Overview

Use Cases

Use Cases

Container Authentication

User authentication is generally handled by the Servlet container, i.e. Tomcat, JBoss AS, Jetty, etc. Authenticated requests will arrive at Fedora servlets with a non-null values for getRemoteUser() and getUserPrincipal().

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• fedoraAdmin - Grants superuser permissions to the the Fedora repository. Bypasses the configured policy enforcement point (PEP).
• fedoraUser - The policy enforcement point (PEP) grants permissions on the basis of this authenticated user and the credentials on the request.
• fedoraProxy - The policy enforcement point (PEP) grants permissions on the basis of end-user security credentials that are forwarded via extended request headers.

See the overview on configuring servlet container authentication for more details.

Additional Security Principals

Access may hinge on additional security principals that are specific to an organization. These principals are often based on Shibboleth, LDAP, CAS, databases and other sources. Additional principals can be included in authorization by implementing a PrincipalFactory. A PrincipalFactory examines Servlet requests and returns a set of additional principals. Examples include a named IP range, an affiliation or group from a Shibboleth header, principals extracted from SAML payloads, etc.. Fedora provides a configurable HeaderPrincipalFactory that extracts principals from headers.

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OAuth 2.0 User Authentication

This feature allows a user to sign-in via a third-party service, such as Google, Yahoo or Facebook. The result of the OAuth 2.0 authentication flow is a username and access to whatever user account details are within the authorized scope, such as email address. Fedora is then free to use these user details to create a local user account or assign privileges as required for Fedora authorization. (All that this work flow provides is user authentication.)

OAuth Roles

• Client Application - Fedora
• Authorization Service - Google, etc..
• Resource Server - Fedora

OAuth 2.0 Application Authorization

From the OAuth 2.0 specification:

The OAuth 2.0 authorization framework enables a third-party application to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf.

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OAuth Roles

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OAuth Token Scopes

* for future consideration: A user with the fedoraUser role could grant tokens within a scope that is limited by their own user id credentials. The application would be able to act on their behalf. One token per app user is the OAuth model we commonly see. Otherwise an app would have to track which token to use within some smaller context.

FAQ

• Are OAuth mitigated operations subject to the access restrictions imposed on the user who authorized the token? (or the on-behalf-of user)
  
  • Then ACL restrictions on the user would need to apply equally to the token-based requests they have authorized.
• Can an OAuth tokens be used as principals and assigned access roles within the repository?
  • Yes, access tokens may be assigned roles within the repository. This is especially useful for limited application access to a subtree.
• How are scopes combined?
  • Each scope imposes additional limitations upon the access granted to the token. So "read only" and "fedora administrator" combine to make a token that can read all the data in the repository. It doesn't make much sense to combine "on-behalf-of" with "fedora administrator" or "forward credentials" since the result token would effectively only have on-behalf-of X access.

Forwarding Security Credentials

Since applications often act on behalf of end users with extended security attributes, such as those from Shibboleth, the ability to forward credentials to a central point of authorization is key. Regardless of the approach used for authentication of third-party applications, these applications will need to forward security attributes on behalf of end users for authorization. An example of this pattern is the X-Forwarded-For header often used in web proxies, which we can use to forward the end-user IP address.

Fedora supports both end users and application users. It is helpful to feed both local and forwarded security credentials into a same pipeline for extracting security principals that are the basis for authorization.

The ability to forward credentials in request headers must be restricted to specific users:

• In servlet container authentication, forwarding with require the container role of fedoraProxy.
• In OAuth token authentication, the token must include the scope forward credentials.

Access Roles API

The access roles API is a Fedora module that allows you manage the assignment of access roles throughout the repository tree. For details, please see the Access Roles Module.

Fedora Policy Enforcement Point (PEP)

Fedora includes an extension point that allows installers to build their own enforcement logic for all Fedora actions. A PEP enforces appropriate access for fedora users and their proxies, i.e. applications acting on their behalf. The PEP interface is simple, for details please see Policy Enforcement PointsAuthorization Delegates. Some policy enforcement points may be roles-aware, meaning that they leverage role assignments from the Access Roles API.

Authorization for Other REST API Endpoints

These endpoints in the REST API will require the fedoraAdmin container role or the fedora administrator OAuth token scope:

TBD

Code Repository

The Fedora AuthN/AuthZ modules are in development here:

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