I noticed that if a link accesses a cgi script, I can use the os.getenv('HTTP_REFERER');
The calling url may be a javascript call from html or a flex URLRequest obj. Is this possible?
Basically I want to make sure that the call comes from within my webserver and not from an external hijacker.
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Something like the following, in your Apache httpd.conf Virtual Host should block access to any CGI script, unless HTTP_REFERER contains you domain name:
RewriteEngine On
RewriteCond %{HTTP_REFERER} !www.yousite.com
RewriteRule .cgi$ - [F]
You might want to make it more selective, and technically you could spoof the HTTP_REFERER.
> .. I want to make sure that the call comes from within my webserver
short answer: i.g. impossible
long answer: the out-of-the-box check would be the referer, but this is 101% unreliable as it can be spoofed or missing; you may add a unique token (as hidden field for example) and check for its existance when you receive the request.
@ahoffmann:
The only problem with the hidden token is that if someone can get watch the data going out in the url call, then the token or key would be useless. I guess it is impossible from what you are saying.
@arober11
I am not following what you are saying. Correct me if I am not understanding you correctly. I want to see the HTTP_REFERER of the GET or POST call, not a Referal link. The HTTP_REFERER I can check in the scripts or how you are stating, but that only works if the call has a HTTP_REFERER. And that is what I am trying to get.
Probably missread your question, by:
"I want to make sure that the call comes from within my webserver and not from an external hijacker."
Do you only want requests originating from the Web server (From a (Virtual) Web browser running on the actual server) to be able to POST / GET requests to .cgi scripts?
If that's the case the the following might work (depending on how many IP's the server has).
RewriteCond %{REMOTE_ADDR} !%{SERVER_ADDR}
RewriteRule .cgi$ - [F]
ELSE if your trying to ensure all external requests to .cgi scripts are initiated from a bit of your own code, in one of your Web pages, you'll probably be wanting to send / check for a unique session cookie, with each page.
> but that only works if the call has a HTTP_REFERER. And that is what I am trying to get.
exactly. You cannot get, and not check obviously, the referer if it is not there
> .. someone can get watch the data going out in the url call, then the token or key ..
how can someone get these data?
Well spoofing might be possible which is not that simple as it requieres a vulnerability elsewhere also. You can get rid of the spoofing threat by using SSL.
If someone analyses your site with a script or whatever, then (s)he gets the token and may construct a proper request anyway. You never can distinguish a scripted request from a browser request.
If you mean that a script get the token once and then constructs and sends multiple requests, then you implemented the token the wrong way. I said:
add a unique token
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by: cafechrisPosted on 2009-09-17 at 20:24:53ID: 25362754
Basically,
Is there any way to ensure that the service that is calling my cgi script exists on my webserver. Hope this all makes sense. If it doesn't please ask any ?s and I will explain.