Subject: kerb: Fix LDAP null deref on empty arg [CVE-2016-3119]
From: Greg Hudson

In the LDAP KDB module's process_db_args(), strtok_r() may return NULL
if there is an empty string in the db_args array.  Check for this case
and avoid dereferencing a null pointer.

CVE-2016-3119:

In MIT krb5 1.6 and later, an authenticated attacker with permission
to modify a principal entry can cause kadmind to dereference a null
pointer by supplying an empty DB argument to the modify_principal
command, if kadmind is configured to use the LDAP KDB module.

    CVSSv2 Vector: AV:N/AC:H/Au:S/C:N/I:N/A:C/E:H/RL:OF/RC:ND

ticket: 8383 (new)
target_version: 1.14-next
target_version: 1.13-next
tags: pullup

Upstream-Status: Backport

Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com>
Index: krb5-1.13.2/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c
===================================================================
--- krb5-1.13.2.orig/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c	2015-05-09 07:27:02.000000000 +0800
+++ krb5-1.13.2/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c	2016-04-11 15:17:12.874140518 +0800
@@ -267,6 +267,7 @@
     if (db_args) {
         for (i=0; db_args[i]; ++i) {
             arg = strtok_r(db_args[i], "=", &arg_val);
+            arg = (arg != NULL) ? arg : "";
             if (strcmp(arg, TKTPOLICY_ARG) == 0) {
                 dptr = &xargs->tktpolicydn;
             } else {