Password does not match after being encrypted using crypt() and password_hash() function

Question

I modified my old post. I tried the crypt() function and now trying to work with password_hash() and password_verify() to verify the encrypted password coming from database but on each call, password_hash() function retuns a different encrypted string and password_verify() cannot match it.

This is how I am doing this.

 //please ignore the syntax error if any

$data = '11';
$dbpass = password_hash($data, PASSWORD_BCRYPT);
echo $dbpass;  // displays the random strings on each page refresh.

Once password is saved into database does not get match during the login process. Below is my actual function.

   private function process_data($password){
    $password = __STR.$password.__STR;
    return  password_hash($password, PASSWORD_BCRYPT);

  }
  private function processed($login_password, $dbpassword){
    $login_password = __STR.$login_password.__STR;
    return password_verify($login_password, $dbpassword);
  }

On each function call for creating a hashed string for password, the function returns the different string next time.

Answer 1

Ok, Let's go through this one by one.

First, it's hashing, not encryption. Encryption is two-way, hashing is one way. We want to hash. We never want to encrypt. Yes, terminology matters. Please use the correct terminology.

Next, each call to password_hash is supposed to return a different hash. That's because it's generating a strong random salt. This is how it was designed, and how you really should be using it.

Further, DO NOT do the "pepper" thing of adding __STR before and after the password. You're doing nothing but potentially weakening the users password (which is not good). If you want more information around why that's a bad idea: Read This Answer.

Continuing, I would highly recommend that you do not use crypt directly. It is actually surprisingly easy to screw up and generate extremely weak hashes. This is why the password_* api was designed. crypt is a low level library, you want to use a high level library in your code. For more information on ways to screw up bcrypt, check out my blog: Seven Ways To Screw Up Bcrypt.

The Password API was designed to be a simple, one-stop shop. If it's not working for you check the following things:

1. Are you using PHP >= 5.5.0? Or are you using PHP >= 5.3.7 with password_compat?

   1. Is your database column wide enough?

      It needs to be at least 60 characters long.

   2. Are you checking that the result of the function is a string, and not bool(false)?

      If there is an internal error, it will return a non-string from password_hash.

   3. Are you getting any errors?

      Have you turned on error_reporting to its maximum setting (I recommend -1 to catch everything) and checked that the code isn't throwing any errors?

   4. Are you sure you are using it correctly?

      function saveUser($username, $password) {
          $hash = password_hash($password, PASSWORD_BCRYPT);
          // save $username and $hash to db
      }
      function login($username, $password) {
          // fetch $hash from db
          return password_verify($password, $hash);
      }
      

      Note that each one should be called only once.

2. Are you using PHP < 5.3.7 with password_compat? If so, this is your problem. You are using the compatability library on an unsupported version of PHP. You may get it to work (certain RedHat distributions have backported the necessary fixes), but you are using an unsupported version. Please upgrade to a reasonable release.

If all else fails, please try running this code and reporting back the output:

$hash = '$2y$04$usesomesillystringfore7hnbRJHxXVLeakoG8K30oukPsA.ztMG';
$test = crypt("password", $hash);
$pass = $test == $hash;

echo "Test for functionality of compat library: " . ($pass ? "Pass" : "Fail");
echo "\n";

If that returns Fail, you are running an unsupported version of PHP and should upgrade. If it returns pass, than the error is somewhere in your logic (the library is functioning fine).

Answer 2

The best way to store passwords is to use PHP's function password_hash(). It automatically generates a cryptographically safe salt for each password and includes it in the resulting 60-character string. You won't have to worry about the salt at all!

// Hash a new password for storing in the database.
// The function automatically generates a cryptographically safe salt.
$hashToStoreInDb = password_hash($password, PASSWORD_BCRYPT);

// Check if the hash of the entered login password, matches the stored hash.
// The salt and the cost factor will be extracted from $existingHashFromDb.
$isPasswordCorrect = password_verify($password, $existingHashFromDb);

Your own scheme is very weak, first you are using MD5 which is ways too fast for generating password hashes, then you use a static salt, which defeats the purpose of a salt. Maybe you want to have a look at my tutorial about safely storing passwords.

Edit to answer updated question:

It is not necessary to add the __STR to the password (if you want to add a pepper there are better ways), but your example functions should actually work. The returned value of password_hash() will be different each time because of the random salt. This is correct, the function password_verify() is able to extract this salt for the verification. In your case the database field is probably the problem. Make sure it can hold a 60 character string.