Nevis Components

As outlined in High-Level Architecture, Nevis Mobile Authentication depends on Nevis components to provide FIDO UAF authentication functionality. This section describes the involved Nevis components in more detail.

nevisProxy

nevisProxy serves as an authentication gateway in the Nevis Mobile Authentication solution.

Endpoint Protection

In nevisProxy the protection of an endpoint is done by configuring an IdentityCreationFilter for this endpoint.

This filter makes sure that whoever accesses this endpoint must be authenticated according to the rules defined in this specific nevisAuth configuration. For further details see chapter nevisAuth.

This typically means that you add the following configuration blocks:

• Definition of the IdentityCreationFilter (InterceptionRedirect should be turned off).
• Mapping of the IdentityCreationFilterto a certain nevisProxy endpoint.

Request Dispatching

Incoming FIDO requests must be dispatched from the incoming URL path to the nevisFIDO server with a specific URL path to the use case (for example registration).

This means that the followings must be defined:

• An HttpsConnectorServlet specifying the target nevisFIDO server endpoint (AutoRewrite should be turned off).
• Mapping of the HttpsConnectorServlet to a certain nevisProxy endpoint.

SecToken Delegation

Nevis Mobile Authentication use cases involve sending requests to the nevisFIDO server. Typically, requests must pass through the nevisProxy component, which does the dispatching of the incoming request to nevisFIDO.

However, simply redirecting the incoming request to nevisFIDO is not enough if the user session has already been issued a SecToken by nevisAuth (for example in Registration and Deregistration).

Thus nevisProxy must be configured to pass along existing SecToken together with the incoming request (DelegationFilter). Otherwise nevisFIDO is not aware of the complete context.

For more details see the nevisFIDO Reference Guide nevisProxy configuration section.

nevisFIDO

The nevisFIDO component is responsible for conducting all server-side processing related to the FIDO UAF Protocol. That is, within Nevis Mobile Authentication nevisFIDO functions as a FIDO UAF Server.

In addition, nevisFIDO provides services that augment the FIDO UAF Protocol properly. For example, the notion of tokens and token endpoints allows implementation of flows where one leg of a FIDO UAF conversation happens out-of-band.

FIDO UAF Processing

As a FIDO UAF Server, the primary task of nevisFIDO is specification-conformant processing of FIDO UAF messages.

The complete reference for FIDO UAF version 1.1, can be found in the FIDO UAF specification. The entire specification contents apply to nevisFIDO, with the qualifications noted in Functional Adaptations of the FIDO UAF Specification.

FIDO UAF processing being the main task of nevisFIDO, the authentication policy, metadata, AppId and Facets are defined in the nevisFIDO configuration.

In addition to the messages and endpoints prescribed in the FIDO UAF Specification, nevisFIDO exposes a few proprietary HTTP endpoints and extensions to cover extended use cases. These are documented in full detail in the nevisFIDO Reference Guide.

Authenticator Custom Credentials

The nevisFIDO component does not itself manage authenticator registrations containing the public key material. It delegates storage concerns to the nevisIDM component.

However, the authenticator data model, as used during FIDO UAF processing, must be agreed on between nevisFIDO and nevisIDM, and so a nevisIDM custom credential is introduced in Nevis Mobile Authentication.

In terms of setup and configuration, the custom credentials requires an additional setup step in the nevisIDM database, where the FIDO custom credential must be made available.

nevisAuth

Within Nevis, nevisAuth is responsible to orchestrate authentication flows, perform authentication and issue tokens as proof of authentication (known as SecTokens). Participating in Nevis Mobile Authentication is no different – except that handling of the FIDO UAF Protocol messages is delegated to nevisFIDO. From a UAF Protocol's perspective, nevisAuth is responsible for dispatching UAF protocol messages to nevisFIDO and processing its results.

In a FIDO UAF authentication scenario, nevisAuth authenticates the end user with the help of nevisFIDO. This is implemented by the FidoUafAuthState which is released as part of nevisFIDO. It abstracts certain aspects of UAF message handling and coordinates with nevisFIDO regarding the FIDO operations. The FidoUafAuthState basically acts as a bridge between the FIDO authentication operations in nevisFIDO and the traditional Nevis world. In addition to FIDO authentication, the FidoUafAuthState also supports transaction confirmation scenarios.

The FidoUafAuthState is capable of connecting to a single nevisFIDO instance. If a certain use case requires the configuration of multiple nevisFIDO instances, each will require different nevisAuth instances respectively (or different realms in the same instance). FidoUafAuthState establishes a connection with nevisFIDO using the HTTP facade of nevisFIDO. It is expected that the FidoUafAuthState and nevisFIDO establish a secure TLS connection since the integrity of the authentication operation heavily relies on it.

Within Nevis Mobile Authentication, nevisAuth is also involved if authentication for certain endpoints of nevisFIDO is required. As an example, legacy authentication is required from the end user to be able to initiate a FIDO registration process. This is to avoid that an attacker could initiate and successfully complete registrations on behalf of an arbitrary user. For an exhaustive list of endpoints that need to be protected, refer to the Default HTTP API Endpoints chapter.

info

Only nevisAuth is able to issue authentication tokens within a Nevis environment. Thus, all authentication driven FIDO operations must interact with nevisAuth at some point.

For a detailed guide on how the configuration of nevisAuth within a Nevis Mobile Authentication solution works, refer to the Use Cases and Best Practices section of this document.

nevisIDM

nevisIDM is the component in charge of managing the identities. Nevis Mobile Authentication allows these identities (notably the users) to authenticate using their mobile devices (where the relying party client application is installed). So, it can be considered that nevisIDM extends its authentication capabilities thanks to Nevis Mobile Authentication. Every application using the identities stored in nevisIDM to authenticate, benefits from this new capabilities.

From another perspective (notably regarding nevisFIDO) nevisIDM is acting as a persistent storage for the registered authenticator credentials. nevisFIDO will create, remove and modify these credentials.

It is assumed that the user is already defined in nevisIDM, before FIDO credentials can be created (e.g. nevisFIDO will not perform itself any user enrollment in nevisIDM).

FIDO UAF Credentials Data Model

The following figure outlines the high-level data model of nevisIDM for handling FIDO credential objects. Note that this model is a simplification of the internal nevisIDM data structure.

Responsibilities

In terms of who is responsible for the data to be supplied, the previously described data structure can be split into two categories:

Expected to be supplied	Handled by nevisFIDO
Client User * Credential (legacy login)	Credential Credential properties

Detailed Data Model Information

Client

A client represents a separated population of users. From a nevisFIDO point of view, the client is not very important apart from the possibility to configure it. Some customers use nevisIDM in multi-client mode. More about multi-client mode and its limitations can be found in the FIDO Application and Nevis Components section.

User

A user represents a person or person's account.

In all FIDO use cases throughout the whole process, the user is identified by extId which is the external numeric identifier (not to be confused with the human readable user_id). Therefore, from a FIDO point of view, extId is the only important attribute from the user entity.

Credential

A credential is a piece of data (of various types) which can be used to authenticate a user during a login process. There are two types of credentials from a nevisFIDO point of view:

• Credentials used in the legacy login (not handled by nevisFIDO).
• Credentials generated during a registration operation, allowing the user to authenticate with a FIDO UAF Authenticator.

In the nevisFIDO context, the second credential type is of interest: the credential mainly stores the public key generated by the Authenticator.

For more details on the exact nevisIDM data model, see the nevisIDM reference guide.

Out-of-band Dispatching Data Model

The following figure outlines the high-level data model of nevisIDM for handling the Nevis Mobile Authentication dispatch target objects. Note that this model is a simplification of the internal nevisIDM data structure.

caution

The implementation of the dispatch target does not allow a direct identification of the FIDO credential objects belonging to a specific dispatch target. This is because the two models do not share a database association. However, direct identification is possible through the device_id attribute that is present in both the FIDO UAF credential and the dispatch target. As a precondition, the mobile client application must supply this attribute during credential creation. For more details, see the chapter "Registration" in the Mobile Authentication Client SDK documentation.

Responsibilities

The dispatch target information supplied is solely the responsibility of a third party application or a Nevis Mobile Authentication Client.

Detailed Data Model Information

As the concepts of Client and User have been described in the above chapter, they will be omitted.

Generic Credential

nevisIDM doesn't support the concept of dispatch targets out-of-the box, because of this Nevis Mobile Authentication uses the generic credential feature of nevisIDM to define the dispatch target structure. For detailed information of how to setup nevisIDM using these generic credential objects, see the Reference Guide.

Dispatch Target

A dispatch target identifies a "receiver" of out-of-band messages and is directly bound to a known user. A dispatch target can for example be a physical mobile device.

Dispatch Target Properties

The following properties are part of a dispatch target:

Attribute	Notes
name	Human readable name of the device - e.g Danis Pixel 2.
app_id	The appId of the device - needed to filter devices based on the application they're intended to authenticate agains.
device_id	The optional identifier describing the device. The goal of this attribute is to allow linking FIDO UAF credentials with dispatch targets.
target	The target identifier of the channel. In case of FCM this would be the push token.
channel	The name of the channel (for example: fcmpush, email,...) (Name of the dispatcher, not implementation class).
encryption_key	Encryption key used for encrypting the channel data.
signature_key	The signature key used for signing dispatch channel information sent do the respective HTTP endpoint for updating the database entry.