Peter Jeremy wrote:
On 2007-Jan-18 22:21:52 +0800, XFOCUS Security Team <security@xxxxxxxxxx> wrote:
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.
This vulnerability has been known for years. OpenBSD implemented a
kernel check to block this attack in 1998. FreeBSD and NetBSD have
similar kernel checks and I believe glibc also has checks to block
this. It is disturbing that none of the commercial OS vendors appear
to have bothered to protect against this.
Of course the _real_ problem is the badly written setuid app. Kernel
checks for "special" fds are just a condom to try and protect against
broken code. Not that such checks aren't a good idea (since so much code
is so very broken), but any app that is vulnerable to this attack needs
to be patched.
You'll note that the original advisory fails to specify any setuid apps
that are vulnerable to this attack, other than their broken POC. *yawn*
--
Carson
