72 lines
3.5 KiB
Markdown
72 lines
3.5 KiB
Markdown
# 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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This integration is implemented using a credential exchange API which takes as
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input a credential from the external IDP (or internal federation trust
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relationship) and returns a credential which is understood by the host
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Kubernetes cluster. To learn more about this integration, see [Cluster
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Integration Strategies](#cluster-integration-strategies).
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<img src="img/pinniped_architecture.svg" alt="Pinniped Architecture Sketch" width="300px"/>
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## External Identity Provider Integrations
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Pinniped will consume identity from one or more external identity providers
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(IDPs). Administrators will configure external IDPs via [Kubernetes custom
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resources](https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/),
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allowing Pinniped to be managed using GitOps and standard Kubernetes tools.
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IDP integration support will be driven by empirical use case.
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IDPs that support only just-in-time flows (such as OIDC) can be optionally
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paired with a separate directory backend to enable directory-based flows such as
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first-class support for policy editing UX.
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### Supported External Identity Provider Types
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The currently supported external IDP types are outlined here. More will be added
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in the future.
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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](../cmd/local-user-authenticator/main.go).
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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 near term, cluster integrations will happen via different
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cluster-specific flows depending on the type of cluster. 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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### Supported Cluster Integration Strategies
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The currently supported cluster integration strategies are outlined here. More
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will be added in the future.
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1. 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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## `kubectl` Integration
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With any of the above IDPs and 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](generated).
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## Example Cluster Authentication Sequence Diagram
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