Time and again in discussions about the security of a certification authority, it comes up that abuse of the certification authority could be contained by its security settings.
However, the fact that the integrity of a certification authority is directly tied to its key material and can therefore also be compromised by it is not obvious at first glance.
one must think of the certification authority software as a kind of management around the key material. For example, the software provides a Online interface for Certificate Enrollment takes care of the authentication of the enrollees, the automated execution of signature operations (issuing certificates and Brevocation lists) and their logging (Certification Authority Database, Audit log, Event log).
However, signature operations require nothing more than the private key of the certification authority. The following example shows how an attacker, given access to the certification authority's private key, can generate and issue certificates without the certification authority software and its security mechanisms being aware of this.
With such a certificate, it would even be possible in the worst case, take over the Active Directory forest undetected.
Continue reading „Signieren von Zertifikaten unter Umgehung der Zertifizierungsstelle“
English 
Deutsch