dorfteich/docs/architecture/security.md

Security concept

Threat-driven summary; detailed mechanics live in the referenced ADRs.

Assets & main threats

Wiki content (possibly confidential per pond/label), user credentials and e-mail addresses, instance availability. Threat actors: anonymous internet (public instance with self-signup), malicious registered users, malicious or sloppy plugin authors, compromised dependencies.

Authentication & session security (ADR 0007)

• Argon2id password hashing; opaque server-side sessions in HttpOnly, Secure, SameSite=Lax cookies; CSRF protected by SameSite + origin checks on mutating requests (double-submit token for the file-download edge cases).
• The origin check fails closed (issue #189): a cookie-carrying mutation without Origin and Referer (or with an unparsable one) is rejected with 403 csrf_origin_mismatch. Non-browser clients authenticate with a PAT/bearer token and no cookie, which never reaches the check — the exception is structural, not a header loophole; a request that does carry the session cookie is always checked. Scripted cookie clients must send Origin: <APP_BASE_URL>.
• Session bounds are configurable (issue #190): an absolute lifetime (SESSION_ABSOLUTE_HOURS, default 7 days, never extended by activity — also the cookie maxAge) and an idle timeout (SESSION_IDLE_HOURS, default 3 days), both enforced server-side, the idle bound against lastSeenAt.
• E-mail verification (double opt-in) before an account can create content; password reset via single-use hashed tokens; both rate-limited.
• Rate limiting (DB-backed) on login, signup, reset, and API; lockout backoff on repeated failed logins per account+IP.
• Feed tokens (issue #149) authenticate feed URLs via ?token= — feed readers cannot send headers, which is why the credential lives in the URL at all. Moving it into a path segment was rejected (issue #191): a path lands in the same proxy and request logs as a query string. Instead: the instance switch feeds.enabled hides the whole feed surface with 404 semantics (the VS-NfD reference configuration turns feeds off), tokens are stored hashed, and the api's request log masks ?token= values (common/mask-token-param.ts), so no code path logs the credential.
• Self-registration can be disabled instance-wide; personal-pond quotas (editors/readers/ponds/storage) bound the blast radius of spam accounts.

Authorization

• Single resolution algorithm (permissions.md) in packages/shared, enforced in API guards and at collab token issuance — never in the client.
• Default-closed: no grant → no access. Public access is always an explicit grant.
• Admin actions are audit-logged (operations.md).

Content & upload security

• Editor content is structured (ProseMirror schema) — no raw HTML from users. The HTML render endpoint escapes everything outside the schema; link protocols allowlisted (https, http, mailto).
• Uploads (ADR 0011): MIME/extension allowlist, size limits, magic-byte checks, SVG sanitization or rejection, Content-Disposition: attachment for non-image types, no user content served same-origin as executable (X-Content-Type-Options: nosniff; uploads path never serves text/html).
• App CSP (strict): default-src 'self'; font-src 'self' (ADR 0016); no third-party origins at all — the GDPR posture is "zero external requests".
• The full-text index holds no trashed content (issue #195): trashing a page or pond clears the affected search_vectors, restore rebuilds them, reindexAll converges to the same invariant, and a one-off migration backfilled pre-existing trash. The query-side deleted_at IS NULL joins stay in place as the second, independent layer — a future query path that forgets them still finds no trashed vectors. (The plaintext cache row itself remains until purge; the index is the concern here because it is queryable.)

Security response headers & CORS (issue #197)

Every api response carries this header set, stamped by a hand-rolled 15-line middleware (apps/api/src/common/security-headers.middleware.ts) rather than helmet — the set is small enough to own, each value is a deliberate decision, and the api gains no transitive dependency. It is wired through the AppModule's MiddlewareConsumer, so the e2e harness boots the exact production middleware.

Header	Value	Why
Strict-Transport-Security	max-age=31536000	One year, no includeSubDomains — the api cannot speak for sibling subdomains it does not control. Browsers ignore HSTS over plain http, so it is sent unconditionally.
X-Content-Type-Options	nosniff	No MIME sniffing, anywhere (the uploads path relies on this too, see above).
Referrer-Policy	no-referrer	Page paths are permission-scoped knowledge; leak them to no destination.
X-Frame-Options	SAMEORIGIN	Deliberately not DENY: the plugin sandbox (ADR 0008) embeds /api/v1/plugins/<id>/<version>/frame same-origin, and the frame's CSP has no frame-ancestors — this header governs its framing.
Permissions-Policy	camera=(), microphone=(), geolocation=(), payment=(), usb=()	Powerful browser features denied outright; nothing in the app uses them.

CORS is a stated decision, not an implicit default: no foreign origin is granted anything. The middleware echoes Access-Control-Allow-Origin (plus Allow-Credentials: true) only for the APP_BASE_URL origin itself — where browsers never consult CORS anyway, since the SPA calls the api same-origin (the dev server proxies /api). The echo documents the stance rather than enabling a caller; consequently there is no preflight handling (same-origin requests never preflight), and every response carries Vary: Origin for cache correctness. Cross-origin API access is cookie-less by design anyway (PAT/Bearer, see Public API), and non-browser clients are unaffected by CORS.

Regression fence: apps/api/src/common/security-headers.e2e.test.ts (header set, foreign origin gets no ACAO) and the frame assertion in plugins.e2e.db.test.ts. TLS termination itself is the reverse proxy's job (out of scope, below).

Plugin sandboxing (ADR 0008, operational)

• Code plugins: opaque-origin iframes, no network (connect-src 'none'), capability-scoped postMessage API executed with the viewer's permissions server-side; declared capabilities surfaced to the Site Admin at install time.
• Style plugins: CSS sanitized (no @import/external url()), scoped class names.
• Install surface restricted to Site Admins; packages size-limited and schema-validated; the plugins/ directory watcher only trusts the volume (host-level access implies game over anyway).

Collaboration layer

• WebSocket connect requires a short-lived (≤ 60 s) single-purpose JWT bound to user + page + mode; write revocation closes sessions via LISTEN/NOTIFY (realtime-collaboration.md).
• Update size and document size ceilings prevent resource-exhaustion via crafted CRDT updates.

Secrets & configuration

• Secrets (DB password, token root key, SMTP credentials) live only in the stage .env (mode 600, never in git) and container env — not in the database (instance_settings stores non-secret config; the SMTP password entered in the setup wizard is written to the env-backed secret store, not to a DB row).
• Token key hierarchy (ADR 0020, issue #188): COLLAB_TOKEN_SECRET is a ROOT key. Each token purpose uses its own HKDF-SHA-256 subkey (deriveTokenKey in packages/shared/src/token-crypto.ts): collab for the collaboration JWTs (signed and verified by jose, HS256 as an explicit allowlist), unsubscribe for the digest unsubscribe links. No code path signs with the root key directly, so a compromise of one purpose's tokens is not transferable to the other.
• Dual-verify window: unsubscribe links minted before the key separation live in already-sent mail (90-day TTL). Verification accepts the legacy derivation (root key + purpose prefix) until 2026-11-01 (LEGACY_VERIFY_UNTIL in apps/api/src/notifications/unsubscribe-token.ts), after which the legacy path goes dead automatically. New tokens are only ever signed with the subkey.
• Key rotation: rotating the root key rotates every derived subkey at once (desired: one secret to rotate) via env change plus rolling restart; procedure documented in operations.md runbooks.
• Dependencies: lockfile-pinned; monthly update batch; images pinned to digests in Prod.

Logging

• Application logs are pino JSON on stdout; authorization and cookie headers are redacted, request bodies are never logged, and feed-token query values are masked (issue #191). Log forwarding and retention are the container runtime's job (SIEM division of labour — the application side of that contract is the stable event catalogue, issue #201).
• The persistent audit trail (audit_log, issue #86) records auth and admin events — who changed access or configuration, not who edited what; content activity stays log-only by design.
• Audit retention (issue #196): entries are kept for audit.retentionDays (instance setting, default 365) and pruned by the daily audit-retention job; each pruning run is itself recorded as audit.pruned with count and cutoff, so a gap in the trail is always explainable. The read-access trail (#222–#225) is deliberately not covered by this period — it gets its own.

Privacy (GDPR)

• No external requests from the browser (fonts self-hosted, no CDNs, no analytics by default).
• Instance-configurable legal pages (imprint, privacy policy) are a core feature; dorfteich.online uses the operator's standard texts.
• Data minimization: username, e-mail, password hash, locale — nothing else required. Account deletion: personal pond and authored ponds follow the trash/purge path; authorship on shared content is pseudonymized ("deleted user"). A data-export endpoint (own profile + own ponds as Markdown/ZIP) supports access/portability requests.
• IP addresses appear only in rate-limit counters (short TTL) and reverse proxy logs (host-level rotation) — documented in the privacy-policy template.

Out of scope (v1, explicit)

• No end-to-end encryption of page content (server sees plaintext — needed for search, export, rendering).
• No plugin marketplace/signing — installation is a deliberate Site Admin act of trust in the reviewed package.
• No SSO in MVP (OIDC-ready per ADR 0007).