Question

I’m implementing the ValidateUser method on a custom MembershipProvider class. I’ve seen quite a few examples of this, I’m looking for some guidance on how to properly encode/hash/encrypt my passwords. I’m no crypto expert, and I’m a little anxious about straying from the default implementation. Should I just copy the relevant source code from the SqlMembershipProvider or will any of these work?

http://mattwrock.com/post/2009/10/14/Implementing-custom-Membership-Provider-and-Role-Provider-for-Authinticating-ASPNET-MVC-Applications.aspx

public override bool ValidateUser(string username, string password)
{
    if(string.IsNullOrEmpty(password.Trim())) return false;
    string hash = EncryptPassword(password);
    User user = _repository.GetByUserName(username);
    if (user == null) return false;
    if (user.Password == hash)
    {
    User = user;
    return true;
    }
    return false;
}

protected string EncryptPassword(string password)
{
    // Produses an MD5 hash string of the password
    //we use codepage 1252 because that is what sql server uses
    byte[] pwdBytes = Encoding.GetEncoding(1252).GetBytes(password);
    byte[] hashBytes = System.Security.Cryptography.MD5.Create().ComputeHash(pwdBytes);
    return Encoding.GetEncoding(1252).GetString(hashBytes);
}

ASP.NET membership salt?

public string EncodePassword(string pass, string salt)
{
    byte[] bytes = Encoding.Unicode.GetBytes(pass);
    byte[] src = Encoding.Unicode.GetBytes(salt);
    byte[] dst = new byte[src.Length + bytes.Length];
    Buffer.BlockCopy(src, 0, dst, 0, src.Length);
    Buffer.BlockCopy(bytes, 0, dst, src.Length, bytes.Length);
    HashAlgorithm algorithm = HashAlgorithm.Create("SHA1");
    byte[] inArray = algorithm.ComputeHash(dst);
    return Convert.ToBase64String(inArray);
} 

ASP.NET membership salt?

private const int ITERATIONS = 10000;
private const int SALT_SIZE = 32;
private const int HASH_SIZE = 32;

public void SaltAndHashPassword(string password, out byte[] salt, out byte[] hash)
{
  Rfc2898DeriveBytes rdb = new Rfc2898DeriveBytes(password, SALT_SIZE, ITERATIONS);

  salt = rdb.Salt;
  hash = rdb.GetBytes(HASH_SIZE);
}

ASP.NET membership salt?

internal string GenerateSalt()
{
    byte[] buf = new byte[16];
    (new RNGCryptoServiceProvider()).GetBytes(buf);
    return Convert.ToBase64String(buf);
}

internal string EncodePassword(string pass, int passwordFormat, string salt)
{
    if (passwordFormat == 0) // MembershipPasswordFormat.Clear
        return pass;

    byte[] bIn = Encoding.Unicode.GetBytes(pass);
    byte[] bSalt = Convert.FromBase64String(salt);
    byte[] bAll = new byte[bSalt.Length + bIn.Length];
    byte[] bRet = null;

    Buffer.BlockCopy(bSalt, 0, bAll, 0, bSalt.Length);
    Buffer.BlockCopy(bIn, 0, bAll, bSalt.Length, bIn.Length);
    if (passwordFormat == 1)
    { // MembershipPasswordFormat.Hashed
        HashAlgorithm s = HashAlgorithm.Create("SHA1");
        // Hardcoded "SHA1" instead of Membership.HashAlgorithmType
        bRet = s.ComputeHash(bAll);
    }
    else
    {
        bRet = EncryptPassword(bAll);
    }
    return Convert.ToBase64String(bRet);
}

Answer 1

Download BCrypt.Net. As opposed to typica SHA hashing, which is too fast making anything encrypted with it easy to brute force. BCrypt is slower due to a configurable work factor, so whilst imperceptable to the user, when trying to brute force 700m keys a second, you simply can’t.

Once you have bcrypt all you need to do to hash is:

...
private static readonly int BCRYPT_WORK_FACTOR = 10;
string hashedPassword = BCrypt.Net.BCrypt.HashPassword(account.HashedPassword, BCRYPT_WORK_FACTOR);
...

and to check a password:

bool matched = BCrypt.Net.BCrypt.Verify(password, match.HashedPassword))

More info here: http://www.danharman.net/2011/06/25/encrypting-hashing-passwords-for-your-website/