Use Dropbox to host public files on your own domain name

I’ve been using a Dropbox public folder and some Apache trickery to share files directly from Dropbox on my own domain at pub.noxon.cc. Dropbox is drag-and-drop file sharing at its finest, and by sharing my files on pub.noxon.cc¬†instead of on dl.dropboxusercontent.com, my files are accessible to corporate folks who would otherwise find themselves blocked by an over-zealous web filter. Last but not least, if one of my files becomes too popular, Dropbox won’t shut down my account.

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Dropbox doesn’t offer a custom hosting service, so I had to build it. I already have an Apache server, so I created a new virtual host and added some reverse proxy magic. I set up my virtual host as the origin server for the Amazon CloudFront content distribution network, ensuring a minimal load on my own server and the ability to handle virtually unlimited amounts of traffic.

Here’s a recipe for Apache 2.2, mod_proxy, and mod_rewrite:

DirectoryIndex disabled

ProxyRequests off

RewriteEngine on
RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-d
RewriteRule ^/(.*) http://dl.dropboxusercontent.com/u/xxxxxx/$1 [P,L]
ProxyPassReverse / http://dl.dropboxusercontent.com/u/xxxxxx/

Header unset cache-control
Header unset Pragma
Header merge cache-control max-age=3600
Header merge cache-control must-revalidate
RequestHeader set User-Agent Mozilla

The cache-control settings dictate that CloudFront should cache my content for an hour (3600 seconds). CloudFront currently ignores the specified max-age for 404 results, instead preferring to cache them for about 10 minutes. I’d prefer a shorter lifetime for failed requests, but that’s not easy with Apache 2.2; With 2.4, it’s do-able.

The requesting User-Agent override is necessary because Dropbox blocks requests from the Amazon CloudFront User-Agent.

Using mod_rewrite makes it possible to host overlapping content outside of Dropbox. If it exists on the server, it gets served locally; If it’s missing, Apache tries to fetch it from Dropbox. I locally host the favicon, robots.txt, a 404 handler, and a couple of other things.

If you want to use your own 404 handler, you’ll need this:

ProxyErrorOverride On
ErrorDocument 404 /path/to/404.html

Before you deploy something like this, carefully consider the security implications and make the necessary adjustments. Do you want PHP code in a Dropbox folder running on your server?

Dropbox public folders are not available to users who signed up for Dropbox after July 31, 2012.

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