159 lines
5.0 KiB
Markdown
159 lines
5.0 KiB
Markdown
# RushLink
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A URL shortener and (maybe) a pastebin server for our #ru community.
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## Building
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- `go get -u github.com/go-bindata/go-bindata/...`
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- `go generate ./...`
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- `go build ./cmd/rushlink`
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## Deploying
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We recommend running `rushlink` behind a reverse proxy suitable for processing
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HTTP requests, such as `nginx`, or `haproxy`.
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## Sample `nginx` config
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```
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server {
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location / {
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root /var/www/rushlink;
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proxy_pass http://127.0.0.1:8000;
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proxy_set_header Host rushlink.local;
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proxy_set_header X-Forwarded-For $remote_addr;
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proxy_set_header X-Forwarded-Proto $scheme;
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proxy_http_version 1.1;
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}
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}
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```
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`rushlink` automatically detects whether `http` or `https` is used when
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`X-Forwarded-Proto` is correctly set. Otherwise, pass `-root_url
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https://rushlink.local` to the binary (e.g. in the `systemd` unit file).
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## Sample `systemd` unit file
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As of 1fe9553cc9, `rushlink` expects its database and file store configuration
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in environment variables.
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```
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[Install]
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WantedBy=nginx.service
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[Service]
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Type=simple
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User=rushlink
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Group=nogroup
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Environment=RUSHLINK_DATABASE_DRIVER=sqlite RUSHLINK_DATABASE_PATH=/var/lib/rushlink/rushlink.sqlite3 RUSHLINK_FILE_STORE_PATH=/var/lib/rushlink/filestore/
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ExecStart=/var/lib/rushlink/rushlink -root_url https://rushlink.local
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```
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---
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# Background
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## Libraries
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Use standard-Go-libraries if the job can be done with those. As of now, these
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are the exceptions:
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- `github.com/gorilla/mux` provides useful stuff for routing requests.
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- `github.com/gorilla/sessions` for session management.
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- `go.etcd.io/bbolt` is our database driver.
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- `github.com/pkg/errors` provides a [`Wrap`] function.
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- `github.com/prometheus/client_golang/prometheus/...` has easy Prometheus
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functionality.
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[`Wrap`]: https://godoc.org/github.com/pkg/errors#Wrap
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## Database
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Before 1fe9553cc9 we used [`go.etcd.io/bbolt`]. This file should be the *only* file
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apart from our monolithic binary. All settings and keys should go in here.
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Any read-only data resides in the binary file (possibly compressed).
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Now, we use Gorm and support SQLite and PostgreSQL as backends.
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We provide a migration binary in `cmd/rushlink-migrate-db/`. In environment
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variables, the destination database is configured, and the binary itself
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expects a few flags. Refer to the source for the exact flags.
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[`go.etcd.io/bbolt`]: `go.etcd.io/bbolt`
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## Namespacing
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All shortened URLs exist as a key on the root of the webserver, i.e. `/xd42`.
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That means that we have to separate every other page with some kind of
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namespace. Ideas:
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- `/z/` reserved for flat pages.
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- `/z/static/` reserved for "static files".
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## Paste types
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Previous, I was planning to put pastes (not redirects) in a separate bucket
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and below a url namespace. Then when one was created, we would immediately
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generate a redirect link.
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Turns out it's easier though to just save a unit (we call it a "paste") which
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can be of different types. For example:
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- Redirect
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- Paste
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- File
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- Image
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- Hypothetical other stuff:
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- Dead-drop
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- [...]?
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## Shorten keys and collisions
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First of all: A sextet is a value of 6 bits.
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For generating keys, we will initially generate a random value of 4 sextets,
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where the first bit is set to `0`. If this collides with an existing key, we
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will generate a new one made out of 5 sextets, and set the prefix bits to
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`0b10`. We will keep doing this until we don't have any collisions anymore.
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To get proper-looking keys, we format the key to characters using the
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base64url alphabet described in ([RFC4648, par. 5]). The encoded value will
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be saved in the database.
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[RFC4648, par. 5]: https://tools.ietf.org/html/rfc4648#section-5
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## UI design
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As is tradition in a lot of URL-shortener/pastebin-like services, we will put
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everything in a single `<pre>` tag, and if possible, just serve `text/plain`.
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A good example is <https://0x0.st>.
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The reason we would use `text/html` instead of `text/plain` is basically
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form submissions and JavaScript. Our main API should be cURL, but it would be
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useful if users could also use the website and/or drag-and-drop files and URLs.
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On the other hand, using `text/plain` saves us *so much effort*, because we
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don't have to do any HTML/CSS/JavaScript. We have native terminal support, etc.
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The best thing would probably to do both, and correctly listen to the `Accept`
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header that the client sends. We can still wrap the plain-text page in a single
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`<pre>` to keep it easy for ourselves.
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## Retention
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- If we can, we don't want to have user accounts. We store the sessions
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forever, and store a user's data in there, without having to collect personal
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data in any way.
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- URL-shortening links will be retained for always, unless the submitter
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revokes it, in which case it will be replaced by a `410 Gone` page[*].
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- The probles of pastes are not solved. This is an unsolved problem[*].
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[*] In any case, we going to comply with all European laws and reasonable
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requests for deletion.
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## Privacy
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We will try as hard as possible to not store any data about our users, and will
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only provide any data when we have the legal obligation to do so.
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