Why is password_verify returning false?

Question

I'm using password_verify to check my hashed password. I have PHP 5.5:

// get result row (as an object)
$result_row = $result_of_login_check->fetch_object();

// using PHP 5.5's password_verify() function to check if the provided password fits
// the hash of that user's password
if (password_verify($_POST['user_password'], $result_row->user_password_hash)) {
    // ...
}

I'm getting false on password_verify. I've already checked the posts value and mysql user_password_hash return.

I don't know why it's returning false.

Any ideas?

Answer 1

Probably the problem is with your column length, from the manual: it is recommended to store the result in a database column that can expand beyond 60 characters (255 characters would be a good choice). link

Answer 2

There are a variety of reasons why password_verify could be returning false, it can range from the setup of your table to the actual comparing of the password, below are the common causes of it failing.

Column Setup

• The length of the password column in your table is too short:

  • If you are using PASSWORD_DEFAULT then it is recommended to store the result in a database column that can expand beyond 60 characters (255 characters would be a good choice).
  • If you are using PASSWORD_BCRYPT then it is recommended to store the result in a database column that is 60 characters because PASSWORD_BCRYPT will always result in a 60 character string or FALSE on failure.

Password Sanitization

Another common cause is when developers try to "clean" the user's password to prevent it from being malicious, as a result, this causes the input to be different to what is being stored in the table. It is not even necessary to escape the input, you should use prepared statements instead. You shouldn't even trim the passwords as that could change that which was originally provided.

Password Verification

When using password_verify you need to compare the plaintext password with the hash from the database, not compare hashes (the implication here being that you need to have stored the hashed password of the user when they register):

<?php

$hashed = password_hash('test', PASSWORD_DEFAULT);
$password = 'test';

if (password_verify($password, $hashed)) {
  echo 'success';
} else {
  echo 'fail';
}

?>

Repl

Hardcoded Passwords

In the instance that you are using a hardcoded hash and you are facing issues, ensure that you are using single quotes instead of double quotes when storing the value in the variable as the $ will be interpreted in when using double quotes:

<?php
// Undefined variable: QHpfI0MfQWjvsVQWRdFHSOX6WqG8LSf0iFGiKs0Fz0RvqhpFOpAKu :1
$incorrect = "$2y$10$QHpfI0MfQWjvsVQWRdFHSOX6WqG8LSf0iFGiKs0Fz0RvqhpFOpAKu";

$correct = '$2y$10$QHpfI0MfQWjvsVQWRdFHSOX6WqG8LSf0iFGiKs0Fz0RvqhpFOpAKu';
?>

Repl - Comment out respectively.

Addendum

As per the documentation:

Caution It is strongly recommended that you do not generate your own salt for this function. It will create a secure salt automatically for you if you do not specify one.

As noted above, providing the salt option in PHP 7.0 will generate a deprecation warning. Support for providing a salt manually may be removed in a future PHP release.

Answer 3

Check the parameters order

Just to point something that happened to me, who was reading this same topic trying to solve my problem minutes ago, and can help you to solve the problem as well.
See if you are giving the parameters for password_verify() in the right order:

password_verify(string $password, string $hash)

password is the password you received by post or other method and are trying to validate.

hash is the hash that you want to compare the password to.(e.g. The password hash stored in your Data Base)

It happened to me that I inverted the order of the parameters, so the result wasn't coming as I expected to.

Answer 4

Simple steps to debug the issue:

1. Print out and write down exact values of the raw password and the hash during the registration phase. Something like

    var_dump($password);
    $hash = password_hash($password, PASSWORD_DEFAULT);
    var_dump($hash);
   

   then copy and paste the output into some text file.

2. Print out and write down exact values of the password provided during login phase and the hash returned from DB. Something like

    var_dump($password);
    var_dump($row['password']);
    if(password_verify($password, $row['password'])) ...
   

And then simply compare those values. If password_verify() fails, either raw passwords or hashes don't match. If raw passwords don't match then the entered password is either incorrect or was maimed during some useless "sanitization". If the hash returned from DB doesn't match, then it either was maimed during some useless "sanitization" or it was changed due to incorrect column properties in the database.