Add Eap Method

Skill: Add an EAP Authentication Method

Feature ID: TR-F004 | Milestone: M1 (EAP-TLS)

When to use

When adding a new EAP method (e.g. EAP-TLS) within the existing EAP system.

Pre-research

view internal/radiusd/plugins/eap/coordinator.go         # coordinator, do NOT rewrite
view internal/radiusd/plugins/eap/interfaces.go          # handler interface
file_search "internal/radiusd/plugins/eap/handlers/*_handler.go"
view internal/radiusd/plugins/eap/statemanager/          # EAP state management
grep_search "EapMethod" --include internal/app/**         # enabled-list config

Existing references: md5_handler.go, mschapv2_handler.go, otp_handler.go.

Protocol specs & reference implementations

International standards (read repo-local docs/rfcs/ first):

• rfc3748-eap.txt - EAP framework
• rfc5216-eap-tls.txt - EAP-TLS (handshake, fragmentation, identity)
• rfc3579-radius-eap-support.txt - RADIUS carrying EAP (EAP-Message / Message-Authenticator)
• rfc5247-eap-key-management.txt - EAP key management
• rfc7499-packet-fragmentation.txt - RADIUS fragmentation
• Others: rfc5281-eap-ttls.txt, rfc7170-teap.txt (if extending tunneled methods)

Backfill missing specs per ../reference-rfc/SKILL.md.

Reference implementations (for ideas only; mind licensing and protocol compatibility, do not copy incompatible code):

• BeryJu radius-eap: https://github.com/BeryJu/radius-eap
• Implementation notes: https://beryju.io/blog/2025-05-implementing-eap/

Implementation steps

1. Handler skeleton: implement the handler interface at internal/radiusd/plugins/eap/handlers/<method>_handler.go (mirror mschapv2).
2. State management: reuse statemanager; correlate multi-round handshakes / fragmentation (TLS) via the EAP State, and do not add branches inside the coordinator.
3. Registration: wire into the coordinator and the enabled list (EapMethod config) the same way existing handlers do.
4. Failure semantics: return an explicit reason on failure, convert it to AuthError, and emit metrics (reference internal/radiusd/errors and radius_metrics.go).
5. Config schema: if new config is needed (e.g. certificate paths), see ../add-config-schema/SKILL.md.

Boundaries

• Do not rewrite the EAP coordinator (coordinator.go).
• For EAP-TLS, deliver a minimal working auth path first; certificate revocation / policy come in later milestones.
• eap-otp currently uses a fixed sample OTP; do not copy its fixed value when implementing a real method.

Acceptance

• Handler unit tests + end-to-end auth tests pass
• Failure cases have explicit reject reasons and metrics
• go test ./internal/radiusd/... and golangci-lint run pass
• An end-to-end acceptance test is added under test/integration/ (see ../add-acceptance-test/SKILL.md), executed by CI
• PR references TR-F004 and the M1 subtask ID, and cites the RFC clauses relied upon