Is there a way to convert a MD5
password to something that can be verified by password_verify()
?
I read on the Crypt Wikipedia page that “The printable form of MD5
password hashes starts with $1$
.”
Hence I give this a shot (without any luck):
$password = "abcd1234"; $md5hash = "$1$".md5($password); var_dump(password_verify($password, $md5hash));
Is there any way to make password_verify()
work with MD5
passwords?
Reason for question: I have an old system where the passwords are stored as MD5
hashes. I want to start using the more secure Password Hashing API
. If I’m able to convert the existing password hashes to something that works with password_verify()
, I can just update the database entries (prepend $1$
to all password hashes), and my program would work beautifully using the following code (I don’t have to make a special case for the old MD5
passwords):
$password; // Provided by user when trying to log in $hash; // Loaded from database based on username provided by user if(password_verify($password, $hash)) { // The following lines will both update the MD5 passwords // and all passwords whenever the default hashing algorithm is updated if(password_needs_rehash($hash, PASSWORD_DEFAULT)) { $hash = password_hash($password, PASSWORD_DEFAULT); // Store the new hash in database } // User is logged in } else { // User is not logged in }
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Answer
You can’t do that.
What you can do is to hash the already MD5-hashed passwords via password_hash()
and put an additional flag for these old passwords in your database, so you know to double-verify them afterwards.
Some sample code:
$passwordCompare = ($passwordIsOldFlag === true) ? md5($passwordInput) : $passwordInput; if (password_verify($passwordCompare, $passwordHash)) { if ($passwordisOldFlag === true) { $passwordNewHash = password_hash($passwordInput, PASSWORD_DEFAULT); // Here, you'd update the database with the new, purely bcrypt hash // and set your passwordIsOldFlag to 0 as well } }
Note: MD5 produces a 32 character length string, while password_hash()
is a minimum of 60.
Read the manual:
If and when you do decide to use password_hash()
or the compatibility pack (if PHP < 5.5) https://github.com/ircmaxell/password_compat/, it is important to note that if your present password column’s length is anything lower than 60, it will need to be changed to that (or higher). The manual suggests a length of 255.
You will need to ALTER your column’s length and start over with a new hash in order for it to take effect. Otherwise, MySQL will fail silently.