{{book.project.name}} can be secured by supplied adapters that usually are easier to use and provide better integration with {{book.project.name}}. However,
if there is no adapter available for your programming language, framework or platform you may opt to use a generic OpenID Connect Resource Provider (RP) library
instead. This chapter describes details specific to {{book.project.name}} and doesn't go into low-level details of the protocols. For more details refer to the
http://openid.net/connect/[OpenID Connect specifications] and https://tools.ietf.org/html/rfc6749[OAuth2 specification].
The most important endpoint to know is the `well-known` configuration endpoint. It lists endpoints and other configuration options relevant to the OpenID
Connect implementation in {{book.project.name}}. The endpoint is:
Performs authentication of the end-user. This is done by redirecting user agent to this endpoint.
For more details see http://openid.net/specs/openid-connect-core-1_0.html#AuthorizationEndpoint[Authorization Endpoint] section in OpenID Connect specification.
Used to obtain tokens. Tokens can either be obtained by exchanging an authorization code or by supplying credentials directly depending on what flow is used.
The token endpoint is also used to obtain new access tokens when they expire.
For more details see http://openid.net/specs/openid-connect-core-1_0.html#TokenEndpoint[Token Endpoint] section in OpenID Connect specification.
User agent can be redirected to the endpoint in which case the active user session will be logged out. Afterwards the user agent is redirected back to the application.
The endpoint can also be invoked directly by the application. To invoke this endpoint directly the refresh token needs to be included as well as credentials
Public key used by realm encoded as a JSON Web Key (JWK). This key can be used to verify tokens issued by {{book.project.name}} without making invocations to
the server.
For more details see https://tools.ietf.org/html/rfc7517[JSON Web Key specification].
The Authorization Code flow redirects the user agent to {{book.project.name}}. Once the user has successfully authenticated with {{book.project.name}} an
Authorization Code is created and the user agent is redirected back to the application. The application then uses the authorization code along with its
credentials to obtain an Access Roken, Refresh Token and ID Token from {{book.project.name}}.
The flow is targeted towards web applications, but is also recommended for native applications, including mobile applications, where it is possible to embed
a user agent.
For more details refer to the http://openid.net/specs/openid-connect-core-1_0.html#CodeFlowAuth[Authorization Code Flow] in the OpenID Connect specification.
The Implicit flow redirects works similarly to the Authorization Code flow, but instead of returning a Authorization Code the Access Token and ID Token is
returned. This reduces the need for the extra invocation to exchange the Authorization Code for an Access Token. However, it does not include a Refresh
Token. This results in the need to either permit Access Tokens with a long expiration, which is problematic as it's very hard to invalidate these. Or
requires a new redirect to obtain new Access Token once the initial Access Token has expired. The Implicit flow is useful if the application only wants to
authenticate the user and deals with logout itself.
There's also a Hybrid flow where both the Access Token and an Authorization Code is returned.
One thing to note is that both the Implicit flow and Hybrid flow has potential security risks as the Access Token may be leaked through web server logs and
browser history. This is somewhat mitigated by using short expiration for Access Tokens.
For more details refer to the http://openid.net/specs/openid-connect-core-1_0.html#ImplicitFlowAuth[Implicit Flow] in the OpenID Connect specification.
Resource Owner Password Credentials, referred to as Direct Grant in {{book.project.name}}, allows exchanging user credentials for tokens. It's not recommended
to use this flow unless you absolutely need to. Examples where this could be useful are legacy applications and command-line interfaces.
There are a number of limitations of using this flow, including:
* User credentials are exposed to the application
* Applications need login pages
* Application needs to be aware of the authentication scheme
* Changes to authentication flow requires changes to application
* No support for identity brokering or social login
* Flows are not supported (user self-registration, required actions, etc.)
For a client to be permitted to use the Resource Owner Password Credentials grant the client has to have the `Direct Access Grants Enabled` option enabled.
This flow is not included in OpenID Connect, but is a part of the OAuth 2.0 specification.
For more details refer to the https://tools.ietf.org/html/rfc6749#section-4.3[Resource Owner Password Credentials Grant] chapter in the OAuth 2.0 specification.
The following example shows how to obtain an access token for a user in the realm `master` with username `user` and password `password`. The example is using
Client Credentials is used when clients (applications and services) wants to obtain access on behalf of themselves rather than on behalf of a user. This can
for example be useful for background services that applies changes to the system in general rather than for a specific user.
When using the redirect based flows it's important to use valid redirect uris for your clients. The redirect uris should be as specific as possible. This
especially applies to client-side (public clients) applications. Failing to do so could result in:
* Open redirects - this can allow attackers to create spoof links that looks like they are coming from your domain
* Unauthorized entry - when users are already authenticated with {{book.project.name}} an attacker can use a public client where redirect uris have not be configured correctly to gain access by redirecting the user without the users knowledge
In production for web applications always use `https` for all redirect URIs. Do not allow redirects to http.
This redirect URI is useful for native applications and allows the native application to create a web server on a random port that can be used to obtain the
authorization code. This redirect uri allows any port.
If its not possible to start a web server in the client (or a browser is not available) it is possible to use the special `urn:ietf:wg:oauth:2.0:oob` redirect uri.
