DelegationNotAllowed not being enforced in protocol transition on Samba AD DC.

ID SAMBA:CVE-2019-14870
Type samba
Reporter Samba
Modified 2019-12-10T00:00:00


The S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable. In AD this is implemented by a user attribute delegation_not_allowed (aka not-delegated), which translates to disallow-forwardable. However the Samba AD DC does not do that for S4U2Self and does set the forwardable flag even if the impersonated client has the not-delegated flag set. Note: while the experimental MIT AD-DC build does not support S4U, it should still be patched due to a related bug in regular authentication.