Fix rapid7#4783, raise exception if the payload arch is incompatible

Fix rapid7#4783

Author: wchen-r7

lib/msf/core/exploit/remote/browser_exploit_server.rb

@@ -20,6 +20,8 @@
 module Msf
   module Exploit::Remote::BrowserExploitServer
 
+    class BESException < RuntimeError; end
+
     include Msf::Exploit::Remote::HttpServer::HTML
     include Msf::Exploit::RopDb
     include Msf::Exploit::JSObfu
@@ -521,7 +523,13 @@ def on_request_uri(cli, request)
           try_set_target(profile)
           bad_reqs = get_bad_requirements(profile)
           if bad_reqs.empty?
-            method(:on_request_exploit).call(cli, request, profile)
+            begin
+              method(:on_request_exploit).call(cli, request, profile)
+            rescue BESException => e
+              elog("BESException: #{e.message}\n#{e.backtrace * "\n"}")
+              send_not_found(cli)
+              print_error("BESException: #{e.message}")
+            end
           else
             print_warning("Exploit requirement(s) not met: #{bad_reqs * ', '}. For more info: http://r-7.co/PVbcgx")
             if bad_reqs.include?(:vuln_test)
@@ -586,7 +594,15 @@ def get_payload(cli, browser_info)
       platform = platform.gsub(/^Mac OS X$/, 'OSX')
       platform = platform.gsub(/^Windows.*$/, 'Windows')
 
-      regenerate_payload(cli, platform, arch).encoded
+      p = regenerate_payload(cli, platform, arch)
+
+      unless p.arch.include?(arch)
+        err =  "The payload arch (#{p.arch * ", "}) is incompatible with the #{arch} target. "
+        err << "Please check your payload setting."
+        raise BESException, err
+      end
+
+      return p.encoded
     end
 
     # @return [String] custom Javascript to check if a vulnerability is present