STATE YOUR BIZNESS: Careful with what you Query.

Tuesday, 23 September 2008

Careful with what you Query.

The F5 BigIP load balancers have a feature called iRules. They allow you to manipulate and manage traffic in the Load Balancer.

They are really useful for checking or modifying cookies [HTTP::cookie], the host domain [HTTP::host], path [HTTP::path] and query parameters [HTTP::query] of URLs and requests.

A sligth word of warning though.... any checks made on the QUERY of a HTTP request actually search the URI of the referer as well. As an example, the following iRule would send a HTTP 200 response if you were either requesting a URL with a query parameter of "ThereIsAQuery" OR if you're refer page's URL included a query parameter of "ThereIsAQuery".

when HTTP_REQUEST {
  if {
      ([HTTP::QUERY] eq "ThereIsAQuery")
     }
  {
    HTTP::respond 200 content "<html><body>There is a Query</body></html>"
  }
}

Other attributes such as [HTTP::host], [HTTP::path], and [HTTP::uri] are only valid for the requested URL. They are not checked in the referer header.