I'm currently working with Identity Server 4, at present when the user logs in I need to hash their provided password and then compare with the password stored in the database (also hashed)
After some searching, I was linked to the PasswordHasher within Identity Server to handle this:
var _hasher = new PasswordHasher<User>();
var hashpassword = _hasher.HashPassword(user, context.Password);
User is my custom class that inherits from IdentityUser, however, when checking the hashed password against the one in the database the hash is completely different, I have double checked the password and I can confirm it's correct.
Can anyone suggest why I maybe seeing a different hash compared to the one in the database?
Each time you hash a password with PasswordHasher<T>.HashPassword you will get a total different result because of the salt.
To verify such hashed salted passwords use the given method IPasswordHasher<T>.VerifyPassword.
I was reading this article about hashing passwords when I came to this part:
To Validate a Password
Retrieve the user's salt and hash from the database.
Prepend the salt to the given password and hash it using the same
hash function.
Compare the hash of the given password with the hash from the
database. If they match, the password is correct. Otherwise, the
password is incorrect.
But I am a little confused with the flow this would follow, for example lets assume I have a database with a user table with id,name,password and email and in order to login to some app I need to input my email and password.
Following the the steps above, I first need to get the salt+hashed password of said user stored in the database.
Question:
Assuming I am using a simple stored procedure would the only way be to do it like this...
CREATE PROCEDURE [dbo].[sp_validate_user]
#us_email VARCHAR (MAX)
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
-- Insert statements for procedure here
SELECT us_id,
us_name,
us_pass,
us_email
FROM Users
WHERE us_email = #us_email
END
Then following step two and three:
public static bool ValidatePassword(string inputPassword, string storedPassword)
{
// Extract the parameters from the hash
char[] delimiter = { ':' };
string[] split = storedPassword.Split(delimiter);
int iterations = Int32.Parse(split[ITERATION_INDEX]);
byte[] salt = Convert.FromBase64String(split[SALT_INDEX]);
byte[] hash = Convert.FromBase64String(split[PBKDF2_INDEX]);
byte[] testHash = PBKDF2(inputPassword, salt, iterations, hash.Length);
return SlowEquals(hash, testHash);
}
My concern comes from the fact that if I am creating objects with the data pulled from the table, doesn't that make the information within vulnerable somehow?
Also does that mean that the only way to use this validation is pulling all the user's information based only on a username/email just to check in runtime if the input password and the hashed one match and then letting said user access the information?
I'm sorry if this sounds confusing but any insight would be great.
It looks like you may be thinking of it backwards. The salt is added to the cleartext password before passing to the hash function. Store the end result in the database.
Commonly, the salt is the username. Something unique to each user to thwart dictionary attacks. (A dictionary attack relies on the economy of scale by cracking one password and then looking for other instances of the same crypto-text. It used to work especially well on very large user databases like well known sites that have millions of users, but hopefully those sites use proper salting and key derivation nowadays).
So for username u, password p, assume SHA2 is hash function. Concatenate u + p to get a salted value, then hash it.
hashtext = SHA2(u + p) // in this case, + is concatenate
hashtext is what you store in the database.
For the login, user enters his username u2 and password p2:
tryhash = SHA2(u2 + p2)
Query database for a user record matching u2, with password hashtext of tryhash
Lets say you have an MVC action receiving loginViewModel which is populated with cleartext email or username as well as cleartext password, entered from the page:
var loginUser = new User(loginViewModel);
CalcHash(loginUser);
var realUser = users.Find(loginUser.username);
if(realUser.HashPassword == loginUser.HashPassword)
// success
While it is also possible to add the hashed password as a second argument to your Data Access method, ie. users.Find(username, hashPass), it is usually not done this way, because you need to access the user record even if the password fails, in order to increment password failure count and lockout the account.
The article covers ASP.NET (C#) Password Hashing Code but you seem to want to use a database?
You have three things to worry about; the unique key for the user (username), your chosen hashing algorithm and adding a salt to the password attempt (prevents rainbow table attacks).
To validate a password you should create a sql stored procedure that accepts the username and password attempt as parameters. This data is in plain text and has been entered into the web form, passed to the web server and will be passed into the database server via the stored procedure.
The stored procedure will do the following;
Lookup the data row for user based on matching the username parameter with the username field and
select the stored salt field
Append the salt from (1) to the password parameter and hash the result
Lookup the data row for the user based on matching the username parameter with the username field
and the hash result from (2) with the hashed password field.
If there is no row found the password hashes don't match and are wrong so return a suitable error code
If there is a row found return the useful user data i.e. First Name, Address
If the stored procedure handles all this then the web server never needs to know what the salt is or the hashing algorithm. At no point does the hash result or the salt get transmitted out of the database server.
I think you understood it correctly, this is the usual workflow:
Get the password-hash by username SELECT password_hash FROM user WHERE email=?.
Extract the salt from the password_hash, or get the salt from a separate field.
Calculate the hash of the entered password with the extracted salt and compare the hashes.
Validating the password cannot be done in a single query, because you first have to extract the salt. Appropriate hash functions like PBKDF2, BCrypt or SCrypt are often not supported by the database system, so you have to do the validation in your code. Additionally to the salt you also have to store other parameters like the cost factor and the algorithm (to be future-proof), so it is a good idea to store all these parameters in the same database field.
The salt should be a random string of at least 20 characters, so it is not safe to use the username as salt, or to derrive the salt from other information.
I have and encrypting method incorporated into my program login that Takes the Plain Text Password runs Thru SHA1 Base64 hashing to get a hash then takes the password hash and compares to MySQL database value to See if they match then grants access if they don't match denies access.
My Problem is the C# syntax to call the hashed password then look in mysql Database at this User name and match the password hashes.
Hash from Login == Hash from database im trying to figure out how to do it.
private void btn_ProLogin_Click(object sender, EventArgs e)
{
string s = txt_ProgramPass.Text.ToString(); //Password TextBox
byte[] data = Encoding.ASCII.GetBytes(s);
SHA1 algorithm = SHA1.Create();
byte[] hash = algorithm.ComputeHash(data);
string base64 = Convert.ToBase64String(hash);
//Database Connection query SELECT 'value' From accounts.UPassword
// then Compare Values if match the allow else Deny access MSG Box Ect
}
The Question im asking is what the syntax is for c# to compare a generated hash from login to database hash previously entered?
P.S. The actual Database info is not included. The Table in DB is accounts Column is UPassword and value is the hash in Database.
Background
We are using the ASPNET membership provider that stores member login information, along with MongoDB to store a secondary set of information.
Because MongoDB does not offer built-in encryption we have decided to encrypt some of the data before inserting it into the database using the member's salt that is in the ASPNET membership provider tables.
Objective
How would I go about exposing the salt so that it is accessible in code? I cannot find any methods for this in the default provider classes.
Alternative
Either that or could anybody suggest a better approach? One of the benefits of having the salt saved in a different place is to protect it from "interlopers".
Thanks,
Max.
Here is one approach, you can use the username, e-mail to salt.
public static string hashCalculator(string username, string password)//Use username as salt.
{
byte[] stringbytes = System.Text.Encoding.Unicode.GetBytes(username.ToLower() + password);
return Convert.ToBase64String(new SHA384Managed().ComputeHash(stringbytes));
}
I am using a SqlMembershipProvider and storing my passwords as hashed. I am also keeping a history of the (hashed) passwords in another table. I want to be able to compare the password a user tries to change their password to, to their old passwords and throw an error if it was too recent. I do not seem to be able to figure out how to use the hashing functions to do this. Basically what I am looking for is a method like this:
public bool PasswordCompare(string plaintextPassword, string salt, string hashedPassword)
{
//where the salt and hashedPassword are pulled out of the aspnet_Membership table
//which are automatically generated by the provider
}
I hope this is clear, thank you.
This post has some good info. Looks like you have to:
...implement your own customized
MembershipProvider, record the
password history and encrypt the
password by your self.
SQLMembershipProvider: Comparing Hashed Passwords