Help me make my password storage safe

Question

How much more safer is this than just md5? I've just started look into password security. Im pretty new with php.

$salt = 'csdnfgksdgojnmfnb';

$password = md5($salt.$_POST['password']);
$result = mysql_query("SELECT id FROM users 
                       WHERE username = '".mysql_real_escape_string($_POST['username'])."' 
                       AND password = '$password'");

if (mysql_num_rows($result) < 1) {
    /* Access denied */
    echo "The username or password you entered is incorrect.";

} else {
    $_SESSION['id'] = mysql_result($result, 0, 'id');
 #header("Location: ./");
 echo "Hello $_SESSION[id]!"; 
}

Some input or comments would be nice

Thank you

Answer 1

You users will be much safer if you used parameterized queries instead of concatenating SQL statements.

And salt should be unique for each user and should be stored along with password hash.

Answer 2

That's fine with me. Mr Atwood wrote about the strength of MD5 against rainbow tables, and basically with a long salt like that you're sitting pretty (though some random punctuation/numbers, it could improve it).

You could also look at SHA-1, which seems to be getting more popular these days.

Answer 3

You can use the pwd class (http://code.google.com/p/samstyle-php-framework/source/browse/trunk/class/pwd.class.php) to help you generate a 72-characters hash which includes salting.

You can verify the hashes and compare against passwords whether they are the same or not.

Understanding salting:

A salt is a random string that is generated to make each hash unique even if the password is the same.

So when you generate a hash, you do this:

<?php
// generates a 8 character hexadecimal CRC32 string
function crc($o){
  return str_pad(dechex(crc32($o)),8,0,STR_PAD_LEFT);
}

$salt = crc(mt_rand().time); // a unique fixed length salt
$hash = sha1($password . $salt).$salt; // generates a 40 character hash (32+8)

?>

You store the $hash off into the database.

When checking the user-entered password against the hash, you do this:

<?php

$hash = $TheHashFromDatabase;

$salt = substr($hash,-8);
$generated_hash = sha1($_POST['user_pwd'] . $salt).$salt;

if($generated_hash == $hash){
  // logged in - password is correct
}
?>

Answer 4

A better way would be for each user to have a unique salt.

The benefit of having a salt is that it makes it harder for an attacker to pre-generate the MD5 signature of every dictionary word. But if an attacker learns that you have a fixed salt, they could then pre-generate the MD5 signature of every dictionary word prefixed by your fixed salt.

A better way is each time a user changes their password, your system generate a random salt and store that salt along with the user record. It makes it a bit more expensive to check the password (since you need to look up the salt before you can generate the MD5 signature) but it makes it much more difficult for an attacker to pre-generate MD5's.

Answer 5

The easiest way to get your password storage scheme secure is by using a standard library.

Because security tends to be a lot more complicated and with more invisible screw up possibilities than most programmers could tackle alone, using a standard library is almost always easiest and most secure (if not the only) available option.

The standard library:
Take a look at: Portable PHP password hashing framework: phpass and make sure you use the CRYPT_BLOWFISH algorithm if at all possible.

example of code using phpass (v0.2):

require('PasswordHash.php');

$pwdHasher = new PasswordHash(8, FALSE);

// $hash is what you would store in your database
$hash = $pwdHasher->HashPassword( $password );

// $hash would be the $hashed stored in your database for this user
$checked = $pwdHasher->CheckPassword($password, $hash);
if ($checked) {
    echo 'password correct';
} else {
    echo 'wrong credentials';
}

PHPass has been implemented in some quite well known projects:

• phpBB3
• WordPress 2.5+ as well as bbPress
• the Drupal 7 release, (module available for Drupal 5 & 6)
• others

The good thing is that you do not need to worry about the details, those details have been programmed by people with experience and reviewed by many folks on the internet.

For more information on password storage schemes, read Jeff`s blog post: You're Probably Storing Passwords Incorrectly

Whatever you do if you go for the 'I'll do it myself, thank you' approach, do not use MD5 anymore. It is a nice hashing algorithm, but broken for security purposes.

Currently, using crypt, with CRYPT_BLOWFISH is the best practice.
CRYPT_BLOWFISH in PHP is an implementation of the Bcrypt hash. Bcrypt is based on the Blowfish block cipher, making use of it's expensive key setup to slow the algorithm down.