The initial design for ticket flags was implementing this logic:
* If a ticket policy is defined for the principal entry, use flags from
this policy if they are set. Otherwise, use default ticket flags.
* If no ticket policy is defined for the principal entry, but there is a
global one, use flags from the global ticket policy if they are set.
Otherwise, use default ticket flags.
* If no policy (principal nor global) is defined, use default ticket
flags.
However, this logic was broken by a1165ffb which introduced creation of
a principal-level ticket policy in case the ticket flag set is modified.
This was typically the case for the -allow_tix flag, which was set
virtually by the KDB driver when a user was locked until they initialize
their password on first kinit pre-authentication.
This was causing multiple issues, which are mitigated by the new
approach:
Now flags from each level are combined together. There flags like
+requires_preauth which are set systematically by the KDB diver, as
well as -allow_tix which is set based on the value of "nsAccountLock".
This commit also adds the implicit -allow_svr ticket flag for user
principals to protect users against Kerberoast-type attacks. None of
these flags are stored in the LDAP database, they are hard-coded in the
KDB driver.
In addition to these "virtual" ticket flags, flags from both global and
principal ticket policies are applied (if these policies exist).
Principal ticket policies are not supported for hosts and services, but
this is only an HTTP API limitation. The "krbTicketPolicyAux" object
class is supported for all account types. This is required for ticket
flags like +ok_to_auth_as_delegate. Such flags can be set using "ipa
host-mod" and "ipa serivce-mod", or using kadmin's "modprinc".
It is possible to ignore flags from the global ticket policy or default
flags like -allow_svr for a user principal by setting the
"final_user_tkt_flags" string attribute to "true" in kadmin. In this
case, any ticket flag can be configured in the principal ticket policy,
except requires_preauth and allow_tix.
When in IPA setup mode (using the "ipa-setup-override-restrictions" KDB
argument), all the system described above is disabled and ticket flags
are written in the principal ticket policy as they are provided. This is
required to initialize the Kerberos LDAP container during IPA server
installation.
This fixes CVE-2024-3183
Signed-off-by: Julien Rische <jrische@redhat.com>
4a61184da6