OpenID Connect OAuth 2.0 Token Enforcement Policy

Policy Name

OpenID Connect OAuth 2.0 Token Enforcement

Summary

Allows access only to authorized client applications

Category

Security

First Flex Gateway version available

v1.0.0

Returned Status Codes

400 - Invalid token

401 - Unauthorized access or error when connecting to the authorization server

403 - Forbidden, invalid client application credentials

500 - Bad response from authorization server

Summary

The OpenID Connect Access Token Enforcement policy restricts access to a protected resource to only those HTTP requests that provide a valid Oauth2 token belonging to a client application with API access. The policy does not generate tokens but only validates them.

This policy is available only to an organization that is configured to use the OpenID Connect dynamic client registration as a client-management solution.

Configuring Policy Parameters

Flex Gateway Local Mode

The OpenID Connect Access Token Enforcement policy doesn’t support in Flex Gateway running in Local Mode.

Managed Flex Gateway and Flex Gateway Connected Mode

When you apply the policy from the UI, the following parameters are displayed:

Element Description Example

Element	Description	Example
Scopes	Displays a space-separated list of supported scopes.	READ, WRITE, READ and WRITE
Scope Validation Criteria	Determines if the token must contain all defined scopes or just one. The values are `Contains all scopes` and `Contains any scope`.	If the 'Contains all scopes' value is selected, the tokens with the scopes `READ` and `WRITE` are accepted. If the 'Contains any scopes' value is selected, the tokens with the scopes `READ, WRITE, and READ AND WRITE` are accepted.
Expose Headers	In a proxy scenario, specifies whether headers must be exposed in the request to the backend. User properties returned by the federation server are prefixed with 'X-AGW-' and sent as headers to the backend.
Skip Client Id Validation	Skips the client application’s API contract validation.	If selected, Step 4 of the diagram in the How This Policy Works section is skipped.
Authentication request timeout	Sets the maximum time, in milliseconds, to wait for a response when authenticating with the Access Token validation endpoint.	`10000`
Enable Protected Resource Metadata	Enables RFC 9728 OAuth 2.0 Protected Resource Metadata. When enabled, all `401` responses include a `WWW-Authenticate` header with the resource metadata URL `{api_path}/.well-known/oauth-protected-resource`. When a client makes a GET request to this path, Flex Gateway responds with a JSON document containing the authorization server metadata. By default, Flex Gateway derives the authorization server URL supplied in the metadata from the introspection endpoint URL. For example, `https://auth.example.com/introspect` becomes `https://auth.example.com`.
Override Protected Resource Metadata Authorization Server Url	Overrides the authorization service URL with a custom URL. For example, when the authorization service uses a different path, such as Keycloak realms.
Protected Resource Metadata Authorization Server Url	Server base URL to use when `overrideProtectedResourceMetadataAuthorizationServerUrl` is enabled.

Scopes

Displays a space-separated list of supported scopes.

READ, WRITE, READ and WRITE

Scope Validation Criteria

Determines if the token must contain all defined scopes or just one. The values are Contains all scopes and Contains any scope.

If the 'Contains all scopes' value is selected, the tokens with the scopes READ and WRITE are accepted. If the 'Contains any scopes' value is selected, the tokens with the scopes READ, WRITE, and READ AND WRITE are accepted.

Expose Headers

In a proxy scenario, specifies whether headers must be exposed in the request to the backend. User properties returned by the federation server are prefixed with 'X-AGW-' and sent as headers to the backend.

Skip Client Id Validation

Skips the client application’s API contract validation.

If selected, Step 4 of the diagram in the How This Policy Works section is skipped.

Authentication request timeout

Sets the maximum time, in milliseconds, to wait for a response when authenticating with the Access Token validation endpoint.

10000

Enable Protected Resource Metadata

Enables RFC 9728 OAuth 2.0 Protected Resource Metadata. When enabled, all 401 responses include a WWW-Authenticate header with the resource metadata URL {api_path}/.well-known/oauth-protected-resource.
When a client makes a GET request to this path, Flex Gateway responds with a JSON document containing the authorization server metadata. By default, Flex Gateway derives the authorization server URL supplied in the metadata from the introspection endpoint URL. For example, https://auth.example.com/introspect becomes https://auth.example.com.

Override Protected Resource Metadata Authorization Server Url

Overrides the authorization service URL with a custom URL. For example, when the authorization service uses a different path, such as Keycloak realms.

Protected Resource Metadata Authorization Server Url

Server base URL to use when overrideProtectedResourceMetadataAuthorizationServerUrl is enabled.

How This Policy Works

The following diagram illustrates the OpenID Connect Access Token Enforcement policy workflow:

A flowchart illustrating the process of a user engaging with an API via a PingFederate policy

As shown in the diagram:

The user first sends an HTTP request to the API protected by the policy.
The policy extracts the token from the request and sends it to the validation endpoint to verify the integrity of the token.
The token validation endpoint returns token metadata, including the client ID of the client application.
Using a local database updated with contracts previously obtained from Anypoint Platform, the policy verifies whether the client ID has access to the API.
If all the validations are successfully completed, the request is allowed to reach the backend.

Leveraging Token Validation Endpoint Information

When a token validation endpoint successfully validates a token, certain information, such as configurable fields from OpenID Connect, are returned to the policy.

The following example illustrates the token validation response from the authorization server:

{
    "uid":"john.doe",
    "mail":"john.doe@example.com"
    "token_type":"Bearer",
    "exp": 1516239022
    "alias" : ["Jhon", "Jhonny", "Mr Doe"],
    "address" : {
        "city": "london",
        "road": “abbey road"
    }
}

The fields returned by the OAuth provider are processed by the policy, propagated throughout the flow, and finally exposed to the backend if the application requesting the access uses an HTTP requester.

Token Caching in Local Mode

After the system validates a token, that token is cached (by default), until it expires, thereby improving the performance of the policy. In certain cases, such as in the case of revoked tokens, you might want to minimize or even disable caching.

The validation endpoint sends multiple properties to the policy, including the expiration time of the token. If the expiration information is not available, tokens are not cached.

To control the time taken to cache the tokens, before you attempt revalidating against the token validation endpoint, configure the following parameter in your declarative configuration file:

 - policyRef:
     name: openidconnect-access-token-enforcement-flex
   config:
     ...
     maxFederationExpirationTime: <expiration time in seconds>

Setting this property caches the token for the specified amount of time or until the tokens expire, whichever occurs first. If you have enabled this property and the validation endpoint does not send the expiration information, tokens are not cached.

To control the number of tokens that can be cached simultaneously, configure the following parameter in your declarative configuration file.

  - policyRef:
     name: openidconnect-access-token-enforcement-flex
    config:
     ...
     maxCacheSize: <amount of tokens to be cached; default value is 1.000; specify 0 to disable caching>

Token Validation Endpoint Authentication

To complete validating the provided token, the policy sends a request to the validation endpoint. The policy then obtains the credentials from the client provider configuration in access management, per the Token Introspection Client section of the OAuth 2.0 Authorization Framework specification. These credentials are sent in the request body, as specified in the Client Authentication section of the OAuth 2.0 Authorization Framework specification.

Other authentication methods for the token validation endpoint are currently not supported.

Configuring the Expose Headers Option

If you configured the Expose Headers option in the policy and if the application (for example, out-of-the-box proxies) uses the HTTP requester, the properties are redirected to the backend as headers.

For each field, the original request to the protected resource is enriched with the HTTP headers using the format: X-AGW- + <key>=<value>. For the example response from the previous section, the following headers are added:

X-AGW-uid=john.doe
X-AGW-mail=john.doe@example.com
X-AGW-token_type=Bearer

The propagated properties do not include the scope, and exp objects and arrays.

For further processing within the flow, the original unparsed response from the validation endpoint is made available. The information is stored in an authentication object.

For example, if a mail field is returned to the policy, you can access the value of the field by using the following DataWeave 2.0 expression:

#[authentication.properties.userProperties.mail]

You can obtain the client ID of the OAuth2 token by using the following DataWeave 2.0 expression:

#[authentication.principal]

FAQs

The OpenID Connect Access Token Enforcement policy does not appear in the list of policies to apply to the API.

If the policy does not appear in the policies list, ensure that you have configured the OpenID client provider in Access Management. For information, see Configure OpenID Connect Client Management. If you are using multiple IdPs, verify that the OpenID connect client is properly configured in the API.

Can I generate OAuth 2.0 tokens with the policy?

No. The policy only validates the tokens.

How are the OAuth tokens cached?

OAuth 2.0 tokens are cached only in memory and are never written to disk.

Can I configure the Rate-Limiting SLA policy after I configure the OpenID Connect Access Token Enforcement policy?

Yes, you can. Apply the Rate-Limiting SLA policy after the OpenID Connect Access Token Enforcement policy and provide a Client ID Expression value using the following DataWeave 2.0 expression:

#[authentication.principal]

Because the identity of the requester is already validated by the OpenID Connect Access Token Enforcement policy, you can leave the Client Secret Expression field empty.