Authentication
An authentication system determines the identity of a user or agent and the level of trust associated with this identity.
For authentication, the ESS Solid OIDC Broker Service implements the Solid-OIDC specification. Solid-OIDC specification builds upon the OpenID Connect (OIDC) standards, which itself builds on the OAuth 2.0 authorization framework.
OAuth 2.0 defines a framework for authorization, in which a client obtains an access token to obtain access to resources.
OpenID Connect defines a standard mechanism by which a web application leads a user through a login flow. The login flow results in a signed ID token, which is a JSON Web Token (JWT) that asserts the identity of the user. Since OpenID Connect builds on the OAuth 2.0 framework, OpenID Connect flow produces both access tokens and ID tokens. As the token names suggest, access tokens are generally used to gain access to resources whereas ID tokens are used to identify a user.
Identity
WebID
Rather than representing the identity of users with any string (e.g., user1234 , etc.), Solid identifies users with a WebID. A WebID is a URL (e.g., https://id.<ESS Domain>.com/user1234 ) that can be dereferenced to an RDF profile document.
ESS includes a WebID Service. WebIDs issued by ESS have the form:
https://id.<ESS DOMAIN>/<username>Client Identifier (Client ID)
In Solid-OIDC, an application identifies itself using a client identifier (Client ID).
A Client ID can be:
a URL that dereferences to a Client ID Document.
a value that has been registered using either OIDC dynamic or static registration.
Solid-OIDC Client ID Document
ESS supports Client Identifiers (Client IDs) that are of type URL and dereference to a JSON-LD document, the Client ID Document .
Client Registration
For applications that do not use identifiers that dereference to a Client ID Document, they can register with ESS’ Solid OIDC Broker service (the Broker) .
To register, a client provides various metadata about itself as part of its registration request (see RFC7591: 3.1 Client Registration Request).
Upon successful registration, the Broker responds with a unique client_id . The response may include additional fields. For details, see RFC7591: 3.2 Client Registration Responses .
Dynamic Registration
To dynamically register an application, an application POSTs to the Broker’s client registration_endpoint with the client’s metadata.
Inrupt’s JavaScript client libraries provide login APIs that handle dynamic registration of applications.
Static Registration
ESS supports static registration of client applications associated with a user (i.e., WebID). Static registration results in client credentials (i.e., client_id and client_secret ). ESS’ application registration returns client_id of type UUID.
Single-user scripts and bots can use these client credentials to authenticate (on behalf of the user) without requiring browser-based user interactions with the Identity Provider.
For details, see Application Registration.
Client IDs in Allow Lists and Access Policies
ESS supports the use of Client IDs in client allow list configurations and access policies to specify which clients can be used.
For details, see Authorization and Clients.
Tokens
As part of the ESS login flow, which implements the Solid-OIDC specification, ESS’ Solid OIDC Broker Service issues ID tokens and access tokens. The Solid OIDC Broker Service includes the WebID and the Client ID as claims in these tokens.
ID Tokens
An ID token asserts the identity of the user and is represented as a JSON Web Token (JWT).
ID Token Structure
The OpenID specification defines an extensible data structure for ID Tokens. This data structure is serialized as a JSON Web Token.
See also Broker Token Claims.
Lifespan
ESS ID tokens have a default lifespan of 5 minutes (see SMALLRYE_JWT_NEW_TOKEN_LIFESPAN).
Signed Access Token
The ESS login flow results in signed access tokens. Access tokens provide access to resources. An access token issued by ESS is represented as a JSON Web Token (JWT).
ESS verifies the token signature and that the token has not expired. An invalid token cannot be used to gain access to resources.
Signed Access Token Structure
ESS uses the JWT-based structure for access tokens.
See also Broker Token Claims.
Lifespan
ESS access tokens have a default lifespan of 5 minutes (see SMALLRYE_JWT_NEW_TOKEN_LIFESPAN).
Demonstration of Proof-of-Possession (DPoP) Token
As an additional layer of protection against token stealing and various replay attacks, Solid clients can send an additional HTTP header (specifically a DPoP proof).
A DPoP proof can be used to verify that a client is in legitimate possession of an access token while also scoping the request to a particular Pod resource. This helps prevent against token exfiltration attacks.
ESS uses version 00 of DPoP.
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