philba888 philba888 - 2 months ago 65
C# Question

Convert C# PBKDF2 using Rfc2898DeriveBytes to PHP

Long story short have a membership system built in .NET that we are porting to WordPress and need to replicate the PBKDF2 encryption so users don't need to reset their passwords.

Using a know hashed password I've been able to replicate this in .NET easily, with the following code:

static void Main(string[] args)
{
var isValid = CheckPassword("#0zEZcD7uNmv", "5SyOX+Rbclzvvit3MEM2nBRaPVo2M7ZTs7n3znXTfyW4OhwTlJLvpcUlCryblgkQ");
}

public static int PBKDF2IterCount = 10000;
public static int PBKDF2SubkeyLength = 256 / 8; // 256 bits
public static int SaltSize = 128 / 8; // 128 bits

private static bool CheckPassword(string Password, string ExistingHashedPassword)
{
byte[] saltAndPassword = Convert.FromBase64String(ExistingHashedPassword);
byte[] salt = new byte[SaltSize];

Array.Copy(saltAndPassword, 0, salt, 0, SaltSize);

Console.WriteLine("--Salt--");
Console.WriteLine(Convert.ToBase64String(salt));

string hashedPassword = HashPassword(Password, salt);

Console.WriteLine("--HashedPassword--");
Console.WriteLine(hashedPassword);

return hashedPassword == ExistingHashedPassword;
}

private static string HashPassword(string Password, byte[] salt)
{
byte[] hash = new byte[PBKDF2SubkeyLength];
using (var pbkdf2 = new Rfc2898DeriveBytes(Password, salt, PBKDF2IterCount))
{
hash = pbkdf2.GetBytes(PBKDF2SubkeyLength);
}

byte[] hashBytes = new byte[PBKDF2SubkeyLength + SaltSize];
Array.Copy(salt, 0, hashBytes, 0, SaltSize);
Array.Copy(hash, 0, hashBytes, SaltSize, PBKDF2SubkeyLength);

string hashedPassword = Convert.ToBase64String(hashBytes);
return hashedPassword;
}


The console app will produce the following:

--Salt--
5SyOX+Rbclzvvit3MEM2nA==
--HashedPassword--
5SyOX+Rbclzvvit3MEM2nBRaPVo2M7ZTs7n3znXTfyW4OhwTlJLvpcUlCryblgkQ
--IsValid--
True


However in the PHP side I can't get the same results. My code so far is below.

$mySalt = base64_decode('5SyOX+Rbclzvvit3MEM2nA==');
$dev = pbkdf2('sha1', '#0zEZcD7uNmv', $mySalt, 10000, 48, true);
$key = substr($dev, 0, 32); //Keylength: 32
$iv = substr($dev, 32, 16); // IV-length: 16

echo 'PHP<br/>';
echo 'PASS: '.base64_encode($dev).'<br/>';
echo 'SALT: '.base64_encode($iv).'<br/><br/>';

echo '.NET<br/>';
echo 'PASS: 5SyOX+Rbclzvvit3MEM2nBRaPVo2M7ZTs7n3znXTfyW4OhwTlJLvpcUlCryblgkQ<br/>';
echo 'SALT: 5SyOX+Rbclzvvit3MEM2nA==<br/><br/>';

function pbkdf2($algorithm, $password, $salt, $count, $key_length, $raw_output = false)
{
$algorithm = strtolower($algorithm);
if(!in_array($algorithm, hash_algos(), true))
die('PBKDF2 ERROR: Invalid hash algorithm.');
if($count <= 0 || $key_length <= 0)
die('PBKDF2 ERROR: Invalid parameters.');

$hash_length = strlen(hash($algorithm, "", true));
$block_count = ceil($key_length / $hash_length);

$output = "";
for($i = 1; $i <= $block_count; $i++) {
// $i encoded as 4 bytes, big endian.
$last = $salt . pack("N", $i);
// first iteration
$last = $xorsum = hash_hmac($algorithm, $last, $password, true);
// perform the other $count - 1 iterations
for ($j = 1; $j < $count; $j++) {
$xorsum ^= ($last = hash_hmac($algorithm, $last, $password, true));
}
$output .= $xorsum;
}
return substr($output, 0, $key_length);
}


And the results are:

PHP
PASS: FFo9WjYztlOzuffOddN/Jbg6HBOUku+lxSUKvJuWCRCsYe+1Tgbb8Ob4FtxumMal
SALT: rGHvtU4G2/Dm+BbcbpjGpQ==

.NET
PASS: 5SyOX+Rbclzvvit3MEM2nBRaPVo2M7ZTs7n3znXTfyW4OhwTlJLvpcUlCryblgkQ
SALT: 5SyOX+Rbclzvvit3MEM2nA==


Any help would be appreciated.

Answer

Ended up getting it working using the https://github.com/defuse/password-hashing libraries, with some minor changes match the format of hashes I was working with database I'm importing.

But my main problem was with these lines where I'm trying to get a key out of a hash.

$dev = pbkdf2('sha1', '#0zEZcD7uNmv', $mySalt, 10000, 48, true);
$key = substr($dev, 0, 32); //Keylength: 32
$iv = substr($dev, 32, 16); // IV-length: 16

Changing it to the below, so that it is creating a hash hash that is 32 bits long and joining the returning hash to the salt fixed the issue.

$dev = pbkdf2('sha1', '#0zEZcD7uNmv', $mySalt, 10000, 32, true);
echo 'PASS: '.base64_encode($mySalt.$dev).'<br />';

With the output below now matching .NET:

PASS: 5SyOX+Rbclzvvit3MEM2nBRaPVo2M7ZTs7n3znXTfyW4OhwTlJLvpcUlCryblgkQ