CVE-2013-2207, BZ #15755: Disable pt_chown.

The helper binary pt_chown tricked into granting access to another
user's pseudo-terminal.

Pre-conditions for the attack:

 * Attacker with local user account
 * Kernel with FUSE support
 * "user_allow_other" in /etc/fuse.conf
 * Victim with allocated slave in /dev/pts

Using the setuid installed pt_chown and a weak check on whether a file
descriptor is a tty, an attacker could fake a pty check using FUSE and
trick pt_chown to grant ownership of a pty descriptor that the current
user does not own.  It cannot access /dev/pts/ptmx however.

In most modern distributions pt_chown is not needed because devpts
is enabled by default. The fix for this CVE is to disable building
and using pt_chown by default. We still provide a configure option
to enable hte use of pt_chown but distributions do so at their own
risk.

1 files changed, 3 insertions, 0 deletions

diff --git a/config.h.in b/config.h.in
index 6284e2a99b..a85f131255 100644
--- a/config.h.in
+++ b/config.h.in
@@ -238,4 +238,7 @@
 /* The ARM hard-float ABI is being used.  */
 #undef HAVE_ARM_PCS_VFP
 
+/* The pt_chown binary is being built and used by grantpt.  */
+#undef HAVE_PT_CHOWN
+
 #endif