feat: attestation-bootstrapped JWT-SVID issuance — bootstrap ref + in-workload redemption + Modal/Cloudflare verifiers

[rsharath]

Summary

Attestation-bootstrapped JWT-SVID issuance for sandboxes (and any workload with provider-native identity evidence): a one-time bootstrap reference issued at registration, redeemed from inside the workload with provider evidence + an in-workload DPoP key, yielding a short-lived JWT-SVID whose trust tier is decided by the evidence class. This is ODIS-L1-11 (attestation-bootstrapped trust) as a single generic door — platform evidence today, hardware evidence (#61) later, same endpoint.

Driving consumer: highflame-forge per-sandbox identity (see the forge companion issue). Today forge's mint injects a zid_sk_ API key as a plaintext env var — a bearer secret with authority, delivered over the channel forge's own credentials.py guard exists to prohibit.

Flow

1. Register (control plane): the trusted broker (forge) registers the agent as today but receives a bootstrap ref instead of an API key — single-use, ≤2 min TTL, no intrinsic authority (grants only the right to attempt redemption). Registration carries expected-evidence constraints (provider, workspace/app, instance binding claims).
2. Redeem (in-workload): POST /v1/attest/redeem with {bootstrap_ref, provider_evidence, DPoP proof}. ZeroID consumes the ref (single-use — reuse the WIMSE nonce machinery), dispatches to the matching attestation verifier, cross-checks evidence claims against the registration's expectations (e.g. Modal container_id binds this instance), assigns trust tier from evidence class, and issues the JWT-SVID.
3. Renew: same DPoP key, registration-active check (ODIS-L2-14); full re-attestation only on confirmed compromise signals (ODIS-L1-12). Revocation unchanged: registration delete / CAE cascade / TTL backstop.

Work items

• Bootstrap-ref issuance on registration (opt-in alongside the existing api_key response) + single-use redemption store
• POST /v1/attest/redeem — verify ref + evidence + DPoP binding, mint JWT-SVID with cnf.jkt, emit act chain from the broker's OBO exchange (per forge docs/PER-SANDBOX-IDENTITY.md end-state)
• Modal OIDC verifier (iss: https://oidc.modal.com; claims: workspace, environment, app, function, container_id) — sits beside the existing GitHub Actions / GCP WIF / K8s verifiers
• Cloudflare sandbox-auth verifier (their Apr-2026 identity tokens, designed for exchange)
• Evidence-class → trust-tier mapping in AttestationPolicy (forge-brokered-only → lowest; provider OIDC → verified_third_party; hardware report (feat: Hardware attestation — HSM/enclave key confinement and attestation document binding #61) → highest)
• JWT-SVID conformance profile on the token service: sub = existing SPIFFE URI, single-aud enforcement (rides RFC 8707 resource parameter on the token endpoint — the minting half of INV-IDN-006 #258/OAuth access tokens: aud defaults to the issuer — adopt RFC 8707 resource indicators so it names the target resource server #199 resource-indicator work), typ conventions, and verify /.well-known/spiffe-trust-bundle.json and JWKS publish the same keys — standard SPIFFE SDKs must validate unmodified
• Compliance tests in house style (TestSPIFFE_JWTSVID_...) + COMPLIANCE.md row

Non-goals

• X.509-SVIDs — SPIFFE: No X.509-SVID support #49 stands; revisit only when a concrete mTLS consumer exists (forge ForgeChannel is Phase-5 roadmap). SPIRE is deliberately not deployed: its value is node attestation on infrastructure we own; on Modal/Cloudflare the provider's own OIDC evidence is stronger than any join token we could mint.
• Hardware verifiers (SEV-SNP / Nitro / Confidential Space) — tracked by feat: Hardware attestation — HSM/enclave key confinement and attestation document binding #61; they plug into this same redeem endpoint as additional evidence classes.

Related

• feat: Hardware attestation — HSM/enclave key confinement and attestation document binding #61 (hardware attestation — evidence-class plugin to this endpoint) · SPIFFE: No X.509-SVID support #49 (no X.509, upheld) · RFC 8707 resource parameter on the token endpoint — the minting half of INV-IDN-006 #258 / OAuth access tokens: aud defaults to the issuer — adopt RFC 8707 resource indicators so it names the target resource server #199 (single-aud / resource indicators)
• highflame-authn#88 (direct OIDC federation — the broker's own secret-zero fix)
• highflame-forge: service/zeroid_mint.py, docs/PER-SANDBOX-IDENTITY.md, credentials.py (INV-ENF-004), forge companion issue
• ODIS L1-11 / L2-14 / L1-12; ADR 0028 (as amended); ergonomics reference issue (Teleport join-method patterns) — filed alongside

[rsharath]

Companions: highflame-ai/highflame-forge#117 (the forge half — bootstrap migration, in-sandbox redemption step, INV-ENF-005 gating) and #309 (design checklist: Teleport join-method ergonomics to hold this API against before shapes freeze).