uncensored-send/README.md

# Uncensored Send

A small self-hosted file drop. Uploads land in a flat data directory, expire on
their own, and are served back as inert attachments.

Built for sharing large binaries with friends — a 400 MB Godot export is a
normal day here — without a `tmp/` folder that grows forever.

- One static Go binary. No database, no dependencies outside the standard
  library, no CSS or JavaScript build step.
- Anyone who can reach the page may upload, within a size cap and a lifetime.
- Named tokens raise those limits and unlock custom URLs.
- Everything expires unless a token says otherwise.

## Building

```
go build -o send .
```

Go 1.25 or newer. There is nothing to install: the frontend is embedded in the
binary.

## Running

```
./send --data /var/lib/send --listen 127.0.0.1:8080
```

It binds to loopback by default and expects to sit behind a reverse proxy that
terminates TLS. Make sure the proxy does not buffer request bodies and does not
impose its own upload size limit, or large uploads will die before they arrive.

Options take **one hyphen with a single letter** and **two with a full word**:
`-s 4GiB` and `--max-size=4GiB` are the same option, `-max-size` is an error.
Every option can also be set from the environment as `SEND_MAX_SIZE` and so on.
`./send --help` lists them all.

`--port` is a convenience over `--listen`: it replaces only the port, so
`./send -p 9000` listens on `127.0.0.1:9000` and `--listen 0.0.0.0 -p 9000`
listens on all interfaces.

| Option | Default | Meaning |
|---|---|---|
| `-l`, `--listen` | `127.0.0.1:8080` | address to listen on |
| `-p`, `--port` | — | port to listen on, replacing the one in `--listen` |
| `-d`, `--data` | `./data` | data directory |
| `-b`, `--base-url` | `/` | path prefix when mounted under a subdirectory |
| `-u`, `--public-url` | — | absolute base URL used in generated links |
| `-s`, `--max-size` | `2GiB` | per-upload cap; `unlimited` to remove it |
| `-e`, `--max-expiry` | `3d` | longest lifetime a caller may ask for; `never` to remove the cap |
| `--default-expiry` | `3d` | lifetime applied when the caller does not ask |
| `--max-total-bytes` | `unlimited` | whole-store quota |
| `--min-free-bytes` | `1GiB` | refuse uploads below this much free disk |
| `--tokens` | `<data>/tokens.json` | token file |
| `--trusted-proxy` | — | networks whose `X-Forwarded-For` is believed |
| `--sweep-interval` | `1m` | how often expired files are removed |
| `--upload-rate` | `60` | uploads per hour per client |
| `--upload-burst` | `10` | uploads allowed back-to-back |
| `--max-concurrent` | `8` | uploads in flight at once |

Sizes accept `2GiB`, `500MB`, `4G` or a plain byte count. Durations accept `3d`,
`12h`, `90m`, `1w` or `never`.

## Tokens

A token grants its own limits. Anything left unset is inherited from the
server's defaults, so a bare token behaves exactly like the anonymous tier
except that it may claim custom names.

```
./send token add thayol --vanity --max-size 8GiB --max-expiry never
./send token list
./send token rm thayol
```

The token is printed once and never again; only its SHA-256 is stored. Send it
as `Authorization: Bearer <token>`, or paste it into the form's token field.

`tokens.json` may also be edited by hand; the server picks up changes on its own
and on `SIGHUP`. It must stay mode `0600` — the server refuses to start
otherwise, since it holds credential material.

### Logging in

Open **Log in**, paste a token, and the browser keeps it until you log out. The
header then shows who you are, the upload page shows your real limits, and
**Administration** appears if the token is an admin one. Tick *stay logged in*
and it survives a browser restart; leave it unticked and it dies with the
browser, which is the right choice on a machine that is not yours.

The upload form also keeps a collapsed **Use a different token for this upload**
field. That one applies to a single upload and never changes the session, so a
quick upload under another token does not mean logging in and out.

The session cookie is `HttpOnly`, so the page's own script cannot read it — the
server resolves the session and renders it. That is deliberately unlike
`localStorage`, where any script injected into the origin could read the token
straight out. It is also `SameSite=Strict`, so no other site can make your
browser upload or delete anything with it attached.

Nothing about the session involves JavaScript: every page states who you are
because the server rendered it that way. Callers sending `Authorization: Bearer`
are never given a cookie; an API client keeps its own credentials.

## Uploading

From the browser, just use the page. It works with JavaScript disabled; with it
enabled you get a progress bar, drag-and-drop and a copy-link button.

From the command line, `POST /api/upload` with the file as the whole body:

```
curl --data-binary @MyGame.zip \
     -H 'Content-Disposition: attachment; filename="MyGame.zip"' \
     -H 'Authorization: Bearer <token>' \
     -H 'Vanity: my-game' \
     -H 'Expiry: 7d' \
     -H 'Accept: application/json' \
     https://send.example.com/api/upload
```

`Content-Disposition`, `Vanity` and `Expiry` are all optional. Without a vanity
name you get a UUIDv4; vanity names require a token. These headers work with a
`multipart/form-data` body too, where a non-empty form field of the same name
overrides them. The reply carries the
download URL and a **delete token**, shown exactly once:

```json
{
  "id": "my-game",
  "url": "https://send.example.com/d/my-game",
  "expires": "2026-09-19T10:00:00Z",
  "delete_token": "…",
  "delete_url": "https://send.example.com/api/d/my-game/delete"
}
```

The same endpoint accepts `multipart/form-data` from the web form. In that shape
the `token`, `expiry` and `vanity` fields **must precede the file part** — the
body is streamed, so the limits have to be known before the first byte of the
file is accepted.

## Downloading and deleting

| Route | |
|---|---|
| `GET /d/{id}` | the file, as an attachment; supports resuming |
| `GET /i/{id}` | a page showing name, size, expiry, digest — and where a delete token is used |
| `POST /api/d/{id}/delete` | delete, with `token=` in the form or `Authorization: Bearer` |
| `GET /login`, `POST /login` | start a browser session with a token |
| `POST /logout` | end it |
| `GET /admin` | administration page; admin tokens only |
| `GET /api/limits` | what the presented credential may do; for scripts, the pages do not use it |

Deleting accepts the object's delete token, the token that uploaded it, or any
admin token.

The delete token is shown once, when the file is uploaded. To use it later,
open the file's info page and expand **Remove this file** — that page is the
link worth keeping, since it holds everything about the file including the way
to withdraw it. Anyone whose own token already owns the file, or who is an
admin, gets a plain button there instead of a field. A wrong token returns to
the same page with the reason rather than to a generic error, and repeated
failures are throttled per address; a correct token is never delayed by
someone else's guessing.

## Administration

An admin token adds a page at `/admin`, linked from the header whenever the
token you are using is one. It is the view that privilege is for: every stored
file, whoever uploaded it, with a delete button on each row.

- Files, with size, owner, upload time and expiry, sortable by column. Expired
  files are not listed even if the sweeper has not reached them yet, since they
  are already gone as far as anything else is concerned.
- Totals: how many files, how much is stored, how much of the quota is used and
  how much disk is left.
- The configured tokens with their limits — names only. Hashes are never
  rendered, and there is no way to mint or revoke a token from the page.
  Anything that hands out credentials stays in the CLI, off the network.

Deleting from the table returns to the table. A non-admin gets `403` and never
sees the link.

## Data directory

```
<data>/
  objects/<id>/blob        the bytes                     0664
  objects/<id>/meta.json   name, size, digest, expiry    0664
  tokens.json              credential hashes             0600
```

Objects and their metadata are group-writable and world-readable, so a second
account or a cleanup script can manage them. `tokens.json` is the deliberate
exception.

There is no index to corrupt: the in-memory index is rebuilt from `meta.json`
files at startup, and an object directory without one is either mid-upload or
the remains of a killed one, invisible either way and swept after 24 hours.

## Notes on the security posture

Worth knowing if you are going to run this somewhere real.

- **Uploads are never sized by what the client claims.** `Content-Length` is
  not consulted anywhere; the cap is enforced on bytes actually written, and the
  transfer is cut off the moment it is exceeded.
- **Nothing served from `/d/` can execute.** `Content-Type` is always
  `application/octet-stream`, the disposition is always `attachment`, and the
  response carries `nosniff` and `default-src 'none'; sandbox`. Upload an HTML
  file and a browser will download it, not render it.
- **Filenames are metadata, never paths.** Every path is built from a validated
  ID: lowercase, 2–64 characters, no separators, no traversal, no route names.
  The uploaded filename only reaches the `Content-Disposition` header, where the
  ASCII form is built from a character whitelist and the real name rides along
  in an RFC 5987 parameter.
- **Object files are opened through an `os.Root`.** Because the data directory
  is group-writable, a planted symlink could otherwise redirect a read or a
  write outside it. It cannot.
- **Expiry is checked on every read**, not only by the sweeper, so a stalled
  sweeper can never serve a file past its lifetime. A missing file and an
  expired one give identical 404s.
- **Uploads are published atomically**: the blob is fsynced and renamed into
  place before the metadata that advertises it is written, also by rename. A
  crash at any point leaves something invisible rather than something broken.
- **Vanity names are claimed before the body is read**, so a collision costs one
  round trip rather than a 2 GiB transfer.
- **Slow uploads are fine, stalled ones are not.** There is no server-wide read
  timeout — any value large enough for a legitimate 2 GiB upload would be no
  protection — so the upload handler maintains a per-read deadline instead.
- **`X-Forwarded-For` is ignored** unless the peer is a configured
  `--trusted-proxy`, and then only to skip further trusted hops.
- **The session lives in an `HttpOnly`, `SameSite=Strict` cookie**, not in
  `localStorage`, so neither an injected script nor another website can get at
  it. `Secure` is set whenever the service knows it is being served over
  HTTPS — from `--public-url`, from a TLS connection, or from a trusted proxy's
  `X-Forwarded-Proto`.
- **Every `POST` must be same-origin.** `SameSite` covers requests that need a
  cookie, but logging in needs none: without this check a hostile page could
  sign a visitor into an account it controls and collect what they upload next.
  Browsers label their own requests with `Sec-Fetch-Site`, falling back to
  `Origin`; a request carrying neither is not a browser and is allowed through,
  since a bearer token cannot be attached by a third party anyway.
- **Failed credential attempts are throttled per address** — a wrong delete
  token or a wrong login — while correct ones are never delayed, because only
  failures consume the budget.
- Rate limiting is per client address, with a separate bound on uploads in
  flight. Both are in memory and reset on restart.

## Development

```
go test ./...
go vet ./...
```

The tests cover the parts where a mistake would be expensive: size limits
against a chunked body with no declared length, vanity collisions, expiry on
read, traversal and reserved names, `Content-Disposition` for hostile filenames,
delete authorisation, symlink escapes and crash debris.