fix(devolutions-gateway): kdc proxy: fake KDC target hostname

[Pavlo Myroniuk (TheBestTvarynka)]

Hi,

I fixed the target hostname for the fake KDC inside the KDC proxy. I tried to write the minimal possible solution.

The problem: during the credentials injection, the RDP client does the Kerberos authentication via a KDC proxy with a fake KDC. In that case, the target hostname (Kerberos service name for the TGS) must be a proxy hostname. But prior to this PR, the KDC proxy always configured the internal KDC to the real target machine hostname. This problem was introduced in #1768.

For example, my local configuration:

• Devolutions-Gateway hostname: dgateway.tbt.com.
• Target machine behind the proxy: WIN-956CQOSSJTF.tbt.com.

When I connect to the target machine using credentials injection, my FreeRDP command looks like this:

.\sdl-freerdp.exe /v:dgateway.tbt.com:8181 /u:fake_user /d:603077ae-b66b-4256-ae48-a458db5b90b0.jet /p:fake_password /sec:nla /log-level:TRACE /sspi-module:"<sspi.dll path>" /pcb:<token>

During the FreeRDP's NLA stage, it should perform Kerberos auth against dgateway.tbt.com (instead of WIN-956CQOSSJTF.tbt.com).

I hope I explained the problem well 😄.

[github-actions]

Let maintainers know that an action is required on their side

• Add the label release-required Please cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module) when you request a maintainer to cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module)

• Add the label release-blocker Follow-up is required before cutting a new release if a follow-up is required before cutting a new release

• Add the label publish-required Please publish libraries (`Devolutions.Gateway.Utils`, OpenAPI clients, etc) when you request a maintainer to publish libraries (Devolutions.Gateway.Utils, OpenAPI clients, etc.)

• Add the label publish-blocker Follow-up is required before publishing libraries if a follow-up is required before publishing libraries