protected byte[] KeyStretching(byte[] data, byte[] hash)
{
byte[] stretching = new byte[data.Length + hash.Length + Salt.Length];
data.CopyTo(stretching, 0);
hash.CopyTo(stretching, data.Length);
Salt.CopyTo(stretching, data.Length + hash.Length);
return(stretching);
}
public void TestSaltCopy()
{
Salt s = new Salt();
byte[] bytes = new byte[s.Length];
s.CopyTo(bytes, 0);
Assert.AreEqual(s.ToArray(), bytes);
Assert.AreEqual(s.GetHashCode(), Salt.FromBytes(bytes).GetHashCode());
Salt strcpy = Salt.FromString(s.ToString());
Assert.AreEqual(s.ToArray(), strcpy.ToArray());
Assert.AreEqual(s.ToString(), strcpy.ToString());
Assert.AreEqual(s.GetHashCode(), strcpy.GetHashCode());
}
private static TextReader DecodeWebSaveData(string encodedSaveData)
{
const string AntiCheatCode = "Fe12NAfA3R6z4k0z";
var antiCheatCodeIndex = encodedSaveData.IndexOf(AntiCheatCode, StringComparison.Ordinal);
if (antiCheatCodeIndex == -1)
{
// Couldn't find anti-cheat
return(null);
}
// Remove every other character, AKA "unsprinkle".
// Handle odd lengthed strings even though it shouldn't happen.
var unsprinkledChars = new char[(antiCheatCodeIndex / 2) + (antiCheatCodeIndex % 2)];
for (var i = 0; i < antiCheatCodeIndex; i += 2)
{
unsprinkledChars[i / 2] = encodedSaveData[i];
}
// Validation
const string Salt = "af0ik392jrmt0nsfdghy0";
var expectedHashStart = antiCheatCodeIndex + AntiCheatCode.Length;
var saltedChars = new char[unsprinkledChars.Length + Salt.Length];
unsprinkledChars.CopyTo(saltedChars, 0);
Salt.CopyTo(0, saltedChars, unsprinkledChars.Length, Salt.Length);
using (MD5 md5 = MD5.Create())
{
byte[] data = md5.ComputeHash(Encoding.UTF8.GetBytes(saltedChars));
var actualHash = new StringBuilder(data.Length * 2);
for (int i = 0; i < data.Length; i++)
{
var expectedHashPartIndex = expectedHashStart + (i * 2);
var actualHashPart = data[i].ToString("x2");
if (actualHashPart[0] != encodedSaveData[expectedHashPartIndex] ||
actualHashPart[1] != encodedSaveData[expectedHashPartIndex + 1])
{
// Hash didn't match
return(null);
}
}
}
// Decode
var bytes = Convert.FromBase64CharArray(unsprinkledChars, 0, unsprinkledChars.Length);
// Wrap in a text reader
return(new StreamReader(new MemoryStream(bytes)));
}
protected override byte[] ComputeHash()
{
byte[] dataPlusSalt = new byte[Data.Length + Salt.Length];
Data.CopyTo(dataPlusSalt, 0);
Salt.CopyTo(dataPlusSalt, Data.Length);
byte[] hash = SHA512.Create().ComputeHash(dataPlusSalt);
byte[] stretching = new byte[0];
for (uint i = Iterations; i > 1; i--)
{
stretching = KeyStretching(stretching, hash);
hash = SHA512.Create().ComputeHash(stretching);
}
return(hash);
}
public void TestSaltCopy()
{
Salt s = new Salt();
byte[] bytes = new byte[s.Length];
s.CopyTo(bytes, 0);
Assert.AreEqual(s.ToArray(), bytes);
Assert.AreEqual(s.GetHashCode(), Salt.FromBytes(bytes).GetHashCode());
Salt strcpy = Salt.FromString(s.ToString());
Assert.AreEqual(s.ToArray(), strcpy.ToArray());
Assert.AreEqual(s.ToString(), strcpy.ToString());
Assert.AreEqual(s.GetHashCode(), strcpy.GetHashCode());
}
