Execute an Authorization Code Grant Flow
The Authorization Code is an OAuth 2.0 grant that regular web apps use in order to access an API. In this document we will work through the steps needed in order to implement this: get the user's authorization, get a token and access the API using the token.
Before beginning this tutorial, please:
To begin an Authorization Code flow, your web application should first send the user to the authorization URL:
audience: The unique identifier of the API the web app wants to access. Use the Identifier value on the Settings tab for the API you created as part of the prerequisites for this tutorial.
scope: The scopes which you want to request authorization for. These must be separated by a space. You can request any of the standard OIDC scopes about users, such as
offline_accessto get a Refresh Token (make sure that the Allow Offline Access field is enabled in the API Settings). The custom scopes must conform to a namespaced format. For more information on this, refer to the Namespacing Custom Claims panel.
response_type: Denotes the kind of credential that Auth0 will return (code vs token). For this flow, the value must be
client_id: Your application's Client ID. You can find this value at your Application's Settings.
state: An opaque value the application adds to the initial request that Auth0 includes when redirecting back to the application. This value must be used by the application to prevent CSRF attacks. For more information, see State Parameter.
redirect_uri: The URL to which Auth0 will redirect the browser after authorization has been granted by the user. The Authorization Code will be available in the
codeURL parameter. This URL must be specified as a valid callback URL under your Application's Settings.
The purpose of this call is to obtain consent from the user to invoke the API (specified in
audience) to do certain things (specified in
scope) on behalf of the user. Auth0 will authenticate the user and obtain consent, unless consent has been previously given.
Note that if you alter the value in
scope, Auth0 will require consent to be given again.
Now that you have an Authorization Code, you must exchange it for an Access Token that can be used to call your API. Using the Authorization Code (
code) from the previous step, you will need to
POST to the Token URL:
grant_type: This must be
client_id: Your application's Client ID.
client_secret: Your application's Client Secret.
code: The Authorization Code received from the initial
redirect_uri: The URL must match exactly the
The response contains the
token_type values, for example:
refresh_token will only be present in the response if you included the
offline_access scope AND enabled Allow Offline Access for your API in the Dashboard. For more information about Refresh Tokens and how to use them, see our documentation.
It is important to understand that the Authorization Code flow should only be used in cases such as a Regular Web Application where the Client Secret can be safely stored. In cases such as a Single-Page Application, the Client Secret is available to the application (in the web browser), so the integrity of the Client Secret cannot be maintained. That is why the Implicit Grant flow is more appropriate in that case.
3. Call the API
Once the Access Token has been obtained it can be used to make calls to the API by passing it as a Bearer Token in the
Authorization header of the HTTP request:
4. Verify the Token
Once your API receives a request with a Bearer Access Token, the first thing to do is to validate the token. This consists of a series of steps, and if any of these fails then the request must be rejected.
For details on the validations that should be performed refer to Verify Access Tokens.
Optional: Customize the Tokens
You can use Rules to change the returned scopes of the Access Token and/or add claims to it (and the ID Token) with a script like this:
Namespacing Custom Claims
Auth0 returns profile information in a structured claim format as defined by the OIDC specification. This means that in order to add custom claims to ID Tokens or Access Tokens, they must conform to a namespaced format to avoid possible collisions with standard OIDC claims. For example, if you choose the namespace
https://foo.com/ and you want to add a custom claim named
myclaim, you would name the claim
https://foo.com/myclaim, instead of
myclaim. You can add namespaced claims using Rules.
If you wish to execute special logic unique to the Authorization Code grant, you can look at the
context.protocol property in your rule. If the value is
oidc-basic-profile, then the rule is running during the Authorization Code grant.