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RE: http-methods & http-trace NSE Script Enhancement Ideas
From: King Thorin <kingthorin () hotmail com>
Date: Wed, 23 May 2012 13:33:44 -0400


I just had a quick look at http-cors. It does not appear to follow redirects or check status codes at all, only setting 
and getting header values. I'm not sure if those header values would or wouldn't be present in a redirect.

I still need someone (or a bunch of people) to confirm if I'm correct in my experiences with allow and public being 
lacking on redirect responses. Also I still need to know how to provide updates for the scripts in question.

I'd propose a script parameter such as:
redirect_count

So code for htt-trace.nse could look like ( I threw this together quickly, it's not necessarily perfect or useable in 
this form):

--- Validates the HTTP response and returns header list
-- () param response The HTTP response
-- () param response_headers The HTTP response headers 
local validate = function(response, response_headers, followed_redirects)
  local output_lines = {}

  if not(response:match("HTTP/1.[01] 200") or response:match("TRACE / HTTP/1.[01]")) then
    return
  else
    output_lines[ #output_lines+1 ] = "TRACE is enabled"
    if followed-redirects > 0
      output_lines[ #output_lines+1 ] = "Followed " .. followed_redirects .. " redirects." -- We followed some 
redirects, tell the user
  end
  if nmap.verbosity() >= 2 then 
    output_lines[ #output_lines+1 ]= "Headers:"
    for _, value in pairs(response_headers) do
      output_lines [ #output_lines+1 ] = value
    end
  end
  if #output_lines > 0 then
    return stdnse.strjoin("\n", output_lines)
  end 
end

---
--MAIN
---
action = function(host, port)
  local path = stdnse.get_script_args("http-trace.path") or "/"
  local num_redirects = stdnse.get_script_args("http-trace.redirect_count") or 2 -- Set default low [2] and let user 
make it bigger if needed
  local followed_redirects = 0  

  local req = http.generic_request(host, port, "TRACE", path) -- Request zero
  while (req.status == 301 or req.status == 302) and req.header["location"] and followed_redirects < num_redirects do 
-- Follow 2 or redirect_count redirects
    req = http.generic_request(host, port, "TRACE", req.header["location"])
    followed_redirects = followed_redirects + 1
  end -- Hopefully when we finish looping we received a HTTP 200 OK after following some redirects (at least we tried)

  return validate(req.body, req.rawheader, followed_redirects)
end

PS > The thread has now had two top and one bottom reply, what's the actual preference on this list?


Date: Wed, 23 May 2012 18:41:06 +0300
Subject: Re: http-methods & http-trace NSE Script Enhancement Ideas
From: toni.ruottu () iki fi
To: paulino () calderonpale com
CC: kingthorin () hotmail com; nmap-dev () insecure org

Does this affect http-cors too?

On Wednesday, 23 May 2012, Paulino Calderon  wrote:
On 23/05/2012 07:17 a.m., King Thorin wrote:



I was just looking through some online docs and some nmap results. I've

never seen a server that includes public or allow header(s) on a

redirect response [maybe my experience is limited?]. It seems to me that the http-methods NSE should follow

redirects (HTTP 301, 302, 303) in order to perform the necessary OPTIONS

  request on a page/resource that's providing a HTTP 200.





Perhaps similar to the http-trace script:

http://nmap.org/svn/scripts/http-trace.nse

Though

  even that only follows one 301 or 302 redirect.



Further, maybe both scripts should follow a configurable

  # of redirects (default 2, 3, 4 and configurable further) looking for a

  HTTP 200&  handle 301, 302, and 303 redirect codes.





Reference:

http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html



I've emailed the devs of both scripts without any luck.







I'd be glad to provide the necessary changes, if someone can simply fill me in as to how they should be submitted.



                                        

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I think adding a configuration value for redirects will work better in some cases. I would say most of the libraries 
follow 2-3 redirects but no more than that. In your experience, what would be a good default?



-- 

Paulino Calderón Pale

Website: http://calderonpale.com

Twitter: http://twitter.com/calderpwn



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