Authlete has a feature for authorization servers to authenticate their clients with TLS client certificate. This article describes overview of the feature and instructions to enable it.
How TLS client authentication works in Authlete
The TLS client authentication feature of Authlete employs “client ID” and “subject name” (subject distinguished name / subject alternative name) to authenticate clients.
On processing token requests, an authorization server is responsible to provide those two properties to Authlete. Client ID is included in content of a token request by a client, so an authorization server doesn't have to care. “Subject name” is not in the content but in a client certificate, that can be obtained from a mutual TLS connection between a client and an authorization server.
On Authlete's side, you have to enable “TLS_CLIENT_AUTH” client authentication method and register the client's ”subject name.” mtls-client-authentication.png60.71 KB
Service settings
Log in to Authlete’s Service Owner Console, click “Edit” button in the bottom of the page to make settings editable, and go to Authorization tab. There should be Token Endpoint section.
Check the box next to “TLS_CLIENT_AUTH” at Supported Client Authentication Methods and click “Update” button in the bottom of the page. Press “OK” in a dialog for confirmation.
WIth those settings above, Authlete will support mutual TLS authentication as a client authentication method and apply the method to process token requests from the client above. Subject DN CN=client.example.org, ... is used as the identifier of the client.
Example
The following is an example of a request to /auth/token API (folded for readability). An authorization server establishes a mutual TLS connection with a client, obtains the client's certificate from the connection, and makes the request to the API.
Content of a token request, that includes a client ID (client_id), is specified as a value of "parameters," and a client certificate as a value of "clientCertificate".
This article describes setup instructions for Authlete to use “Mutual-TLS certificate-bound access tokens,” defined in “RFC 8705 OAuth 2.0 Mutual-TLS Client Authentication and Certificate-Bound Access Tokens.”
This video is one of the sessions at “Financial APIs Workshop 2018”, held on July 24th, 2018 in Tokyo. Justin Richer from Authlete talks about comparison of Authlete’s unique semi-hosted approach and traditional approaches for deploying OAuth infrastructure, and how Authlete has extended its client authentication functions and supported mutual TLS to implement Financial-grade API (FAPI).
