# File Drop (VYBECODED)

A minimal, self-hosted private file hosting service built with **Bun** and
**TypeScript**. Upload a file, get a secret, unguessable download link. Files are
stored permanently on the local filesystem and never expire.

Everything lives on disk — the filesystem is the source of truth. There is no
database, no object storage, no queue, and no automatic cleanup.

## Features

- Drag & drop / file-picker uploads with progress, straight from the browser.
- **Required per-file password**: every download is protected by a password.
- Permanent storage on the local filesystem; files survive restarts.
- A cryptographically secure, unguessable download key for every file.
- Streaming uploads and downloads — no full buffering in RAM, large files work.
- Configurable maximum upload size (`413` when exceeded).
- Authenticated deletion (possession of the file's secret key is required).
- Rate-limited download/delete endpoints to blunt brute force.
- Zero runtime dependencies (Bun is the only runtime).

## Requirements

- [Bun](https://bun.sh) >= 1.1 (developed and tested against 1.3).
- Any platform Bun runs on (Linux, macOS, Windows).

## Installation

```bash
bun install
```

There are no runtime dependencies; the only packages are dev-time
(`typescript`, `@types/bun`) used for type-checking.

## Configuration

All configuration is via environment variables. Bun auto-loads `.env`, so you
can copy the example and edit it:

```bash
cp .env.example .env
```

| Variable               | Default       | Description                                                       |
| ---------------------- | ------------- | ----------------------------------------------------------------- |
| `HOST`                 | `0.0.0.0`     | Bind address.                                                     |
| `PORT`                 | `3000`        | Bind port.                                                        |
| `STORAGE_DIR`          | `./storage`   | Directory where files + metadata are stored (relative to CWD).    |
| `MAX_FILE_SIZE`        | `5GB`         | Max upload size. Units: `B`, `KB`, `MB`, `GB`, `TB` (or plain int). |
| `RATE_LIMIT_ENABLED`   | `1`           | Enable per-IP rate limiting on `/d/` and `/api/files/`.            |
| `RATE_LIMIT_MAX`       | `300`         | Max requests per IP per window.                                   |
| `RATE_LIMIT_WINDOW_MS` | `60000`       | Rate-limit window length in ms.                                   |
| `TRUST_PROXY`          | `0`           | Set `1` only behind a proxy that sets `X-Forwarded-For`.          |

## Running locally

```bash
bun run start        # production (env-driven)
bun run dev          # watch mode, restarts on change
```

Then open http://localhost:3000.

## Usage

1. Open the site.
2. Drop `example.zip` (or click to pick a file).
3. The server stores it permanently and returns a URL like
   `https://files.example.com/d/8fJ...random-secret...`.
4. Copy the URL. Anyone possessing it can download the file — **after entering
   the password you set at upload**. Nobody without the secret URL and the
   password can download it.
5. The file stays available indefinitely. It is removed only by explicit
   deletion.

## Filesystem layout

```
storage/
├── .secret                   # server signing secret (0600), auto-generated
├── files/
│   ├── <file-id>            # the raw uploaded bytes
│   └── <file-id>
└── metadata/
    ├── <file-id>.json       # metadata for each file
    └── <file-id>.json
```

Example metadata record (`storage/metadata/<file-id>.json`):

```json
{
  "id": "YOWJyhDXxhe3-L8MpEFBbA",
  "originalName": "example.zip",
  "size": 123456,
  "mimeType": "application/zip",
  "downloadKeyHash": "669870d2e66b57edbd5128d85d803db0bed262efde61ef1f9e6dcef5c5ffa166",
  "createdAt": "2026-08-14T22:08:36.730Z"
}
```

Only a SHA-256 **hash** of the download key is stored — the plaintext key exists
only inside the URL shown to the uploader. If a download password is set, only
its scrypt hash is stored (see [password protection](#password-protection)).
The server signing secret for download cookies lives in `storage/.secret`
(`0600`), created on first start and reused across restarts.

Uploads are first streamed to a `<file-id>.part` temp file and atomically renamed
into place on completion. At startup the server sweeps for orphans (a file
without metadata or metadata without a file, plus leftover `.part` files) and
removes them. This is consistency repair, not expiration — real files are never
touched.

## API

### `POST /api/upload`

Multipart/form-data with a `file` field and a **required** `password` field
(this is what the web UI uses). Uploads without a password are rejected with
`400`.

```bash
curl -F "password=hunter2" -F "file=@secret.zip" http://localhost:3000/api/upload
```

```json
{
  "id": "xmK5lLMRErlN",
  "key": "xmK5lLMRErlN",
  "url": "/d/xmK5lLMRErlN",
  "originalName": "example.zip",
  "size": 123456,
  "protected": true
}
```

`id` and `key` are the same 12-character base64url token (~72 bits of entropy);
the short length keeps share URLs tidy, and the required password adds a second
factor of protection.

### `GET /d/:key` (also `HEAD`)

Every file is password-protected. Without a valid auth cookie the server shows a
password prompt; a wrong or non-existent key returns a generic `404`.

```bash
curl -O http://localhost:3000/d/xmK5lLMRErlN   # prompts for password first
```

### Password protection

Every file requires its password:

1. `GET /d/:key` returns a small HTML password form.
2. The browser submits it to `POST /api/auth/:key` with `password=...`.
3. On success the server sets a short-lived (30 min), HttpOnly, SameSite=Lax,
   signed cookie and redirects back to `/d/:key`, which then streams the file.

```bash
curl -c cookies.txt -X POST -d "password=hunter2" http://localhost:3000/api/auth/:key
curl -b cookies.txt -O http://localhost:3000/d/:key
```

The cookie is signed with a server secret (`storage/.secret`) so it cannot be
forged, and it survives server restarts. Without it, a file is never
downloadable — not even by the uploader.

### `DELETE /api/files/:id`

Permanently deletes the file and its metadata. The correct download key must be
sent in the `X-Delete-Key` header — proving you hold the secret.

```bash
curl -X DELETE -H "X-Delete-Key: YOWJyh...7OQ" http://localhost:3000/api/files/YOWJyhDXxhe3-L8MpEFBbA
```

### `GET /api/health`

```json
{ "status": "ok", "uptimeSeconds": 42 }
```

### Status codes

`400` invalid request · `404` unknown/invalid key · `413` file too large ·
`429` rate limited · `500` internal error. Errors are generic JSON and never leak
paths or stack traces.

## Security model

- **Secrets.** Each file gets a fresh 72-bit (9 random bytes) base64url key via
  `crypto.randomBytes`, used as both the share id and the download key. Keys are
  encoded base64url; guessing one is infeasible at scale, and the required
  password is an added second factor. No timestamps, incrementing ids,
  `Math.random()`, or filenames are ever used as secrets.
- **At-rest.** Only a SHA-256 hash of the key is persisted. Comparisons use
  constant-time `timingSafeEqual`.
- **Passwords.** Every file has a password stored only as an **scrypt** hash
  (salted), never in plaintext. Successful entry mints a short-lived HMAC-signed
  cookie, so access is granted by the server and cannot be forged.
- **Path safety.** Filesystem paths are built only from server-generated,
  regex-validated ids (`^[A-Za-z0-9_-]{22}$`). The original filename is metadata
  only and is sanitized (basename, control/null bytes stripped) before being
  stored or emitted in `Content-Disposition`. Path traversal, `../`, encoded
  traversal, null bytes, and symlink injection via user input are not possible.
  Downloads additionally refuse symlinks (`lstat`) as defense in depth.
- **MIME / XSS.** Downloads are sent as `Content-Disposition: attachment` (browsers
  download rather than render) with `X-Content-Type-Options: nosniff`, so a spoofed
  `text/html` or `image/svg+xml` cannot execute scripts.
- **Secrecy of URLs.** All responses carry `Referrer-Policy: no-referrer`, and
  downloads use `Cache-Control: private, no-store`, so the keyed URL is not leaked
  to referrers or shared caches.
- **Isolation.** Only the frontend, health, upload, download, and delete routes
  exist; everything else is a `404`. `storage/` is never served.
- **Brute force.** Download and delete endpoints are rate-limited per client IP.
  Set `TRUST_PROXY=1` only when a proxy sets `X-Forwarded-For`, otherwise clients
  can spoof it.
- **Log hygiene.** Logs record file ids, sizes, and sanitized names — never
  download keys or full private URLs.
- **Overwrite.** Random ids make collisions effectively impossible; uploads write
  to a unique `.part` file and atomically rename.

## Reverse proxy

The app does not handle TLS; put nginx, Caddy, or Cloudflare in front. It works
behind any proxy because it uses relative URLs and doesn't require HTTPS
termination.

Important: large uploads only work if your proxy does **not** buffer the request
body.

### nginx

```nginx
server {
    listen 80;
    server_name files.example.com;

    client_max_body_size 6g;          # >= MAX_FILE_SIZE
    proxy_request_buffering off;      # stream uploads, don't buffer

    location / {
        proxy_pass http://127.0.0.1:3000;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_read_timeout 300s;      # slow/large downloads
    }
}
```

### Caddy

```
files.example.com {
    reverse_proxy 127.0.0.1:3000

    request_body {
        max_size 6GB
    }
}
```

> Cloudflare note: the free plan caps uploads at ~100MB (and downloads at
> ~100MB/500MB depending on plan). For larger files, bypass the proxy for
> `/api/upload` and `/d/` (e.g. a cache rule or origin rule) so traffic hits the
> origin directly.

## Production deployment

> Follow the step-by-step **[HOSTING.md](./HOSTING.md)** guide for a complete
> VPS setup (Bun install, systemd, nginx/Caddy + TLS, firewall, Cloudflare,
> backups, troubleshooting). Summary below.

```bash
# 1. install bun and copy the project
mkdir -p /opt/filehost && cp -r . /opt/filehost && cd /opt/filehost
bun install

# 2. create a dedicated user and writable storage
useradd --system --home /opt/filehost filehost
mkdir -p /opt/filehost/storage && chown -R filehost:filehost /opt/filehost

# 3. configure
cp .env.example /opt/filehost/.env
# edit .env (PORT, STORAGE_DIR, MAX_FILE_SIZE, TRUST_PROXY, ...)

# 4. install the systemd unit (see deploy/filehost.service)
cp deploy/filehost.service /etc/systemd/system/filehost.service
systemctl daemon-reload
systemctl enable --now filehost
systemctl status filehost

# 5. put a reverse proxy in front (above)
```

## Backup

Backup the whole `storage/` directory. Because files and metadata live in the
filesystem, a simple `tar` gives you a consistent, restorable snapshot:

```bash
tar -czf filehost-backup-$(date +%F).tar.gz /opt/filehost/storage
```

A nightly cron job:

```cron
0 2 * * * tar -czf /var/backups/filehost-$(date +\%F).tar.gz -C /opt/filehost/storage .
```

To restore: stop the service, replace the `storage/` directory, start the
service. Files that have their metadata survive; anything incomplete is repaired
by the startup sweep. For crash-consistency you can stop the service during
backup (or rely on `tar` on a quiet filesystem). Metadata writes are atomic
(tmp + rename), so partial records are rare.

## Running the smoke test

```bash
# start the server, then:
./scripts/smoke-test.sh
BASE_URL=http://127.0.0.1:3000 ./scripts/smoke-test.sh   # explicit URL
```

It exercises upload, download, invalid keys, id-only denial, storage isolation,
Unicode names, path traversal sanitization, a 16MB binary round-trip, and
authenticated deletion. The same checks performed manually during development
also included restart persistence, a 256MB streaming round-trip (peak RSS
~80MB), `413` handling, rate limiting, and log-hygiene (keys never logged).

## Project layout

```
src/
├── server.ts          # entry point: config, routing, static files, startup
├── config.ts          # env parsing + size parsing
├── storage.ts         # filesystem source of truth (save, metadata, delete, sweep)
├── multipart.ts       # streaming multipart parser (no full-body buffering)
├── security.ts        # key generation, hashing, timing-safe compare, sanitization
├── ratelimit.ts       # simple per-IP fixed-window limiter
├── http.ts            # response/error helpers + security headers
├── log.ts             # timestamped logging
├── routes/
│   ├── upload.ts      # POST /api/upload
│   ├── download.ts    # GET /d/:key
│   └── delete.ts      # DELETE /api/files/:id
└── public/            # plain HTML/CSS/JS frontend (no framework)
```

Intentionally small: no framework, no DI, no ORM, no repositories. Bun +
TypeScript + filesystem + a simple frontend + secret URLs.