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docs: Add OIDC section
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Patrik Oldsberg
2022-10-06 16:28:26 +02:00
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---
id: oidc
title: OIDC provider from scratch
description: This section shows how to use an OIDC provider from scratch, same steps apply for custom providers.
---
This section shows how to use an OIDC provider from scratch, same steps apply for custom
providers. Please note these steps are for using a provider, not how to implement one,
and Backstage recommends creating custom providers specific to the IDP, so we'll use a
`azureOIDC` provider throughout this example, feel free to change any of those refs
to your provider name.
## Summary
To add providers not enabled by default like OIDC, we need to follow some steps, we
assume you already have a sign in page to which we'll add the provider so users can
sign in through the provider. In simple steps here's how you enable the provider:
- Create an API reference to identify the provider.
- Create the API factory that will handle the authentication.
- Add or reuse an auth provider so you can authenticate.
- Add or reuse a resolver to handle the result from the authentication.
- Configure the provider to access your 3rd party auth solution.
- Add the provider to sign in page so users can login with it.
We'll explain each step more in detail next.
### The API reference
An API reference exist for the sake of **Dependency Injection**, check [Utility APIs][4]
for extended explanation.
In this OIDC example, we'll create the API reference directly in the
`packages/app/src/apis.ts` file, it is not a requirement to put the reference in this
file. Any location will do as long as it's available to be imported to where the API
factory is, as well as easily accessible to the rest of the application so any package
and plugin can inject the API instance when necessary.
An example of such would be when you use an auth provider from a library installed with
NPM, or any other library repository, you would import the API ref from the library.
```ts
export const azureOIDCAuthApiRef: ApiRef<
OpenIdConnectApi & ProfileInfoApi & BackstageIdentityApi & SessionApi
> = createApiRef({
id: 'auth.my-custom-provider',
});
```
Please note a few things, the ID can be anything you want as long as it doesn't conflict
with other refs, backstage recommends to use a custom name that references your custom
provider, for example we are using OIDC protocol with Azure, so we could use something
like `auth.azure.oidc` as well.
Also we're exporting this reference, as well as the `typings`, we need to
be able to import this reference anywhere in the app, and the `typings` will tell typescript
what instance we're getting from DI when injecting the API. In this case we are defining
an API for authentication, so we tell TS that this instance complies with 4 API
interfaces:
- The OICD API that will handle authentication.
- Profile API for requesting user profile info from the auth provider in question.
- Backstage identity API to handle and associate the user profile with backstage identity.
- Session API, to handle the session the user will have while logged in.
### The API Factory
A factory is a function that can take some parameters or dependencies and return an
instance of something, in our case it will be a function that requests some backstage
APIs and use them to create an instance of an OIDC API provider.
Please note that this function only runs (creates the instance) when somewhere else in
the app you request the DI to give you an instance of the OIDC provider using the API ref
defined above, and the DI will only run this function the first time, from then on any
other DI injection will just receive the same instance created the first time, basically
the instance is cached by the DI library, a singleton.
Let's add our OIDC API factory to the APIs array in the `packages/app/src/apis.ts` file:
```diff
+ import { OAuth2 } from '@backstage/core-app-api';
export const apis: AnyApiFactory[] = [
+ createApiFactory({
+ api: azureOIDCAuthApiRef,
+ deps: {
+ discoveryApi: discoveryApiRef,
+ oauthRequestApi: oauthRequestApiRef,
+ configApi: configApiRef,
+ },
+ factory: ({ discoveryApi, oauthRequestApi, configApi }) =>
+ OAuth2.create({
+ discoveryApi,
+ oauthRequestApi,
+ provider: {
+ id: 'my-auth-provider',
+ title: 'My custom auth provider',
+ icon: () => null,
+ },
+ environment: configApi.getOptionalString('auth.environment'),
+ defaultScopes: [
+ 'openid',
+ 'profile',
+ 'email',
+ ],
+ }),
+ }),
```
Please note we're importing the `OAuth2` class from `@backstage/core-app-api` effectively
delegating the authentication to it. Also we're using the `my-auth-provider` ID to tell
`OAuth2` to use the auth provider we'll define in the next section, and added the default
scopes to request ID, profile, email and user read permissions.
## The Auth Provider
The Auth Provider is responsible for authenticating with the 3rd party service, and give
us back the credentials, here's where you pick which protocol to use, be it Auth0, OAuth2,
OIDC, SAML or any other that your 3rd party IDP provider supports.
For this example we'll use OIDC, we pass a factory to the `providerFactories` object with
the ID you picked to represent the Auth provider, this ID has to match with the provider's
`id` inside the API factory, the yaml config provider key under `auth.providers`, and the
callback URI provider segment (you'll have to configure your IDP to handle the callback
URI properly).
```diff
export default async function createPlugin(
env: PluginEnvironment,
): Promise<Router> {
return await createRouter({
logger: env.logger,
config: env.config,
database: env.database,
discovery: env.discovery,
tokenManager: env.tokenManager,
providerFactories: {
...defaultAuthProviderFactories,
+ 'my-auth-provider': providers.oidc.create({
+ }),
}
```
### The Resolver
Resolvers exist to map user identity from the 3rd party (in this case an azure IDP
provider) to the backstage user identity, for a detailed explanation check the
[Identity Resolver][1] page, it explains how to write a custom resolver as well as
linking the built in resolvers of backstage.
The default OIDC provider does not support SignIn, we need to add such support by
adding a resolver for a SignIn request.
The OIDC provider doesn't provide any build-in resolvers, so we'll need to define our own:
```diff
import {
DEFAULT_NAMESPACE,
+ stringifyEntityRef,
} from '@backstage/catalog-model';
export default async function createPlugin(
env: PluginEnvironment,
): Promise<Router> {
return await createRouter({
logger: env.logger,
config: env.config,
database: env.database,
discovery: env.discovery,
tokenManager: env.tokenManager,
providerFactories: {
...defaultAuthProviderFactories,
'my-auth-provider': providers.oidc.create({
+ signIn: {
+ resolver(info, ctx) {
+ const userRef = stringifyEntityRef({
+ kind: 'User',
+ name: info.result.userinfo.sub,
+ namespace: DEFAULT_NAMESPACE,
+ });
+ return ctx.issueToken({
+ claims: {
+ sub: userRef, // The user's own identity
+ ent: [userRef], // A list of identities that the user claims ownership through
+ },
+ });
+ },
+ },
}),
}
```
### The configuration
Since we are using our custom OIDC Auth Provider, we need to add a configuration based
on the provider used, in this case based on OIDC protocol (remember the 3rd party has to
support the protocol).
In this example we'll configure OIDC with `my-auth-provider`, to do so we need to
[Create app registration][2] in the Azure console, the only difference is that the
`http://localhost:7007/api/auth/microsoft/handler/frame` URL needs to change to
`http://localhost:7007/api/auth/my-auth-provider/handler/frame`.
Then we need to configure the env variables for the provider, based on the provider's code
in `plugins/auth-backend/src/providers/oidc/provider.ts` we need the following variables
in the `app-config.yaml`:
```yaml
auth:
environment: development
### Providing an auth.session.secret will enable session support in the auth-backend
session:
secret: ${SESSION_SECRET}
providers:
my-auth-provider:
development:
metadataUrl: https://example.com/.well-known/openid-configuration
clientId: ${AUTH_MY_CLIENT_ID}
clientSecret: ${AUTH_MY_CLIENT_SECRET}
```
Anything enclosed in `${}` can be replaced directly in the yaml, or provided as
environment variables, the way you obtain all these except `scope` and `prompt` is to
check the App Registration you created:
- `clientId`: Grab from the Overview page.
- `clientSecret`: Can only be seen when creating the secret, if you lose it you'll need a
new secret.
- `metadataUrl`: In Overview > Endpoints tab, grab OpenID Connect metadata document URL.
- `authorizationUrl` and `tokenUrl`: Open the `metadataUrl` in a browser, that json will
hold these 2 urls somewhere in there.
- `tokenSignedResponseAlg`: Don't define it, use the default unless you know what it does.
- `scope`: Only used if we didn't specify `defaultScopes` in the provider's factory,
basically the same thing.
- `prompt`: Recommended to use `auto` so the browser will request login to the IDP if the
user has no active session.
Note that for the time being, any change in this yaml file requires a restart of the app,
also you need to have the `session.secret` part to use OIDC (some other providers might
need this as well) to support user sessions.
### The Sign In provider
The last step is to add the provider to the `SignInPage` so users can sign in with your
new provider, please follow the [Sing In Configuration][3] docs, here's where you import
and use the API ref we defined earlier.
## Note
These steps apply to most if not all the providers, including custom providers, the main
difference between different providers will be the contents of the API factory, the code
in the Auth Provider Factory, the resolver, and the different variables each provider
needs in the YAML config or env variables.
[1]: https://backstage.io/docs/auth/identity-resolver
[2]: https://backstage.io/docs/auth/microsoft/provider#create-an-app-registration-on-azure
[3]: https://backstage.io/docs/auth/#sign-in-configuration
[4]: https://backstage.io/docs/api/utility-apis