The nnCoection response header
I thought I’ve stumbled on some hand-crafted response from Amazon:
$ nc -vv www.amazon.com 80 Connection to www.amazon.com 80 port [tcp/http] succeeded! GET / HTTP/1.1 HTTP/1.1 400 Bad Request Date: Wed, 17 Jun 2009 22:31:39 GMT Server: Server Content-Length: 226 nnCoection: close Content-Type: text/html; charset=iso-8859-1 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>400 Bad Request</title> </head><body> <h1>Bad Request</h1> <p>Your browser sent a request that this server could not understand.<br /> </p> </body></html>Note the
nnCoection: close response header. The 400 response is returned, in this case, because of a missing Host request header.
Turns out the spelling mistake is intentional – Andrew Wooster’s excellent post claims that the header is changed by a load-balancing service, overriding the web server’s directive. A comment on that post identifies the service as the Citrix NetScaler appliance, and explains the logic of scrambling rather than removing the header altogether. Cool stuff.
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