Name: EAP Method Update
Acronym: EMU
Area: SEC
Personnel
- Chairs: Joe Salowey and Peter Yee
- Area Director: Paul Wouters
The Extensible Authentication Protocol (EAP) [RFC 3748] is a network access authentication framework used, for instance, in VPN and mobile networks. EAP itself is a simple protocol and actual authentication happens in EAP methods. Several EAP methods have been developed at the IETF and support for EAP exists in a broad set of devices. Previous larger EAP-related efforts at the IETF included rewriting the base EAP protocol specification and the development of several standards track EAP methods.
EAP methods are generally based on existing security technologies such as Transport Layer Security (TLS) and mobile network Authentication and Key Agreement (AKA). Our understanding of security threats is continuously evolving. This has driven the evolution of several of these underlying technologies. As an example, IETF has standardized a new and improved version of TLS in RFC 8446. The group will therefore provide guidance and update EAP method specifications where necessary to enable the use of new versions of these underlying technologies.
At the same time, some new use cases for EAP have been identified. EAP is now more broadly in mobile network authentication. The group will update existing EAP methods such as EAP-AKA' to stay in sync with updates to the referenced 3GPP specifications. RFC 7258 notes that pervasive monitoring is an attack. Perfect Forward Secrecy (PFS) is an important security property for modern protocols to thwart pervasive monitoring. The group will therefore work on an extension to EAP-AKA' for providing PFS.
Out-of-band (OOB) refers to a separate communication channel independent of the primary in-band channel over which the actual network communication takes place. OOB channels are now used for authentication in a variety of protocols and devices (draft-ietf-oauth-device-flow-13, WhatsApp Web, etc.). Many users are accustomed to tapping NFC or scanning QR codes. However, EAP currently does not have any standard methods that support authentication based on OOB channels. The group will therefore work on an EAP method where authentication is based on an out-of-band channel between the peer and the server.
EAP authentication is based on credentials available on the peer and the server. However, some EAP methods use credentials that are time or domain limited (such as EAP-POTP), and there may be a need for creating long term credentials for re-authenticating the peer in a more general context. The group will investigate minimal mechanisms with which limited-use EAP authentication credentials can be used for creating general-use long-term credentials.
EDHOC (Ephemeral Diffie-Hellman Over COSE) is a very compact and lightweight authenticated Diffie-Hellman key exchange with ephemeral keys that is suitable in constrained environments in which many of the existing EAP methods are not a good fit. EDHOC offers the useful properties of mutual authentication, forward secrecy, and identity protection. The group will accordingly produce a specification for an EAP method incorporating the EDHOC mechanism (RFC 9528).
While TLS-based EAP mechanisms provide strong channel protections, if the client does not authenticate and validate the server's credentials properly (possibly owing to a lack of provisioned information necessary to undertake that validation), an EAP mechanism running over TLS that relies on passwords is vulnerable to client credential theft, much the same as password authentication over plain TLS is. The FIDO Alliance and the W3C have developed a passwordless authentication scheme known as FIDO2, which combines elements of the W3C's WebAuthn and FIDO's CTAP standards. The group will devise an EAP method suitable for use with passwordless authentication schemes such as the CTAP2 version of FIDO2.
In summary, the working group shall produce the following documents:
* An update to enable the use of TLS 1.3 in the context of EAP-TLS (RFC 5216). This document will update the security considerations relating to EAP-TLS, document the implications of using new vs. old TLS versions. It will add any recently gained new knowledge on vulnerabilities and discuss the possible implications of pervasive surveillance.
* Several EAP methods such EAP-TTLS and EAP-FAST use an outer TLS tunnel. Provide guidance or update the relevant specifications explaining how those EAP methods (PEAP/TTLS/TEAP) will work with TLS 1.3. This will also involve maintenance work based on errata found in published specifications (such as EAP-TEAP).
* Define session identifiers for fast re-authentication for EAP-SIM, EAP-AKA, EAP-PEAP and EAP-AKA’. The lack of this definition is a recently discovered bug in the original RFCs.
* Update the EAP-AKA' specification (RFC 5448) to ensure that its capability to provide a cryptographic binding to network context stays in sync with updates to the referenced 3GPP specifications. The document will also contain any recently gained new knowledge on vulnerabilities or the possible implications of pervasive surveillance.
* Develop an extension to EAP-AKA' such that Perfect Forward Secrecy can be provided. There may also be privacy improvements that have become feasible with the introduction of recent identity privacy improvements in 3GPP networks.
* Gather experience regarding the use of large certificates and long certificate chains in the context of TLS based EAP methods, as some implementations and access networks may limit the number of EAP packet exchanges that can be handled. Document operational recommendations or other mitigation strategies to avoid issues.
* Define a standard EAP method for mutual authentication between a peer and a server that is based on an out-of-band channel. The method itself should be independent of the underlying OOB channel and shall support a variety of OOB channels such as NFC, dynamically generated QR codes, audio, and visible light.
* Define mechanisms by which EAP methods can support creation of long-term credentials for the peer based on initial limited-use credentials.
* Develop an EAP method for use in constrained environments that wish to leverage the EDHOC key exchange mechanism.
* Devise a passwordless EAP method that can incorporate use of CTAP2 or other similar authentication mechanism.
The working group is expected to stay in close collaboration with the EAP deployment community, the TLS working group (for work on TLS based EAP methods), the FIDO Alliance, and the 3GPP security architecture group (for EAP-AKA' work).
-
April 2024: WG adopts initial draft on an EAP method for use of EDHOC
-
April 2024: WG adopts initial draft on an EAP method for using FIDO CTAP2
-
April 2024: WG adopts an ancillary draft on use of the eap.arpa domain for use in other EAP methods