PingAM

Client credentials grant

Endpoints

The client credentials grant is intended for clients who are also resource owners that need to access their own data rather than acting on behalf of a user.

For example, an application that needs access to a protected resource to update its configuration might use the client credentials grant to get an access token.

The client credentials grant flow supports confidential clients only.

In the client credentials grant, the client authenticates as itself, so the access token represents the client rather than an end user. If you need to add custom claims to a client credentials access token, use access token modification. Don’t use OIDC claims customization for this flow. OIDC claims apply to end-user flows, not to tokens issued to a client acting on its own behalf. Learn more in Access token modification.

Common use cases

Use this grant when a workload needs access to resources on its own behalf, with no end user in the flow:

  • Service-to-service APIs: A microservice calls another internal API, and the API needs to know which service is calling, not which user. The calling service authenticates with its own credentials and receives a token that represents itself.

  • Scheduled jobs: A nightly batch process synchronizes records or generates reports against an API. No user starts the job, so it authorizes as itself.

  • Machine and workload identities: A deployment pipeline or monitoring agent accesses cloud resources under its own identity. Each workload has its own client profile, so administrators can revoke or scope its access independently.

When the client must act on behalf of an end user, use a user-authorized flow instead, such as the authorization code grant. When it must act on behalf of a user with an existing token, use token exchange to delegate.

The client credentials grant flow

AM supports the client credentials grant.
Figure 1. OAuth 2.0 client credentials grant flow

  1. The client sends its credentials to the authorization server to authenticate and requests an access token.

  2. If the client credentials are valid, the authorization server returns an access token to the client.

  3. The client requests access to the protected resource from the resource server.

  4. The resource server contacts the authorization server to validate the access token.

  5. The authorization server validates the token and responds to the resource server.

  6. If the token is valid, the resource server allows the client to access the protected resource.

Demonstrate the client credentials grant flow

Perform these steps to get an access token:

  1. Prepare the demonstration

  2. Get an access token using the client credentials grant

Prepare the demonstration

Complete these steps to prepare the client credentials grant flow demonstration:

  • AM is configured as an OAuth 2.0 authorization server. Ensure that:

    • The Client Credentials grant type is configured in the Grant Types field.

    For more information, refer to Authorization server configuration.

  • A confidential client called myClient is registered in AM with the following configuration:

    • Client secret: mySecret

    • Scopes: write

    • Grant Types: Client Credentials

For more information, refer to Client application registration.

Get an access token using the client credentials grant

As the client, call /oauth2/access_token specifying the client’s credentials and grant_type=client_credentials.

Confidential clients can authenticate to the OAuth 2.0 endpoints in several ways. This example uses the following form parameters:

  • client_id=your-client-id

  • client_secret=your-client-secret

For more information, refer to OAuth 2.0 client authentication.

If the OAuth 2.0 provider is configured for a subrealm rather than the Top Level Realm, you must specify it in the endpoint. For example, if the OAuth 2.0 provider is configured for the /alpha realm, use /oauth2/realms/root/realms/alpha/access_token.

For example:

$ curl \
--request POST \
--data "grant_type=client_credentials" \
--data "client_id=myClient" \
--data "client_secret=mySecret" \
--data "scope=write" \
"https://am.example.com:8443/am/oauth2/realms/root/realms/alpha/access_token"

The scope parameter is optional if default values are configured in the authorization server or the client.

The authorization server returns an access token, for example:

{
  "access_token": "<access-token>",
  "scope": "write",
  "token_type": "Bearer",
  "expires_in": 3599
}