Security

Foldergram is built for local-only and self-hosted browsing. Its security model is intentionally narrow even though it now supports an optional shared-password gate for homelab and LAN use.

What Foldergram assumes

• you run it on your own machine or behind a trusted local-network or reverse-proxy setup
• the app is not exposed directly to the public internet without additional protection
• the built-in auth story is a single shared password, not a multi-user account system

Shared-password protection

Foldergram can optionally protect the library with one shared password configured from the Settings page.

When enabled:

• Foldergram stores a one-way password hash, salt, and session metadata in SQLite app_settings
• the browser unlocks access with a signed HttpOnly session cookie
• /api routes require that session, except for GET /api/health, GET /api/auth/status, POST /api/auth/login, and POST /api/auth/logout
• generated media under /thumbnails and /previews also require that session
• authenticated API and media responses are marked Cache-Control: no-store and Vary: Cookie
• the production service worker skips caching protected thumbnail and preview responses

Changing the password rotates the session version, which invalidates older sessions. Disabling password protection clears the stored auth settings.

Mutation protection

All mutating API routes pass through requireTrustedMutationRequest.

That middleware does two things:

1. Requires x-foldergram-intent: 1
2. Rejects non-loopback Origin or Referer values when those headers are present

Allowed hostnames are:

• localhost
• 127.0.0.1
• ::1

Allowed ports are:

• DEV_SERVER_PORT and the reserved DEV_CLIENT_PORT through DEV_CLIENT_PORT + 3 range in development or test
• SERVER_PORT in production, with loopback origins or the exact host that served the app accepted for browser mutations
• explicit extra origins can be allowed through CSRF_TRUSTED_ORIGINS

What this protects against

With password protection enabled, this design helps reduce opportunistic browsing of the library from other machines on the same network.

Separately, the mutation checks help reduce accidental or cross-site browser-triggered mutations from untrusted origins.

It is especially relevant for:

• feed and folder reads when password protection is enabled
• generated thumbnails and previews when password protection is enabled
• delete actions
• like toggles
• manual rescans
• rebuild operations

Path confinement

Foldergram does not serve arbitrary filesystem paths from the client.

Original-file serving

GET /api/originals/:id:

• looks up the post by numeric ID
• resolves the stored absolute path
• confirms that path is still within GALLERY_ROOT
• confirms the file still exists

Delete actions

Delete flows resolve target files and directories inside configured roots before removing them. If a stored path falls outside the expected root, the operation throws instead of deleting blindly.

Storage availability behavior

On startup, Foldergram checks:

• gallery directory
• thumbnails directory
• previews directory
• database directory

If the database directory is unavailable, it falls back to an in-memory database. If the gallery or derivative directories are unavailable, the library is marked unavailable and the UI receives explicit storage-state information.

This is a resilience measure, not a security feature.

Rate limiting

Foldergram includes small in-memory rate limiters for:

• authentication attempts
• admin mutation routes such as rescan and rebuild operations

These limiters are process-local and intentionally simple. They are useful for basic abuse reduction, not for hardened distributed deployments.

Important limitations

Foldergram does not currently provide:

• multi-user authentication
• per-user authorization
• TLS termination
• audit logging
• hardened remote deployment defaults
• external identity provider integration
• per-user isolation

Practical advice

Use Foldergram like a local app:

• use a strong shared password if you expose it on a homelab or LAN
• keep it on loopback unless you know exactly how you are proxying and protecting it
• terminate HTTPS upstream if the app is reachable off-box
• remember that on plain HTTP, both the password and session cookie are visible to anyone who can sniff that local network traffic
• do not assume the shared-password layer and mutation checks are a full internet-facing security boundary
• treat delete actions as destructive and permanent

A precise caveat about headers

If a mutating request omits both Origin and Referer, the middleware still accepts it as long as x-foldergram-intent: 1 is present. That is acceptable for the current local-only model, but it is one reason these checks should not be described as a full remote-hardening story.

What Foldergram does not try to be

Foldergram is not attempting to be:

• a cloud photo product
• a multi-user NAS portal
• a public media server with account management
• a zero-trust network service

The implementation is much closer to a private local gallery with a browser UI.