cert=@/var/run/secrets/kubernetes.io/serviceaccount/ca.crt \
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issuer="\"test-aks-cluster-dns-d6cbb78e.hcp.uksouth.azmk8s.io\""
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```
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## Configuring Kubernetes
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This auth method accesses the [Kubernetes TokenReview API][k8s-tokenreview] to
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validate the provided JWT is still valid. Kubernetes should be running with
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`--service-account-lookup`. This is defaulted to true in Kubernetes 1.7, but any
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versions prior should ensure the Kubernetes API server is started with this
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setting. Otherwise deleted tokens in Kubernetes will not be properly revoked and
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will be able to authenticate to this auth method.
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Service Accounts used in this auth method will need to have access to the
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TokenReview API. If Kubernetes is configured to use RBAC roles, the Service
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Account should be granted permissions to access this API. The following
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example ClusterRoleBinding could be used to grant these permissions:
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```yaml
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apiVersion: rbac.authorization.k8s.io/v1beta1
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kind: ClusterRoleBinding
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metadata:
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name: role-tokenreview-binding
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namespace: default
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roleRef:
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apiGroup: rbac.authorization.k8s.io
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kind: ClusterRole
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name: system:auth-delegator
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subjects:
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- kind: ServiceAccount
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name: vault-auth
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namespace: default
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```
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## API
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The Kubernetes Auth Plugin has a full HTTP API. Please see the
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[API docs](/api/auth/kubernetes) for more details.
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[k8s-tokenreview]: https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.19/#tokenreview-v1beta1-authentication-k8s-io
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