Why does password_verify
return false?
This question is intended to be canonical and has been created simply based on the amount of questions that have been asked on this topic.
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Answer
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 becausePASSWORD_BCRYPT
will always result in a 60 character string or FALSE on failure.
- If you are using
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/file/some-other-storage-method, 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'; } ?>
Ensure that you are actually passing a hash to password_verify
and not something else by dumping it.
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.
Troubleshooting
var_dump()
the hashed password on registration right before you insert it into your database, and var_dump()
it again after you fetch it from your database when you are about to password_verify()
it. Ensure both hashes are identical. If they are, and the plaintext passwords are identical too, there’s no reason for password_verify
to fail. It only fails if the hash gets modified in some way on its roundtrip through the database, or if the plaintext passwords aren’t identical.
Ensure that you are passing a correct algorithm to password_hash
has the second parameter.
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.