Decrypt SecureString from Powershell with C#

Question

I have following Powershell-Code to encrypt my password

$my_secure_password = convertto-securestring "myPW" -asplaintext -force $my_encrypted_string = convertfrom-securestring $my_secure_password -key(1..16)

The Output is something like this 76492d1116743f0423413b16050a5345MgB8AHMASgB1AFMARwBxAFMAYgA1AFIAYwAyAE4AOABqAHMAOQBaADgAbwBGAEEAPQA9AHwANwBk................

How can I decrypt this output in C# in order to use it as a SecureString in C#?

I've tested something like this but this didn't work for me

var runSpace_new = RunspaceFactory.CreateRunspace();
runSpace_new.Open();

PowerShell PSinstance = PowerShell.Create();
PSinstance.AddScript("$decrypt = convertto-securestring -key (1..16) -string 76492d1116743f0423413b.......");
var psOutput_new = PSinstance.Invoke();
var a = runSpace_new.SessionStateProxy.PSVariable.GetValue("decrypt");

But a is null....

UPDATE I have found a solution for this:

SecureString new_sec_pass = new SecureString();
PowerShell instance = PowerShell.Create();

instance.AddScript("convertto-securestring -key (1..16) -string 76492d1...");

foreach (PSObject psOutput in instance.Invoke())
{
    new_sec_pass = psOutput.BaseObject as SecureString;
}

PSCredential new_credentials = new PSCredential(Username, new_sec_pass);

Vitaly · Accepted Answer · 2017-08-14 09:39:45Z

1

You may try this (maybe it help for you - for me - it is work):

using System.Collections.ObjectModel;
using System.Management.Automation;

     static void Main(string[] args)
        {

            var variable = PowerShell.Create().AddScript("$xtr = convertto-securestring -key (1..16) -string" + 
            " '76492d1116743f0423413b16050a5345MgB8AEQAbQBIAEIASQB6ADcAeQA0AH" + 
            "UAaAB6AFEAawBJAEYAVAA0AHcAUwBoAGcAPQA9AHwAMQAzAGUANwBmADIAOAAxADEANwAwAGUAZQBjADMANwBlAG" +
            "QAYQAxADcAZABlADEAMQBhAGYAZgBiADkAOQBiADIAMAAwAGMAMgA1AGEAZgAxADcAMABhADAAYwBjAGIAMQBhADAAZAAwADMAMwAzADMAOQAwADcAYQAzAGMANwA='" + 
            ";$PwdPointer = [Runtime.InteropServices.Marshal]::SecureStringToBSTR($xtr);"+
            "$PlainTextPassword = [Runtime.InteropServices.Marshal]::PtrToStringAuto($PwdPointer);$PlainTextPassword").AddCommand("out-string");
        Collection<PSObject> results = variable.Invoke();

            foreach (var str in results)
            {

                Console.WriteLine(str);
                Console.ReadKey();

            }
        }

edited Aug 14, 2017 at 9:39

answered Aug 14, 2017 at 8:16

Vitaly

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6 Comments

user7445564 Over a year ago

When I do this str is = System.Security.SecureString But how can I use this then in var credentials = new PSCredential(Username, new_sec_pass); ?

Vitaly Over a year ago

Ok. Can you do this? : foreach (var str in results) { Console.WriteLine(Convert.ToString(str)); Console.ReadKey(); }

user7445564 Over a year ago

My Script looks like this:

instance.AddScript("$decryptedpw = convertto-securestring -key (1..16) -string 76492d1.....; $decryptedpw").AddCommand("out-string"); var psOutput = instance.Invoke();                      foreach (var result in psOutput)                     {                         Console.WriteLine(result);                         Console.WriteLine(Convert.ToString(result));

Both same Output: System.Security.SecureString

Vitaly Over a year ago

Yes. Sorry. =). You can convert it. I edit my answer. If you run this code - it will converting you security string to unsecurity password

user7445564 Over a year ago

Thank you. Look for the update in my first post, I have found another solution.

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