Security hardening

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Operator-tunable hardening knobs introduced or sharpened in v0.12.0. These are the runtime security surface that static gates cannot exhaustively cover from source diffs alone — they are owned by the operator running the instance, not by code review.

Use this reference when:

Standing up a hosted / multi-tenant Neotoma deployment.
Auditing whether a self-hosted instance is in a defensible default state.
Investigating an alert that touches loopback trust, OAuth bearers, guest tokens, or peer-sync envelopes.

Loopback rewrite and trust

Neotoma classifies inbound requests as loopback only when the underlying TCP socket is on 127.0.0.1 / ::1. isLocalRequest (in src/utils/local_request.ts) is the single source of truth — it walks the socket peer address, not the Host header, and is used by both the HTTP API and the Inspector to gate developer-only surfaces.

NEOTOMA_TRUST_PROD_LOOPBACK=1 — opt-in escape hatch for production instances that need to expose loopback-only routes to a same-host reverse proxy. Defaults off. When unset, prod runs refuse loopback-tagged surfaces from any caller.

Gate stack (G1–G5)

The five operator-visible gates wrap every write path:

Gate	Purpose
G1 — Bearer scope	Validates the `Authorization` bearer token (or AAuth signature) against the requested action's scope.
G2 — Subject	Resolves the user, agent, and (when present) `external_actor` triple from the bearer or AAuth thumbprint.
G3 — Loopback	Applies `isLocalRequest` + `NEOTOMA_TRUST_PROD_LOOPBACK` for surfaces marked `loopback-only`.
G4 — Rate limit	Per-key throttle keyed by AAuth thumbprint > hashed guest token > IP.
G5 — Schema / payload	Schema validation and `ERR_STORE_RESOLUTION_FAILED` repair hints for malformed payloads.

OAuth Bearer enforcement on `/mcp`

Pre-v0.12, an unrecognized OAuth Bearer token on /mcp could fall through to anonymous attribution if the token was syntactically a UUID. v0.12 closes that gap:

Unknown / expired bearers return HTTP 401 with a JSON-RPC envelope (code: -32001, data.error: "invalid_token") and a WWW-Authenticate: Bearer realm="neotoma", resource_metadata="<url>" header pointing at the OAuth protected-resource metadata.
UUID-shaped tokens passed as access_token= query params or Authorization: Bearer … no longer downgrade to anonymous on validation failure.
Regression coverage: tests/subscriptions/subscription_guest_auth.test.ts and tests/unit/security_hardening.test.ts.

MCP proxy: fail-closed mode

neotoma mcp proxy --aauth (and operator-deployed AAuth-signed proxies) accept an opt-in flag that refuses unsigned downstream requests when AAuth signing or session preflight fails:

MCP_PROXY_FAIL_CLOSED=1 (env) or failClosed: true (proxy options).
Default is fail-open (legacy behavior); set fail-closed in any hosted deployment so a misconfigured upstream cannot silently downgrade to anonymous writes.

See docs/developer/mcp/proxy.md for the proxy options reference.

Guest write rate limit & token TTL

Variable	Default	Purpose
`NEOTOMA_GUEST_WRITE_RATE_LIMIT_PER_MIN`	`30`	Per-key throttle on `/issues/submit`, `/issues/add_message`, `/subscribe`, `/unsubscribe`. Key precedence is AAuth thumbprint > hashed guest token > IP, so a shared NAT cannot starve another operator. Lower this in hosted multi-tenant environments.
`NEOTOMA_GUEST_TOKEN_TTL_SECONDS`	`2592000` (30 days)	Lifetime of guest access tokens issued by `generateGuestAccessToken`. Tokens carry a `revoked_at` column and become invalid the moment that column is set, regardless of TTL. Generation errors surface (not swallowed) so operators see when persistence fails.

These knobs do not affect authenticated abuse: a software / hardware AAuth tier write is rate-limited under its own attribution row, not the guest bucket. They exist so a leaked guest token cannot DoS the issue / subscription surfaces.

Peer-sync hostname enforcement

NEOTOMA_HOSTED_MODE=1 enables an inbound check on POST /sync/webhook: any sender_peer_url whose hostname resolves to a private, loopback, or link-local address (RFC 1918, 127.0.0.0/8, 169.254.0.0/16, IPv6 fc00::/7, fe80::/10, the localhost family) is rejected. Single-tenant self-hosted operators normally leave it unset; hosted control planes MUST set it. See peer sync for the full inbound flow.

Inspector auth bypass advisory

For the May 2026 Inspector auth-bypass that motivated the loopback rewrite, see docs/security/advisories/2026-05-11-inspector-auth-bypass.md. The advisory documents the trust model the v0.12 changes restored.

Operator checklist

Set NEOTOMA_HOSTED_MODE=1 on hosted / multi-tenant instances.
Set MCP_PROXY_FAIL_CLOSED=1 on AAuth-signed hosted MCP proxies.
Lower NEOTOMA_GUEST_WRITE_RATE_LIMIT_PER_MIN and NEOTOMA_GUEST_TOKEN_TTL_SECONDS from the single-tenant defaults if guests can reach you.
Audit any NEOTOMA_TRUST_PROD_LOOPBACK=1 opt-in — it should only exist where a trusted same-host reverse proxy actually fronts the API.

Full reference

SECURITY.md is the operator landing page. docs/security/threat_model.md covers the threat surface end to end, including the v0.12 operator hardening knobs section. docs/developer/mcp/proxy.md documents the AAuth proxy + fail-closed semantics.

See peer sync, issue reporting, API reference, and MCP reference.