Month: November 2017

PowerShell remoting – source vs destination

Powershell remoting, the ability to remotley manage and influence devices is a key part of PowerShell. By default PowerShell remoting is enabled on servers and one of the lazy “security” features you can use is to only allow connections from specified networks.

In a domain network this is very easy to do, all you need is a small group policy that sets the networks. There is one thing you need to note, that is not really documented.

The Group Policy

The group policy is a regular computer policy setting found under “Computer\Policies\Administrative Templates\Windows Components\Windows Remote Management (WinRM)\WinRM Service” and the actual poliy item is named “Allow remote server management through WinRM”

When you enable this policy you can enter networks the server will consider trusted.  So lets say you have your server on the network 192.168.1.0, that would mean you set the filder to 192.168.1.1-.192.168.1.254.

The issue

What you need to consider is the following. Say you have servers on two seperate networks and one is considered management network, lets say it uses 172.16.1.0/24. This means you now specify the management network as approved. But the servers you are accessing is on your primary server network 192.168.1.0/24. You have to specifiy both source and destination networks for this to work as this also controls the actual listners and if you only specify the 172.16.1.0/24 network the listners on the servers on network 192.168.1.0/24 will not be enabled.

The solution

For the scenario above make sure to specify both networks in your GPO. So the filter will be set to 192.168.1.1-192.168.1.254,172.16.1.1-172.16.1.254

winrm

/Peter

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Strange Case of the failed Remote Desktop Gateway

I have been having a kind of a strange issue for a longe while and finally got around to troubleshooting and figuring out why so here is a breakdown of the strange case of the failed remote desktop gateway connection.

The setup is as follow, using diffrent machines Windows 10, 8.1 and 7 to connect to diffrent remote desktop gateway solutions and for some reason the connection failed with wrong username and password to a couple of the RDGWs.

So after som digging and alot of help from my good friend over at isloation.se we found the issue and how to check if you are also running into this issue.

The check

On the RDGW check under incomming connections/monitoring and if the connections display as RPC-HTTP. This is the clue that something is not all right.

rdgw1

The cause

So over the years the has been alot of fixes and version of the RDP client for each version of Windows. In the later release support was introduced for RDP over HTTP with UDP as a performance booster. However due to bugs and other things happening there have been posts and information about setting a registry value to make RDP work again. The value is called RDGClientTransport. It is a DWORD and you set it to 1 to get everyting working again.

However what this does is force the RDP client to fall back to RPC-HTTP connections instead of HTTP/UDP. This in turn can cause connection issues if you have modern solutions.

The solution

Depsite several blogs and forum posts saying this the value should be 1 you really should change the default value of 0.

So here is the full path to set the value.

HKEY_CURRENT_USER\Software\Microsoft\Terminal Server Client\RDPClientTransport

As you probably noted it is a current user setting and since I am very lazy. Most of my configuration is done through either Configuration Manager or GPO so in this case it was a GPO setting the value to 1 for all my users. Hence the problem was only on my devices and not my coworkers devices.

rdgw2

/Peter

Techdays 2017 Pre-Conf Slides

Me and Jörgen Nilsson (@ccmexec) did a pre-conf together at Techdays in sweden. And after much slacking here are now the slide deck from that pre-conf.

Here is the link to download the slidedeck!
https://1drv.ms/b/s!ArAh2CEqOjRkk-8ZDAVJ1vRqi8Glxg

Techday2017

/Peter