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Merge pull request #11978 from backstage/rugvip/authdocs

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docs: merge and clean up auth contribution docs
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Patrik Oldsberg
2022-06-13 11:32:32 +02:00
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docs/auth/add-auth-provider.md
+179 -98
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@@ -1,9 +1,113 @@
---
id: add-auth-provider
title: Adding authentication providers
description: Documentation on Adding authentication providers
title: Contributing New Providers
description: Documentation on adding new authentication providers
---
> NOTE: The primary audience for this documentation are contributors to the main
> Backstage project that want to add support for new authentication providers.
> While you can follow it to implement your own custom providers it is much
> more advanced than using our built-in providers.
## How Does Authentication Work?
The Backstage application can use various external authentication providers for
authentication. An external provider is wrapped using an
`AuthProviderRouteHandlers` interface for handling authentication. This
interface consists of four methods. Each of these methods is hosted at an
endpoint (by default) `/api/auth/[provider]/method`, where `method` performs a
certain operation as follows:
```
/auth/[provider]/start -> Initiate a login from the web page
/auth/[provider]/handler/frame -> Handle a finished authentication operation
/auth/[provider]/refresh -> Refresh the validity of a login
/auth/[provider]/logout -> Log out a logged-in user
```
The flow is as follows:
1. A user attempts to sign in.
2. A popup window is opened, pointing to the `auth` endpoint. That endpoint does
initial preparations and then re-directs the user to an external
authenticator, still inside the popup.
3. The authenticator validates the user and returns the result of the validation
(success OR failure), to the wrapper's endpoint (`handler/frame`).
4. The `handler/frame` rendered webpage will issue the appropriate response to
the webpage that opened the popup window, and the popup is closed.
5. The user signs out by clicking on a UI interface and the webpage makes a
request to logout the user.
## Implementing Your Own Auth Wrapper
The core interface of any auth wrapper is the `AuthProviderRouteHandlers`
interface. This interface has four methods corresponding to the API described in
the initial section. Any auth wrapper will have to implement this interface.
When initiating a login, a pop-up window is created by the frontend, to allow
the user to initiate a login. This login request is done to the `/start`
endpoint which is handled by the `start` method.
The `start` method re-directs to the external auth provider who authenticates
the request and re-directs the request to the `/frame/handler` endpoint, which
is handled by the `frameHandler` method.
The `frameHandler` returns an HTML response, containing a script that does a
`postMessage` to the frontend window, containing the result of the request.
The `WebMessageResponse` type is the message sent by the `postMessage` to the
frontend.
A `postMessageResponse` utility function wraps the logic of generating a
`postMessage` response that ensures that CORS is successfully handled. This
function takes an `express.Response`, a `WebMessageResponse` and the URL of the
frontend (`appOrigin`) as parameters and return an HTML page with the script and
the message.
There is a helper class for [OAuth2](https://oauth.net/2/) based authentication providers, [OAuthAdapter](../reference/plugin-auth-backend.oauthadapter.md). This class implements the `AuthProviderRouteHandlers` interface
for you, and instead requires you to implement [OAuthHandlers](../reference/plugin-auth-backend.oauthhandlers.md), which
is significantly easier.
### Auth Environment Separation
The concept of an `env` is core to the way the auth backend works. It uses an
`env` query parameter to identify the environment in which the application is
running (`development`, `staging`, `production`, etc). Each runtime can
simultaneously support multiple environments at the same time and the right
handler for each request is identified and dispatched to, based on the `env`
parameter.
`OAuthEnvironmentHandler` is a utility wrapper for an `OAuthHandlers` that
implements the `AuthProviderRouteHandlers` interface while supporting multiple
`env`s.
To instantiate OAuth providers (the same but for different environments), use
`OAuthEnvironmentHandler.mapConfig`. It's a helper to iterate over a
configuration object that is a map of environments to configurations. See one of
the existing OAuth providers for an example of how it is used.
Given the following configuration:
```yaml
development:
clientId: abc
clientSecret: secret
production:
clientId: xyz
clientSecret: supersecret
```
The `OAuthEnvironmentHandler.mapConfig(config, envConfig => ...)` call will
split the config by the top level `development` and `production` keys, and pass
on each block as `envConfig`.
For convenience, the `AuthProviderFactory` is a factory function that has to be
implemented which can then generate a `AuthProviderRouteHandlers` for a given
provider.
All of the supported providers provide an `AuthProviderFactory` that returns an
`OAuthEnvironmentHandler`, capable of handling authentication for multiple
environments.
## Passport
We chose [Passport](http://www.passportjs.org/) as our authentication platform
@@ -46,13 +150,13 @@ plugins/auth-backend/src/providers/providerA
**`plugins/auth-backend/src/providers/providerA/provider.ts`** defines the
provider class which implements a handler for the chosen framework.
#### Adding an OAuth based provider
### Adding an OAuth based provider
If we're adding an `OAuth` based provider we would implement the
[OAuthProviderHandlers](#OAuthProviderHandlers) interface. By implementing this
`OAuthHandlers` interface. By implementing this
interface we can use the `OAuthProvider` class provided by `lib/oauth`, meaning
we don't need to implement the full
[AuthProviderRouteHandlers](#AuthProviderRouteHandlers) interface that providers
`AuthProviderRouteHandlers` interface that providers
otherwise need to implement.
The provider class takes the provider's options as a class parameter. It also
@@ -65,7 +169,7 @@ export type ProviderAProviderOptions = OAuthProviderOptions & {
// extra options here
}
export class ProviderAAuthProvider implements OAuthProviderHandlers {
export class ProviderAAuthProvider implements OAuthHandlers {
private readonly _strategy: ProviderAStrategy;
constructor(options: ProviderAProviderOptions) {
@@ -87,13 +191,10 @@ export class ProviderAAuthProvider implements OAuthProviderHandlers {
}
```
#### Adding an non-OAuth based provider
_**Note**: We have prioritized OAuth-based providers and non-OAuth providers
should be considered experimental._
### Adding an non-OAuth based provider
An non-`OAuth` based provider could implement
[AuthProviderRouteHandlers](#AuthProviderRouteHandlers) instead.
`AuthProviderRouteHandlers` instead.
```ts
type ProviderAOptions = {
@@ -119,13 +220,19 @@ export class ProviderAAuthProvider implements AuthProviderRouteHandlers {
}
```
#### Factory function
#### Integration Wrapper
Each provider exports a factory function that instantiates the provider. The
factory should implement [AuthProviderFactory](#AuthProviderFactory), which
Each provider exports an object that provides a way to create new instances
of the provider, along with related utilities like predefined sign-in resolvers.
The object is created using `createAuthProviderIntegration`, with the most
important part being the `create` method that acts as the factory function
for our provider.
The factory should return an implementation of `AuthProviderFactory`, which
passes in a object with utilities for configuration, logging, token issuing,
etc. The factory should return an implementation of
[AuthProviderRouteHandlers](#AuthProviderRouteHandlers).
`AuthProviderRouteHandlers`.
The factory is what decides the mapping from
[static configuration](../conf/index.md) to the creation of auth providers. For
@@ -133,48 +240,70 @@ example, OAuth providers use `OAuthEnvironmentHandler` to allow for multiple
different configurations, one for each environment, which looks like this;
```ts
export const createOktaProvider: AuthProviderFactory = ({
globalConfig,
config,
tokenIssuer,
}) =>
OAuthEnvironmentHandler.mapConfig(config, envConfig => {
// read options from config
const clientId = envConfig.getString('clientId');
const clientSecret = envConfig.getString('clientSecret');
export const okta = createAuthProviderIntegration({
create(options?: {
/**
* The profile transformation function used to verify and convert the auth response
* into the profile that will be presented to the user.
*/
authHandler?: AuthHandler<OAuthResult>;
// instantiate our OAuthProviderHandlers implementation
const provider = new OktaAuthProvider({
audience,
clientId,
clientSecret,
callbackUrl,
});
/**
* Configure sign-in for this provider, without it the provider can not be used to sign users in.
*/
signIn?: {
/**
* Maps an auth result to a Backstage identity for the user.
*/
resolver: SignInResolver<OAuthResult>;
};
}) {
return ({ providerId, globalConfig, config, resolverContext }) =>
OAuthEnvironmentHandler.mapConfig(config, envConfig => {
// read options from config
const clientId = envConfig.getString('clientId');
const clientSecret = envConfig.getString('clientSecret');
// Wrap the OAuthProviderHandlers with OAuthProvider, which implements AuthProviderRouteHandlers
return OAuthProvider.fromConfig(globalConfig, provider, {
providerId,
tokenIssuer,
});
});
// Use provided auth handler, or create a default one
const authHandler: AuthHandler<OAuthResult> = options?.authHandler
? options.authHandler
: async ({ fullProfile, params }) => ({
profile: makeProfileInfo(fullProfile, params.id_token),
});
// instantiate our OAuthHandlers implementation
const provider = new OktaAuthProvider({
audience,
clientId,
clientSecret,
callbackUrl,
authHandler,
signInResolver: options?.signIn?.resolver,
resolverContext,
});
// Wrap the OAuthHandlers with OAuthProvider, which implements AuthProviderRouteHandlers
return OAuthProvider.fromConfig(globalConfig, provider, {
providerId,
tokenIssuer,
});
});
},
resolvers: {
/**
* Looks up the user by matching their email local part to the entity name.
*/
emailLocalPartMatchingUserEntityName: () => commonByEmailLocalPartResolver,
// ... additional predefined resolvers
},
});
```
The purpose of the different environments is to allow for a single auth-backend
to serve as the authentication service for multiple different frontend
environments, such as local development, staging, and production.
The factory function for other providers can be a lot simpler, as they might not
have configuration for each environment. Looking something like this:
```ts
export const createProviderAProvider: AuthProviderFactory = ({ config }) => {
const a = config.getString('a');
const b = config.getString('b');
return new ProviderAAuthProvider({ a, b });
};
```
#### Verify Callback
> Strategies require what is known as a verify callback. The purpose of a verify
@@ -202,7 +331,7 @@ export { createProviderAProvider } from './provider';
**`plugins/auth-backend/src/providers/factories.ts`** When the `auth-backend`
starts it sets up routing for all the available providers by calling
`createAuthProviderRouter` on each provider. You need to import the factory
the factory function of each provider. You need to import the factory
function from the provider and add it to the factory:
```ts
@@ -232,51 +361,3 @@ You can `curl -i localhost:7007/api/auth/providerA/start` and which should
provide a `302` redirect with a `Location` header. Paste the URL from that
header into a web browser and you should be able to trigger the authorization
flow.
---
##### OAuthProviderHandlers
```ts
export interface OAuthProviderHandlers {
start(
req: express.Request,
options: Record<string, string>,
): Promise<RedirectInfo>;
handler(req: express.Request): Promise<{
response: AuthResponse<OAuthProviderInfo>;
refreshToken?: string;
}>;
refresh?(
refreshToken: string,
scope: string,
): Promise<AuthResponse<OAuthProviderInfo>>;
logout?(): Promise<void>;
}
```
##### AuthProviderRouteHandlers
```ts
export interface AuthProviderRouteHandlers {
start(req: express.Request, res: express.Response): Promise<any>;
frameHandler(req: express.Request, res: express.Response): Promise<any>;
refresh?(req: express.Request, res: express.Response): Promise<any>;
logout(req: express.Request, res: express.Response): Promise<any>;
}
```
##### AuthProviderFactory
```ts
export type AuthProviderFactoryOptions = {
globalConfig: AuthProviderConfig;
config: Config;
logger: Logger;
tokenIssuer: TokenIssuer;
};
export type AuthProviderFactory = (
options: AuthProviderFactoryOptions,
) => AuthProviderRouteHandlers;
```
docs/auth/auth-backend-classes.md
-206
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@@ -1,206 +0,0 @@
---
id: auth-backend-classes
title: Auth backend classes
description: Documentation on Auth backend classes
---
## How Does Authentication Work?
The Backstage application can use various external authentication providers for
authentication. An external provider is wrapped using an
`AuthProviderRouteHandlers` interface for handling authentication. This
interface consists of four methods. Each of these methods is hosted at an
endpoint (by default) `/api/auth/[provider]/method`, where `method` performs a
certain operation as follows:
```
/auth/[provider]/start -> Initiate a login from the web page
/auth/[provider]/handler/frame -> Handle a finished authentication operation
/auth/[provider]/refresh -> Refresh the validity of a login
/auth/[provider]/logout -> Log out a logged-in user
```
The flow is as follows:
1. A user attempts to sign in.
2. A popup window is opened, pointing to the `auth` endpoint. That endpoint does
initial preparations and then re-directs the user to an external
authenticator, still inside the popup.
3. The authenticator validates the user and returns the result of the validation
(success OR failure), to the wrapper's endpoint (`handler/frame`).
4. The `handler/frame` rendered b´webpage will issue the appropriate response to
the webpage that opened the popup window, and the popup is closed.
5. The user signs out by clicking on a UI interface and the webpage makes a
request to logout the user.
There are currently two different classes for two authentication mechanisms that
implement this interface: an `OAuthAdapter` for [OAuth](https://oauth.net/2/)
based mechanisms and a `SAMLAuthProvider` for
[SAML](http://docs.oasis-open.org/security/saml/Post2.0/sstc-saml-tech-overview-2.0.html).
If you do not have an `OAuth2` or `SAML` based authentication provider, look in
the section [below](#implementing-your-own-auth-wrapper).
### OAuth Mechanisms
For more information on how these methods are used and for which purpose, refer
to the [OAuth documentation](oauth.md).
Currently OAuth is assumed to be the de facto authentication mechanism for
Backstage based applications.
Backstage comes with a "batteries-included" set of supported commonly used OAuth
providers: Okta, GitHub, Google, GitLab, and a generic OAuth2 provider. For a
list of available providers, look at the available wrappers in
`backstage/plugins/auth-backend/src/providers/`.
All of these use the **authorization flow** of OAuth2 to implement
authentication.
If your authentication provider is any of the above mentioned providers, you can
configure them by setting the right variables in `app-config.yaml` under the
`auth` section.
### SAML
The SAML Provider is currently under development. Additional validation and
profile handling is still required before use in production.
To configure the SAML Auth provider, look at the configuration parameters
supported by
[Passport-SAML](https://github.com/node-saml/passport-saml#config-parameter-details)
under the `auth.providers.saml` key
For security reasons, validate that the response from the IdP is indeed signed
by also providing the `cert` configuration.
### Configuration
Each authentication provider (except SAML) needs six parameters: an OAuth client
ID, a client secret, an authorization endpoint, a token endpoint, an optional
list of scopes (as a string separated by spaces) that may be required by the
OAuth2 Server to enable end-user sign-on, and an app origin. The app origin is
the URL at which the frontend of the application is hosted, and it is read from
the `app.baseUrl` config. This is required because the application opens a popup
window to perform the authentication, and once the flow is completed, the popup
window sends a `postMessage` to the frontend application to indicate the result
of the operation. Also this URL is used to verify that authentication requests
are coming from only this endpoint.
These values are configured via the `app-config.yaml` present in the root of
your app folder.
```
auth:
providers:
google:
development:
clientId: ${AUTH_GOOGLE_CLIENT_ID}
clientSecret: ${AUTH_GOOGLE_CLIENT_SECRET}
github:
development:
clientId: ${AUTH_GITHUB_CLIENT_ID}
clientSecret: ${AUTH_GITHUB_CLIENT_SECRET}
enterpriseInstanceUrl: ${AUTH_GITHUB_ENTERPRISE_INSTANCE_URL}
gitlab:
development:
clientId: ${AUTH_GITLAB_CLIENT_ID}
oauth2:
development:
clientId: ${AUTH_OAUTH2_CLIENT_ID}
clientSecret: ${AUTH_OAUTH2_CLIENT_SECRET}
authorizationUrl: ${AUTH_OAUTH2_AUTH_URL}
tokenUrl: ${AUTH_OAUTH2_TOKEN_URL}
scope: ${AUTH_OAUTH2_SCOPE}
saml:
entryPoint: ${AUTH_SAML_ENTRY_POINT}
issuer: ${AUTH_SAML_ISSUER}
...
```
## Implementing Your Own Auth Wrapper
The core interface of any auth wrapper is the `AuthProviderRouteHandlers`
interface. This interface has four methods corresponding to the API described in
the initial section. Any auth wrapper will have to implement this interface.
When initiating a login, a pop-up window is created by the frontend, to allow
the user to initiate a login. This login request is done to the `/start`
endpoint which is handled by the `start` method.
The `start` method re-directs to the external auth provider who authenticates
the request and re-directs the request to the `/frame/handler` endpoint, which
is handled by the `frameHandler` method.
The `frameHandler` returns an HTML response, containing a script that does a
`postMessage` to the frontend's window, containing the result of the request.
The `WebMessageResponse` type is the message sent by the `postMessage` to the
frontend.
A `postMessageResponse` utility function wraps the logic of generating a
`postMessage` response that ensures that CORS is successfully handled. This
function takes an `express.Response`, a `WebMessageResponse` and the URL of the
frontend (`appOrigin`) as parameters and return an HTML page with the script and
the message.
### OAuth Wrapping Interfaces.
Each OAuth external provider is supported by a corresponding
[Passport](https://github.com/jaredhanson/passport) strategy. For a generic
OAuth2 provider, passport has a `passport-oauth2` strategy. The strategy class
handles the implementation details of working with each provider.
Each strategy is wrapped by an `OAuthHandlers` interface.
This interface cannot be directly used as an Express HTTP request handler. To do
so, `OAuthHandlers` are wrapped in an `OAuthAdapter`, which implements the
`AuthProviderRouterHandlers` interface.
#### Env
The concept of an `env` is core to the way the auth backend works. It uses an
`env` query parameter to identify the environment in which the application is
running (`development`, `staging`, `production`, etc). Each runtime can
simultaneously support multiple environments at the same time and the right
handler for each request is identified and dispatched to, based on the `env`
parameter.
`OAuthEnvironmentHandler` is a utility wrapper for an `OAuthHandlers` that
implements the `AuthProviderRouteHandlers` interface while supporting multiple
`env`s.
To instantiate OAuth providers (the same but for different environments), use
`OAuthEnvironmentHandler.mapConfig`. It's a helper to iterate over a
configuration object that is a map of environments to configurations. See one of
the existing OAuth providers for an example of how it is used.
Given the following configuration:
```yaml
development:
clientId: abc
clientSecret: secret
production:
clientId: xyz
clientSecret: supersecret
```
The `OAuthEnvironmentHandler.mapConfig(config, envConfig => ...)` call will
split the config by the top level `development` and `production` keys, and pass
on each block as `envConfig`.
For convenience, the `AuthProviderFactory` is a factory function that has to be
implemented which can then generate a `AuthProviderRouteHandlers` for a given
provider.
All of the supported providers provide an `AuthProviderFactory` that returns an
`OAuthEnvironmentHandler`, capable of handling authentication for multiple
environments.
### OAuth2 Provider
The `oauth2` provider abstracts a generic **OAuth2 + OIDC** based authentication
provider. What this means is that after the application has been given
permission by the user, the `authorization code` will be exchanged for an
`access_token`, a `refresh_token` and an `id_token`. This `id_token` is used to
obtain an email id of the user, which is then used for creating the session.