Date: Thu, 2 Oct 2003 18:43:14 +0200
From: Joost Pol <[email protected]>
To: [email protected]Subject: PINE-CERT-20030902: Integer Overflow in FreeBSD Kernel [uio]
Cc: [email protected]
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
- -------------------------------------------------------------------------------
Pine Digital Security Advisory
- -------------------------------------------------------------------------------
Advisory ID : PINE-CERT-20030902
Authors : Joost Pol
Vendor Informed : 2003-23-09
Issue date : 2003-01-10
Application : kernel / uio
Version(s) : All Versions
Platforms : FreeBSD
Availability : http://www.pine.nl/press/pine-cert-20030902.txt
- -------------------------------------------------------------------------------
Synopsis
While performing an audit for a customer, Pine Digital Security
encountered an integer overflow/underflow condition which
could lead to the disclosure of kernel memory.
Versions
All known FreeBSD versions are vulnerable.
Impact
Serious.
Local users on a machine with procfs enabled could exploit this
vulnerability to cause a system panic (denial of service) or
potentially elevate their privileges.
Description
The process file system, or procfs, implements a view of the system
process table inside the file system. It is normally mounted on
/proc, and is required for the complete operation of programs
such as ps(1) and w(1).
On several places in the procfs implementation the "uio" offset
parameter is used without proper validation, the following
code fragment illustrates this:
/usr/src/sys/miscfs/procfs/procfs_regs.c (edited, line 59-84):
struct reg r; char *kv; int kl;
..
kl = sizeof(r);
kv = (char *) &r;
...
kv += uio->uio_offset;
kl -= uio->uio_offset;
if (kl > uio->uio_resid) kl = uio->uio_resid;
...
if (kl < 0) error = EINVAL;
...
if (error == 0) error = uiomove(kv, kl, uio);
As the above code fragment illustrates and since the uio->uio_offset
parameter is under (indirect) control of the user it is possible
to disclose large amounts of kernel memory by specifying an
extremely large or negative value.
Exploitability
Local users can cause an effective denial of service by attempting
to read from non resident kernel memory and thus generating
a system panic.
Local users could also potentially elevate their privileges by
reading from terminal input buffers and thus stealing other
users passwords.
Appendum
The FreeBSD security officer team spotted a similiar vulnerability
in the pseudofs implementation. Pine Digital Security recommends
upgrading even if you do not use procfs.
Disclaimer
Pine Digital Security does not release exploits.
Patches
The FreeBSD Project has updated their CVS repositories.
References
FreeBSD-SA-03:17.procfs.asc
http://www.pine.nl/press/pine-cert-20030902.txt
file://usr/include/sys/file.h
file://usr/src/sys/miscfs/procfs/procfs_dbregs.c
file://usr/src/sys/miscfs/procfs/procfs_fpregs.c
file://usr/src/sys/miscfs/procfs/procfs_regs.c
file://usr/src/sys/miscfs/procfs/procfs_rlimit.c
file://usr/src/sys/miscfs/procfs/procfs_status.c
file://usr/src/sys/kern/vfs_syscalls.c
- --
Service Provider :: Pine Digital Security :| www.pine.nl || +31 (0)70 311 10 10
:: PGP id 0xF360BB93 fpr ABED 303C 0120 E057 633A 1CB1 D236 C82A F360 BB93 ::
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.1 (SunOS)
iEYEARECAAYFAj98VaEACgkQ0jbIKvNgu5NkQgCfUlXJfIedVg776CvE/xmqjzsz
6B0AnRxpZkZghoSF+Gpgeme86sTaN/W0
=95pa
-----END PGP SIGNATURE-----
