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Explore EAP usage scenarios, RFC 3748 applicability, & process for analyzing new EAP applications in network authentication. Understand limitations, requirements, & key management framework.
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ICOS BOF EAP Applicability Bernard Aboba IETF 62, Minneapolis, MN
Outline • EAP usage scenarios • RFC 3748 applicability statement • Process of analyzing new applications
EAP Usage Scenarios • EAP parties: EAP peer, EAP server/AAA server, authenticator • Basic scenarios • Peer and authenticator speak some other protocol, authenticator and AAA server speak AAA protocol • This is basic AAA usage (prior to EAP) • Peer and authenticator speak EAP; authenticator and EAP server/AAA server speak EAP over AAA • This is the basic EAP/AAA scenario (e.g. 802.11i) • Peer and authenticator speak some other protocol, but use keys derived from a previous EAP conversation between the same EAP peer and EAP server • This is a new application not yet defined.
RFC 3748 Applicability Statement • Applies to Scenario 2 only: EAP over the wire • Realm of applicability • EAP was designed for use in network access authentication, where IP layer connectivity may not be available. • Use of EAP for other purposes, such as bulk data transport, is NOT RECOMMENDED. • Limitations • Just enough support for the reliable transport of authentication protocols, and no more. • EAP assumes ordering guarantees from the lower layer; out of order transmission not supported • EAP authentication methods generating payloads larger than the EAP MTU need to provide fragmentation support • It may be necessary for an authentication algorithm to add one or two additional messages (at most one roundtrip) in order to run over EAP. • Where certificate-based authentication is supported, the number of additional roundtrips may be much larger due to fragmentation of certificate chains. • Where significant packet loss occurs along the path, EAP methods requiring many round-trips can experience difficulties.
Process for Analyzing New EAP Applications • System level security analysis required for EAP key management applications • Requirements outlined by Russ Housley at IETF 56 • All EAP key management applications need to meet these requirements • EAP methods used in those applications need to meet the requirements as well • EAP Key Management Framework document (work in progress) • Focus is on Scenario 2: defining and analyzing existing usage • EAP Key Management Extensions may handle new applications (Scenario 3)
Acceptable solution MUST…(Housley, IETF 56) • Be algorithm independent protocol • For interoperability, select at least one suite of algorithms that MUST be implemented • Establish strong, fresh session keys • Maintain algorithm independence • Include replay detection mechanism • Authenticate all parties • Maintain confidentiality of authenticator • NO plaintext passwords
Acceptable solution MUST also … • Perform client and NAS authorization • Maintain confidentiality of session keys • Confirm selection of “best” ciphersuite • Uniquely name session keys • Compromise of a single NAS cannot compromise any other part of the system, including session keys and long-term keys • Bind key to appropriate context