Good overview of Kerberoasting, still a common attack chain. A couple things though: To obtain access to a service, you actually need to get a service ticket (TGS) from the KDC (Domain Controller) to authenticate to the service, not a TGT. The TGT is the first ticket acquired during authentication to the domain. In addition, the "salt" is not a true salt but a concatenation of the domain and principal name, so even worse. Active Directory (invented at MIT) supports RC4, AES128, and AES256 encryption types, however you can effectively disable RC4 via Group Policy. The reason RC4 is still supported is to support legacy systems. Many organizations use old software that only supports RC4. For example, I've run into many manufacturing and small businesses that have no choice but to use it and can't upgrade the software due to $$$. Anyway, good stuff! Shout out to Tim Medin, who published this back in 2014.
Just to add to this, the salt (domain [realm] and username) is only used to generate the AES keys, not the RC4. The RC4 key is simply the NT hash.
And thanks for the shout out!
I have a vague understanding of Kerberos, and this is where I’m mystified. Why is the KDC or anything else willing to issue a TGS ticket encryption against a service password before the requesting user authorizes themselves? Or is the issue that authentication and authorization are split and the KDC has no idea whether the requesting user is authorized.