server-go

Golang PhotoBackup server

Browsing through F-Droid one day, I came across PhotoBackup - ever since I stopped using Owncloud, the lack of automatic photo uploads from my phone to my server has been bugging me, so I installed the client and started looking at the server. The concept is reasonable, the API is simple, but the implementations are a bit terrifying, so here's my attempt.

It's written in Go to avoid runtime dependencies; some glaring errors in the Python implementation have been corrected. To build from source (assuming you already have a Go runtime):

	$ go get github.com/lupine/photobackup-server-go
	$ cd $GOPATH/src/github.com/lupine/photobackup-server-go
	$ go build
	$ cp config.example ~/.photobackup
	$ vi ~/.photobackup # Add a Password= or PasswordBcrypt= line
	$ ./photobackup-server-go

There's now a HTTP server running on 127.0.0.1:8420 that will upload to ./incoming with the given password.

If there's demand, I'll put up some precompiled blobs. I wouldn't generally recommend using precompiled blobs you find on the Internet, though.

Deployment strategy

I'd say stick it under runit or systemd, bound to localhost, behind a HTTPS reverse proxy (nginx, say). For bonus points, run it as an unprivileged user in a jail. This is made much easier by the lack of runtime dependencies, of course.

Here's an nginx reverse proxy directive:

	location /photobackup {
	    proxy_pass http://127.0.0.1:8420;
	}

Here's a systemd unit file:

	[Unit]
	Description=HTTP server for PhotoBackup
	After=network.target

	[Service]
	ExecStart=/home/lupine/bin/photobackup-server-go
	User=lupine
	WorkingDirectory=/home/lupine
	Restart=always

Features

Improvements on photobackup-python

• Stores the secret on disc in a different format to on the wire (bcrypt(sha512(secret))
• Constant-time comparison of the secret, to avoid timing attacks
• Doesn't have to bind to the IPv4 wildcard
• Supports HTTP prefixes
• Uses 405 Method Not Allowed where appropriate
• Uses 409 Conflict where an upload would overwrite an existing file
• Doesn't read POST data beyond the filesize parameter

To add

• Direct HTTPS support
• Sensible multi-user support (support for, say, POST /:username[/test])
• Config file management like the python version's "init" stuff.