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• shall only establish connections to servers, including HelseID, using TLS. All TLS connections shall be set up using TLS version 1.2 or later, and follow RFC 7525.

• shall use Authorization Code flow, as described by IETF in OAuth 2.0 and by OIDF in OpenID Connect for interactive sessions (end-user sessions), OR

• shall use the Client Credentials flow as described in RFC 6749.

• shall be confidential clients, meaning that the client secrets used to authenticate the clients are known to HelseID prior to the authentication.

• shall pass request parameters as JWT as described by OIDF in OpenID Connect, and as detailed by HelseID.

• shall support client authentication usin:

  • “private_key_jwt”, as described by OpenID Connect for interactive sessions.

  • Client Assertions as described by RFC 7521 and RFC 7523

  • The requirements for client authentication are further detailed by HelseID

• shall support sender-constrained tokens using

  • Demonstrating Proof-of-Possession at the Application Layer (DPoP) as described by draft-ietf-oauth-dpop.

• shall use PKCE, as defined by IETF in RFC 76936 - Proof Key for Code Exchange, to mitigate against code interception and other attacks.

• shall send access tokens in http authorization headers, as described by RFC 6750.

• shall use the “authorization_details” structure, as defined by IETF in the specification Rich Authorization Requests, to convey fine grained authorization requirements to HelseID.

  • These requirements are further detailed by HelseID.

• shall check the the validity of the “iss” parameter in the authorization response to prevent mix-up attacks.

• shall implement protection against XSS and CSRF attacks. Please refer to external sources as OWASP for details about how to test and secure a client.

• shall not expose to open redirectors where the client is vulnerable to malicious redirections . Please refer to external sources to find descriptions of mitigations to these types of attacks.

  • the client shall protect against attacks via HTTP Header

  • the client shall protect against attacks via Javascript (e.g. XSS attacks)

Cryptography and secrets

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Cryptography

The following algorithms are supported when using “private_key_jwt” and request objects.

• It is recommended to use PS256 or PS512

• RSA shall have a minimum length of 2048 bits

• Elliptic curve shall have a minimum length of 160 bits

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