This page provides an overview of authenticating.
All Kubernetes clusters have two categories of users: service accounts managed by Kubernetes, and normal users.
It is assumed that a cluster-independent service manages normal users in the following ways:
In this regard, Kubernetes does not have objects which represent normal user accounts. Normal users cannot be added to a cluster through an API call.
Even though a normal user cannot be added via an API call, any user that presents a valid certificate signed by the cluster's certificate authority (CA) is considered authenticated. In this configuration, Kubernetes determines the username from the common name field in the 'subject' of the cert (e.g., "/CN=bob"). From there, the role based access control (RBAC) sub-system would determine whether the user is authorized to perform a specific operation on a resource. For more details, refer to the normal users topic in certificate request for more details about this.
In contrast, service accounts are users managed by the Kubernetes API. They are bound to specific namespaces, and created automatically by the API server or manually through API calls. Service accounts are tied to a set of credentials stored as Secrets, which are mounted into pods allowing in-cluster processes to talk to the Kubernetes API.
API requests are tied to either a normal user or a service account, or are treated as anonymous requests. This means every process inside or outside the cluster, from a human user typing kubectl on a workstation, to kubelets on nodes, to members of the control plane, must authenticate when making requests to the API server, or be treated as an anonymous user.
Kubernetes uses client certificates, bearer tokens, or an authenticating proxy to authenticate API requests through authentication plugins. As HTTP requests are made to the API server, plugins attempt to associate the following attributes with the request:
kube-admin or [email protected].system:masters or devops-team.All values are opaque to the authentication system and only hold significance when interpreted by an authorizer.
You can enable multiple authentication methods at once. You should usually use at least two methods:
When multiple authenticator modules are enabled, the first module to successfully authenticate the request short-circuits evaluation. The API server does not guarantee the order authenticators run in.
The system:authenticated group is included in the list of groups for all authenticated users.
Integrations with other authentication protocols (LDAP, SAML, Kerberos, alternate x509 schemes, etc) can be accomplished using an authenticating proxy or the authentication webhook.
Client certificate authentication is enabled by passing the --client-ca-file=SOMEFILE option to API server. The referenced file must contain one or more certificate authorities to use to validate client certificates presented to the API server. If a client certificate is presented and verified, the common name of the subject is used as the user name for the request. As of Kubernetes 1.4, client certificates can also indicate a user's group memberships using the certificate's organization fields. To include multiple group memberships for a user, include multiple organization fields in the certificate.
For example, using the openssl command line tool to generate a certificate signing request:
openssl req -new -key jbeda.pem -out jbeda-csr.pem -subj "/CN=jbeda/O=app1/O=app2"
This would create a CSR for the username "jbeda", belonging to two groups, "app1" and "app2".
See Managing Certificates for how to generate a client cert.
The API server reads bearer tokens from a file when given the --token-auth-file=SOMEFILE option on the command line. Currently, tokens last indefinitely, and the token list cannot be changed without restarting the API server.
The token file is a csv file with a minimum of 3 columns: token, user name, user uid, followed by optional group names.
If you have more than one group the column must be double quoted e.g.
token,user,uid,"group1,group2,group3"
When using bearer token authentication from an http client, the API server expects an Authorization header with a value of Bearer THETOKEN. The bearer token must be a character sequence that can be put in an HTTP header value using no more than the encoding and quoting facilities of HTTP. For example: if the bearer token is 31ada4fd-adec-460c-809a-9e56ceb75269 then it would appear in an HTTP header as shown below.
Authorization: Bearer 31ada4fd-adec-460c-809a-9e56ceb75269
Kubernetes v1.18 [stable] To allow for streamlined bootstrapping for new clusters, Kubernetes includes a dynamically-managed Bearer token type called a Bootstrap Token. These tokens are stored as Secrets in the kube-system namespace, where they can be dynamically managed and created. Controller Manager contains a TokenCleaner controller that deletes bootstrap tokens as they expire.
The tokens are of the form [a-z0-9]{6}.[a-z0-9]{16}. The first component is a Token ID and the second component is the Token Secret. You specify the token in an HTTP header as follows:
Authorization: Bearer 781292.db7bc3a58fc5f07e
You must enable the Bootstrap Token Authenticator with the --enable-bootstrap-token-auth flag on the API Server. You must enable the TokenCleaner controller via the --controllers flag on the Controller Manager. This is done with something like --controllers=*,tokencleaner. kubeadm will do this for you if you are using it to bootstrap a cluster.
The authenticator authenticates as system:bootstrap:<Token ID>. It is included in the system:bootstrappers group. The naming and groups are intentionally limited to discourage users from using these tokens past bootstrapping. The user names and group can be used (and are used by kubeadm) to craft the appropriate authorization policies to support bootstrapping a cluster.
Please see Bootstrap Tokens for in depth documentation on the Bootstrap Token authenticator and controllers along with how to manage these tokens with kubeadm.
A service account is an automatically enabled authenticator that uses signed bearer tokens to verify requests. The plugin takes two optional flags:
--service-account-key-file A file containing a PEM encoded key for signing bearer tokens. If unspecified, the API server's TLS private key will be used.--service-account-lookup If enabled, tokens which are deleted from the API will be revoked.Service accounts are usually created automatically by the API server and associated with pods running in the cluster through the ServiceAccount Admission Controller. Bearer tokens are mounted into pods at well-known locations, and allow in-cluster processes to talk to the API server. Accounts may be explicitly associated with pods using the serviceAccountName field of a PodSpec.
serviceAccountName is usually omitted because this is done automatically. apiVersion: apps/v1 # this apiVersion is relevant as of Kubernetes 1.9
kind: Deployment
metadata:
name: nginx-deployment
namespace: default
spec:
replicas: 3
template:
metadata:
# ...
spec:
serviceAccountName: bob-the-bot
containers:
- name: nginx
image: nginx:1.14.2
Service account bearer tokens are perfectly valid to use outside the cluster and can be used to create identities for long standing jobs that wish to talk to the Kubernetes API. To manually create a service account, use the kubectl create serviceaccount (NAME) command. This creates a service account in the current namespace and an associated secret.
kubectl create serviceaccount jenkins
serviceaccount "jenkins" created
Check an associated secret:
kubectl get serviceaccounts jenkins -o yaml
apiVersion: v1 kind: ServiceAccount metadata: # ... secrets: - name: jenkins-token-1yvwg
The created secret holds the public CA of the API server and a signed JSON Web Token (JWT).
kubectl get secret jenkins-token-1yvwg -o yaml
apiVersion: v1 data: ca.crt: (APISERVER'S CA BASE64 ENCODED) namespace: ZGVmYXVsdA== token: (BEARER TOKEN BASE64 ENCODED) kind: Secret metadata: # ... type: kubernetes.io/service-account-token
The signed JWT can be used as a bearer token to authenticate as the given service account. See above for how the token is included in a request. Normally these secrets are mounted into pods for in-cluster access to the API server, but can be used from outside the cluster as well.
Service accounts authenticate with the username system:serviceaccount:(NAMESPACE):(SERVICEACCOUNT), and are assigned to the groups system:serviceaccounts and system:serviceaccounts:(NAMESPACE).
WARNING: Because service account tokens are stored in secrets, any user with read access to those secrets can authenticate as the service account. Be cautious when granting permissions to service accounts and read capabilities for secrets.
OpenID Connect is a flavor of OAuth2 supported by some OAuth2 providers, notably Azure Active Directory, Salesforce, and Google. The protocol's main extension of OAuth2 is an additional field returned with the access token called an ID Token. This token is a JSON Web Token (JWT) with well known fields, such as a user's email, signed by the server.
To identify the user, the authenticator uses the id_token (not the access_token) from the OAuth2 token response as a bearer token. See above for how the token is included in a request.
access_token, id_token and a refresh_token
kubectl, use your id_token with the --token flag or add it directly to your kubeconfig
kubectl sends your id_token in a header called Authorization to the API serverid_token hasn't expiredkubectl
kubectl provides feedback to the userSince all of the data needed to validate who you are is in the id_token, Kubernetes doesn't need to "phone home" to the identity provider. In a model where every request is stateless this provides a very scalable solution for authentication. It does offer a few challenges:
id_token can't be revoked, it's like a certificate so it should be short-lived (only a few minutes) so it can be very annoying to have to get a new token every few minutes.kubectl proxy command or a reverse proxy that injects the id_token.To enable the plugin, configure the following flags on the API server:
| Parameter | Description | Example | Required |
|---|---|---|---|
--oidc-issuer-url | URL of the provider which allows the API server to discover public signing keys. Only URLs which use the https:// scheme are accepted. This is typically the provider's discovery URL without a path, for example "https://accounts.google.com" or "https://login.salesforce.com". This URL should point to the level below .well-known/openid-configuration | If the discovery URL is https://accounts.google.com/.well-known/openid-configuration, the value should be https://accounts.google.com
| Yes |
--oidc-client-id | A client id that all tokens must be issued for. | kubernetes | Yes |
--oidc-username-claim | JWT claim to use as the user name. By default sub, which is expected to be a unique identifier of the end user. Admins can choose other claims, such as email or name, depending on their provider. However, claims other than email will be prefixed with the issuer URL to prevent naming clashes with other plugins. | sub | No |
--oidc-username-prefix | Prefix prepended to username claims to prevent clashes with existing names (such as system: users). For example, the value oidc: will create usernames like oidc:jane.doe. If this flag isn't provided and --oidc-username-claim is a value other than email the prefix defaults to ( Issuer URL )# where ( Issuer URL ) is the value of --oidc-issuer-url. The value - can be used to disable all prefixing. | oidc: | No |
--oidc-groups-claim | JWT claim to use as the user's group. If the claim is present it must be an array of strings. | groups | No |
--oidc-groups-prefix | Prefix prepended to group claims to prevent clashes with existing names (such as system: groups). For example, the value oidc: will create group names like oidc:engineering and oidc:infra. | oidc: | No |
--oidc-required-claim | A key=value pair that describes a required claim in the ID Token. If set, the claim is verified to be present in the ID Token with a matching value. Repeat this flag to specify multiple claims. | claim=value | No |
--oidc-ca-file | The path to the certificate for the CA that signed your identity provider's web certificate. Defaults to the host's root CAs. | /etc/kubernetes/ssl/kc-ca.pem | No |
Importantly, the API server is not an OAuth2 client, rather it can only be configured to trust a single issuer. This allows the use of public providers, such as Google, without trusting credentials issued to third parties. Admins who wish to utilize multiple OAuth clients should explore providers which support the azp (authorized party) claim, a mechanism for allowing one client to issue tokens on behalf of another.
Kubernetes does not provide an OpenID Connect Identity Provider. You can use an existing public OpenID Connect Identity Provider (such as Google, or others). Or, you can run your own Identity Provider, such as dex, Keycloak, CloudFoundry UAA, or Tremolo Security's OpenUnison.
For an identity provider to work with Kubernetes it must:
A note about requirement #3 above, requiring a CA signed certificate. If you deploy your own identity provider (as opposed to one of the cloud providers like Google or Microsoft) you MUST have your identity provider's web server certificate signed by a certificate with the CA flag set to TRUE, even if it is self signed. This is due to GoLang's TLS client implementation being very strict to the standards around certificate validation. If you don't have a CA handy, you can use this script from the Dex team to create a simple CA and a signed certificate and key pair. Or you can use this similar script that generates SHA256 certs with a longer life and larger key size.
Setup instructions for specific systems:
The first option is to use the kubectl oidc authenticator, which sets the id_token as a bearer token for all requests and refreshes the token once it expires. After you've logged into your provider, use kubectl to add your id_token, refresh_token, client_id, and client_secret to configure the plugin.
Providers that don't return an id_token as part of their refresh token response aren't supported by this plugin and should use "Option 2" below.
kubectl config set-credentials USER_NAME \ --auth-provider=oidc \ --auth-provider-arg=idp-issuer-url=( issuer url ) \ --auth-provider-arg=client-id=( your client id ) \ --auth-provider-arg=client-secret=( your client secret ) \ --auth-provider-arg=refresh-token=( your refresh token ) \ --auth-provider-arg=idp-certificate-authority=( path to your ca certificate ) \ --auth-provider-arg=id-token=( your id_token )
As an example, running the below command after authenticating to your identity provider:
kubectl config set-credentials mmosley \
--auth-provider=oidc \
--auth-provider-arg=idp-issuer-url=https://oidcidp.tremolo.lan:8443/auth/idp/OidcIdP \
--auth-provider-arg=client-id=kubernetes \
--auth-provider-arg=client-secret=1db158f6-177d-4d9c-8a8b-d36869918ec5 \
--auth-provider-arg=refresh-token=q1bKLFOyUiosTfawzA93TzZIDzH2TNa2SMm0zEiPKTUwME6BkEo6Sql5yUWVBSWpKUGphaWpxSVAfekBOZbBhaEW+VlFUeVRGcluyVF5JT4+haZmPsluFoFu5XkpXk5BXqHega4GAXlF+ma+vmYpFcHe5eZR+slBFpZKtQA= \
--auth-provider-arg=idp-certificate-authority=/root/ca.pem \
--auth-provider-arg=id-token=eyJraWQiOiJDTj1vaWRjaWRwLnRyZW1vbG8ubGFuLCBPVT1EZW1vLCBPPVRybWVvbG8gU2VjdXJpdHksIEw9QXJsaW5ndG9uLCBTVD1WaXJnaW5pYSwgQz1VUy1DTj1rdWJlLWNhLTEyMDIxNDc5MjEwMzYwNzMyMTUyIiwiYWxnIjoiUlMyNTYifQ.eyJpc3MiOiJodHRwczovL29pZGNpZHAudHJlbW9sby5sYW46ODQ0My9hdXRoL2lkcC9PaWRjSWRQIiwiYXVkIjoia3ViZXJuZXRlcyIsImV4cCI6MTQ4MzU0OTUxMSwianRpIjoiMm96US15TXdFcHV4WDlHZUhQdy1hZyIsImlhdCI6MTQ4MzU0OTQ1MSwibmJmIjoxNDgzNTQ5MzMxLCJzdWIiOiI0YWViMzdiYS1iNjQ1LTQ4ZmQtYWIzMC0xYTAxZWU0MWUyMTgifQ.w6p4J_6qQ1HzTG9nrEOrubxIMb9K5hzcMPxc9IxPx2K4xO9l-oFiUw93daH3m5pluP6K7eOE6txBuRVfEcpJSwlelsOsW8gb8VJcnzMS9EnZpeA0tW_p-mnkFc3VcfyXuhe5R3G7aa5d8uHv70yJ9Y3-UhjiN9EhpMdfPAoEB9fYKKkJRzF7utTTIPGrSaSU6d2pcpfYKaxIwePzEkT4DfcQthoZdy9ucNvvLoi1DIC-UocFD8HLs8LYKEqSxQvOcvnThbObJ9af71EwmuE21fO5KzMW20KtAeget1gnldOosPtz1G5EwvaQ401-RPQzPGMVBld0_zMCAwZttJ4knw
Which would produce the below configuration:
users:
- name: mmosley
user:
auth-provider:
config:
client-id: kubernetes
client-secret: 1db158f6-177d-4d9c-8a8b-d36869918ec5
id-token: eyJraWQiOiJDTj1vaWRjaWRwLnRyZW1vbG8ubGFuLCBPVT1EZW1vLCBPPVRybWVvbG8gU2VjdXJpdHksIEw9QXJsaW5ndG9uLCBTVD1WaXJnaW5pYSwgQz1VUy1DTj1rdWJlLWNhLTEyMDIxNDc5MjEwMzYwNzMyMTUyIiwiYWxnIjoiUlMyNTYifQ.eyJpc3MiOiJodHRwczovL29pZGNpZHAudHJlbW9sby5sYW46ODQ0My9hdXRoL2lkcC9PaWRjSWRQIiwiYXVkIjoia3ViZXJuZXRlcyIsImV4cCI6MTQ4MzU0OTUxMSwianRpIjoiMm96US15TXdFcHV4WDlHZUhQdy1hZyIsImlhdCI6MTQ4MzU0OTQ1MSwibmJmIjoxNDgzNTQ5MzMxLCJzdWIiOiI0YWViMzdiYS1iNjQ1LTQ4ZmQtYWIzMC0xYTAxZWU0MWUyMTgifQ.w6p4J_6qQ1HzTG9nrEOrubxIMb9K5hzcMPxc9IxPx2K4xO9l-oFiUw93daH3m5pluP6K7eOE6txBuRVfEcpJSwlelsOsW8gb8VJcnzMS9EnZpeA0tW_p-mnkFc3VcfyXuhe5R3G7aa5d8uHv70yJ9Y3-UhjiN9EhpMdfPAoEB9fYKKkJRzF7utTTIPGrSaSU6d2pcpfYKaxIwePzEkT4DfcQthoZdy9ucNvvLoi1DIC-UocFD8HLs8LYKEqSxQvOcvnThbObJ9af71EwmuE21fO5KzMW20KtAeget1gnldOosPtz1G5EwvaQ401-RPQzPGMVBld0_zMCAwZttJ4knw
idp-certificate-authority: /root/ca.pem
idp-issuer-url: https://oidcidp.tremolo.lan:8443/auth/idp/OidcIdP
refresh-token: q1bKLFOyUiosTfawzA93TzZIDzH2TNa2SMm0zEiPKTUwME6BkEo6Sql5yUWVBSWpKUGphaWpxSVAfekBOZbBhaEW+VlFUeVRGcluyVF5JT4+haZmPsluFoFu5XkpXk5BXq
name: oidc
Once your id_token expires, kubectl will attempt to refresh your id_token using your refresh_token and client_secret storing the new values for the refresh_token and id_token in your .kube/config.
--token OptionThe kubectl command lets you pass in a token using the --token option. Copy and paste the id_token into this option:
kubectl --token=eyJhbGciOiJSUzI1NiJ9.eyJpc3MiOiJodHRwczovL21sYi50cmVtb2xvLmxhbjo4MDQzL2F1dGgvaWRwL29pZGMiLCJhdWQiOiJrdWJlcm5ldGVzIiwiZXhwIjoxNDc0NTk2NjY5LCJqdGkiOiI2RDUzNXoxUEpFNjJOR3QxaWVyYm9RIiwiaWF0IjoxNDc0NTk2MzY5LCJuYmYiOjE0NzQ1OTYyNDksInN1YiI6Im13aW5kdSIsInVzZXJfcm9sZSI6WyJ1c2VycyIsIm5ldy1uYW1lc3BhY2Utdmlld2VyIl0sImVtYWlsIjoibXdpbmR1QG5vbW9yZWplZGkuY29tIn0.f2As579n9VNoaKzoF-dOQGmXkFKf1FMyNV0-va_B63jn-_n9LGSCca_6IVMP8pO-Zb4KvRqGyTP0r3HkHxYy5c81AnIh8ijarruczl-TK_yF5akjSTHFZD-0gRzlevBDiH8Q79NAr-ky0P4iIXS8lY9Vnjch5MF74Zx0c3alKJHJUnnpjIACByfF2SCaYzbWFMUNat-K1PaUk5-ujMBG7yYnr95xD-63n8CO8teGUAAEMx6zRjzfhnhbzX-ajwZLGwGUBT4WqjMs70-6a7_8gZmLZb2az1cZynkFRj2BaCkVT3A2RrjeEwZEtGXlMqKJ1_I2ulrOVsYx01_yD35-rw get nodes
Webhook authentication is a hook for verifying bearer tokens.
--authentication-token-webhook-config-file a configuration file describing how to access the remote webhook service.--authentication-token-webhook-cache-ttl how long to cache authentication decisions. Defaults to two minutes.--authentication-token-webhook-version determines whether to use authentication.k8s.io/v1beta1 or authentication.k8s.io/v1 TokenReview objects to send/receive information from the webhook. Defaults to v1beta1.The configuration file uses the kubeconfig file format. Within the file, clusters refers to the remote service and users refers to the API server webhook. An example would be:
# Kubernetes API version
apiVersion: v1
# kind of the API object
kind: Config
# clusters refers to the remote service.
clusters:
- name: name-of-remote-authn-service
cluster:
certificate-authority: /path/to/ca.pem # CA for verifying the remote service.
server: https://authn.example.com/authenticate # URL of remote service to query. 'https' recommended for production.
# users refers to the API server's webhook configuration.
users:
- name: name-of-api-server
user:
client-certificate: /path/to/cert.pem # cert for the webhook plugin to use
client-key: /path/to/key.pem # key matching the cert
# kubeconfig files require a context. Provide one for the API server.
current-context: webhook
contexts:
- context:
cluster: name-of-remote-authn-service
user: name-of-api-server
name: webhook
When a client attempts to authenticate with the API server using a bearer token as discussed above, the authentication webhook POSTs a JSON-serialized TokenReview object containing the token to the remote service.
Note that webhook API objects are subject to the same versioning compatibility rules as other Kubernetes API objects. Implementers should check the apiVersion field of the request to ensure correct deserialization, and must respond with a TokenReview object of the same version as the request.
authentication.k8s.io/v1beta1 token reviews for backwards compatibility. To opt into receiving authentication.k8s.io/v1 token reviews, the API server must be started with --authentication-token-webhook-version=v1. {
"apiVersion": "authentication.k8s.io/v1",
"kind": "TokenReview",
"spec": {
# Opaque bearer token sent to the API server
"token": "014fbff9a07c...",
# Optional list of the audience identifiers for the server the token was presented to.
# Audience-aware token authenticators (for example, OIDC token authenticators)
# should verify the token was intended for at least one of the audiences in this list,
# and return the intersection of this list and the valid audiences for the token in the response status.
# This ensures the token is valid to authenticate to the server it was presented to.
# If no audiences are provided, the token should be validated to authenticate to the Kubernetes API server.
"audiences": ["https://myserver.example.com", "https://myserver.internal.example.com"]
}
}
{
"apiVersion": "authentication.k8s.io/v1beta1",
"kind": "TokenReview",
"spec": {
# Opaque bearer token sent to the API server
"token": "014fbff9a07c...",
# Optional list of the audience identifiers for the server the token was presented to.
# Audience-aware token authenticators (for example, OIDC token authenticators)
# should verify the token was intended for at least one of the audiences in this list,
# and return the intersection of this list and the valid audiences for the token in the response status.
# This ensures the token is valid to authenticate to the server it was presented to.
# If no audiences are provided, the token should be validated to authenticate to the Kubernetes API server.
"audiences": ["https://myserver.example.com", "https://myserver.internal.example.com"]
}
}
The remote service is expected to fill the status field of the request to indicate the success of the login. The response body's spec field is ignored and may be omitted. The remote service must return a response using the same TokenReview API version that it received. A successful validation of the bearer token would return:
{
"apiVersion": "authentication.k8s.io/v1",
"kind": "TokenReview",
"status": {
"authenticated": true,
"user": {
# Required
"username": "[email protected]",
# Optional
"uid": "42",
# Optional group memberships
"groups": ["developers", "qa"],
# Optional additional information provided by the authenticator.
# This should not contain confidential data, as it can be recorded in logs
# or API objects, and is made available to admission webhooks.
"extra": {
"extrafield1": [
"extravalue1",
"extravalue2"
]
}
},
# Optional list audience-aware token authenticators can return,
# containing the audiences from the `spec.audiences` list for which the provided token was valid.
# If this is omitted, the token is considered to be valid to authenticate to the Kubernetes API server.
"audiences": ["https://myserver.example.com"]
}
}
{
"apiVersion": "authentication.k8s.io/v1beta1",
"kind": "TokenReview",
"status": {
"authenticated": true,
"user": {
# Required
"username": "[email protected]",
# Optional
"uid": "42",
# Optional group memberships
"groups": ["developers", "qa"],
# Optional additional information provided by the authenticator.
# This should not contain confidential data, as it can be recorded in logs
# or API objects, and is made available to admission webhooks.
"extra": {
"extrafield1": [
"extravalue1",
"extravalue2"
]
}
},
# Optional list audience-aware token authenticators can return,
# containing the audiences from the `spec.audiences` list for which the provided token was valid.
# If this is omitted, the token is considered to be valid to authenticate to the Kubernetes API server.
"audiences": ["https://myserver.example.com"]
}
}
An unsuccessful request would return:
{
"apiVersion": "authentication.k8s.io/v1",
"kind": "TokenReview",
"status": {
"authenticated": false,
# Optionally include details about why authentication failed.
# If no error is provided, the API will return a generic Unauthorized message.
# The error field is ignored when authenticated=true.
"error": "Credentials are expired"
}
}
{
"apiVersion": "authentication.k8s.io/v1beta1",
"kind": "TokenReview",
"status": {
"authenticated": false,
# Optionally include details about why authentication failed.
# If no error is provided, the API will return a generic Unauthorized message.
# The error field is ignored when authenticated=true.
"error": "Credentials are expired"
}
}
The API server can be configured to identify users from request header values, such as X-Remote-User. It is designed for use in combination with an authenticating proxy, which sets the request header value.
--requestheader-username-headers Required, case-insensitive. Header names to check, in order, for the user identity. The first header containing a value is used as the username.--requestheader-group-headers 1.6+. Optional, case-insensitive. "X-Remote-Group" is suggested. Header names to check, in order, for the user's groups. All values in all specified headers are used as group names.--requestheader-extra-headers-prefix 1.6+. Optional, case-insensitive. "X-Remote-Extra-" is suggested. Header prefixes to look for to determine extra information about the user (typically used by the configured authorization plugin). Any headers beginning with any of the specified prefixes have the prefix removed. The remainder of the header name is lowercased and percent-decoded and becomes the extra key, and the header value is the extra value.For example, with this configuration:
--requestheader-username-headers=X-Remote-User
--requestheader-group-headers=X-Remote-Group
--requestheader-extra-headers-prefix=X-Remote-Extra-
this request:
GET / HTTP/1.1 X-Remote-User: fido X-Remote-Group: dogs X-Remote-Group: dachshunds X-Remote-Extra-Acme.com%2Fproject: some-project X-Remote-Extra-Scopes: openid X-Remote-Extra-Scopes: profile
would result in this user info:
name: fido groups: - dogs - dachshunds extra: acme.com/project: - some-project scopes: - openid - profile
In order to prevent header spoofing, the authenticating proxy is required to present a valid client certificate to the API server for validation against the specified CA before the request headers are checked. WARNING: do not reuse a CA that is used in a different context unless you understand the risks and the mechanisms to protect the CA's usage.
--requestheader-client-ca-file Required. PEM-encoded certificate bundle. A valid client certificate must be presented and validated against the certificate authorities in the specified file before the request headers are checked for user names.--requestheader-allowed-names Optional. List of Common Name values (CNs). If set, a valid client certificate with a CN in the specified list must be presented before the request headers are checked for user names. If empty, any CN is allowed.When enabled, requests that are not rejected by other configured authentication methods are treated as anonymous requests, and given a username of system:anonymous and a group of system:unauthenticated.
For example, on a server with token authentication configured, and anonymous access enabled, a request providing an invalid bearer token would receive a 401 Unauthorized error. A request providing no bearer token would be treated as an anonymous request.
In 1.5.1-1.5.x, anonymous access is disabled by default, and can be enabled by passing the --anonymous-auth=true option to the API server.
In 1.6+, anonymous access is enabled by default if an authorization mode other than AlwaysAllow is used, and can be disabled by passing the --anonymous-auth=false option to the API server. Starting in 1.6, the ABAC and RBAC authorizers require explicit authorization of the system:anonymous user or the system:unauthenticated group, so legacy policy rules that grant access to the * user or * group do not include anonymous users.
A user can act as another user through impersonation headers. These let requests manually override the user info a request authenticates as. For example, an admin could use this feature to debug an authorization policy by temporarily impersonating another user and seeing if a request was denied.
Impersonation requests first authenticate as the requesting user, then switch to the impersonated user info.
The following HTTP headers can be used to performing an impersonation request:
Impersonate-User: The username to act as.Impersonate-Group: A group name to act as. Can be provided multiple times to set multiple groups. Optional. Requires "Impersonate-User".Impersonate-Extra-( extra name ): A dynamic header used to associate extra fields with the user. Optional. Requires "Impersonate-User". In order to be preserved consistently, ( extra name ) should be lower-case, and any characters which aren't legal in HTTP header labels MUST be utf8 and percent-encoded.Impersonate-Uid: A unique identifier that represents the user being impersonated. Optional. Requires "Impersonate-User". Kubernetes does not impose any format requirements on this string.( extra name ) could only contain characters which were legal in HTTP header labels. Impersonate-Uid is only available in versions 1.22.0 and higher. An example of the impersonation headers used when impersonating a user with groups:
Impersonate-User: [email protected] Impersonate-Group: developers Impersonate-Group: admins
An example of the impersonation headers used when impersonating a user with a UID and extra fields:
Impersonate-User: [email protected] Impersonate-Extra-dn: cn=jane,ou=engineers,dc=example,dc=com Impersonate-Extra-acme.com%2Fproject: some-project Impersonate-Extra-scopes: view Impersonate-Extra-scopes: development Impersonate-Uid: 06f6ce97-e2c5-4ab8-7ba5-7654dd08d52b
When using kubectl set the --as flag to configure the Impersonate-User header, set the --as-group flag to configure the Impersonate-Group header.
kubectl drain mynode
Error from server (Forbidden): User "clark" cannot get nodes at the cluster scope. (get nodes mynode)
Set the --as and --as-group flag:
kubectl drain mynode --as=superman --as-group=system:masters
node/mynode cordoned
node/mynode drained
kubectl cannot impersonate extra fields or UIDs. To impersonate a user, group, user identifier (UID) or extra fields, the impersonating user must have the ability to perform the "impersonate" verb on the kind of attribute being impersonated ("user", "group", "uid", etc.). For clusters that enable the RBAC authorization plugin, the following ClusterRole encompasses the rules needed to set user and group impersonation headers:
apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: impersonator rules: - apiGroups: [""] resources: ["users", "groups", "serviceaccounts"] verbs: ["impersonate"]
For impersonation, extra fields and impersonated UIDs are both under the "authentication.k8s.io" apiGroup. Extra fields are evaluated as sub-resources of the resource "userextras". To allow a user to use impersonation headers for the extra field "scopes" and for UIDs, a user should be granted the following role:
apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: scopes-and-uid-impersonator rules: # Can set "Impersonate-Extra-scopes" header and the "Impersonate-Uid" header. - apiGroups: ["authentication.k8s.io"] resources: ["userextras/scopes", "uids"] verbs: ["impersonate"]
The values of impersonation headers can also be restricted by limiting the set of resourceNames a resource can take.
apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: limited-impersonator rules: # Can impersonate the user "[email protected]" - apiGroups: [""] resources: ["users"] verbs: ["impersonate"] resourceNames: ["[email protected]"] # Can impersonate the groups "developers" and "admins" - apiGroups: [""] resources: ["groups"] verbs: ["impersonate"] resourceNames: ["developers","admins"] # Can impersonate the extras field "scopes" with the values "view" and "development" - apiGroups: ["authentication.k8s.io"] resources: ["userextras/scopes"] verbs: ["impersonate"] resourceNames: ["view", "development"] # Can impersonate the uid "06f6ce97-e2c5-4ab8-7ba5-7654dd08d52b" - apiGroups: ["authentication.k8s.io"] resources: ["uids"] verbs: ["impersonate"] resourceNames: ["06f6ce97-e2c5-4ab8-7ba5-7654dd08d52b"]
Kubernetes v1.22 [stable] k8s.io/client-go and tools using it such as kubectl and kubelet are able to execute an external command to receive user credentials.
This feature is intended for client side integrations with authentication protocols not natively supported by k8s.io/client-go (LDAP, Kerberos, OAuth2, SAML, etc.). The plugin implements the protocol specific logic, then returns opaque credentials to use. Almost all credential plugin use cases require a server side component with support for the webhook token authenticator to interpret the credential format produced by the client plugin.
In a hypothetical use case, an organization would run an external service that exchanges LDAP credentials for user specific, signed tokens. The service would also be capable of responding to webhook token authenticator requests to validate the tokens. Users would be required to install a credential plugin on their workstation.
To authenticate against the API:
kubectl command.TokenReview to the external service.Credential plugins are configured through kubectl config files as part of the user fields.
apiVersion: v1
kind: Config
users:
- name: my-user
user:
exec:
# Command to execute. Required.
command: "example-client-go-exec-plugin"
# API version to use when decoding the ExecCredentials resource. Required.
#
# The API version returned by the plugin MUST match the version listed here.
#
# To integrate with tools that support multiple versions (such as client.authentication.k8s.io/v1alpha1),
# set an environment variable, pass an argument to the tool that indicates which version the exec plugin expects,
# or read the version from the ExecCredential object in the KUBERNETES_EXEC_INFO environment variable.
apiVersion: "client.authentication.k8s.io/v1"
# Environment variables to set when executing the plugin. Optional.
env:
- name: "FOO"
value: "bar"
# Arguments to pass when executing the plugin. Optional.
args:
- "arg1"
- "arg2"
# Text shown to the user when the executable doesn't seem to be present. Optional.
installHint: |
example-client-go-exec-plugin is required to authenticate
to the current cluster. It can be installed:
On macOS: brew install example-client-go-exec-plugin
On Ubuntu: apt-get install example-client-go-exec-plugin
On Fedora: dnf install example-client-go-exec-plugin
...
# Whether or not to provide cluster information, which could potentially contain
# very large CA data, to this exec plugin as a part of the KUBERNETES_EXEC_INFO
# environment variable.
provideClusterInfo: true
# The contract between the exec plugin and the standard input I/O stream. If the
# contract cannot be satisfied, this plugin will not be run and an error will be
# returned. Valid values are "Never" (this exec plugin never uses standard input),
# "IfAvailable" (this exec plugin wants to use standard input if it is available),
# or "Always" (this exec plugin requires standard input to function). Required.
interactiveMode: Never
clusters:
- name: my-cluster
cluster:
server: "https://172.17.4.100:6443"
certificate-authority: "/etc/kubernetes/ca.pem"
extensions:
- name: client.authentication.k8s.io/exec # reserved extension name for per cluster exec config
extension:
arbitrary: config
this: can be provided via the KUBERNETES_EXEC_INFO environment variable upon setting provideClusterInfo
you: ["can", "put", "anything", "here"]
contexts:
- name: my-cluster
context:
cluster: my-cluster
user: my-user
current-context: my-cluster
apiVersion: v1
kind: Config
users:
- name: my-user
user:
exec:
# Command to execute. Required.
command: "example-client-go-exec-plugin"
# API version to use when decoding the ExecCredentials resource. Required.
#
# The API version returned by the plugin MUST match the version listed here.
#
# To integrate with tools that support multiple versions (such as client.authentication.k8s.io/v1alpha1),
# set an environment variable, pass an argument to the tool that indicates which version the exec plugin expects,
# or read the version from the ExecCredential object in the KUBERNETES_EXEC_INFO environment variable.
apiVersion: "client.authentication.k8s.io/v1beta1"
# Environment variables to set when executing the plugin. Optional.
env:
- name: "FOO"
value: "bar"
# Arguments to pass when executing the plugin. Optional.
args:
- "arg1"
- "arg2"
# Text shown to the user when the executable doesn't seem to be present. Optional.
installHint: |
example-client-go-exec-plugin is required to authenticate
to the current cluster. It can be installed:
On macOS: brew install example-client-go-exec-plugin
On Ubuntu: apt-get install example-client-go-exec-plugin
On Fedora: dnf install example-client-go-exec-plugin
...
# Whether or not to provide cluster information, which could potentially contain
# very large CA data, to this exec plugin as a part of the KUBERNETES_EXEC_INFO
# environment variable.
provideClusterInfo: true
# The contract between the exec plugin and the standard input I/O stream. If the
# contract cannot be satisfied, this plugin will not be run and an error will be
# returned. Valid values are "Never" (this exec plugin never uses standard input),
# "IfAvailable" (this exec plugin wants to use standard input if it is available),
# or "Always" (this exec plugin requires standard input to function). Optional.
# Defaults to "IfAvailable".
interactiveMode: Never
clusters:
- name: my-cluster
cluster:
server: "https://172.17.4.100:6443"
certificate-authority: "/etc/kubernetes/ca.pem"
extensions:
- name: client.authentication.k8s.io/exec # reserved extension name for per cluster exec config
extension:
arbitrary: config
this: can be provided via the KUBERNETES_EXEC_INFO environment variable upon setting provideClusterInfo
you: ["can", "put", "anything", "here"]
contexts:
- name: my-cluster
context:
cluster: my-cluster
user: my-user
current-context: my-cluster
Relative command paths are interpreted as relative to the directory of the config file. If KUBECONFIG is set to /home/jane/kubeconfig and the exec command is ./bin/example-client-go-exec-plugin, the binary /home/jane/bin/example-client-go-exec-plugin is executed.
- name: my-user
user:
exec:
# Path relative to the directory of the kubeconfig
command: "./bin/example-client-go-exec-plugin"
apiVersion: "client.authentication.k8s.io/v1"
interactiveMode: Never
The executed command prints an ExecCredential object to stdout. k8s.io/client-go authenticates against the Kubernetes API using the returned credentials in the status. The executed command is passed an ExecCredential object as input via the KUBERNETES_EXEC_INFO environment variable. This input contains helpful information like the expected API version of the returned ExecCredential object and whether or not the plugin can use stdin to interact with the user.
When run from an interactive session (i.e., a terminal), stdin can be exposed directly to the plugin. Plugins should use the spec.interactive field of the input ExecCredential object from the KUBERNETES_EXEC_INFO environment variable in order to determine if stdin has been provided. A plugin's stdin requirements (i.e., whether stdin is optional, strictly required, or never used in order for the plugin to run successfully) is declared via the user.exec.interactiveMode field in the kubeconfig (see table below for valid values). The user.exec.interactiveMode field is optional in client.authentication.k8s.io/v1beta1 and required in client.authentication.k8s.io/v1.
interactiveMode Value | Meaning |
|---|---|
Never | This exec plugin never needs to use standard input, and therefore the exec plugin will be run regardless of whether standard input is available for user input. |
IfAvailable | This exec plugin would like to use standard input if it is available, but can still operate if standard input is not available. Therefore, the exec plugin will be run regardless of whether stdin is available for user input. If standard input is available for user input, then it will be provided to this exec plugin. |
Always | This exec plugin requires standard input in order to run, and therefore the exec plugin will only be run if standard input is available for user input. If standard input is not available for user input, then the exec plugin will not be run and an error will be returned by the exec plugin runner. |
To use bearer token credentials, the plugin returns a token in the status of the ExecCredential
{
"apiVersion": "client.authentication.k8s.io/v1",
"kind": "ExecCredential",
"status": {
"token": "my-bearer-token"
}
}
{
"apiVersion": "client.authentication.k8s.io/v1beta1",
"kind": "ExecCredential",
"status": {
"token": "my-bearer-token"
}
}
Alternatively, a PEM-encoded client certificate and key can be returned to use TLS client auth. If the plugin returns a different certificate and key on a subsequent call, k8s.io/client-go will close existing connections with the server to force a new TLS handshake.
If specified, clientKeyData and clientCertificateData must both must be present.
clientCertificateData may contain additional intermediate certificates to send to the server.
{
"apiVersion": "client.authentication.k8s.io/v1",
"kind": "ExecCredential",
"status": {
"clientCertificateData": "-----BEGIN CERTIFICATE-----\n...\n-----END CERTIFICATE-----",
"clientKeyData": "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----"
}
}
{
"apiVersion": "client.authentication.k8s.io/v1beta1",
"kind": "ExecCredential",
"status": {
"clientCertificateData": "-----BEGIN CERTIFICATE-----\n...\n-----END CERTIFICATE-----",
"clientKeyData": "-----BEGIN RSA PRIVATE KEY-----\n...\n-----END RSA PRIVATE KEY-----"
}
}
Optionally, the response can include the expiry of the credential formatted as a RFC3339 timestamp. Presence or absence of an expiry has the following impact:
{
"apiVersion": "client.authentication.k8s.io/v1",
"kind": "ExecCredential",
"status": {
"token": "my-bearer-token",
"expirationTimestamp": "2018-03-05T17:30:20-08:00"
}
}
{
"apiVersion": "client.authentication.k8s.io/v1beta1",
"kind": "ExecCredential",
"status": {
"token": "my-bearer-token",
"expirationTimestamp": "2018-03-05T17:30:20-08:00"
}
}
To enable the exec plugin to obtain cluster-specific information, set provideClusterInfo on the user.exec field in the kubeconfig. The plugin will then be supplied this cluster-specific information in the KUBERNETES_EXEC_INFO environment variable. Information from this environment variable can be used to perform cluster-specific credential acquisition logic. The following ExecCredential manifest describes a cluster information sample.
{
"apiVersion": "client.authentication.k8s.io/v1",
"kind": "ExecCredential",
"spec": {
"cluster": {
"server": "https://172.17.4.100:6443",
"certificate-authority-data": "LS0t...",
"config": {
"arbitrary": "config",
"this": "can be provided via the KUBERNETES_EXEC_INFO environment variable upon setting provideClusterInfo",
"you": ["can", "put", "anything", "here"]
}
},
"interactive": true
}
}
{
"apiVersion": "client.authentication.k8s.io/v1beta1",
"kind": "ExecCredential",
"spec": {
"cluster": {
"server": "https://172.17.4.100:6443",
"certificate-authority-data": "LS0t...",
"config": {
"arbitrary": "config",
"this": "can be provided via the KUBERNETES_EXEC_INFO environment variable upon setting provideClusterInfo",
"you": ["can", "put", "anything", "here"]
}
},
"interactive": true
}
}
© 2022 The Kubernetes Authors
Documentation Distributed under CC BY 4.0.
https://kubernetes.io/docs/reference/access-authn-authz/authentication