Hacking printers: for fun and profit

Hacking printers: for fun and profit
Hacking printers:
for fun and profit
 Andrei Costin
 Author of MFCUK
MiFare Classic Universal toolKit
 Day-time programmer (after-8pm type of hobbyist hacker)
Not part of printing industry though
 Generally interested in:
Programming/hacking: RFID, GSM, biometrics, embedded
Almost everything which:
Is connected to networks/communications lines
 Have smart-cards (contact and contactless)
 Have crypto involved somewhere down the line
 Is or should be secure
Corporate/Enterprise IT support software & security
 While more and more new devices (routers, smartphones, etc.) are getting
connected to our SOHO/enterprise environments, all-colour hats are
getting plenty of focus on their security: defend and harden on one side;
exploit and develop malware on the other.
 However, a special class of network devices (specifically network
printers/scanners/MFPs), which are networked for more than 15 years, are
constantly out of the modern security watchful eye.
 And even though we entrust them even the most confidential documents or
the most sacred credentials (LDAP, PINs, RFID badges, etc.), we don’t
realize closely how weak and unsecured they are, despite the few minor
security bulletins that started to pop-up here and there in the recent few
 In this presentation, we will try to analyze the reasons why hacking
network printers/MFPs is a reasonable and accomplishable idea. Also, we
will take a look at current state of (weak) affairs in the vulnerability and
security research available. Then we will try to envision types of possible
exploitation scenarios, backed-up with a printer remote-exploit demo. We
will conclude the presentation with possible solutions and what can be
done to protect ourselves as well as our network environments.
 No Warranties or Liability. Information is provided as-is, though every effort has
been made to ensure the accuracy of the information presented. Author of the
presentation is not legally liable under any circumstances for any damages such as
but not limited to (including direct, indirect, incidental, special, consequential,
exemplary or punitive damages) resulting from the use or application of the
presented information.
 Unless explicitly noted in forms such as but not limited to "the XYZ Company says",
etc., the opinions expressed in this presentation are solely and entirely my own.
They should not be interpreted as representing the positions of any organization
(past, present, future, existent, non-existent, public, private, or otherwise) with
which I may or may not have been, are or are not, or will or will not be affiliated at
some time in the past, present, or future.
 All trademarks and registered names are the property of their respective owners. All
the effort has been made to link to the original material used as exhibition items in
the presentation, and those items are property of their respective owners.
 This presentation: © 2010, Andrei Costin. Released under:
*big fat one – because everybody loves fineprints
\H1B%-12345X@PJL JOB “HackingPrinters”
 This presentation is about:
 Hacking “the PC inside printers/MFPs”
Why would someone hack a printer/MFP
 How would someone hack “the PC inside printers/MFPs”?
 How easy/feasible is MFP firmalware creation and exploitation
 How to protect yourself and your so-much-loved MFP?
Laying foundation for further community security
 This presentation is NOT about:
 Printers’ display hack (RDYMSG, OPMSG, STMSG)
 Printers’ embedded web-server hacks (mostly not)
 Printers’ SNMP configuration hacks (mostly not)
 Exhaustive guide to hack every and last MFP (not yet!)
MFPs Exploitation – Why?
 First, my term for MFP = Mfp, Fax, Printer
 Many would ask “Why would you exploit an MFP?” –
answer derives from questions below:
How many persons would expect their MFP infected?
How many users/admins/security-auditors audit and hard-secure
their/network MFPs?
How many persons or anti-malware products could clean such a
Even if they do, do MFP vendor pay attention to security?
 Bottom-line is always “It’s just a damn printer/MFP!”
Afaik, 0(zero) antimalware products for (huge) printers/MFPs market
Why not (net/port/vuln)scan the network from a printer which is not
Why not hide the malware/payload on a network printer and then
make your way through the network/data?
Etc., etc., etc.
MFPs Exploitation – Why?
 First of all – (most) printers/MFPs are already full-
blown computers! (or even space-ships  )
 Have goodies to play/own:
Some flavor of (RT)OS (VxWorks, LynxOS, Nucleus, Linux)
Embedded Java VM (eg.: ChaiServer)
Embedded Web Server (eg.: Virata EmWeb)
Eventually HDD – nice to scan/dump
Not covering TCP/UDP/IP stack attacks, but there are examples
Eg.: recent CBSNews Investigation Case – with much hype
Eventually SecureJet-like extensions – sweet thing !
Eventually Fax board
Eventually Mailboxes
MFPs Exploitation – Why?
 MFPs interact with (hence can get access to):
 RFID badges
Smart/swipe cards
LDAP/domain passwords
Aren’t these some-of sweet things we are hunting after all?
MFPs Exploitation – Why?
 Looking for confidential documents?
 Why taking the trouble for infecting a PC-host on a network
(eg. both elements being secured, updated & monitored) just
to get a document with strong crypto using long-enough key
and then not being able to decrypt it…
 …when instead wait for it to be in-printer decrypted (eg.
SecureDimm) and printed (and I guess secret documents are
still being printed on paper occasionally for selected eyes) so
you get it decrypted in plain text
MFPs Exploitation – Why?
 Not so much information in this area (compared to PC or
mobile devices)
PJL UPGRADE – approx 6 results
PJL LPROGRAMRIP – 1 result (security paper)
PJL DMINFO – approx 300 results
PJL DMCMD – approx 75 results
Compare with this PDF "/Launch“ – approx 55 Mln results
 Too few known (more or less) public research:
slobotron, phenoelit, irongeek, Protek Research Lab’s, DSecRG, SEC
Consult + few other brave enthusiasts
 Recent disclosures mainly focused on web-admin, snmp,
XSS and uncontrolled buffer overflows
Not too much detailed analysis on OS, kernel and firmware level
MFPs Exploitation – Why?
Big number of devices – according to Gartner:
Theoretically, magnitude of 10 x mlns of devices (24 mlns/yr):
Perfectly exploitable & non-easy-cleanable
 Always on, no antivirus & firewall running inside of them
MFPs Exploitation – Why?
 The Holy Grail would be to own “securities printers”
 Currency/financial assets printing machines
Unfortunately limited to very closed circles  - for obvious reasons
 No updates/patches on internet to poke around
Industrial currency check/count machines
More or less accessible
 From BPS 2000/3000 Banknote Processing Systems for Central
Bank Applications “The operating system software and all
production data can be authenticated to protect data integrity
and guard against tampering (optional)” – isn’t it just sweet 
Passport/ID printing machines
Eg.: Oberthur, Giesecke&Devrient, others
These are not part of this presentation … yet !
Current available public research
 FX@phenoelit
 Earliest public research on printers’ security
 Presented at BlackHat 2002
 Demonstrated various HP/PJL flaws
 Irongeek
 Most comprehensive printers’ security guide/article
 Presented at Notacon 2006
 Summarizes flaws at various levels in printers from different
Current main players
Konica Minolta
Dell is selling Lexmark – “So, Lexmark makes Dell's printers?”
Eg.: BRQP205.ffb is for Lexmark E342N/Dell Personal Laser 1710
Kyocera Mita
Ricoh, Lanier, Nashuatec, Infotek, OCE, OKI
Current state of vulnerabilities
 Xerox – Total 44
 XRX04/10, XRX05/9, XRX06/7, XRX07/2, XRX08/10, XRX09/4, XRX10/2
 HP – CVE-HP-printer, CVE-HP-MFP = Total 20
 More and more
 Lexmark – CVE-Lexmark-printer = Total 7
 Canon – CVE-Canon-printer = Total 2
 Kyocera – CVE-Kyocera-printers = Total 2
 OKI – CVE-OKI = Total 2
 Fuji – CVE-Fuji = Total 2
 Ricoh – SB05-005 = Total 1
 OCE – CVE-OCE = Total 1
 Brother – CVE-Brother-printer = Total 1
 Nashuatec – CVE-Nashuatec = Total 1
 Too few for such a complex, big & old industry!
 This can’t be true - the exploits are there waiting for us 
MFPs Exploitation – Real (miss)use scenarios
 PDOS aka bricking
 Can be at most a teenage prank. Fun first 1-2 times.
 HDMoore: “It seems like if you can do a remote update of
firmware, it would better to deliver a Trojan'ed firmware
image, instead of just a DOS”
 Idle-time processing
 Port/network/exploits scanner
 Computing/hash-cracking/sniffing
 Malware/upload storage
 “Stealth”/uncleanable command and control
 Unencrypted data theft
MFPs Exploitation – Real (miss)use scenarios
 Corporate/enterprise/intelligence assets data theft
 Exploiting security extensions and data those process:
 FollowMe
 SecureDIMM
 Produce PDFs with 0-day exploits
 Just infect/replace the PDF output engine or replace output
PDF file
 Usually, DSS and scanners are trusted internal sources
 Spam inside/outside networks
 Many devices have emailing capabilities (not all configured
MFPs Exploitation – Scanned data theft
 Also independently discovered by Zscaler
 Root cause – lax security/policy on MFPs
 HP specific:
 Abuse1:
 Find the target host (intranet or internet)
 Start with current time in epoch format
 Option1: Go downwards in increments of 1 (1 sec)
Makes sense to stop once a period of 6 months were iterated
Option2: Keep polling the “current time”, hopefully someone is scanning
Try to retrieve the documents
Hopefully retention is set in out favour
And the device has enough space in ramdisk/hdd
 Abuse2:
 Configure device so that all scans are BCCed to attacker
MFPs Exploitation – Real (miss)use scenarios
 Ransomware (as it becomes more widespread)
Install the ransom-ware, which takes care to overtake the firmware
upgrade module
So ransomware accepts only secured&signed upgrades/unlocks from
it’s creators – anything else rejected
Store & forward (if external connection detected) documents-to-print
to the creator
But instead of printing any document, print something like:
“This printer is hijacked. Get unlock got from: www.printerhijacker.com using
these details: [brand] [model] [serial_number] [ethernet_MAC] [other_bits]”
Based on printer model (it’s price, year), the ransom amount can be
decided (obviously a fraction of the catalog/second-hand cost)
If the victim pays, unlock code/firmware is provided (customized for
that printer only based on serial#/MAC/etc)
Otherwise, victim risks to “loose” his/her device (sometimes quite
expensive - $32K)
MFPs Exploitation – Futuristic/unreal scenarios
 Espionage/blackmail (high-profile)
 Very-unlikely, but possible. Target mainly models with HDD in
high-profile organizations (those afford HDD models  )
 Store the documents which hit keywords (Eg.: strategic, attack,
intelligence, transactions, $$$) – hint: good as MFPs AI
 When storage is full, display [critical_dummy] error ,
document the error as “ship to 800-fake-service”, get data
from HDD, ship back 
 “Spies in the Xerox Machine”
Russian saying goes “Everything new is actually well-forgotten
MFPs Exploitation – Physical attacks
“The paper's speed keeps it from burning as it passes through
the fuser assembly”. Temp approx: 185 C/ 365 F
Attack1: Supply paper impregnated match-head powder/
Attack2: Firmware-controlled motors speed + fuser temp +
Supported by default: set fuser to HIGH2, motors auto slows to
lower ppm and then use thin paper/transparency
 Custom firmware under research – gives more control
MFPs Exploitation – Targeted attacks
 Visualization (of target/enemy) is powerful!
 Useful if interest lies in specific:
 Geo-locations, Device Class, Vendors, Models
 Basic scripting gives us a nice map like below:
 Live demo
Main printer specifications
 Myriad of specs and languages… %)
 UEL – Universal Exit Language
 Just one command
<esc>%-12345X (<esc> is 0x1B aka \H1B aka ESCape)
Harmless by itself, lethal in specific combinations
 PJL – Printer Job Language
 Developed by HP
 Job level controls: printer language switching, job separation,
environment, status readback, device attendance and file system
 Have essential security design flaws, hence exploitable
 Examples:
<esc>%-12345X@PJL JOB\r\n
@PJL RDYMSG = “Sample PJL Job”\r\n
@PJL EOJ\r\n<esc>%-12345X
Main printer specifications
 PCL – Printer Control Language
Developed by HP
Well, actually it’s not a control language (PJL is)… name
It’s more a formatting-control language, like PS
Harmless, but parsers and interpreters could be exploited
Usually PCL jobs start with:
 <esc>E\r\n
 Sample commands in the job:
 <esc>&l1T
• Toggles the printer's job separation mechanism
• Instructs to print 3 copies
Mandatory PCL jobs end with:
 <esc>E\r\n
Main printer specifications
 PS – PostScript Language
 Developed by Adobe
 Mostly formatting-control language, but has “device control” commands
as well 
 On top, it is a programming language as well… (see later)
 Also, parsers and interpreters could be attacked
 Hence can be exploited
 Examples:
%%LanguageLevel: 2
%%BeginFeature: *PageSize A4
1 1 sub ==
 PPD – Adobe PS Printer Description
 Describe the entire set of features and capabilities available for their
PostScript printers
 Contains the PostScript code (commands) – way to hack
Main printer specifications
 PML – Printer Management Language
 HP’s object-oriented request-reply protocol to exchange device
management information
 PML can be used to query SNMP values from a printer device
 So… turning SNMP off doesn’t solve all problems 
 Examples:
 ASCIIHEX=“PmlReply”\r\n\f
 ASCIIHEX=“PmlTrapRequest”\r\n\f
 GPD – Generic Printer Description
 Windows GDI-based spec, similar to PPD
 Used for creating unidrv.dll minidrivers for non-PS printers
 Something like a customization plugin over unidrv.dll (not a bad idea)
 Usually here: c:\windows\system32\spool\drivers\
 Examples of attack later
 PJL holes:
 No provisions for standard, secure and vendor/arch/osindependent way for binary/firmware upload/upgrades
Everyone reinvented their own wheel – sadly, most did it wrong…
 PJL holes:
 No standard provisions for strong authentication
 No standard provisions for encryption
All usernames, PINs & passwords are in clear-text
 @PJL SET USERNAME=“HackingPrinters"
 @PJL SET KMUSERKEY2 = "password“
Print job PIN security (@PJL HOLDKEY)
We are in 2010 – we get 0-9999 PIN/password range… 
 Also, specs say nothing about N-tries-and-fails scenario actions
 Again, the wheel…
 PS/PPD holes:
 setdevparams/setsystemparams
Can be powerful (and dangerous )
 Can be helpful, if you trust .PS file or know what you are doing
 Can also set security/password settings on device – sweet
Think this: *.doc/*.pdf attacks PC, *.ps attacks MFP
Also, since PS is an interpreted programming language
Fuzz/smash the stack with PS recurssion or stack operations
*Password PS-field in the PPD file is in clear-text
PPD have nice *PatchFile and *JobPatchFile commands
Explained later
MFPs Exploitation – How to approach?
 Remote-initiated printing (RIP) exploiting channel
 Java is our best friend here
 Flash and Silverlight are not too friendly… yet
 JavaScript is good as well – use CrossSitePrinting
 Will Google Cloud Printing be as well? Time will show
 Locally-initiated printing (LIP) exploiting channel
 MS Word can somewhat help us
 Adobe LiveCycle XDC files can help us
 GhostView is not too friendly yet
 Exploiting “test print” access in printers’ EWS
 Not always available
 Easy to patch – though easy patches are hard to get right for
MFPs Exploitation – How to approach?
 Exploit printer management software
 Successful on HP Web JetAdmin
 To be tested on: Lexmark MarkVision, Xerox CentreWare
 Internal interpreters’ exploit
 PostScript, PCL – most widely used interpreters
 Can borrow ideas from GhostScript exploits
 Locally-executed applications with rogue firmware
 Requires social engineering
 Printer subsystem hacks
 Printer driver hacks for furher MFP exploitation
 Printing hacks for host PC exploitation
Remote-initiated printing exploit
 Printing Payload Exploit (PPE) over Java Applets
requires some user intervention
 Lure the users to a site and then trick to print
Eg: print tickets, print discount coupons, print charity-related stuff,
print government/tax related forms/discounts, etc.
 Auto-start printing trick
“mayscript” yes, “scriptable” true, jso = JSObject.getWindow(this),
 Can be successful using social engineering/nagging
Similar to VBScript F1/Help Keypress Vulnerability
Demo – Remote-initiated printing exploit
 User lured: clicked “Print” (optional) and checked
“Always…” (mandatory)
Demo – Remote-initiated printing exploit
 Printer exploited: reset, malware upload, etc.
Remote-initiated printing exploit
 Possible exploitation problems
 User doesn’t check the box
This can be detectable by subsequent calls to java print services
 Then annoy user until user checks the box (detectable by timebased analysis between java print services calls)
 Eg: JS - window.location.reload
Printer name != precise target name
Java print services gives us only printer name 
 Use 1 binary with all known printers exploits
 Hope one sub-firmalware hits the target, others will be
 Big data file is not quite invisible
 Use “magic” detection (eg. like “%HP%”) and then fire one or a
subset of firmalwares
Remote-initiated printing exploit
 Restart (on HPs) is accomplished by
 @PJL DMINFO ASCIIHEX = "040006020501010301040104“
 Same as phenoelit’s trick (BH2002)
SNMP set .iso. = 4
 However, PJL DMINFO is actually “SNMP thru PJL”
 Java hints
 PrintService
 PrintServiceLookup
 DocPrintJob
 JobName
 SimpleDoc
 … and DocPrintJob.print()
Locally-initiated printing exploit
 MS Word
 “Print and get your printer owned” type of exploit
 Will video demo in next slide
 Adobe LiveCycle XDC files (XML files)
 Used in SAP® environments
 “Infect”/replace all XDC files with required firmalware payload
Doesn’t necessarily need admin rights
Good example how to do this is here on page 15
Demo – Locally-initiated printing exploit
 “File upload” PPE over MS Word
Demo – Locally-initiated printing exploit
 “Printer-display change” PPE over MS Word
Demo – Locally-initiated printing exploit
 “Printer reset” PPE over MS Word
Solutions for remote+local initiated exploits
 How to fix?
 Not easy, since it’s PJL design + device vendors’ faults
 Java, Word, LiveCycle, etc. have no big blame
They act as “channels” for delivering the
exploits/malware/malicious commands
 Rather than fixing channels, better fix specifications and devices
Perhaps correct PJL specs + follow standard and safe low-level
communication with devices on top of PJL
Paranoid solution:
Print everything thru a virtual/proxy/filtering printer
 That will filter out unsafe/suspect payloads (and alert!), producing
“safe” docs to print on real devices
 Unless the virtual printer has bugs/is exploitable itself 
Exploiting “test print” access in printers’ EWS
 Print is unprotected! (and leaks internal network IP)
 Do vendors think diagnostics actions can be harmless?
Exploiting “test print” access in printers’ EWS
 Accepts file as direct upload :
 Filters based only on extension: txt, pdf, pcl, ps
 Will not accept:
print_my_hexor.rfu or
 print_my_hexor.fmw
Will accept:
 Yes, in PCL we can embed PJL UPGRADE/equivalent commands
Also, extension check doesn’t enforce content check:
Rename print_my_hexor.pcl into print_my_hexor.pdf
 And here we go again 
 Example: use HP_LJ5200_restart.pcl.pdf
Exploiting “test print” access in printers’ EWS
 Accepts file as URL link to a printable document:
Exploit as in previous direct local upload
 Other interesting uses:
Check if printer can access external addresses (cool for commandand-control type of attacks)
Might reveal internal/external topology, as well as proxies along the
If the chain is not properly configured and secured
Try to DoS the MFP in two types of slowloris
Attacker’s http-client “slowloris”es MFP’s EWS
 Attacker’s http-server “slowloris”es the MFP’s initiated http-clients to
our URL-document
 Do both from above simultaneously 
Find race conditions in parsers: direct print, direct URL print, port
9100 print and print-server print; include also PJL/non-PDL cmds
Exploit printer management software
 MITM – HP Example – firmware.glf:
Contains the links for DLD/RFU firmwares
Used in WJA, HP Download Manager
Uses plain HTTP (not even HTTPS), hence not a problem to MITM
Once MITMed, malicious DLD/RFU firmware binaries are supplied
 Combined MITM+XSS attack:
MITM and supply malicious firmware binaries (as described above)
Exploit XSS bugs in admin panel of printer management software
Eg: HP WJA (or alike)
Use XSS to trigger automatic upgrade of devices
Two targets in one shot:
Devices infected
 Web-admin software owned by XSS (can serve other purposes as well)
Exploit printer management software
 Use XSS as an infection-trigger step in combined
MITM+XSS attack
Eg.: HP WJA has various persistent-XSS bugs, injectable from
external channels
PostScript interpreters exploitation
 PostScript interpreters have bugs as well
 GhostScript exploitable on your PC
 “MfpPsInterpreter” exploitable on your MFP
 Stack and recursion are nice weapons
%%[ Error: execstackoverflow; OffendingCommand: --nostringval-- ]%%
This is simple, but more complex/inconsistent stack operations can be done
Fuzzing the interpreter and stack is a good way to find out
PostScript interpreters exploitation
 PostScript-related exploits
CVE-2004-1717 – Remote buffer overflow
CVE-2008-0411 / CESA-2008-001 – Stack-based buffer overflow
CVE-2009-0583 / CVE-2009-0584
CVE-2009-4195 – Buffer overflow
CVE-2010-1869 – Stack based overflow
 Try/tweak them out on your MFPs fleet
Some might surprise you
Got some (unreliable) crashes by tweaking few of the above
Locally-executed apps with rogue firmware
 If all other fail
 Because of: fixes in webserver, script-blockers, etc.
 Social engineer the user to “download and play a nice
game” application
 Doesn’t have to be a PC virus, a valid app will do ok:
It will be just a printer malware
So zero antivirus detection guaranteed still 
 Just connect to TCP port 9100 printer job spooler
 Dump the exploit/malware
 Use @PJL UPGRADE style commands
 Use @PJL FS* style commands
Locally-executed – Print subsystem hacks
 Find exploit stream for unidrv.dll/pscript5.dll
 Get LOCAL SYSTEM privileges (spoolsv.exe)
 unidrv/pscript5 dlls called from user space
No need for admin
Called locally
Called remotely – via shared printers
Stuxnet, well yeah!
 Contained 0day exploiting spoolsv.exe / StartDocPrinter / policies
 Well, 0day back in Apr 2009
 I’ve been warning back in Apr 2010
 Nobody cared, except perhaps SIGINTs-related
 Printing sub-systems are broken…
Locally-executed – Printer driver hacks
 Other require social engineering+admin level
 Replace the driver *.dlls
Stuxnet, got HP/other MFPs driver signature private keys?
Provide an “enhanced” driver, with printer-malware inside
 “Infect” the GPD files
 Replace with legitimate *Cmd containing malware payload
Locally-executed – Printer driver hacks
 “Infect” the PPD files
 *PatchFile, *JobPatchFile
 Represents a PS language sequence that is a downloadable
patch to ROM code or into initial VM
 *FileSystem
 The *?FileSystem query can be used to dynamically determine
whether or not a file system is actually present
MFPs attack vectors – Overall diagram
Privacy/transparency concerns
 Not satisfied with printer tracking dots?
 Satisfaction guaranteed with:
 HP Download Manager – a story from backstagedoor
 Will present minimal analysis of hpjdwnld.exe
Privacy/transparency concerns
Important note:
It’s not managing a PC-backdoor
 It is managing an MFP-backdoor
 strings utility is enough to spot it
 Checks for %HOME%\upgrades\jetdirect\SpecialUpgrades.txt
 Checks special firmware files for ShortStack/CodeImage
 If you have samples for above 2 items, please share them!
 Possibly similar to AMD K8 Microcode backdoor update feature
Have few others HP call-home features under investigation
Are vendors being responsible when including backdoor/callhome features?
Well-known PR fiascos: Energizer, Sony
Privacy – What about PhoneHome feature?
 Phone Home feature in HPs
 Present in EWS of devices (telnet/web/snmp interfaces)
 “Use an SNMP management or command line utility to set the
object identifier (OID) . to zero (0)”
 telnet
 “…use the Telnet "phone-home-config: 0” …“
Present in WJA software package
Privacy – Some thoughts
 PhoneHome ( privacy
statement says:
“If permitted to do so, HP will collect this information as statistical
data only and use it to improve product features and services.
Personal data is not collected in accordance with HP privacy
Well, name implies something else
We want all its juicy details 
 PhoneHome + JetDirect Firmware Backdoor
Can be easily misused by HP
Raises (at least should!) privacy concerns
Not very well documented by vendors
Can be misused by malicious attackers
After all, multiple naming FAIL!
Printer debugging (or lack of it)
 syslogd messages - examples
Most HP syslogd’s are not very debugging-friendly
Interesting fact - when resuming from sleep, it does:
“error <51> printer: offline or intervention needed”
 “info <54> printer: error cleared” (auto-heal?)
 Perhaps VxWorks debugging by hdm
Had no luck in finding one with this enabled
DevEnv – How?
 My vision (yours might be slightly/totally different)
Unpack/mount the firmware
Need to reverse most important formats out of myriad
 Crack any crypto + signature is a “desirable option” of course
Map it’s arch + OS
Wiki, hex-view, specs, IDA, obj* suite
Fine-tune IDA, binutils, obj* army for that specific combination
Reverse the workings of (each) specific executable
Introduce the payload:
Byte-patch, if you talk code-machine better than your native lang
 Compile a binary in an emulated env (if all prerequisites permit)
Test payload:
Directly on hardware – tricky, may brick it, need good HW skills, etc.
 In an emulated env – very convinient, but again not always possible
DevEnv – Why?
 A DevEnv+Emulator tandem is preferred for:
 Vendor firmware testing for vulnerabilities (parsers, etc.)
 Develop malicious payloads/firmware for a device/device-class
 Allows easier fuzzing
 Is a more formal approach, rather than trial-and-error
 Unless:
 You want a BIG net of BIG bricks (not bots) and BIG angry
corps on your 455!
 You own a warehouse of MFPs for tests
DevEnv – What?
 Toolchains:
Crosstool-ng, buildroot, scratchbox
 Emulators
Qemu, OVP, RTEMS, ARMulator
 OSes on most printers/MFPs:
Linux (for various non-std architectures)
 Processors on most printers/MFPs:
MIPS (PCM-Sierra)
RISCs (Toshiba TMPR4955)
ARM (Marvell ARMv5TE-compliant, custom HP-ARM)
SPARC (Fujitsu MB86830 series)
DevEnv – first things first – Linux
 Lexmark luckily went Linux/GPL
 But VxWorks and LynxOS are not out-of community
 Best start for devenv setup & research bootstrap
 E23x_E33x_141_C20.FLI is a good kernel-loading example
 Interacts with NVRAM and other stuff (good to understand)
 Have “|BIN” wrapped image of Linux kernel
Can also be built from sources, though EAN.KA.K009 not released
DevEnv – Firmware Unpack/Mount
 Firmware image unpackers:
 Simple script-like C-tools
 Do not work yet with encrypted firmware package
 Strip proprietary-PJL wrappers and spit binary raw inside
Some have a single ELF file (example: E23X_.fli)
 Some have a FS-like object with tree-structure and binary content
Can adopt and use libPJL from phenoelit
 Ultimate goal:
 File-based FS drivers
 To be as simple as:
./mount –t hp-fru HPLJ5200.fru /mount/fw_test
DevEnv – Firmware Unpack/Mount
Example: excerpt from a single block of HP simple-FS, many
of these found inside a single RFU firmware file:
Sample firmware under microscope
 BarSTORM barcode printers
 Linux FS image with default unsalted passwords
 root:$1$$I2o9Z7NcvQAKp7wyCTlia0:10933:0:99999:7:::
 lp:$1$$RfHkehRv/LWAGZdCEvUU90:10933:0:99999:7:::
 bcadmin:$1$$YSpLiaVeoDkQidsOLxlm5/:10933:0:99999:7:::
 engineer:$1$$YSpLiaVeoDkQidsOLxlm5/:10933:0:99999:7:::
 admin:$1$$I2o9Z7NcvQAKp7wyCTlia0:10933:0:99999:7:::
 crypt(“password”)=$1$$I2o9Z7NcvQAKp7wyCTlia0
Sample firmware under microscope
 IBM InfoPrint IP 6700
pRiNtrOnIx firmware and components
Seems like a H4X0R designed the firmwares 
 Has RFID from awidasia
SDK and samples to play with are here
 Some keywords to get you interested:
PaRtITiOn OF RFID, rfidfirm.bin, rfidchip.inf, rfidtag.inf
AWID MPR-1510 V2.6h UHF MODULE Firmware Ver4.27
Why not spy on RFID tags or KIL all tags?
Sample firmware under microscope
 SMS Printers (examples)
Eg.: DPSPro, Gatetel, Possio GRETA, Secugis
 Empty paper roll DOS attack (most printers)
Avg ~ 62 SMSes (160 new-line chars each SMS) for 50m rolls
 Configuration commands attack
Against DPSPro. Others might have hidden conf commands as well!
“#V1: 0=SMS 1=VOICE CALL [0]. This variable chooses whether the
Printer will confirm with an SMS or placing a call.”
“#Y: Programs ACCEPT number to which ACCEPT SMS will be
sent. Note1: if the CALL option is enabled, the unit will place a call
Make it call your/friend’s premium number is the answer 
 Nice to have – reflash by TPDU-SMS 
“Secure Thinking” in quotes
 HP Security Solutions
 “Q23. Are current HP multifunction printers susceptible to
viruses and worms? No, since the majority of viruses
and worms exploit vulnerabilities in Windows-based
computers. HP MFPs use non-standard operating systems
other than Windows. Consequently, they are immune to these
viruses and worms. In practice, there have been no
known instances of viruses or worms infecting HP
Well, PoC-community or some haxor or some IT-criminals might
change that “in practice” then!
“Firmware generally behind software in terms of secure
development & deployment” – more than true
Wonder if HP's SecLab PhlashDance ever reached HP's MFP R&D
“Secure Thinking” in quotes
 Sharp Security Suite
 “Sharp MFP products use unique embedded firmware and are
not based on Windows operating systems. Therefore, Sharp
MFP’s internal systems are not subject to the same
Virus vulnerability as Microsoft operating systems.
We believe this approach provides the internal systems of our
products with protection against common Windows
executable viruses and other similar infectious software
Well, possibly are vulnerable to other (i.e. not same) virus
“Secure Thinking” in quotes
 Lexmark MFP Security, Samsung MFP Security
 “In other areas, the security considerations around
printers/MFPs are substantially different: they generally
don’t run conventional operating systems, they don’t
have network file shares that need to be secured,
they probably don’t need or support antivirus
software, etc.”
Who did copy from who that text? Or they just assumed the leader
is right and mutually-copy-pasted?
 “…probably…” ?!
 Nowadays, if you have an OS, a FS and externally connected
execution environment, most likely you need internal
“Secure Thinking” in quotes
 Final thought on above “secure thinking” quotes
 Remember psyb0t? To summarize
 Non-conventional arch – true – MIPS
 Non-conventional OS – true - Mipsel Linux
 Doesn’t support antivirus – true – “why should we?!”
 Got owned – very true – ~100k devices in a sophisticated
command-and-control botnet
If you need more arguments for securing/cleaning embedded
devices, running unconventional OS+arch which do not
support secure/antimalware standards/frameworks
Perhaps security is your lowest priority hobby – my $0.02…
Solutions – Printer Vendors’ Side
 First, accept that present day printers (especially
network ones) are:
Full-blown computers themselves
A security target/threat
To be considered as part of Secure
Development/Testing/Audit Lifecycles
 Fix those specs and parsers (PJL, PCL, PML, PDF,
 Fix those damn web/telnet/ftp/snmp/etc. interfaces
 If first random 200 bytes fuzz string crashes/bricks
your device…
…time to put in practice SDL. we are in 2010, remember?...
Solutions – Printer Vendors’ Side
 Authenticate uploader, crypt, sign and verify signature of
the uploaded firmware
Btw, homebrew or kindergarten crypto is NOT crypto!
Or make (some) implementations FOSS – so open and secure
standards can be implemented (oh, these utopist ideas…)
 Be fair!
Transparent and backdoor-free systems/software
 Collaborate with antimalware vendors for your platforms
Could win you a nice marketing step
 Last but not least – remove default passwords and make
mandatory strong-password changes as part of the initial
setup procedures/installations
Solutions – Antimalware Vendors’ Side
 Collaborate with vendors and security community
 Make vendors understand those MFPs are real exploitable targets
 Also, it could be a good marketing step “First antimalware on
 Develop open and secure practices/protocols for in-printer antivirus
management and updates
 If above collaboration does not work
 Sponsor high-profile MFP exploit botnet – volunteers are out there
 You have your foot in the “MFP antimalware market”`s door
 This point is more to be joke 
 Though, not that there were no surprising developments
 Setup honey-pots for most-spread MFPs EWS :
 Similar to renowned /etc/passwd
 Study blackhats/bots actions to train IDS/IPS for MFPs
 Get samples of firmalware or exploit payloads (PJL, PS, PCL)
 … even though AV concept is being considered obsolete
Solutions – Admins’ Side
 Develop and follow secure periodic practices and
checklists for all your MFPs/printers
Use and analyze extensive logging using MFPs
management platforms
Properly isolate MFPs on appropriate network
Perhaps implement stricter domain-level printing
Well, last but not least – don’t leave those default
accounts/passwords on
Solutions – IDS/IPS
 Update and improve printer-based IDS/IPS sigs
 Addresses to antimalware and admin side
 Dilemma
 Start filtering in paranoid mode, but…
Can impact a scheduled mass upgrade of net-administered MFPs
 Can impact pretty valid print jobs
Where should the balance be…?
Real solution is to fix the specs
Solutions – IDS/IPS
 Snort IDS signature samples
 The RDYMSG is only annoying
PDOSing is not fun anymore - is already a concern
Don’t SNORT it, cron it on repetitive (RDY/OP/SYS)MSG reset
Though this SNORT rule sucks. Do you see why?
The real pain is MFP malware (PJL UPGRADE types)
Your pride starts having pains in your back… unless fixed
 pcre:”/ENTER[\x20]+LANGUAGE…”
Solutions – Users’ Side
 Stay updated to latest firmware of the printer’s vendor
Make sure you choose a security-aware vendor (but skip the
marketing BS between the lines)
 Don’t print anything from untrusted sources
Well, this is hard… everybody is untrusted today
 Don’t open unknown files
Not guaranteed that malware detection is triggered for printersrelated malware
Important point – exploits the MFP, no need for admin rights on PC!
 Log and monitor printers’ activity
Connects from it’s IP
Paranoid mode – USB data filter from the printer to host PC
You never know what bugs do printer’s driver have on the PC
 Use safe virtual printers to produce malware-free docs
 As PoC shown, printers are exploitable
 Specs have holes and are outdated for the new IT security
Device and antimalware vendors seem to ignore the issues… yet
 MFPs are more than “dummy printers” – these are full-
blown machines with great power and connectivity
 MFPs tend to interact with same (or even bigger) number
of technologies as computers:
 MFPs have access to almost same set of secrets as PCs
Credits/Props/Recommended reading
 Slobotron on Hacking Printers
 phenoelit’s HP resources
 Irongeek’s “Hacking Network Printers”
 SANS Auditing and Securing Multifunction/MFP
Amuzing note: “Using this port and the right utility you can,
among other things, change what shows up on the LCD
display. Modification of the LCD panel, either causing
confusion ("Out of Service") or opening the door for social
engineering purposes ("Error. Call 555-5151.").”
Credits/Props/Recommended reading
 “Vulnerabilities in Not-So-Embedded Systems”
 “Exploiting Printers by Analyzing Their Firmware”
(nowhere to find on the net… censored?!)
“Juste une imprimante”
“Network Printing” book
MFP Security for Enterprise Environments
@PJL COMMENT = “Insert coin to continue”
\H1B%-12345X@PJL EOJ “HackingPrinters”
 Print-in-touch:
 lpr –Phoneypot-printer@andreicostin.com –Y –J “Hacking
Printers” –T “Comments/suggestions/collaboration” –m
andrei@andreicostin.com –m zveriu@gmail.com --  Till next time… keep your MFPs safe as golden:
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