Implement HttpClient options generation from URL

To address the complexity which comes with the flexibility offered
by Rex::Proto::Http::Client and its Msf mixin descendant, a simple
process needs to be implemented for issuing a request using only
the URL string in order to provide ease of access to users who may
not have the time to study how these clients work in detail.

Implement :request_opts_from_url in Msf's HttpClient mixin such as
to extract the options required for :send_request_* from a URL
string passed into the method. This approach reduces HTTP requests
in the mixin to `send_request_raw(request_opts_from_url(url))` when
`url` is just a string.

Implement this approach in the http_pdf_authors gather module to
further reduce infrastructure complexity around the simple need to
acquire PDF files via HTTP/S.

Testing:
  Local to this module only, and in Pry of course. Seems to work...

lib/msf/core/exploit/http/client.rb

@@ -508,6 +508,23 @@ module Exploit::Remote::HttpClient
     end
   end
 
+  #
+  # Returns a hash of request opts from a URL string
+  def request_opts_from_url(url)
+    tgt = URI.parse(url)
+    opts = { 'rhost' => tgt.host, 'rport' => tgt.port, 'uri' => tgt.request_uri }
+    opts['SSL'] = true if tgt.scheme == 'https'
+    if tgt.query and tgt.query.size > 13
+      # Assming that this is going to be mostly used for GET requests as string -> req
+      opts['vars_get'] = {}
+      tgt.query.split('&').each do |pair|
+        k,v = pair.split('=',2)
+        opts['vars_get'][k] = v
+      end
+    end
+    return opts
+  end
+
   # removes HTML tags from a provided string.
   # The string is html-unescaped before the tags are removed
   # Leading whitespaces and double linebreaks are removed too

modules/auxiliary/gather/http_pdf_authors.rb

@@ -88,25 +88,8 @@ class MetasploitModule < Msf::Auxiliary
   def download(url)
     print_status "Downloading '#{url}'"
 
-    begin
-      target = URI.parse url
-      raise 'Invalid URL' unless target.scheme =~ %r{https?}
-      raise 'Invalid URL' if target.host.to_s.eql? ''
-    rescue => e
-      print_error "Could not parse URL: #{e}"
-      return
-    end
 
-    options = {
-      'rhost'  =>  target.host,
-      'rport'  => target.port,
-      'method' => 'GET',
-      'uri'    => target.request_uri
-    }
-
-    options['SSL'] = true if target.scheme.eql? 'https'
-
-    res = send_request_raw(options)
+    res = send_request_raw(request_options_from_url(url))
     disconnect
 
     print_status "HTTP #{res.code} -- Downloaded PDF (#{res.body.length} bytes)"