Merge pull request #1444 from spotify/rugvip/authdocs
docs/auth: add some more information about Identities
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# User Authentication and Authorization in Backstage
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## Summary
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The purpose of the Auth APIs in Backstage are to identify the user, and to
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provide a way for plugins to request access to 3rd party services on behalf of
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the user (OAuth). This documentation focuses on the implementation of that
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solution and how to extend it. For documentation on how to consume the Auth APIs
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in a plugin, see [TODO](#TODO).
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### Accessing Third Party Services
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The main pattern for talking to third party services in Backstage is
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user-to-server requests, where short-lived OAuth Access Tokens are requested by
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plugins to authenticate calls to external services. These calls can be made
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either directly to the services or through a backend plugin or service.
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By relying on user-to-server calls we keep the coupling between the frontend and
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backend low, and provide a much lower barrier for plugins to make use of third
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party services. This is in comparison to for example a session-based system,
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where access tokens are stored server-side. Such a solution would require a much
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deeper coupling between the auth backend plugin, its session storage, and other
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backend plugins or separate services. A goal of Backstage is to make it as easy
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as possible to create new plugins, and an auth solution based on user-to-server
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OAuth helps in that regard.
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The method with which frontend plugins request access to third party services is
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through [Utility APIs](../getting-started/utility-apis.md) for each service
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provider. For a full list of providers, see [TODO](#TODO).
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### Identity - WIP
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Identity management is still work in progress, but there are already a couple of
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pieces in place that can be used.
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#### Identity for Plugin Developers
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As a plugin developer, there are two main touchpoints for identities: the
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`IdentityApi` exported by `@backstage/core` via the `identityApiRef`, and a not
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yet existing middleware exported by `@backstage/backend-common`.
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The `IdentityApi` gives access to the signed-in user's identity in the frontend.
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It provides access to the user's ID, lightweight profile information, and an ID
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token used to make authenticated calls within Backstage.
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The middleware that will be provided by `@backstage/backend-common` allows
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verification of Backstage ID tokens, and optionally loading additional
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information about the user. The progress is tracked in
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https://github.com/spotify/backstage/issues/1435.
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#### Identity for App Developers
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If you're setting up your own Backstage app, or want to add a new identity
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provider, there are three touchpoints: the frontend auth APIs in
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`@backstage/core-api`, the backend auth providers in `auth-backend`, and the
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`SignInPage` component configured in the Backstage app via `createApp`.
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The frontend APIs and backend providers are tightly coupled together for each
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auth provider, and together they implement an e2e auth flow. Only some auth
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providers also act as identity providers though. For example, at the moment of
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writing, the Google Auth provider is able to act as a Backstage identity
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provider, but the GitHub one can not. For an auth provider to also act as an
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identity provider, it needs to implement the `BackstageIdentityApi` in the
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frontend, and in the backend it needs to return a `BackstageIdentity` structure.
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It is up to each provider to implement the mapping between a provider identity
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and the corresponding Backstage identity. That is currently still work in
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progress, and as a stop-gap for example the Google provider returns the local
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part of the user's email as the user ID.
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The final piece of the puzzle is the `SignInPage` component that can be
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configured as part of the app. Without a sign-in page, Backstage will fall back
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to a `guest` identity for all users, without any ID token. To enable sign-in, a
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`SignInPage` needs to be configured, which in turn has to supply a user to the
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app. The `@backstage/core` package provides a basic sign-in page that allows
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both the user and the app developer to choose between a couple of different
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sign-in methods.
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## Further Reading
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More details are provided in dedicated sections of the documentation.
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- [OAuth](./oauth): Description of the generic OAuth flow implemented by the
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[auth-backend](../../plugins/auth-backend).
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- [Glossary](./glossary): Glossary of some common terms related to the auth
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flows.
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@@ -1,44 +0,0 @@
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# User Authentication and Authorization in Backstage
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## Summary
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The purpose of the Auth APIs in Backstage are to identify the user, and to
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provide a way for plugins to request access to 3rd party services on behalf of
|
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the user (OAuth). This documentation focuses on the implementation of that
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solution and how to extend it. For documentation on how to consume the Auth APIs
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in a plugin, see [TODO](#TODO).
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### Accessing Third Party Services
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||||
|
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The main pattern for talking to third party services in Backstage is
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user-to-server requests, where short-lived OAuth Access Tokens are requested by
|
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plugins to authenticate calls to external services. These calls can be made
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either directly to the services or through a backend plugin or service.
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|
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By relying on user-to-server calls we keep the coupling between the frontend and
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backend low, and provide a much lower barrier for plugins to make use of third
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party services. This is in comparison to for example a session-based system,
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where access tokens are stored server-side. Such a solution would require a much
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deeper coupling between the auth backend plugin, its session storage, and other
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backend plugins or separate services. A goal of Backstage is to make it as easy
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as possible to create new plugins, and an auth solution based on user-to-server
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OAuth helps in that regard.
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The method with which frontend plugins request access to third party services is
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through [Utility APIs](../getting-started/utility-apis.md) for each service
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provider. For a full list of providers, see [TODO](#TODO).
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### Identity - TODO
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This documentation currently only covers the OAuth use-case, as identity
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management is not settled yet and part of an
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[upcoming milestone](https://github.com/spotify/backstage/milestone/12).
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## Further Reading
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More details are provided in dedicated sections of the documentation.
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- [OAuth](./oauth): Description of the generic OAuth flow implemented by the
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[auth-backend](../../plugins/auth-backend).
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- [Glossary](./glossary): Glossary of some common terms related to the auth
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flows.
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