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Trust Model — VayuPress

Status: Authoritative
Last reviewed: 2026-06-13

Trust Levels

Level Entity What it can do
L0 — Untrusted Anonymous HTTP clients, ActivityPub remotes, plugin stdin/stdout Read public content only; all input validated and escaped
L1 — Authenticated user Authors with valid session token Create/edit own content; cannot access admin endpoints
L2 — Admin Authenticated admin session Full content management; plugin install/uninstall; config changes
L3 — Host process VayuPress Go binary (non-root) DB reads/writes; subprocess management; metric collection
L4 — Operator SSH access to host machine Systemd management; backup restore; key rotation

Component Trust Assignments

Component Trust level of its callers Trust level it grants
Nginx L0 (internet) Forwards sanitised requests to L3
Go HTTP handlers L0-L1-L2 (depending on auth) Invoke L3 services
Plugin subprocess Treated as L0 (untrusted) Reads PLUGIN_SCRATCH only
SQLite DB Accessible only to L3 Authoritative data store
ActivityPub inbox L0 (remote actors) Queued for validation before processing
DID authenticator L0 (challenge/response) Grants L1 on successful verify
AI runtime L3 internal only No external network access
Signing keys L4 operator Signs articles; key not accessible to L0-L2

What We Explicitly Do NOT Trust

  1. Plugin stdout — parsed as untrusted JSON; log lines forwarded after sanitisation
  2. ActivityPub content field — HTML-sanitised before storage or display
  3. Federation actor claims — HTTP Signature verification required (Ω2)
  4. User-supplied file paths — validated against allowlist prefix; no traversal
  5. Config values from environment — schema-validated at startup; invalid = fatal
  6. Plugin binary on disk — SHA-256 hash checked against Manifest.ExecutableHash

Key Management

Key Type Location Rotation
Article signing key Ed25519 private /etc/vayupress/signing.key (mode 0600) Manual; re-sign on rotation
DID authentication key Ed25519 per-DID Generated per-user; stored in user record User-initiated
TLS certificate RSA-2048 / ECDSA Nginx + certbot / Let's Encrypt Auto-renewed 30d before expiry

Private keys are never:

  • Written to the database
  • Logged (even at debug level)
  • Included in error messages
  • Accessible to plugin subprocesses

Signing Chain

Operator generates Ed25519 keypair
  └─ Private key: /etc/vayupress/signing.key (L4 access only)
  └─ Public key:  published in /.well-known/vayupress-signing-key

Author submits article
  └─ ArticlePayload serialised to canonical JSON (sorted keys)
  └─ Ed25519 signature computed by host process (L3)
  └─ SignedArticle stored: {payload, public_key_hex, signature_hex}

Reader fetches article
  └─ signing.Verify() called before serving
  └─ Tampered articles → 500 + incident log

Compatibility & Stability Guarantees

See docs/compatibility/stability-matrix.md.