MVC - How to hash and salt

Question

I managed to get hash working, but the salt-part is still an issue.. I've been searching and testing examples without success. This is my code with hash:

        [Required]
        [StringLength(MAX, MinimumLength = 3, ErrorMessage = "min 3, max 50 letters")]
        public string Password { get; set; }
        public string Salt { get; set; }

Hash password function(without salt):

 public string HashPass(string password) { 

       byte[] encodedPassword = new UTF8Encoding().GetBytes(password);
       byte[] hash = ((HashAlgorithm) CryptoConfig.CreateFromName("MD5")).ComputeHash(encodedPassword);
       string encoded = BitConverter.ToString(hash).Replace("-", string.Empty).ToLower();

          return encoded;//returns hashed version of password
      }

Register:

        [HttpPost]
        public ActionResult Register(User user) {
            if (ModelState.IsValid) {

                        var u = new User {
                            UserName = user.UserName,                               
                            Password = HashPass(user.Password)//calling hash-method
                        };

                        db.Users.Add(u);
                        db.SaveChanges();

                    return RedirectToAction("Login");
                }
            }return View();    
        }

Login:

     public ActionResult Login() {
            return View();
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Login(User u) {
            if (ModelState.IsValid) 
            {
                using (UserEntities db = new UserEntities()) {

                    string readHash = HashPass(u.Password);

                    var v = db.Users.Where(a => a.UserName.Equals(u.UserName) &&
                                              a.Password.Equals(readHash)).FirstOrDefault();
                    if (v != null) {

                        return RedirectToAction("Index", "Home"); //after login
                    }
                }
            }return View(u);
        }

So far hash work.. But how do I make salt work here?

I would prefer a demonstrate on my code as I find it very hard to understand by words.

I'm using database first.

Answer 1

When it comes to security don't try to reinvent the wheel. Use Claims based authentication.

If you still must manage usernames and passwords use Hash-based message authentication code ( HMAC )

I would also recommend investing sometime and reading Enterprise Security Best Practices . There are already smarter people who solved this problems why reinvent the wheel. And .NET has all the goodies there.

Example below:

//--------------------MyHmac.cs-------------------
public static class MyHmac
{
    private const int SaltSize = 32;

    public static byte[] GenerateSalt()
    {
        using (var rng = new RNGCryptoServiceProvider())
        {
            var randomNumber = new byte[SaltSize];

            rng.GetBytes(randomNumber);

            return randomNumber;

        }
    }

    public static byte[] ComputeHMAC_SHA256(byte[] data, byte[] salt)
    {
        using (var hmac = new HMACSHA256(salt))
        {
            return hmac.ComputeHash(data);
        }
    }
}



//-------------------Program.cs---------------------------
string orgMsg = "Original Message";
        string otherMsg = "Other Message";


        Console.WriteLine("HMAC SHA256 Demo in .NET");

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

        var salt = MyHmac.GenerateSalt();

        var hmac1 = MyHmac.ComputeHMAC_SHA256(Encoding.UTF8.GetBytes(orgMsg), salt);
        var hmac2 = MyHmac.ComputeHMAC_SHA256(Encoding.UTF8.GetBytes(otherMsg), salt);


        Console.WriteLine("Original Message Hash:{0}", Convert.ToBase64String(hmac1));
        Console.WriteLine("Other Message Hash:{0}", Convert.ToBase64String(hmac1));

NOTE: Salts do not have to be kept secret and can be stored alongside the hash itself. It's to increase security from rainbow table attack.

Answer 2

Use the System.Web.Helpers.Crypto NuGet package from Microsoft. It takes care of the salt for you.

You hash a password like this: var hash = Crypto.HashPassword("foo");

You verify a password like this: var verified = Crypto.VerifyHashedPassword(hash, "foo");