Credential disclosure - Revision history

Admin at 12:01, 22 November 2017

2017-11-22T12:01:29Z

Admin at 15:55, 8 February 2017

2017-02-08T15:55:07Z

92.228.38.179 at 13:02, 8 February 2017

2017-02-08T13:02:36Z

92.228.38.179 at 13:00, 8 February 2017

2017-02-08T13:00:19Z

92.228.38.179: /* PostScript */

2017-02-08T10:31:37Z

‎PostScript

84.153.135.37 at 08:51, 31 January 2017

2017-01-31T08:51:42Z

Admin at 19:16, 22 January 2017

2017-01-22T19:16:59Z

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Admin at 12:22, 22 January 2017

2017-01-22T12:22:36Z

Admin at 12:18, 22 January 2017

2017-01-22T12:18:23Z

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Admin at 12:34, 21 January 2017

2017-01-21T12:34:05Z

@@ Line 14: / Line 14: @@
   @PJL DEFAULT CPLOCK=ON
-PJL passwords however are vulnerable to brute-force attacks because of their limited 16 bit key size as demonstrated by <ref>''Attacking Networked Embedded Devices'', Black Hat USA, FX and FtR of Phenoelit, 2002</ref> who were able to unlock the disk protection within 6 hours in the worst case. With PJL interpreters having gotten faster while the PJL standard was never updated and still limits passwords to numerical values ranging from 1 to 65535 <ref>''[http://h10032.www1.hp.com/ctg/Manual/bpl13208.pdf Printer Job Language Technical Reference Manual]'', HP Inc., 1997, ch. 6-21</ref>, cracking time has efficiently decreased. In a test with 20 devices, between 50 and 1,000 passwords could be evaluated per second leading to average cracking times between 30 seconds and 10 minutes.
+PJL passwords however are vulnerable to brute-force attacks because of their limited 16 bit key size as demonstrated by <ref>''Attacking Networked Embedded Devices'', Black Hat USA, FX and FtR of Phenoelit, 2002</ref> who were able to unlock the disk protection within 6 hours in the worst case. With PJL interpreters having gotten faster while the PJL standard was never updated and still limits passwords to numerical values ranging from 1 to 65,535 <ref>''[http://h10032.www1.hp.com/ctg/Manual/bpl13208.pdf Printer Job Language Technical Reference Manual]'', HP Inc., 1997, ch. 6-21</ref>, cracking time has efficiently decreased. In a test with 20 devices, between 50 and 1,000 passwords could be evaluated per second leading to average cracking times between 30 seconds and 10 minutes.
 While PJL passwords can be set on various devices, actual disk lock and/or control panel lock is only supported by few printers. It is unclear if the password has any undocumented, proprietary effects on these machines or is just a dummy variable. Furthermore, non-compliant with the PJL standard, Brother based devices do not even verify the password to lock or unlock the control panel, rendering it practically useless.
@@ Line 38: / Line 38: @@
 '''Who can perform this attack?'''
-Anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]]. Feedback from the printer is not required because attackers can blindly remove the password protection by including all 65535 possible combinations in a single print job.
+Anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]]. Feedback from the printer is not required because attackers can blindly remove the password protection by including all 65,535 possible combinations in a single print job.
 === PostScript ===
-PostScript offers two types of passwords: The ''SystemParamsPassword'' is used to change print job settings like paper size, while the ''StartJobPassword'' is required to exit the server loop and therefore permanently alter the PostScript environment. The ''checkpassword'' operator which takes either an integer or a string as input checks for both passwords at once <ref>''[http://ftp.ktug.org/obsolete/info/adobe/devtechnotes/pdffiles/ps2016.supplement.pdf PostScript Language Reference Manual Supplement for Version 2016]'', Adobe Systems Inc., 1995, p. 194</ref>. The key size is very large: PostScript strings can contain arbitrary ASCII characters and have a maximum length of 65,565 <ref>''[https://www.adobe.com/products/postscript/pdfs/PLRM.pdf PostScript Language Reference Manual, 3rd Edition]'', Adobe Systems Inc., 1999, p. 739</ref> which theoretically allows 524,280 bit passwords. On the positive side (from an attackers point of view) brute-force attacks against PostScript passwords can be performed extremely fast because the PostScript interpreter can be programmed to literally crack itself. A simple PostScript password cracker testing for numerical values as passwords is given below:
+PostScript offers two types of passwords: The ''SystemParamsPassword'' is used to change print job settings like paper size, while the ''StartJobPassword'' is required to exit the server loop and therefore permanently alter the PostScript environment. The ''checkpassword'' operator which takes either an integer or a string as input checks for both passwords at once <ref>''[http://ftp.ktug.org/obsolete/info/adobe/devtechnotes/pdffiles/ps2016.supplement.pdf PostScript Language Reference Manual Supplement for Version 2016]'', Adobe Systems Inc., 1995, p. 194</ref>. The key size is very large: PostScript strings can contain arbitrary ASCII characters and have a maximum length of 65,535 <ref>''[https://www.adobe.com/products/postscript/pdfs/PLRM.pdf PostScript Language Reference Manual, 3rd Edition]'', Adobe Systems Inc., 1999, p. 739</ref> which theoretically allows 524,280 bit passwords. On the positive side (from an attackers point of view) brute-force attacks against PostScript passwords can be performed extremely fast because the PostScript interpreter can be programmed to literally crack itself. A simple PostScript password cracker testing for numerical values as passwords is given below:
 <syntaxhighlight lang=postscript>

← Older revision		Revision as of 15:55, 8 February 2017
Line 1:		Line 1:
−	Printers are commonly deployed with a default password or no initial password at all. In both cases, end-users or administrators have to actively set a password to secure the device. This article discusses generic brute-force attacks against PJL and PostScript passwords as well as model specific password disclosure.	+	Printers are commonly deployed with a default password or no initial password at all. In both cases, end-users or administrators have to actively set a password to secure the device. This article discusses generic brute-force attacks against PJL and PostScript passwords as well as model-specific password disclosure.

	== Brute-Force Attacks ==		== Brute-Force Attacks ==

@@ Line 54: / Line 54: @@
 Tested printers were capable of performing between 5,000 and 100,000 password verifications per second. Such enormous cracking rates can be achieved because a printer's RIP is highly optimized for fast processing of PostScript code. Brother based devices are exceptions as ''BR-Script'' only accepts one password per second but also checks for the very first character of the password only which effectively limits the key size to 256 characters or 8 bit. As it seems, Kyocera's ''KPDL'' does not support setting permanent PostScript passwords at all.
-Another approach is to '''bypass PostScript passwords''' by resetting them with Adobe's proprietary ''superexec'' operator. This operator resides in the ''internaldict'' dictionary, which is ‘protected’ by a static, magic password (<code>1183615869</code>, see <ref>''[http://www.tinaja.com/glib/interdic.pdf PostScript’s Internaldict, Superexec & the pdfmark Instruction Set]'', D. Lancaster, 2002</ref>). Wrapping PostScript code into the operator allows an attacker to bypass various protection mechanisms of the language, which would normally raise an ''invalidaccess'' error. This can be used to set PostScript passwords without initially submitting the current password as shown below:
+Another approach is to '''bypass PostScript passwords''' by resetting them with Adobe's proprietary ''superexec'' operator. This operator resides in the ''internaldict'' dictionary, which is ‘protected’ by a static, magic password (<code>1183615869</code>, see <ref>''[http://www.tinaja.com/glib/interdic.pdf PostScript’s Internaldict, Superexec & the pdfmark Instruction Set]'', D. Lancaster, 2002</ref>). Wrapping PostScript code into ''superexec'' allows an attacker to ignore various protection mechanisms of the language, which would normally raise an ''invalidaccess'' error. This can be used to set PostScript passwords without initially submitting the current password as shown below:
 <syntaxhighlight lang=postscript>

@@ Line 53: / Line 53: @@
 Tested printers were capable of performing between 5,000 and 100,000 password verifications per second. Such enormous cracking rates can be achieved because a printer's RIP is highly optimized for fast processing of PostScript code. Brother based devices are exceptions as ''BR-Script'' only accepts one password per second but also checks for the very first character of the password only which effectively limits the key size to 256 characters or 8 bit. As it seems, Kyocera's ''KPDL'' does not support setting permanent PostScript passwords at all.
 '''How to test this attack?'''
-The ''lock'' and ''unlock'' commands of [[PRET]] can be used to test brute-force attacks against numeric (integer) PostScript passwords:
+The ''lock'' and ''unlock'' commands of [[PRET]] can be used to test brute-force attacks against numeric (integer) PostScript passwords or to bypass them with ''superexec'' magic:
   ./pret.py -q printer ps
@@ Line 65: / Line 74: @@
   printer:/> unlock
   No password given, cracking.
-  Found password: 999
+  Device unlocked with password: 999
 '''Who can perform this attack?'''

@@ Line 52: / Line 52: @@
 </syntaxhighlight>
-Tested printers were capable of performing between 5,000 and 100,000 password verifications per second. Such enormous cracking rates can be achieved because a printer's RIP is highly optimized for fast processing of PostScript code. Brother based devices are exceptions as ''BR-Script'' only accepts one password per second but also checks for the very first character of the password only which effectively limits the key size to 256 characters or 8 bit. As it seems, Kyocera's ''KPDL'' does not support permanent PostScript passwords at all.
+Tested printers were capable of performing between 5,000 and 100,000 password verifications per second. Such enormous cracking rates can be achieved because a printer's RIP is highly optimized for fast processing of PostScript code. Brother based devices are exceptions as ''BR-Script'' only accepts one password per second but also checks for the very first character of the password only which effectively limits the key size to 256 characters or 8 bit. As it seems, Kyocera's ''KPDL'' does not support setting permanent PostScript passwords at all.
 '''How to test this attack?'''

@@ Line 1: / Line 1: @@
-Printers are commonly deployed with a default password or no initial password at all. In both cases, end-user or administrators have to actively set a password to secure the device. This article discusses generic brute-force attacks against PJL and PostScript passwords as well as model specific password disclosure.
+Printers are commonly deployed with a default password or no initial password at all. In both cases, end-users or administrators have to actively set a password to secure the device. This article discusses generic brute-force attacks against PJL and PostScript passwords as well as model specific password disclosure.
 == Brute-Force Attacks ==
-Besides credentials leaked from sources like [[File system access|file system]] or [[memory access]], [[#SNMP|SNMP]] and the printer's [[#Pass-Back|embedded web server]], printing languages offer limited passwords protection mechanisms themselves. Breaking such mechanisms has a priority in this wiki because it focuses on printer-specific weaknesses. Furthermore, whilst the routines to set the password for a printer's embedded web server differ from model to model they are standardized for both, [[PJL]] and [[PostScript]]. Although it is not very common for end-users or even administrators to set or actually know about these passwords, if enabled they can break some of the attacks discussed in this wiki. Attackers should therefore have a motivation to crack or bypass them if necessary.
+Besides credentials leaked from sources like [[File system access|file system]] or [[memory access]], [[#SNMP|SNMP]] and the printer's [[#Pass-Back|embedded web server]], printing languages offer limited passwords protection mechanisms themselves. Breaking such mechanisms has a priority in this wiki because it focuses on printer-specific weaknesses. Furthermore, whilst the routines to set the password for a printer's embedded web server differ from model to model they are standardized for both [[PJL]] and [[PostScript]]. Although it is not very common for end-users or even administrators to set or actually know about these passwords, if enabled they can disable some of the attacks discussed in this wiki. Attackers should therefore have a motivation to crack or bypass them if necessary.
 === PJL ===
@@ Line 14: / Line 14: @@
   @PJL DEFAULT CPLOCK=ON
-PJL passwords however are vulnerable to brute-force attacks because of their limited 16 bit key size as demonstrated by <ref>''Attacking Networked Embedded Devices'', Black Hat USA, FX and FtR of Phenoelit, 2002</ref> who were able to unlock the disk protection within six hours in the worst case. With PJL interpreters having gotten faster while the PJL standard was never updated and still limits passwords to numerical values ranging from 1 to 65535 <ref>''[http://h10032.www1.hp.com/ctg/Manual/bpl13208.pdf Printer Job Language Technical Reference Manual]'', HP Inc., 1997, ch. 6-21</ref>, cracking time has efficiently decreased. In a test with 20 devices, between 50 and 1,000 passwords could be verfied per second leading to average cracking times between 30 seconds and ten minutes.
+PJL passwords however are vulnerable to brute-force attacks because of their limited 16 bit key size as demonstrated by <ref>''Attacking Networked Embedded Devices'', Black Hat USA, FX and FtR of Phenoelit, 2002</ref> who were able to unlock the disk protection within 6 hours in the worst case. With PJL interpreters having gotten faster while the PJL standard was never updated and still limits passwords to numerical values ranging from 1 to 65535 <ref>''[http://h10032.www1.hp.com/ctg/Manual/bpl13208.pdf Printer Job Language Technical Reference Manual]'', HP Inc., 1997, ch. 6-21</ref>, cracking time has efficiently decreased. In a test with 20 devices, between 50 and 1,000 passwords could be evaluated per second leading to average cracking times between 30 seconds and 10 minutes.
 While PJL passwords can be set on various devices, actual disk lock and/or control panel lock is only supported by few printers. It is unclear if the password has any undocumented, proprietary effects on these machines or is just a dummy variable. Furthermore, non-compliant with the PJL standard, Brother based devices do not even verify the password to lock or unlock the control panel, rendering it practically useless.
@@ Line 38: / Line 38: @@
 '''Who can perform this attack?'''
-Any anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]]. Feedback from the printer is not required because attackers can blindly remove the password protection by including all 65535 possible combinations in a single print job.
+Anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]]. Feedback from the printer is not required because attackers can blindly remove the password protection by including all 65535 possible combinations in a single print job.
 === PostScript ===
-PostScript offers two types of passwords: The ''SystemParamsPassword'' is used to change print job settings like paper size while the ''StartJobPassword'' is required to exit the server loop and therefore permanently alter the PostScript environment. The ''checkpassword'' operator which takes either an integer or a string as input checks for both passwords at once <ref>''[http://ftp.ktug.org/obsolete/info/adobe/devtechnotes/pdffiles/ps2016.supplement.pdf PostScript Language Reference Manual Supplement for Version 2016]'', Adobe Systems Inc., 1995, p. 194</ref>. The key size is very large: PostScript strings can contain arbitrary ASCII characters and have a maximal length of 65,565 <ref>''[https://www.adobe.com/products/postscript/pdfs/PLRM.pdf PostScript Language Reference Manual, 3rd Edition]'', Adobe Systems Inc., 1999, p. 739</ref> which theoretically allows 524,280 bit passwords. On the positive side (from an attackes point of view) brute-force attacks against PostScript passwords can be performed extremely fast because the PostScript interpreter can be programmed to literally crack itself. A simple PostScript password cracker testing for numerical values as passwords is given below:
+PostScript offers two types of passwords: The ''SystemParamsPassword'' is used to change print job settings like paper size, while the ''StartJobPassword'' is required to exit the server loop and therefore permanently alter the PostScript environment. The ''checkpassword'' operator which takes either an integer or a string as input checks for both passwords at once <ref>''[http://ftp.ktug.org/obsolete/info/adobe/devtechnotes/pdffiles/ps2016.supplement.pdf PostScript Language Reference Manual Supplement for Version 2016]'', Adobe Systems Inc., 1995, p. 194</ref>. The key size is very large: PostScript strings can contain arbitrary ASCII characters and have a maximum length of 65,565 <ref>''[https://www.adobe.com/products/postscript/pdfs/PLRM.pdf PostScript Language Reference Manual, 3rd Edition]'', Adobe Systems Inc., 1999, p. 739</ref> which theoretically allows 524,280 bit passwords. On the positive side (from an attackers point of view) brute-force attacks against PostScript passwords can be performed extremely fast because the PostScript interpreter can be programmed to literally crack itself. A simple PostScript password cracker testing for numerical values as passwords is given below:
 <syntaxhighlight lang=postscript>
@@ Line 50: / Line 50: @@
    {dup checkpassword {== flush stop} {pop} ifelse} for
 } stopped pop
 </syntaxhighlight>
@@ Line 70: / Line 69: @@
 '''Who can perform this attack?'''
-Any anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]]. Feedback from the printer is not required because attackers can blindly remove the password protection by cracking it in a single print job.
+Anyone who can print, for example through [[USB drive or cable]], [[Port 9100 printing]] or [[Cross-site printing]]. Feedback from the printer is not required because attackers can blindly remove the password protection by cracking it in a single print job.
 == Password Disclosure ==
@@ Line 87: / Line 86: @@
 </syntaxhighlight>
-Vulnerable devices will return the password in hex-decimal (here: ''AAA''), while newer devices do only respond with zerobytes.
+Vulnerable devices will return the password in hexadecimal (here: ''AAA''), while newer devices do only respond with zerobytes.
 '''Who can perform this attack?'''
@@ Line 95: / Line 94: @@
 === Pass-Back ===
-Another interesting class of attacks is pass-back attacks were ‘an MFP device is directed into authenticating [...] against a rogue system rather than the expected server’ <ref>''[http://foofus.net/goons/percx/praeda/pass-back-attack.pdf Anatomy of a Pass-Back-Attack: Intercepting Authentication Credentials Stored in Multifunction Printers]'', D. Heiland and M. Belton, 2011</ref>. This works in setups where a printer/MFP verifies users by requesting and external [https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol LDAP] server. Note that the password to access the LDAP server is stored on the MFP itself. If the MFP allows an attacker to change the address of the LDAP server while keeping the old password, whenever someone (for example, the attacker itself) tries to authenticate with the MFP, the MFP leaks the original LDAP password to the attacker-controlled server. This example shows that passwords resident on printers may not only harm the device itself if integrated into a company's network. Printers and MFPs – which may offer insufficient protection – are therefore a good starting point in network penetration tests.
+Another interesting class of attacks is pass-back attacks were ‘an MFP device is directed into authenticating [...] against a rogue system rather than the expected server’ <ref>''[http://foofus.net/goons/percx/praeda/pass-back-attack.pdf Anatomy of a Pass-Back-Attack: Intercepting Authentication Credentials Stored in Multifunction Printers]'', D. Heiland and M. Belton, 2011</ref>. This works in setups where a printer/MFP authenticates users via an external [https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol LDAP] server. Note that the credentials to access the LDAP server are stored on the MFP itself. If the MFP allows an attacker to change the address of the LDAP server while keeping the stored credentials, whenever someone (for example, the attacker itself) tries to authenticate with the MFP, the MFP leaks the original LDAP credentials to the attacker-controlled server. This example shows that passwords resident on printers may not only harm the device itself if integrated into a company's network. Printers and MFPs – which may offer insufficient protection – are therefore a good starting point in network penetration tests.
 '''How to test this attack?'''

@@ Line 22: / Line 22: @@
 === Pass-Back ===
-One remarkable class of attacks to be mentioned is pass-back attacks were `an MFP device is directed into authenticating [...] against a rogue system rather than the expected server' <ref>''[http://foofus.net/goons/percx/praeda/pass-back-attack.pdf Anatomy of a Pass-Back-Attack: Intercepting Authentication Credentials Stored in Multifunction Printers]'', D. Heiland and M. Belton, 2011</ref>. This works in setups where an MFP verifies users by requesting and external [https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol LDAP] server. Note that the password to access the LDAP server is stored on the MFP itself. If the MFP allows an attacker to change the address of the LDAP server while keeping the old password, whenever someone (for example, the attacker itself) tries to authenticate with the MFP, the MFP leaks the original LDAP password to the attacker-controlled server. This example shows that passwords resident on printers may not only harm the device itself if integrated into a company's network. Printers and MFPs – which may offer insufficient protection – are therefore a good starting point in network penetration tests.
+One remarkable class of attacks to be mentioned is pass-back attacks were ‘an MFP device is directed into authenticating [...] against a rogue system rather than the expected server’ <ref>''[http://foofus.net/goons/percx/praeda/pass-back-attack.pdf Anatomy of a Pass-Back-Attack: Intercepting Authentication Credentials Stored in Multifunction Printers]'', D. Heiland and M. Belton, 2011</ref>. This works in setups where an MFP verifies users by requesting and external [https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol LDAP] server. Note that the password to access the LDAP server is stored on the MFP itself. If the MFP allows an attacker to change the address of the LDAP server while keeping the old password, whenever someone (for example, the attacker itself) tries to authenticate with the MFP, the MFP leaks the original LDAP password to the attacker-controlled server. This example shows that passwords resident on printers may not only harm the device itself if integrated into a company's network. Printers and MFPs – which may offer insufficient protection – are therefore a good starting point in network penetration tests.
 '''How to test this attack?'''
@@ Line 30: / Line 30: @@
 '''Who can perform this attack?'''
-Usually anyone who can access the printer's embedded web server. This may include [[https://en.wikipedia.org/wiki/Cross-site_request_forgery CRSF]] attacker, if the web application has no CSRF protection.
+Usually anyone who can access the printer's embedded web server. This may include [https://en.wikipedia.org/wiki/Cross-site_request_forgery CRSF] attacker, if the web application running on the printer has no CSRF protection.
 == Brute-Force Attacks ==
-Besides credentials leaked from sources like [[#SNMP|SNMP]], the printer's [[#Pass-Back|embedded web server]], [[File system access|file system]] or [[memory access]] printing languages offer limited passwords protection mechanisms themselves. Breaking such mechanisms has a priority in this wiki because it focuses on printer-specific weaknesses. Furthermore, whilst the routines to set the password for a printer's embedded web server differ from model to model they are standardized for both, PJL and PostScript. Although it is not very common for end-users or even administrators to set or actually know about these passwords, if enabled they can break some of the attacks discussed in this wiki. Attackers should therefore have a motivation to crack or bypass them if necessary.
+Besides credentials leaked from sources like [[#SNMP|SNMP]], the printer's [[#Pass-Back|embedded web server]], [[File system access|file system]] or [[memory access]], printing languages offer limited passwords protection mechanisms themselves. Breaking such mechanisms has a priority in this wiki because it focuses on printer-specific weaknesses. Furthermore, whilst the routines to set the password for a printer's embedded web server differ from model to model they are standardized for both, PJL and PostScript. Although it is not very common for end-users or even administrators to set or actually know about these passwords, if enabled they can break some of the attacks discussed in this wiki. Attackers should therefore have a motivation to crack or bypass them if necessary.
 === PJL ===
-PJL offers the possibility to set a password to lock access to the printer's hard disk and/or control panel. The standard however allows only numerical values ranging from 1 to 65,535 as key space <ref>''[http://h10032.www1.hp.com/ctg/Manual/bpl13208.pdf Printer Job Language Technical Reference Manual]'', HP Inc., 1997, ch. 6-21</ref>. Brute-force attacks as proposed by <ref>''Attacking Networked Embedded Devices'', Black Hat USA, FX and FtR of Phenoelit, 2002</ref> thus seem feasible. PostScript offers two types of passwords: one to change long-term system settings, the other to permanently alter the PostScript environment. The standard makes no explicit statement about key sizes, however both passwords are of type ''string'' which means up to 65,535 characters <ref>''[https://www.adobe.com/products/postscript/pdfs/PLRM.pdf PostScript Language Reference Manual, 3rd Edition]'', Adobe Systems Inc., 1999, p. 739</ref>. On the other hand, for simple passwords brute-force is very fast as passwords can be verified within a PostScript program running on the printer device itself. Performance can therefore be compared to offline cracking.
+PJL offers the possibility to set a password to lock access to the printer's hard disk and/or control panel. The standard however allows only numerical values ranging from 1 to 65,535 as key space <ref>''[http://h10032.www1.hp.com/ctg/Manual/bpl13208.pdf Printer Job Language Technical Reference Manual]'', HP Inc., 1997, ch. 6-21</ref>. Brute-force attacks as proposed by <ref>''Attacking Networked Embedded Devices'', Black Hat USA, FX and FtR of Phenoelit, 2002</ref> thus seem feasible.
 An evaluation of brute-force attacks against PJL and PostScript passwords is given in \autoref{par:eval-credential-disclosure}. In the prototype implementation, the \texttt{lock} and \texttt{unlock} commands are used for setting and cracking passwords.
@@ Line 76: / Line 78: @@
 === PostScript ===
 PostScript has similar protection mechanisms: The ''SystemParamsPassword'' is used to change print job settings like paper size while the ''StartJobPassword'' is required to exit the server loop and therefore permanently alter the PostScript environment. The ''checkpassword'' operator which takes either an integer or a string as input checks for both passwords at once <ref>''[http://ftp.ktug.org/obsolete/info/adobe/devtechnotes/pdffiles/ps2016.supplement.pdf PostScript Language Reference Manual Supplement for Version 2016]'', Adobe Systems Inc., 1995, p. 194</ref>. The key size is very large: PostScript strings can contain arbitrary ASCII characters and have a maximal length of 65,565 <ref>''[https://www.adobe.com/products/postscript/pdfs/PLRM.pdf PostScript Language Reference Manual, 3rd Edition]'', Adobe Systems Inc., 1999, p. 739</ref> which theoretically allows 524,280 bit passwords. On the positive side (from an attackes point of view) brute-force attacks against PostScript passwords can be performed extremely fast because the PostScript interpreter can be programmed to literally crack itself. A simple PostScript password cracker testing for numerical values as passwords is given below:

@@ Line 10: / Line 10: @@
 <syntaxhighlight lang=sh>
-$ snmpget -v1 -c public printer iso.3.6.1.4.1.11.2.3.9.1.1.13.0
+snmpget -v1 -c public printer iso.3.6.1.4.1.11.2.3.9.1.1.13.0
-iso.3.6.1.4.1.11.2.3.9.1.1.13.0 = Hex-STRING: 41 41 41 41 41 00 …
+iso.3.6.1.4.1.11.2.3.9.1.1.13.0 = Hex-STRING: 41 41 41 00 …
 </syntaxhighlight>
-Vulnerable devices will return the password in hex-decimal (here: ''AAAAA''), while newer devices do only respond with zerobytes.
+Vulnerable devices will return the password in hex-decimal (here: ''AAA''), while newer devices do only respond with zerobytes.
 '''Who can perform this attack?'''
@@ Line 20: / Line 20: @@
 Anyone who can send network packets to port 161/udp of the printer device.
-=== Pass-Back Attacks ===
+=== Pass-Back ===
-Printers are commonly deployed with a default password or no initial password at all. In both cases, end-user or administrators have to actively set a password to secure the device. One approach to systematically collect credentials and other information from the web server is the [[Praeda] tool. Besides exploiting vulnerabilities that lead to disclosure of device passwords, the program gathers usernames and email addresses, which are often publicly available via the printer's web interface and can be used for further network penetration tests. One remarkable class of attacks to be mentioned in this context is pass-back attacks were `an MFP device is directed into authenticating [...] against a rogue system rather than the expected server' <ref>''[http://foofus.net/goons/percx/praeda/pass-back-attack.pdf Anatomy of a Pass-Back-Attack: Intercepting Authentication Credentials Stored in Multifunction Printers]'', D. Heiland and M. Belton, 2011</ref>. This works in setups where an MFP verifies users by requesting and external [https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol LDAP] server. Note that the password to access the LDAP server is stored on the MFP itself. If the MFP allows an attacker to change the address of the LDAP server while keeping the old password, whenever someone (for example, the attacker itself) tries to authenticate with the MFP, the MFP leaks the original LDAP password to the attacker-controlled server. This example shows that passwords resident on printers may not only harm the device itself if integrated into a company's network. Printers and MFPs – which may offer insufficient protection – are therefore a good starting point in network penetration tests.
+Printers are commonly deployed with a default password or no initial password at all. In both cases, end-user or administrators have to actively set a password to secure the device. One approach to systematically collect credentials and other information from the web server is the [[Praeda]] tool. Besides exploiting vulnerabilities that lead to disclosure of device passwords, the program gathers usernames and email addresses, which are often publicly available via the printer's web interface and can be used for further network penetration tests. One remarkable class of attacks to be mentioned in this context is pass-back attacks were `an MFP device is directed into authenticating [...] against a rogue system rather than the expected server' <ref>''[http://foofus.net/goons/percx/praeda/pass-back-attack.pdf Anatomy of a Pass-Back-Attack: Intercepting Authentication Credentials Stored in Multifunction Printers]'', D. Heiland and M. Belton, 2011</ref>. This works in setups where an MFP verifies users by requesting and external [https://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol LDAP] server. Note that the password to access the LDAP server is stored on the MFP itself. If the MFP allows an attacker to change the address of the LDAP server while keeping the old password, whenever someone (for example, the attacker itself) tries to authenticate with the MFP, the MFP leaks the original LDAP password to the attacker-controlled server. This example shows that passwords resident on printers may not only harm the device itself if integrated into a company's network. Printers and MFPs – which may offer insufficient protection – are therefore a good starting point in network penetration tests.
 '''How to test this attack?'''