What is PowerShell:
- Used for task automation and management
- A framework by Microsoft.
- It is supported by .NET Framework. (As you can see below, you can play around with .Net functionality)
PowerShell has:
- Command-line shell, which is similar to cmd in Windows or terminal in Linux.
- Associated scripting language.
How to install:
You can follow the guide at
Installing PowerShell Windows.
If you have installed Microsoft Visual Studio, it also have options to install PowerShell.
How to Start with command-line shell after installation:
- You can follow this guide at
Starting the 32-bit Version of PowerShell
Normally in Windows, you also can click "Start" and search for PowerShell.
After starting, the screen is as below. You can type: get-command to see all commands.
PowerShell command-line
Getting Started With PowerShell Command-line
You can play around with PowerShell. In the Command-line Shell,
Below is one way that you can save a password with SecureString to a text file. Although this is not the good way in terms of security, but this is a good start with PowerShell.
Try the following commands !
Command 1:
$key = (3,4,2,3,56,34,254,222,1,1,2,23,42,54,33,233,1,34,2,7,6,5,35,43)
Command 2:
$pw = read-host "Enter Password" –AsSecureString
Command 3:
ConvertFrom-SecureString $pw -key $key | out-file "path\to\password\file\here\textfile.txt"
Now you have a textfile.txt, and its content might look like this:
76492d1116743f0423413b16050a5345MgB8ADMAVQBBAG8AeQAwAC8AdwBaAFgAZgBxAHMAMgBOAHYAUgBhAG8AaQB3AGcAPQA9AHwAMgAwAGIAMQAyADQANwA0ADUAMQBlADAANQA4ADcANwA0AGMAYwA1ADEANwA2AGMAYQAyAGYAMgBhADQAOAA0ADcANAA2ADYAYgBiADAAYwA3AGIAZABlADIAMgAwADgAYQBlADYANAA1ADUAYwBmADMAMwA2ADMAMwA4ADcAMQA=
In order to decrypt the content, try the following command from the command-line Shell:
Command 4:
$password = cat "path\to\password\file\here\textfile.txt" | convertto-securestring -key $key
Command 5:
$Ptr = [System.Runtime.InteropServices.Marshal]::SecureStringToCoTaskMemUnicode($password)
command 6:
$result = [System.Runtime.InteropServices.Marshal]::PtrToStringUni($Ptr)
Command 7:
[System.Runtime.InteropServices.Marshal]::ZeroFreeCoTaskMemUnicode($Ptr)
Command 8:
$result
Here it is, $result is the "password" you entered in command 1.
Just play around with it and you will get more experienced!
UPDATE 1:
Links
It is a little bit off the scope. Below is the C# code to convert the text of a SecureString stored in a text file to an in-memory SecureString.
public static SecureString ConvertToSecureString(string psProtectedString, byte[] key)
{
// '|' is indeed the separater
byte[] asBytes = Convert.FromBase64String(psProtectedString);
string[] strArray = Encoding.Unicode.GetString(asBytes).Split(new[] { '|' });
if (strArray.Length != 3) throw new InvalidDataException("input had incorrect format");
// strArray[0] is a static/magic header or signature (different passwords produce
// the same header) It unused in our case, looks like 16 bytes as hex-string
// you know strArray[1] is a base64 string by the '=' at the end
// the IV is shorter than the body, and you can verify that it is the IV,
// because it is exactly 16bytes=128bits and it decrypts the password correctly
// you know strArray[2] is a hex-string because it is [0-9a-f]
byte[] magicHeader = HexStringToByteArray(psProtectedString.Substring(0, 32));
byte[] rgbIV = Convert.FromBase64String(strArray[1]);
byte[] cipherBytes = HexStringToByteArray(strArray[2]);
// setup the decrypter
SecureString str = new SecureString();
SymmetricAlgorithm algorithm = SymmetricAlgorithm.Create();
ICryptoTransform transform = algorithm.CreateDecryptor(key, rgbIV);
using (var stream = new CryptoStream(new MemoryStream(cipherBytes), transform, CryptoStreamMode.Read))
{
// using this silly loop format to loop one char at a time
// so we never store the entire password naked in memory
int numRed = 0;
byte[] buffer = new byte[2]; // two bytes per unicode char
while ((numRed = stream.Read(buffer, 0, buffer.Length)) > 0)
{
str.AppendChar(Encoding.Unicode.GetString(buffer).ToCharArray()[0]);
}
}
//
// non-production code
// recover the SecureString; just to check
// from http://stackoverflow.com/questions/818704/how-to-convert-securestring-to-system-string
//
IntPtr valuePtr = IntPtr.Zero;
string secureStringValue = "";
try
{
// get the string back
valuePtr = Marshal.SecureStringToGlobalAllocUnicode(str);
secureStringValue = Marshal.PtrToStringUni(valuePtr);
}
finally
{
Marshal.ZeroFreeGlobalAllocUnicode(valuePtr);
}
return str;
}
// from http://stackoverflow.com/questions/311165/how-do-you-convert-byte-array-to-hexadecimal-string-and-vice-versa
public static byte[] HexStringToByteArray(String hex)
{
int NumberChars = hex.Length;
byte[] bytes = new byte[NumberChars / 2];
for (int i = 0; i < NumberChars; i += 2) bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
return bytes;
}
public static SecureString DecryptPassword(string psPasswordFile, byte[] key)
{
if (!File.Exists(psPasswordFile)) throw new ArgumentException("file does not exist: " + psPasswordFile);
string formattedCipherText = File.ReadAllText(psPasswordFile);
return ConvertToSecureString(formattedCipherText, key);
}
