170 lines
8.4 KiB
Markdown
170 lines
8.4 KiB
Markdown
---
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title: "Pinniped Architecture"
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cascade:
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layout: docs
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---
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# Architecture
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The principal purpose of Pinniped is to allow users to access Kubernetes
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clusters. Pinniped hopes to enable this access across a wide range of Kubernetes
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environments with zero configuration.
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Pinniped is composed of two parts.
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1. The Pinniped Supervisor is an OIDC server which allows users to authenticate
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with an external identity provider (IDP), and then issues its own federation ID tokens
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to be passed on to clusters based on the user information from the IDP.
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1. The Pinniped Concierge is a credential exchange API which takes as input a
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credential from an identity source (e.g., Pinniped Supervisor, proprietary IDP),
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authenticates the user via that credential, and returns another credential which is
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understood by the host Kubernetes cluster.
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Pinniped supports various authenticator types and OIDC identity providers and implements different integration strategies
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for various Kubernetes distributions to make authentication possible.
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## Supported Kubernetes Cluster Types
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Pinniped supports the following types of Kubernetes clusters:
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- Clusters where the Kube Controller Manager pod is accessible from Pinniped's pods.
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Support for other types of Kubernetes distributions is coming soon.
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## External Identity Provider Integrations
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The Pinniped Supervisor will federate identity from one or more IDPs.
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Administrators will configure the Pinniped Supervisor to use IDPs via Kubernetes
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custom resources allowing Pinniped to be managed using GitOps and standard
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Kubernetes tools.
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Pinniped supports the following IDPs.
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1. Any [OIDC-compliant](https://openid.net/specs/openid-connect-core-1_0.html)
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identity provider (e.g., [Dex](https://github.com/dexidp/dex),
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[Okta](https://www.okta.com/)).
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The
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[`idp.supervisor.pinniped.dev`](https://github.com/vmware-tanzu/pinniped/blob/main/generated/1.19/README.adoc#k8s-api-idp-supervisor-pinniped-dev-v1alpha1)
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API group contains the Kubernetes custom resources that configure the Pinniped
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Supervisor's upstream IDPs.
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More IDP integrations are coming soon.
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## Authenticators
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The Pinniped Concierge requires one or more **authenticators** to validate external credentials in order to
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issue cluster specific credentials.
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Administrators will configure authenticators via Kubernetes custom
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resources allowing Pinniped to be managed using GitOps and standard Kubernetes tools.
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Pinniped supports the following authenticator types.
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1. Any webhook which implements the
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[Kubernetes TokenReview API](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#webhook-token-authentication).
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In addition to allowing the integration of any existing IDP which implements this API, webhooks also
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serve as an extension point for Pinniped by allowing for integration of arbitrary custom authenticators.
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While a custom implementation may be in any language or framework, this project provides a
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sample implementation in Golang. See the `ServeHTTP` method of
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[cmd/local-user-authenticator/main.go](https://github.com/vmware-tanzu/pinniped/blob/main/cmd/local-user-authenticator/main.go).
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1. A JSON Web Token (JWT) authenticator, which will validate and parse claims
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from JWTs. This can be used to validate tokens that are issued by the
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Pinniped Supervisor, any
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[OIDC-compliant](https://openid.net/specs/openid-connect-core-1_0.html)
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identity provider, or various other identity sources. The JWT authenticator
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provides the same functionality as the [Kubernetes OIDC authentication
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mechanism](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#openid-connect-tokens),
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but it is configurable at cluster runtime instead of requiring flags to be
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set on the `kube-apiserver` process.
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The
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[`authentication.concierge.pinniped.dev`](https://github.com/vmware-tanzu/pinniped/blob/main/generated/1.19/README.adoc#k8s-api-authentication-concierge-pinniped-dev-v1alpha1)
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API group contains the Kubernetes custom resources that configure the Pinniped
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Concierge's authenticators.
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## Cluster Integration Strategies
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Pinniped will issue a cluster credential by leveraging cluster-specific
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functionality. In the longer term,
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Pinniped hopes to contribute and leverage upstream Kubernetes extension points that
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cleanly enable this integration.
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Pinniped supports the following cluster integration strategies.
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* Pinniped hosts a credential exchange API endpoint via a Kubernetes aggregated API server.
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This API returns a new cluster-specific credential using the cluster's signing keypair to
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issue short-lived cluster certificates. (In the future, when the Kubernetes CSR API
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provides a way to issue short-lived certificates, then the Pinniped credential exchange API
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will use that instead of using the cluster's signing keypair.)
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More cluster integration strategies are coming soon, which will allow Pinniped to
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support more Kubernetes cluster types.
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## kubectl Integration
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With any of the above IDPs, authentication methods, and cluster integration strategies, `kubectl` commands receive the
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cluster-specific credential via a
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[Kubernetes client-go credential plugin](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#client-go-credential-plugins).
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Users may use the Pinniped CLI as the credential plugin, or they may use any proprietary CLI
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built with the [Pinniped Go client library](https://github.com/vmware-tanzu/pinniped/tree/main/generated).
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## Pinniped Deployment Strategies
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Pinniped can be configured to authenticate users in a variety of scenarios.
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Depending on the use case, administrators can deploy the Supervisor, the Concierge,
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both, or neither.
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### Full Integration-- Concierge, Supervisor, and CLI
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Users can authenticate with the help of the Supervisor, which will issue tokens that
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can be exchanged at the Concierge for a credential that is understood by the host Kubernetes
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cluster.
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The Supervisor enables users to log in to their external identity provider
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once per day and access each cluster in a domain with a distinct scoped-down token.
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The diagram below shows the components involved in the login flow when both the Concierge
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and Supervisor are configured.
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The diagram below demonstrates using `kubectl get pods` with the Pinniped CLI
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functioning as a [Kubernetes client-go credential plugin](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#client-go-credential-plugins)
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that obtains a federation ID token from the Pinniped Supervisor to be sent to a
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JWT authenticator via the Pinniped Concierge.
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### Dynamic Cluster Authentication-- Concierge and CLI
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Users can authenticate directly with their OIDC compliant external identity provider to get credentials which
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can be exchanged at the Concierge for a credential that is understood by the host Kubernetes
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cluster.
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The diagram below shows the components involved in the login flow when the Concierge is
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configured.
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The diagram below demonstrates using `kubectl get pods` with a [Kubernetes client-go credential plugin](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#client-go-credential-plugins)
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that obtains an external credential to be sent to a webhook authenticator via the Pinniped Concierge.
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### Static Cluster Integration-- Supervisor and CLI
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Users can authenticate with the help of the Supervisor, which will issue tokens that
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can be given directly to a Kubernetes API Server that has been configured with
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[OIDC Authentication.](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#openid-connect-tokens)
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The Supervisor enables users to log in to their external identity provider
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once per day and access each cluster in a domain with a distinct scoped-down token.
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### Minimal-- CLI only
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Users can authenticate directly with their OIDC compliant external identity provider to get credentials
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that can be given directly to a Kubernetes API Server that has been configured with
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[OIDC Authentication.](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#openid-connect-tokens)
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