Simple LAN filesharing with WebDAV

WebDAV is both an overlooked and quite popular way to access and edit files remotely across a wide range of operating systems. Yes it's web stuff, again, but surprisingly fast, lightweight, and that can recover quite well on unstable networks or when the server has to be restarted, or has gone for lunch. A reason why it may be overlooked is possibly because it's often associated with sausage factories like own/nextcloud, or standalone implementations that are not particularly exciting. What is less known is that many web servers come with their own WebDAV implementation out of the box. Out of the usual suspects, nginx, Apache, and lighttpd, the latter has both the most lightweight and most complete implementation. No need for anything else!

In these notes we only cover a simple LAN setup, you can build upon it for more complex use case of course.

Server side

Installation

• This is for Debian, but you're smart

sudo apt install lighttpd lighttpd-mod-webdav

Example Configuration

Basically the configuration are in /etc/lighttpd/conf-available and with symlinks in /etc/lighttpd/conf-enabled. In our simple example we have three shared folders, one that can be mounted read-only by anyone, and two that are read-write but requires a username and password.

• By default a temp config file called 99-unconfigured.conf provides a generic landing page. We don't need it and we just have to enable the authentication config.

sudo lighttpd-disable-mod unconfigured
sudo lighttpd-enable-mod auth

• Create a user and password for the read-write share

sudo apt install apache2-utils
sudo htpasswd -c /etc/lighttpd/user.htpasswd turtleprincess

• create a new configuration file /etc/lighttpd/conf-available/66-webdav.conf with the following:

server.modules += ( "mod_webdav" )
dir-listing.encoding = "utf-8"
  
# This is needed for keepings tracks of locks and props which
# are needed for shares that can be edited
webdav.sqlite-db-name = "/var/cache/lighttpd/lighttpd.webdav.db"
  
# auth
server.modules += ("mod_authn_file")
auth.backend = "htpasswd" 
auth.backend.htpasswd.userfile = "/etc/lighttpd/user.htpasswd"
auth.require = ( "/readwrite1"     => ( "method" => "basic", 
                                 "realm" => "YOU WOT MATE", 
                                 "require" => "valid-user" ),
                 "/readwrite2" => ( "method" => "basic",
                                 "realm" => "YOU WOT MATE",
                                 "require" => "valid-user" ))
  
# read-only stuff
$HTTP["url"] =~ "^/readonly(?:/|$)" {
    alias.url = ( "/readonly" => "/local/path/to/readonly" )
    dir-listing.activate = "enable" 
    webdav.activate = "enable" 
    webdav.is-readonly = "enable" 
}
 
# shared pit of madness
# for users listed in /etc/lighttpd/user.htpasswd
$HTTP["url"] =~ "^/readwrite1(?:/|$)" {
    alias.url = ( "/readwrite1" => "/local/path/to/readwrite1" )
    dir-listing.activate = "enable" 
    webdav.activate = "enable"
    webdav.is-readonly = "disable" 
}
$HTTP["url"] =~ "^/readwrite2(?:/|$)" {
    alias.url = ( "/readwrite2" => "/local/path/to/readwrite2" )
    dir-listing.activate = "enable" 
    webdav.activate = "enable"
    webdav.is-readonly = "disable" 
}

Now if you wonder what kind of magic will happen so that the lighttpd process, local and remote users can happily edit the same files, well, none. It won't work and you will be sad. Then you will start binge drinking to forget about server administration, go in the streets pick up fights with strangers who are in a much better physical condition because they don't spend hours configuring neovim plugins that you don't even use. It will be painful. To avoid this unfortunate situation you need to do two things:

• First, the folder needs to be group-owned by the lighttpd process owner, in this www-data and you also need to set the group ID bit on the folder, so that all newly created files will inherit the group ownership.

sudo chown regular_user:www-data /local/path/to/readwrite1
sudo chmod g+ws /local/path/to/readwrite1

• Second, you need to change the way lighttpd is started so that its umask is set in a way that any permission may be set for user and group (default is just user). On a systemd based system you need to edit /etc/systemd/system/lighttpd.service so that:

ExecStart=/bin/sh -c 'umask 002;/usr/sbin/lighttpd -D -f /etc/lighttpd/lighttpd.conf'

That's it, you have a working simple LAN filesharing with WebDAV check the documentation for more options, and more fun config time.

Client side

Web browser

The nice advantage of the setup above is that all the files can be readily browsed at the local IP of the machine running lighttpd, for instance http://192.168.100.100/readonly. If you're into web stuff have a look at https://github.com/dom111/webdav-js, it would be really trivial to server this js file with the lighttpd server and provide more functionality than just browsing and downloading.

Linux filesystem

Mounting on Linux is straightforward with davfs2 and requires minimal configuration.

• To mount manually the read-only folder:

sudo mount -t davfs http://192.168.100.100/readonly /mnt/readonly