feat(P08): master key seal-to-OIDC + Shamir 3-of-5 (REQ-147, D-241, C-35)
---ci---
project: orca
phase: 8
milestone: v0.12
status: execute
---/ci---
internal/seal/seal.go: AES-256-GCM sealing with HKDF-SHA256 key
derivation from OIDC subject. Seal/Unseal (OIDC mode), SealWithCA/
UnsealWithCA (mTLS-only offline path), SaveSealed/LoadSealed (0600),
VerifySealedKey.
internal/seal/shamir.go: GF(256) Shamir secret sharing. ShamirSplit
(5 shards, threshold 3), ShamirCombine (Lagrange interpolation).
UnsealWithShamir for IdP-lost recovery (C-35).
9 tests: seal/unseal round-trip, wrong-sub fails, Shamir 3-of-5
recovery (multiple subsets), 2-shards fails, CA mode, mode mismatch,
shard encoding, verification. All pass. Full build + vet green.
Jon Chery
2cbfb5d561