Invoke-MTPuTTYConfigDump - read an MTPuTTY configuration file, decrypt the passwords and dump the result

Invoke-MTPuTTYConfigDump.psm1

<#
 .Synopsis
  Decrypt an MTPuTTY configuration file

 .Description
  Read an MTPuTTY configuration file, decrypt the passwords and dump the result

 .Parameter ConfigFile
  Path to the MTPuTTY configuration file

 .Example
   Invoke-MTPuTTYConfigDump mtputty.xml
#>
function Invoke-MTPuTTYConfigDump {
[CmdletBinding(DefaultParameterSetName="ConfigFile")]
Param(
	[Parameter(ParameterSetName = "ConfigFile", Position = 0, Mandatory = $true)]
	[String]
	$ConfigPath
)
    $PROV_RSA_FULL = 1
    $CRYPT_VERIFYCONTEXT = 0xF0000000
    $CALG_SHA = 0x00008004
    $CALG_RC2 = 0x00006602

    Function Get-CryptoAPI {
        $MethodDefinition = @"
        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptAcquireContext(ref IntPtr hProv, string pszContainer, string pszProvider, uint dwProvType, long dwFlags);

        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptReleaseContext(IntPtr hProv, uint dwFlags);

        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptCreateHash(IntPtr hProv, uint algId, IntPtr hKey, uint dwFlags, ref IntPtr phHash);

        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptDestroyHash(IntPtr hHash);

        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptHashData(IntPtr hHash, byte[] pbData, uint dataLen, uint flags);

        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptDeriveKey(IntPtr hProv,int Algid, IntPtr hBaseData, int flags, ref IntPtr phKey);

        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptDestroyKey(IntPtr hKey);   

        [DllImport("advapi32.dll", CharSet=CharSet.Auto, SetLastError=true)]
        [return : MarshalAs(UnmanagedType.Bool)]
        public static extern bool CryptDecrypt(IntPtr hKey, IntPtr hHash, int Final, uint dwFlags, byte[] pbData, ref uint pdwDataLen);
"@
        try {
            $CryptoAPI = Add-Type -MemberDefinition $MethodDefinition -name advapi32 -Namespace CryptoAPI -PassThru
        } catch {}

        return [CryptoAPI.advapi32]
    }

    <# https://devblogs.microsoft.com/powershell/format-xml/ #>
    Function Format-XML ([System.Xml.XmlElement]$xml, $indent=2) {
        $StringWriter = New-Object System.IO.StringWriter
        $XmlWriter = New-Object System.XMl.XmlTextWriter $StringWriter
        $xmlWriter.Formatting = "indented"
        $xmlWriter.Indentation = $Indent
        $xml.WriteContentTo($XmlWriter)
        $XmlWriter.Flush()
        $StringWriter.Flush()
        Write-Output $StringWriter.ToString()
    }

    try {
        [xml]$config = Get-Content -Path $ConfigPath -ErrorAction Stop
    } catch {
        Write-Host $_ -ErrorAction Stop
        return
    }

    $CryptoAPI = Get-CryptoAPI
    [System.IntPtr]$hProv = 0
    $servers = $config.SelectNodes("//Servers")
    if($servers.Count -gt 0 -and $CryptoAPI::CryptAcquireContext([ref]$hProv, $null, $null, $PROV_RSA_FULL, $CRYPT_VERIFYCONTEXT) -ne $false) {
        foreach($node in $config.SelectNodes("//Node")) {
            if($node.Type -eq 0) {
                Write-Host "$($node.DisplayName):"
            } elseif ($node.Type -eq 1) {
                [System.IntPtr]$hHash = 0
                [System.IntPtr]$hKey = 0
                $password = [system.Text.Encoding]::UTF8.GetBytes("1$($node.UserName.Trim())$($node.ServerName.Trim())")
                $ciphertext = [System.Convert]::FromBase64String($node.Password.Trim())
                $ciphertextLength = $ciphertext.Length

                if($CryptoAPI::CryptCreateHash($hProv, $CALG_SHA, 0, 0, [ref]$hHash) -ne $false) {
                    if($CryptoAPI::CryptHashData($hHash, $password, $password.Length, 0) -ne $false) {
                        if($CryptoAPI::CryptDeriveKey($hProv, $CALG_RC2, $hHash, 0, [ref]$hKey) -ne $false) {
                            if($CryptoAPI::CryptDecrypt($hKey, 0, $true, 0, $ciphertext, [ref]$ciphertextLength) -ne $false) {
                                $ciphertext = $ciphertext[0..($ciphertextLength-1)]
                                if($ciphertextLength -ge 2 -and $ciphertext[1] -eq 0) {
                                    $node.Password = [system.Text.Encoding]::Unicode.GetString($ciphertext)
                                } else {
                                    $node.Password = [system.Text.Encoding]::UTF8.GetString($ciphertext)
                                }
                            }
                            $null = $CryptoAPI::CryptDestroyKey($hKey);
                        }
                    }
                    $null = $CryptoAPI::CryptDestroyHash($hHash);
                }
                Format-XML $node
                Write-Host
            }
            Write-Host
        }
        $null = $CryptoAPI::CryptReleaseContext($hProv, 0)
    }
}

Export-ModuleMember -Function Invoke-MTPuTTYConfigDump

Now everything is fine. Thank you!

How are the initialization vectors generated? This is using RC2_CBC correct?

How are the initialization vectors generated? This is using RC2_CBC correct?

Hi @sidrile3310, since there is no call to CryptSetKeyParam I assume the IV is all zeroes, which is the default for the Microsoft Base Cryptographic Provider.

@ykoster Thanks! I am trying to write a version of this using Python but so far not so good. Thought the IV may be the issue but it looks like the problem lies elsewhere. This was a great primer though.

@sidrile3310 could be related to the way the key is derived. There is a Python implementation of CryptDeriveKey here https://www.fireeye.com/content/dam/fireeye-www/global/en/blog/threat-research/flareon2016/challenge2-solution.pdf. Haven't tested it myself.