Security for Scalable Registration, Authentication, and Authorization
1.1.0 - STU1 Update United States of America flag

Security for Scalable Registration, Authentication, and Authorization, published by HL7 International - Security WG. This guide is not an authorized publication; it is the continuous build for version 1.1.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/fhir-udap-security-ig/ and changes regularly. See the Directory of published versions

Consumer-Facing

This guide supports consumer-facing client applications using the authorization code grant type.

Consumer-facing client applications SHALL obtain an access token for access to FHIR resources by following the OAuth 2.0 authorization code grant flow, with the additional options and constraints discussed below.

Obtaining an authorization code

The workflow for obtaining an authorization code is summarized in the following diagram:

Client AppAuthorization ServerAuthorization requestServer incorporates user inputinto authorization decisionAuthorization response

Client applications SHALL request an authorization code as per Section 4.1.1 of RFC 6749, with the following additional constraints. Client applications that also support the SMART App Launch IG are NOT REQUIRED to include a launch scope or launch context requirement scope. Client applications and servers MAY optionally support UDAP Tiered OAuth for User Authentication to allow for cross-organizational or third party user authentication as described in Section 6.

Servers SHALL handle and respond to authorization code requests as per Section 4.1.2 of RFC 6749.

Obtaining an access token

The workflow for obtaining an access token is summarized in the following diagram:

Client AppAuthorization ServerToken requestToken response

Client applications SHALL exchange authorization codes for access tokens as per Section 4.1.3 of RFC 6749, with the following additional options and constraints.

Constructing Authentication Token

If the client app has registered to authenticate using a private key rather than a shared client_secret, then the client SHALL use its private key to sign an Authentication Token as described in this section, and include this JWT in the client_assertion parameter of its token request as described in Section 5.1 of UDAP JWT-Based Client Authentication and detailed further in Section 4.2.2 of this guide. For clients and servers that also support the SMART App Launch IG, this overrides the requirement for the client to use HTTP Basic Authentication with a client_secret in Section 7.1.3 of the SMART App Launch IG v1.0.0.

Authentication Tokens submitted by client apps SHALL conform to the general JWT header requirements above and SHALL include the following parameters in the JWT claims defined in Section 4 of UDAP JWT-Based Client Authentication:

Authentication JWT Claims
iss required The application's client_id as assigned by the Authorization Server during the registration process
sub required The application's client_id as assigned by the Authorization Server during the registration process
aud required The FHIR Authorization Server's token endpoint URL
exp required Expiration time integer for this authentication JWT, expressed in seconds since the "Epoch" (1970-01-01T00:00:00Z UTC).
iat required Issued time integer for this authentication JWT, expressed in seconds since the "Epoch"
jti required A nonce string value that uniquely identifies this authentication JWT. See Section 1.2.4 for additional requirements regarding reuse of values.

The maximum lifetime for an Authentication Token SHALL be 5 minutes, i.e. the value of exp minus the value of iat SHALL NOT exceed 300 seconds. The Authorization Server MAY ignore any unrecognized claims in the Authentication Token. The Authentication Token SHALL be signed and serialized using the JSON compact serialization method.

Submitting a token request

For client applications authenticating with a shared secret, the client application and server SHALL follow the token request and response protocol in Section 4.1.3 and Section 4.1.4 of RFC 6749.

Client applications authenticating with a private key and Authentication Token as per Section 4.2.1 SHALL submit a POST request to the Authorization Server’s token endpoint containing the following parameters as per Section 5.1 of UDAP JWT-Based Client Authentication. Client apps authenticating in this manner SHALL NOT include an HTTP Authorization header or client secret in its token endpoint request. The token request SHALL include the following parameters:

Token request parameters
grant_type required Fixed value: authorization_code
code required The code that the app received from the Authorization Server
redirect_uri conditional The client application's redirection URI. This parameter SHALL be present only if the redirect_uri parameter was included in the authorization request in Section 4.1, and their values SHALL be identical.
client_assertion_type required Fixed value: urn:ietf:params:oauth:client-assertion-type:jwt-bearer
client_assertion required The signed Authentication Token JWT
udap required Fixed value: 1

An Authorization Server receiving token requests containing Authentication Tokens as above SHALL validate and respond to the request as per Sections 6 and 7 of UDAP JWT-Based Client Authentication.

For all successful token requests, the Authorization Server SHALL issue access tokens with a lifetime no longer than 60 minutes.

This guide does not currently constrain the type or format of access tokens issued by Authorization Servers. Note that other implementation guides (e.g. SMART App Launch, IUA, etc.), when used together with this guide, may limit the allowed access token types (e.g. Bearer) and/or formats (e.g. JWT).

Refresh tokens

This guide supports the use of refresh tokens, as described in Section 1.5 of RFC 6749. Authorization Servers MAY issue refresh tokens to consumer-facing client applications as per Section 5 of RFC 6749. Client apps that have been issued refresh tokens MAY make refresh requests to the token endpoint as per Section 6 of RFC 6749. Client apps authenticate to the Authorization Server for refresh requests by constructing and including an Authentication Token in the same manner as for initial token requests.