# Generate Kerberos AES keys from a known password

> Source: <https://gist.github.com/Kevin-Robertson/9e0f8bfdbf4c1e694e6ff4197f0a4372>
> Published: 2017-08-08 15:55:34+00:00

Get-KerberosAESKey.ps1

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function Get-KerberosAESKey

{

    <#

    .SYNOPSIS

    Generate Kerberos AES 128/256 keys from a known username/hostname, password, and kerberos realm. The

    results have been verified against the test values in RFC3962, MS-KILE, and my own test lab.

 

    https://tools.ietf.org/html/rfc3962

    https://msdn.microsoft.com/library/cc233855.aspx

    Author: Kevin Robertson (@kevin_robertson)  

    License: BSD 3-Clause   

    .PARAMETER Password

    [String] Valid password.

    .PARAMETER Salt

    [String] Concatenated string containing the realm and username/hostname.

    AD username format = uppercase realm + case sensitive username (e.g., TEST.LOCALusername, TEST.LOCALAdministrator)

    AD hostname format = uppercase realm + the word host + lowercase hostname without the trailing '$' + . + lowercase

    realm (e.g., TEST.LOCALhostwks1.test.local)

    .PARAMETER Iteration

    [Integer] Default = 4096: Int value representing how many iterations of PBKDF2 will be performed. AD uses the

    default of 4096.

 

    .PARAMETER OutputType

    [String] Default = AES: (AES,AES128,AES256,AES128ByteArray,AES256ByteArray) AES, AES128, and AES256 will output strings.

    AES128Byte and AES256Byte will output byte arrays.

    .EXAMPLE

    Verify results against first RFC3962 sample test vectors in section B.

    Get-KerberosAESKey -Password password -Salt ATHENA.MIT.EDUraeburn -Iteration 1

 

    .EXAMPLE

    Generate keys for a valid AD user.

    Get-KerberosAESKey -Salt TEST.LOCALuser

    .LINK

    https://gist.github.com/kevin-robertson/

    #>

    [CmdletBinding()]

    param

    ( 

        [parameter(Mandatory=$false)][String]$Password,

        [parameter(Mandatory=$true)][String]$Salt,

        [parameter(Mandatory=$false)][ValidateSet("AES","AES128","AES256","AES128ByteArray","AES256ByteArray")][String]$OutputType = "AES",

        [parameter(Mandatory=$false)][Int]$Iteration=4096

    )

 

    if(!$Password)

    {

        $secure_password = Read-Host -Prompt "Enter password" -AsSecureString

        $password_memory = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($secure_password)

        $password = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($password_memory)

    }

 

    [Byte[]]$password_bytes = [System.Text.Encoding]::UTF8.GetBytes($Password)

    [Byte[]]$salt_bytes = [System.Text.Encoding]::UTF8.GetBytes($Salt)

    $AES256_constant = 0x6B,0x65,0x72,0x62,0x65,0x72,0x6F,0x73,0x7B,0x9B,0x5B,0x2B,0x93,0x13,0x2B,0x93,0x5C,0x9B,0xDC,0xDA,0xD9,0x5C,0x98,0x99,0xC4,0xCA,0xE4,0xDE,0xE6,0xD6,0xCA,0xE4

    $AES128_constant = 0x6B,0x65,0x72,0x62,0x65,0x72,0x6F,0x73,0x7B,0x9B,0x5B,0x2B,0x93,0x13,0x2B,0x93

    $IV = 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 

    $PBKDF2 = New-Object Security.Cryptography.Rfc2898DeriveBytes($password_bytes,$salt_bytes,$iteration)

    $PBKDF2_AES256_key = $PBKDF2.GetBytes(32)

    $PBKDF2_AES128_key = $PBKDF2_AES256_key[0..15]

    $PBKDF2_AES256_key_string = ([System.BitConverter]::ToString($PBKDF2_AES256_key)) -replace "-",""

    $PBKDF2_AES128_key_string = ([System.BitConverter]::ToString($PBKDF2_AES128_key)) -replace "-",""

    Write-Verbose "PBKDF2 AES128 Key: $PBKDF2_AES128_key_string"

    Write-Verbose "PBKDF2 AES256 Key: $PBKDF2_AES256_key_string"

    $AES = New-Object "System.Security.Cryptography.AesManaged"

    $AES.Mode = [System.Security.Cryptography.CipherMode]::CBC

    $AES.Padding = [System.Security.Cryptography.PaddingMode]::None

    $AES.IV = $IV

    # AES 256

    $AES.KeySize = 256

    $AES.Key = $PBKDF2_AES256_key

    $AES_encryptor = $AES.CreateEncryptor()

    $AES256_key_part_1 = $AES_encryptor.TransformFinalBlock($AES256_constant,0,$AES256_constant.Length)

    $AES256_key_part_2 = $AES_encryptor.TransformFinalBlock($AES256_key_part_1,0,$AES256_key_part_1.Length)

    $AES256_key = $AES256_key_part_1[0..15] + $AES256_key_part_2[0..15]

    $AES256_key_string = ([System.BitConverter]::ToString($AES256_key)) -replace "-",""    

    # AES 128

    $AES.KeySize = 128

    $AES.Key = $PBKDF2_AES128_key

    $AES_encryptor = $AES.CreateEncryptor()

    $AES128_key = $AES_encryptor.TransformFinalBlock($AES128_constant,0,$AES128_constant.Length)

    $AES128_key_string = ([System.BitConverter]::ToString($AES128_key)) -replace "-",""

 

    switch($OutputType)

    {

 

        'AES'

        {

            Write-Output "AES128 Key: $AES128_key_string"

            Write-Output "AES256 Key: $AES256_key_string"

        }

 

        'AES128'

        {

            Write-Output "$AES128_key_string"

        }

 

        'AES256'

        {

            Write-Output "$AES256_key_string"

        }

 

        'AES128ByteArray'

        {

            Write-Output $AES128_key

        }

 

        'AES256ByteArray'

        {

            Write-Output $AES256_key

        }

 

    }

 

}