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.

Option	Default	Meaning
-l, --listen	127.0.0.1:8080	address to listen on
-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.

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. The reply carries the download URL and a delete token, shown exactly once:

{
  "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 and digest
POST /api/d/{id}/delete	delete, with token= in the form or Authorization: Bearer

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

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.
• 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.