Am I using PHP's crypt() function correctly?

Question

I've been using PHP's crypt() as a way to store and verify passwords in my database. I use hashing for other things, but crypt() for passwords. The documentation isn't that good and there seems to be a lot of debate. I'm using blowfish and two salts to crypt a password and store it in the database. Before I would store the salt and the encrypted password, (like a salted hash) but realized its redundant because the salt is part of the encrypted password string.

I'm a little confused on how rainbow table attacks would work on crypt(), anyway does this look correct from a security standpoint. I use a second salt to append to the password to increase the entropy of short passwords, probably overkill but why not?

function crypt_password($password) {
if ($password) {
    //find the longest valid salt allowed by server
    $max_salt = CRYPT_SALT_LENGTH;

    //blowfish hashing with a salt as follows: "$2a$", a two digit cost parameter, "$", and 22 base 64
    $blowfish = '$2a$10$';

    //get the longest salt, could set to 22 crypt ignores extra data
    $salt = get_salt ( $max_salt );

    //get a second salt to strengthen password
    $salt2 = get_salt ( 30 ); //set to whatever


    //append salt2 data to the password, and crypt using salt, results in a 60 char output
    $crypt_pass = crypt ( $password . $salt2, $blowfish . $salt );

    //insert crypt pass along with salt2 into database.
    $sql = "insert into database....";

    return true;
    }
}  


function get_salt($length) {
$options = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789./';

$salt = '';

for($i = 0; $i <= $length; $i ++) {
    $options = str_shuffle ( $options );
    $salt .= $options [rand ( 0, 63 )];
}
return $salt;
}

function verify_password($input_password)
{
if($input_password)
{
    //get stored crypt pass,and salt2 from the database
    $stored_password = 'somethingfromdatabase';
    $stored_salt2 = 'somethingelsefromdatabase';

    //compare the crypt of input+stored_salt2 to the stored crypt password
    if (crypt($input_password . $stored_salt2, $stored_password) == $stored_password) {
        //authenticated
        return true;
    }
    else return false;
}
else return false;
}

Answer 1

You really should have a look at PHPASS: http://www.openwall.com/phpass/ It's a password hashing framework using crypt() which is used in projects like Wordpress and phpBB.

There is also an excellent article on this website about password hashing, salting and stretching using crypt(): http://www.openwall.com/articles/PHP-Users-Passwords

UPDATE: Currently there's an alternative for the PHPASS library. In the next version of PHP there are special functions for hashing and verifying passwords (using bcrypt): http://www.php.net/manual/en/ref.password.php. There is a compatibility library that implements these functions for PHP 5.3.7+: https://github.com/ircmaxell/password_compat

Answer 2

Your use of crypt() is fine. crypt($input, $stored) == $stored is the way it is designed to be used.

Your get_salt() function is not great, since it is using the often-poor rand() function. You should consider using a stronger random function, like openssl_random_pseudo_bytes(), instead.