I've successfully setup HAProxy in front of an HTTP server which I have no control over.
Is it possible to configure HAProxy to add Simple HTTP Authentication to all sites, bearing in mind I can't configure this on the backend?
I had to do this today myself (because IIS 7.5 bizarrely doesn't actually support authenticating against anything but Windows user accounts or AD!)...
Here's all the code
I documented it a bit better here: http://nbevans.wordpress.com/2011/03/03/cultural-learnings-of-ha-proxy-for-make-benefit/
I think this is actually possible, but right now I can only find an example to get you halfway...
http://haproxy.1wt.eu/download/1.4/doc/configuration.txt is your bible.
Check out section 3.4 (Userlists)
That section explains how to set up a userlist. The example in that section's quite exhaustive so copy that if you need to.
Next, need to figure out how to apply it... I think the answer lies in section 7.5.3 (Matching at Layer 7)
I think it might be as simple as using the following in an acl:
Again, I haven't tested it, but that's what I read the documentation as suggesting is possible.
I hope that's enough to get you started?
If you're looking to do this for the purposes of authenticating an
config, this simpler solution works: http://stackoverflow.com/questions/13325882/haproxy-solr-healthcheck-with-authentication