Peace For All

September 22, 2011

Remotely Executing Commands in PowerShell using C#

Filed under: C#, PowerShell, Programming — Tags: , , — Devlin Bentley @ 4:02 pm

At first glance, this seems like it should be easy. After all: remoting using PowerShell is dirt easy! Once the server is configured you are a single Invoke-Command away from remoting bliss! So how hard could it be in C#? Surely there is some functional equivalent to Invoke-Command that gets exposed, right?

Well no, it is not that simple. It isn’t too bad, but the lack of any examples on MSDN makes some aspects of doing this quite literally impossible to figure out if you are using MSDN documentation alone.

Thankfully by piecing together posts from the MSDN Forums it is possible to get something working. Having done just that, I figure I’d save you all the time and effort.

Precursor

Get a reference to System.Management.Automation into your project. The best way to do this is to manually edit the csproj file and add the line

<Reference Include=”System.Management.Automation” />

Yes this is ghetto. I am not sure why that library is not sitting with the rest of them in the proper location that would get it listed in the “Add References” dialog.

Goal

Calling in from C# code, execute PowerShell  code on a remote machine.

Tools

A bunch of poorly documented object constructors.

The key to getting this all working is to properly construct an instance of WSManConnectionInfo and pass that on to the RunspaceFactory.CreateRunspace(..) method.

Step 1: Constructing a PSCredential

This step is pretty straight forward. PSCredential has only one constructor, it takes in a username and a SecureString password. The only gotcha is that userName includes domain if applicable.

Good luck on the SecureString PW part. Doing it properly (e.g. never storing your PW in a string at any step) can take some planning ahead, depending on your situation of course.

PSCredential remoteMachineCredentials = new PSCredential(domainAndUserName, securePassword);

 Step 2: Constructing WSManConnectionInfo

This is the hard part. Mostly because the documentation on how to use this class is so poor, most of it consisting of how to establish a loopback connection to localhost.

With our particular goal in mind, we only really care about one of the overloads:

public WSManConnectionInfo (
bool useSsl,
string computerName,
 int port,
string appName,
string shellUri,
PSCredential credential
)

The documentation for this constructor (located at http://msdn.microsoft.com/en-us/library/dd978670(v=VS.9).aspx if you want to read it yourself) has such gems as

appName

The application end point to connect to.

Not very useful.

Lets go over these parameters one by one and look at what each one means.

useSsl – Pretty simple, a bool flag indicating if SSL should be used. Highly recommended for use, of course. Note that changing this changes what port number you will be using later on

computerName – The name of the machine you are connecting to. On local networks, this is just the machine name.

port – Thanks to the blog post at http://blogs.msdn.com/b/wmi/archive/2009/07/22/new-default-ports-for-ws-management-and-powershell-remoting.aspx we know what port numbers PowerShell remoting uses. 5985 if you are not using SSL, and 5986 if you are using SSL.

appName – This should be “/wsman”. I don’t know what it is or what other values you can use here, but thanks to the Emeka over on the MSDN forums (thread: http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/a0e5b23c-b605-431d-a32f-942d7c5fd843) we know that “/wsman” will get it working.

shellUri – Again, thanks to Emeka we know that this needs to be http://schemas.microsoft.com/powershell/Microsoft.PowerShell&#8221;. I am not sure what other values are acceptable, but that value does indeed work.

credential – Finally we come back to the PSCredential object we constructed earlier. Simple enough.

Step 3: Creating a Runspace

We thankfully return back to documented things. After constructing the WSManConnectionInfo just pass that into RunspaceFactory.CreateRunspace(…) and be done with it.

Step 4: Putting it all together

string shellUri = "http://schemas.microsoft.com/powershell/Microsoft.PowerShell";
PSCredential remoteCredential = new PSCredential(domainAndUsername, securePW);
WSManConnectionInfo connectionInfo = new WSManConectionInfo(false, remoteMachineName, 5985, "/wsman", shellUri, remoteCredential)

using ( Runspace runspace = RunspaceFactory.CreateRunspace(connectionInfo) )

{

runspace.Open();

Pipeline pipeline = runspace.CreatePipeline("<COMMAND TO EXECUTE REMOTELY>");

var results = pipeline.Invoke();

}

All in all, not too bad. The sad part it, in terms of figuring out what to do it is easier to create a local runspace and use Invoke-Command on it, but once you know what you are doing, it is only one extra line of code to execute scripts remotely!

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4 Comments »

  1. What is needed in order to setup PowerShell on the remote end?

    Comment by deserialized — August 7, 2012 @ 2:06 am

    • That is generally covered pretty well elsewhere. Lots of blogs have good step by step instructions for setting up PS remoting. Look into the “Enable-PSRemoting” cmdlet. Depending on your needs, you may need to do some more stuff. Getting it working across domain boundaries is, as always, not the most fun of tasks.

      Comment by Devlin Bentley — August 7, 2012 @ 5:49 pm

  2. Thanks a lot! Was breaking my head over this for a while and you provided the last bit of magic pixie dust to make it work (the values for the shellUri and appName parameters). Thanks again!

    Comment by Raj — September 9, 2013 @ 7:30 am

  3. Thanks 🙂 1 question : For ComputerName parameter can I use IP address without using https ?

    Comment by sagar — March 6, 2014 @ 2:19 am


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